## U.S. ENVIRONMENTAL PROTECTIONAGENCY REGION9



# REDWOOD CREEK SEDIMENT TOTAL MAXIMUM DAILY LOAD

APPROVED BY:

Alexis Strauss Acting Director Water Division EPA Region IX 

### December 1998

## .,iy~Jl8 Date

### TABLE OF CONTENTS

Section 1. Introduction

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 

### Section 2. TMDL Summary

................................................. 3 Section 3. SupportingDocumentation

......................................... 9 Section 3.1. Problem Statement

......................................... 10 

### Section 3.2. Section 3.3. Section 3.4. Section 3.5. Section 3.6. Section 3.7. Section 3.8. Numeric Targets

...........................................20 SourceAnalysis

........................................... 39 Loading Capacity Linkage Analysis

..........................49 Total Maximum Daily Loads, and Allocations

.................. 52 Margin ofSafety

........................................... 56 SeasonalVariations

........................................ 59 Critical Conditions

.............. : .......................... 59 Section 4. Public Participation

.............................................. 60 Section 5. Implementation and Monitoring Recommendations

................... 60 Section 6. Glossary

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 64 Section 7. References

...................................................... 68

Sediment lMDL for Redwood Creek, CA

## Section 1. Introduction
WhatIs A TMDL? Section 303(d)(1)(A) ofthe Clean Water Act (CWA) requires that "Each State shall identify those waters within its boundaries for which the effluent limitations

...are not stringent enough to implement any water quality standard applicable to such waters." The CWA also requires states to establish a priority ranking for waters onthe 303(d) list ofimpaired waters and establish Total Maximum Daily Loads (TMDLs) for such waters. As part ofCalifornia's 1996 and 1998 303(d) list submittals, the North CoastRegional Water Quality Control Board (RWQCB) identified Redwood Creek as water quality limited due to clean sediment loading and designated the watershed as a high priority for TMDL development. The RWQCB began work onthe sediment TMDL in 1997, and EPA andtl;le RWQCB worked together to complete the sediment TMDL in 1998. The elements ofa TMDL are described in40 CFR 130.2 and 130.7 and Section 303( d) ofthe CWA, 

## aS well as inEPA guidance documents (e.g., EPA, 1991). A TMDL is defined as "the sum of the individual waste load allocations for point sources and load allocations fornonpoint sources and natural background" (40 CFR 130.2) suchthat the capacity ofthe waterbody to assimilate pollutant loadings (the Loading Capacity) is notexceeded. A TMDL is also required to be developed with seasonal variations and include a margin ofsafety to address uncertainty inthe analysis. In addition, pursuantto the regulations at 40 CFR 130.6, states must develop water quality managementplans which incorporate approved TMDLs and implementation measures necessary to implement the TMDLs. Upon establishment ofTMDLs by EPA orthe State, the State is required to incorporate the TMDLs along with appropriate implementation measures into the State Water Quality Management Plan (40 CFR 130.6(c)(1), 130.7). The Regional Board BasinPlan, and applicable state-wide plans, serve as the State Water Quality Management Plan governing the Redwood Creek watershed. Ifthe State subsequently adopts and submitsfor EPA approval TMDLs which are different from the TMDLs established by EPA, EPA will review the State-submitted TMDLs to determine ifthey meet all TMDL requirements. IfEPA approves the State TMDLs, EPA expects the State-established TMDLs would be applicable for the Redwood Creek watershed. Why Is EPAEstablishing These IMDLs? The Environmental Protection Agency (EPA) has oversight authority for the 303( d) program and isrequired to review and either approve or disapprove the TMDLs submitted by states. Ifthe EPA disapproves a TMDL submitted by a state, the EPA is required to establish a TMDL for that waterbody. On October 31, 1997, EPA entered into a consent decree (decree), Pacific Coast Federation ofFishermen's Association. et. aL v. Marcus, (N.D. CaL No. 95-4474 MHP), which established a timetable for development ofTMDLs for several watersheds in northwest California, including Redwood Creek. The decree required development oftwo TMDLs by December 31, 1998. Pursuant to the decree, EPA developed a Supplemental TMDL Establishment Schedule which set December 31, 1998 as the deadline for the establishment ofa sediment TMDL for Redwood Creek.

Sediment TMDL for Redwood Creek, CA 1TheRWQCB has drafted a TMDL for clean sediment for Redwood Creek, buthas nottaken final action to adopt it. Before the TMDL canbe submitted to EPAfor approval, the RWQCB and State Water Resources Control Board must adopt the TMDL, and the State Office ofAdministrative Law must concur onthe TMDL. Because the State has not completed and submitted the Redwood Creek TMDL, EPA is now establishing the Redwood Creek TMDL for sediment, along with a sediment TMDL for South Fork Trinity River, in order to meetthe requirements ofthe decree.
TMDL Organization and Comparison With State TMDLs This TMDL report is organized inthe following sections whichprovide the analytical basis for the TMDLs:

- Problem Statement -Numeric Targets

- Source Analysis

- Loading Capacity Linkage Analysis

- TMDLs and Allocations

- Margin ofSafety

- Seasonal Variations

- Critical Conditions

- Public Participation
In addition, the report discusses TMDL implementation and follow-up monitoring needs. The TMDL proposed in this document very similarto the TMDL public noticed bythe RWQCB onNovember 10, 1998. The organization ofthe EPA report follows the format used 

### in EPARegion 9-established TMDLs. The RWQCB's draft TMDL format is designed to meetthe needs ofthe BasinPlanning administrative procedures and to focus more on specific implementation provisions. Therefore the formats ofthe State and EPA TMDL documents are somewhat different. This final TMDL is based on a draft TMDLproposed by EPA on October 19, 1998. Changes were made inthe final TMDL to address comments received from the public through written comments and oral testimony at a public hearing held November 19, 1998. The final TMDL incorporates changes inthe following areas:

- clarification ofinstream numeric targets

- addition ofhillslope numeric targets -minor clarifications ofthe source analysis, linkage analysis, TMDL, and allocations

- restructuring ofthe margin ofsafety discussion, and

- additional detail inthe implementation andmonitoring recommendations.

2

## Section 2. TMDL Summary
The Redwood Creek TMDL is being established at levels sufficient to result in attainment of applicable water quality standards for clean sediment, including designated beneficial uses and narrative water quality objectives. The TMDL is virtually identical to the draft sediment TMDL developed bythe RWQCB inJuly, 1998 and is very similarto the.TMDL public noticed bythe RWQCB inNovember, 1998. Redwood Creek watershed is a forested watershed located north ofEureka innorthwestern California. Thepurpose ofthe Redwood Creek TMDL is to identifytotal allowable loads and loading allocations that, when implemented, are expectedto result in attainment ofapplicable water quality standards for sediment. Redwood Creek watershed was listed on California's Clean WaterAct (CWA) Section 303(d) list beginning in 1992 as water quality limited due to sedimentation. The level of sedimentation in Redwood Creekwatershed wasjudgedto exceed the existing narrative water quality objectives (WQO)**ne~essary** to protectbeneficial uses ofthe basin, particularly the cold water fishery. Accelerated erosionfrom land use practices and other causes is impacting the migration, spawning, reproduction, and early development ofcold water anadromous fish such as coho salmon, chinook salmon, and steelhead trout. The TMDL includes a problem assessment, which includes an assessment ofexisting instream and hillslope conditions; instream numeric targets, which interpret and are consistent with the narrative water quality standards and also represent the instream conditions for cold water fish where sediment is not a limiting factor, an assessment ofsignificant sediment sources thathave in the past or are presently impacting the stream system; an estimate ofthe loading capacity ofthe system for sediment discharges (and associated reductions) necessary to attain the numeric targets; allocations ofloads among different sediment source categories; and several other sections designed to address considerations set forth in Section 303(d) ofthe Clean Water Act and U.S. EPA's guidance and implementing regulations at 40 CFR 130.7.
The TMDL is based on existing, readily available information concerning Redwood Creek watershed conditions and land managementplans and other watersheds inthe PacificNorthwest, along withTMDLspreviously developed bythe State and U.S. EPA. Detailed explanations ofthe basis for the calculations are provided inthe report, and further background information canbe found inthe Redwood Creek WatershedAnalysis (Redwood National and State Parks, hereinafter referred to as RNP, 1997). 

### Problem Statement
Anadromous fish populations inRedwood Creek have diminished substantially overthe past 40 years (RNP, 1997). Reliable data about historical fish populations inRedwood Creek are lacking. In 1965, the California Department ofFish and Gameroughly estimated spawning escapement of 5000 chinook, 2000 coho, and 10,000 winter steelhead. Although channel deepening and pool development may have begunto increase in all butthe lower few miles ofRedwood Creek, the mainstem generally lacks an adequate pool-riffle structure and cover. Coarse sediment deposited in

3the mainstem allows a large proportion ofsummer base flows to infiltrate and flow subsurface, thereby limitingthe surface water available to fish and increasing surface watertemperatures. Large deltas in some tributaries blocktributary mouths and prevent migration offish. A lack ofsuitable rearing habitat inthe mainstem and tributaries has forcedjuvenile fish to the estuary, where they are subjectto the impacts ofsudden, extreme changes in salinity resulting from breaching ofthe sand barby oceanwaves and currents. Spawning habitat is improving slowly as gravels are cleaned of fine sediment. Key changes inthe mainstem ofRedwood Creek include (1) increases inthe volume ofstored sediment, 

### (2) decreases inpool numbers and depth, 

### (3) increases in stream width and decreases in stream depth, 

### (4) reduced recruitment oflarge woody debris, 

### (5) deposition ofhigh levels offine sediments onthe streambottom, and 

### (6) reduced volumes oflarge woody debris. Redwood Creek isparticularly prone to storm-induced erosional events, and would probably experience extensive erosionunder natural conditions. However, landmanagement activities have accelerated this natural process, overwhelming the stream channel's ability to efficiently move the delivered sediment. Land managementpatterns and practices have contributed to increased erosion beyond natural rates throughmass wasting (landsliding) and fluvial erosion (gullying and stream bank erosion). Theresultant erosion caused sedimentto enterthe stream, filling deep pools and depositing silt in spawning gravels. Past studies indicate that streamside landsliding and fluvial hillslope erosion may be the most importantprocesses delivering sedimentto Redwood Creek. A large proportionofobserved erosion is associated with an extensive road network (7.3 milmF) on private lands, improperly designed and maintained roads and skidtrails, and timber harvesting. Numeric

### Targets
Numeric targets were derived from the literature, available monitoring data for the watershed, recommendations ofagencies commenting onthe TMDL, and bestprofessionaljudgment. The numeric targets are intended to be consistent with the narrative water quality standards in the Basin Plan and focus onthe elimination ofsediment as a limiting factor for salmonids. As such, they are an expression ofdesired future conditions. The TMDL contains numeric targets for instream channel indicators and for hillslope indicators which are associated with stable watersheds capable of supporting healthy salmonid habitat. The numeric targets are included in Table 1 a and 1 b, pp. 5-6. 

### Source Analysis
Tencategories ofsediment delivery were identified for the Redwood Creekwatershed (Table 2), eight ofwhich are to some extent controllable: 1) erosion associated with roads, skidtrails and landings; 2) gully erosion; 3) bare ground erosion associated withhuman activities; 4) stream bank erosion associated with human activities; 5) tributary landslides (road related); 6) tributary landslides (harvestrelated); 7) mainstem landslides (while many are natural, the delivery ofsedimentmay be controllable to varying degrees); and 8) debris torrents. Controllable discharges or depositions are those discharges or depositions resulting from human activities that can influence water quality that can be reasonably controlled. The rates ofdelivery were estimated for those sources as well as sources deemed non-controllable using sediment source information from Redwood National Park. Itwas estimated that on average, about 4750 tons per square mile peryear are produced from the Redwood Creek watershed, about 60% of which is controllable (see Table 2, p. 7).

4Table la. Instream Numeric Targets for the Redwood CreekWatershed.
Parameter Numeric Targets (Desired Conditions) Percent fines <0.85 mm 

### inriffle crests of <14% fish-bearing streams2 Percent fines <6.5 mm in riffle crests offish- <30% bearing streams Percent ofStream Length inRiffles3 < 25-30% ofstream reaches inriffles (reach gradient < 2%) Pool depth inmainstem Redwood Creek the mean depth ofpools at lowflow exceeds reaches withpool-riffle morphology 2m Depths ofpools in 3rd and 4thorder the mean depth ofpools at lowflow exceeds tributaries with pool-riffle morphology4 1-1.5 m Medianparticle size diameter (d50) from riffle 2: 37 mm (minimum for a reach ) crest surfaces 2:69 mm (mean for a reach) Percent fines < 2 mm at riffle crest surfaces <10-20% 

### in fish-bearing streams Large WoodyDebris in any watercourse Improving trend towards increased large capable oftransporting sedimentto a higher woody debris order watercourse

1 Targets should be evaluated as ten year rolling annual averages to avoid premature assessment oftrends

based on inadequate information. This approach addresses the variations in sediment loading and instream indicators which are characteristic ofRedwood Creek and which maynot indicate management related effects. · 2 Fish-Bearing Streams: Fish present seasonally oryear-round, or having fish habitat capable ofsupporting

fish. Fishhabitat is the aquatic environment and the immediately surrounding terrestrial environment that, combined, afford the necessarybiological and physical support systems required by fish species during various life history stages. Generally, these streams have gradients less than 3%. 3 Riffle- low gradient: shallow stream channel areas with swiftly flowing turbulent water with some partially

exposed substrate. Gradient<4 %, substrate is usually cobble dominated. The gradient is the general slope, orrate ofchange in vertical elevation per unit ofhorizontal distance, ofthe water surface ofa flowing stream; orthe rate ofchange ofany characteristic perunit oflength. 4 Stream order is the designation ofthe relative position ofstream segments in the drainage basin network.

Forexample, a first order stream is the smallest, unbranched, tributary which terminates atthe upper point. A second order stream is formed when two first order streamsjoin.

5

### Table lb· Hillslope Numeric Targets for the Redwood CreekWatershed 

# . .

Parameter Numeric Targets (Desired Conditions) Road stream crossings with No crossings have diversion potential (i.e., all crossings are

diversion potential reconfigured permanentlyto assure that no diversion will occur). Road culvert/crossing sizing All culverts and crossings are sized to pass the 50 year flood and associated sediment and debris. In addition, crossings and culverts in the snow zone (generally, upstream ofHighway 299, are sized large enough to accommodate flows and associated sediment and debris caused byprecipitation and snowmelt runoff. Landing and road fill stability All landings and road fills (e.g., sidecasts) on slopes >50% and which could potentially deliver sedimentto a watercourse are pulled back and stabilized. Road surfacing and drainage All roads have surfacing and drainage facilities or structures which are appropriate to their patterns and intensity ofuse. Road inspection, maintenance, All roads are inspected and maintained annually ordecommissioned.

and decommissioning Decommissioned roads (roads which are closed, abandoned, or obliterated) are hydrologically maintenance free. 1 Road location in inner gorge or Roads are not located in steep inner gorge orunstable headwall areas

unstable headwall areas except where alternative road locations are unavailable.2 Use ofclearcut and/or tractor Clearcut and/or tractor yarding harvest methods are not used in steep

yardingtimber harvest inner gorge, unstable, or streamside areas unless a detailed methods geological assessment is performed which shows there is no potential for increased sediment delivery to water courses as a result ofusing these methods.3 1Hydrologically mamtenance free means that:

- drainage in the road area mimics natural hydrology,

- all drainage is dispersed to the slope through use, as appropriate, ofoutsloping or cross-road drains,

- all culverts and associated fill material is removed from crossing areas, -allpotentially unstable road fill and landing sidecasts are pulled back, and

- excavated spoils are placed in locations where they will not enter a water course. 2 This target is intended to address roads located adjacent to water courses with inner gorge topography or

which cross steep, unstable headwall areas, and is not intended to applyto road crossings ofinner gorge areas. Steep inner gorge areas generally exceed 65% in slope and are located adjacent to class 1 and 2 water courses.· Characteristics ofsteep unstable headwall areas generally include the following:

- slopes greater than 50%,

- erosive or incompetent soil types orunderlying geology,

- concave slope shape,

- convergent groundwater present, and/or

- evidence ofpast movement is present. 3 Characteristics ofsteep inner gorge, unstable, or streamside areas generally include the following:

- slopes greater than 50%, -located within 300 feet ofa Class 1, 2, or 3 watercpurse,

- erosive or incompetent soil types or underlying geology,

- concave slope shape,

- convergent groundwater present, and/or

- evidence ofpast movement is present. 6

### Table2. Summary ofSourceLoadingEstimates, Loading Capacity, and TMDL Allocations for theRedwood Creekwatershed.
Historic Percent Controllable Remaining Source Mechanism Sediment Controllable2 

### Load3 

### Load Load1 (t/sq.mi./yr) 

### (Allocation)4 (t/sq.mi./yr) (t/sq.mi./yr) 

### Roads, Landings and 690 85% 586 104 Skid Trails erosion Gully Erosion 1020 85% 870 150 (-90%road related) Bare GroUJ.id Erosion 400 85% 340 60 Stream BankErosion 590 35% 210 380 Tributary Landslides: 210 0% 0 210 Naturally Occurring Tributary Landslides: 360 80% 290 70 Road Related Tributary Landslides: 390 50% 190 200 Harvest Related Mainstem Landslides 810 40% 320 490 (Human Induced and Naturally Occurring) 5 

### Debris Torrents 100 50% 50 50 Other Mass 180 0% 0 180 Movements (Naturally Occurring):

- earthflows

- block slides Totals 4750 60% 6 

### 2850 1900

1The estimated historic sediment load for each source. 2 The percent ofthat historic load that is estimated as controllable. Controllable discharges are those

discharges resulting from human activities that can influence the quality ofthe waters ofthe State andthat can be reasonably controlled. 3 The load that is estimated as controllable (the percent controllable multiplied bythe historic load). 4 The difference between the historic load estimate andthe controllable load estimate. This is the estimated

load atwhich salmonids in the Redwood Creekwatershed would no longer be limited by sediment. 5 Study of586 mainstem landslides revealed that approximately 50 % ofthe slides had one ormore

associated roads (Kelsey, et. aL, 1981) The volume ofeach slide may be variable but may represent an average 50 percent ofthetotal load. ofmainstem landslides. 6 Calculated Controllable Load (2850tlsq.mi./yr.) is 60% ofEstimated Historic load (4750tlsq.mi./yr.).

Reducing 4750tlsq.mi./yr. by sixty percent leaves a remainder of 1900tlsq.mi./yr.

7

### Loading Capacity, Total Maximum Daily Loads. and LoadAllocations After considering the quantitative comparison ofestimated loading rates and controllable portions ofvarious types ofloading, andthe qualitative comparison ofinstream indicators with existing conditions, EPA estimates that a 60% reduction in total sediment loading from historical loading rates is needed inthe Redwood Creek watershed as a whole to meet the instream targets. The estimated total allowable sediment load (the TMDL) is estimated to be approximately 1900 tons per square mile per year. This number was derived from estimated average annual sediment loads for the period 1954 -1997 for three reference watersheds withinthe Redwood Creekbasin. There are no point sources ofdischarge to Redwood Creek; therefore, there are no wasteload allocations establishedthrough this TMDL. The Redwood Creek load allocations: 1) were developed for erosionprocesses; 2) are associated with land use activities where feasible; and 3) are based on: the source analysis ofthe various erosional processes. The load allocations were developed as long term annual average loads per square mile atthe watershed scale and appear in Table 2, p. 7. 

### Margin ofSafety. Seasonal Variations. and Critical Conditions
Inevery one ofthe components used to develop the TMDL, assumptions were made where sufficient data were lacking. Conservative assumptions were made in each case as a way of addressing uncertainty associated with the data; this constitutes an implicit margin ofsafety.
In Redwood Creek, there is inherent annual and seasonal variation inthe delivery of sedimentto stream systems and inthe impacts sedimenthas on aquatic species during different life stages. However, sediment impacts often occur for periods long after the sediment loading to the stream, and in locations far removed from the loading site. Forthis TMDL, it was technically infeasible to vary the TMDL to account for temporal and spatial variations in sediment loadings and impacts. Instead, the TMDL is designed to account for long term erosion patterns and instream impacts associated with sediment in Redwood Creekbyusing longertime frames for implementation and evaluation. Furthermore, allocations are designed to apply to the sources of sediment, themselves, not the movement ofsediment across the landscape ordelivery ofsediment directly to the stream channel. The TMDL and associated allocations are set at levels which reduce sediment loading to the pointthat creekhabitat structure is able to recover and support the beneficial uses ofconcern. 

### Implementation and Monitoring Recommendations Although they are not required components offederally-established TMDLs, this TMDL document includes implementation and monitoring recommendations to assist the State and watershed stakeholders in implementing the TMDL and conducting followup monitoring and review inthe future. EPA strongly supports the RWQCB's draft TMDL implementationplan contained inthe November 10, 1998 draft Water Quality Attainment Strategy for Redwood Creek. EPA also supports the State's commitmentto work with landowners, agencies, and other stakeholders to develop a specific monitoring plan. Inthis document, EPA is recommending several specific provisions which would strengthen the implementation and monitoring provisions proposed bythe State. 8

## Section 3. Supporting Documentation
A Note On Methods Used To Establish theTMDL Redwood Creekhas been extensively studied by many researchers for over 30 years. As a result, substantial information and data concerning erosion causes, trends, and impacts has been developed for the basin, particularly by scientists associated with Redwood National and State Parks (RNP). The Redwood Creek TMDL is based onthis existing body ofanalysis, as supplemented bythe expertjudgment offered by several researchers at RNP and by additional analysis conducted by EPA.
EPA recognizes that erosion processes which are responsible for sediment inputs to the system are highly dynamic and variable from year to year and in different locations in the basin. The maindriving factor influencing variation in erosion and sediment inputs from year to yearis variability inprecipitation and, particularly, periodic highmagnitude storms. Ideally, the TMDL and associated allocations could be expressed in dynamic terms as a function ofthe driving forces which determine the extent oferosion events (e.g., runoffintensity, topography, geology) and their impacts onreceiving waters (e.g., proximity to water courses, stream morphology, and habitat distribution). However, it was infeasible to develop a dynamic predictive model offuture erosion amounts, timing, and locations and the impacts ofsediment delivery onthe waterbody reaches most importantfor aquatic habitatbased on existing information and scientific knowledge. This TMDL analysis was basedprimarily onhistorical data concerning sediment loading, stream flows, and stream responses to erosional impacts, along with information oninstream and hillslope conditions which in other locations were associated with well-functioning watersheds and aquatic ecosystems. It is difficult to predict future erosion and associated impacts based onpast erosion patterns and on aquatic habitat conditions studied elsewhere. However, this TMDL does account for the important issues oftemporal and spatial variability in erosion and streamresponses in several ways: Temporal Considerations
Indicators were selected for use in instream numeric targetdevelopment and follow-up monitoring which are believed to integrate cumulative effects over annual timeframes (e.g. annual lowflow measurements ofstream bottom composition) instead ofindicators whichmeasure instantaneous conditions (e.g. turbidity). Numeric targets (goals for instream indicators), the total allowable load, and specific load allocations are expressed interms of 10 yearrolling averages inrecognition that trends are not discernible within shortertime frames and to allow for natural variation due to seasonal and annual differences. The source analysis is based on sediment loading estimates developed for a time period of more than40 years which encompasses a wide range ofclimatic and land use conditions. This period included several major storms which caused catastrophic sediment inputs as well as significant periods ofdrought during whichprecipitation, runoff, and associated sedimentation

9were far belownormal. This timeframe also includes periods ofwidespread, intensive timber harvesting prior to the implementation ofmodemlogging practices along withperiods in which logging stopped inthe lowerbasin (after the National Park was created) and intensive logging continued inthe middle and upper basinusing modem logging practices required by State timber harvestrules. Future erosion patterns may be different from historic patterns largely due to the removal ofone third ofthe basin from timber harvest management and the institution ofmore protective forest practice rules. However, available information indicates that future erosion potential inthe basin, chiefly associated with roads built before the advent ofmodem forest practice rules, remains very high (RNP, 1997). The degree to which modemtimber harvest practices will protect Redwood Creek from excessive sedimentation has not been established or adequately tested. Therefore, itis reasonable to set a TMDL and associated allocations which will ·guide future land management decisions based onthe extensive historical loading analysis. Spatial Considerations The TMDL was derived basedprimarily on analysis ofconditions in different tributaries to Redwood Creekwhich are representative ofdifferent geologies and associated vulnerabilities to erosion. An effort was made to account for the differences inerosion potential associated with different geological conditions present inthe watershed because geology was believedto be a key driving force influencing variability inerosion potential throughout the basin.
For some indicators, separate numeric targets are identified for different parts ofthe basin ·to accountfor differences in geomorphic conditions and habitat issues in different parts ofthe watershed. That is, separate numeric targets for fish rearing habitat were developed for tributaries versus the mainstem ofRedwood Creek. In addition, hillslope targets are provided which recognize and address the higher erosion potential associated withroads and timberharvesting in steep, unstable terrain near water courses. 

## Section 3.1. Problem Statement
This section is based primarily on information contained inthe draft Redwood Creek Watershed Analysis (RNP, 1997) and otherpublications by RNP researchers. Watershed Overview Redwood Creek watershed is a 285 square mile forested watershed in Humboldt County, California

.. Redwood Creek flows into the Pacific Ocean near Orick. The drainage area upstream ofthe U.S. Geological Survey stream gauging station at Orick is 278 square miles (Figure 1). The Redwood Creek watershed consists mostly ofmountainous, forested terrain from sea level to about 5,300 feet elevation. Primary land uses are tourism and fishing onpark lands and timber and livestockproduction on lands upstream ofRedwood National Park. The watershed is narrow and elongated, about 65 miles in length, from 4 to 7 miles wide. The lower basin includes the Park area and the middle and upper basin are located upstream from the Park. The cold water fishery is identified by the Regional Water Board as a beneficial use ofthe Redwood Creek watershed. The creek historically supported large numbers ofcoho salmon,

10chinook salmon, steelhead trout, and other fish species. Reliable data about historical fish populations inRedwood Creek are lacking. In 1965, the CaliforniaDepartment ofFish and Game roughly estimated spawning escapement of5000 chinook, 2000 coho, and 10,000 winter steelhead. Coho salmon, a species native to the Redwood Creek, is listed by the National Maririe Fisheries Service as a threatened species. In addition, steelhead and chinook salmonpopulations have declined significantly inthe watershed. By 1994, five fish species found in Redwood Creekwere classified as a species ofconcern, threatened or endangeredby U.S. Fish and Wildlife Service and/or the California Department ofFish and Game: tidewater goby, coast cutthroat trout, coho salmon, spring run chinook salmon, and summer steelhead trout (RNP, 1997). Sedimentation due to natural geologic instability, past and present land use practices, and other factors has contributed to the reduction and loss ofhabitat necessary to support cold water fish including salmonids. 

### Climate and Hydrology The climate ofthe Redwood Creek watershed is Mediterranean, with mild, wet winters (November to March), and warm, dry summers. Mean annual precipitation isroughly 80 inches, mostly rain, with snow frequently at altitudes above 1,600 feet. The snow zone ofRedwood Creek watershed is roughly located upstream ofHighway 299, which crosses the watershed approximately atthe boundary between the middle and upper basin. Snowmelt can increase streamflowpeaks during**rain~on·snow** events, as occurred in 1964. Streamflow inRedwood Creek is highly variable from yearto year as a result ofannual rainfall variations. Streamflow also varies seasonally, owing to the highly seasonal distribution of rainfall. Winter flood flows canbe as much as four orders ofmagnitude higherthan summerlow flows. Floods are critical events for the resources ofRedwood Creek because they erode hillslopes, reshape channels, and transport largeproportions offluvial sediment loads. Recent large floods occurred in 1953, 1955, 1964, 1972 (two floods), and 1975. The 1964 storm was a regionally significant event that caused major damage to towns, highways, and other structures, as well as significant hillslope erosion and channel changes.
No large floods occurred after 1975, until the recent 1l·yearreturnperiod flood inJanuary of 1997. During January 1997, therelatively small 11-yearreturn period flood initiated debris torrents ofmud, boulders, and whole trees directly into Redwood Creek adjacentto Tall Trees Grove; the effects ofa major storm would probably be muchmore severe. Withinthe time period from 1975 to 2015, there is an 80% chance ofa 25-yearflood. Ithas been 23 years since the last 25-year flood inRedwood Creek, in 1975. It has been 34 years since the last 50-yearflood, and erosionpotential inthis basinfrom such a storm is estimated at more than 5 million cubic yards. Ofthis, 90% is from the private roads upstream from the park. Within the time period from 1964 to 2014, there is a 64% chance ofa 50-year flood. 

### Geology Geologic Structure inthe Redwood Creek watershed is governed by several parallel northnorthwest trending faults. Formuch ofits length, the channel ofRedwood Creek closely follows the Grogan Fault.
11

## Redwood 

## Creek Watershed

Panther Creek

s

RF 1:400,000 Mapscalein 1\llles Redwood National and State Parks (tint) Estuary

little lost Man Creek

2 0 2 4 fi 8 

## Streams

00216. 2.13.97 Private lands (white)



### 12 

## RoadsRedwoodCreek watershed is characterized by relative steep, unstable hillslopes, very steep inner gorge slopes along much ofthe mainstem and some tributaries, and narrow valley bottoms. Most ofthe Redwood Creek watershed has experienced uplift overthepast several hundred thousand years. The basin is underlain bythe Franciscan complex ofunmetamorphosed sandstones, mudstones, schists, and scattered blocks ofother rock types. Ingeneral, slopes west of the Creek (which generally follows the Grogan fault) are underlain by schist, and slopes east ofthe Creek are underlainby sandstones and mudstones.
A very highpercentage ofthe land area ofRedwood Creek basin is underlain byrocktypes which are relatively weak and susceptible to erosion and mass soil movements (e.g., schists and mudstones). Remaining areas ofthe watershed which are underlain by more competentrock types (e.g. interbedded sandstone/mudstones) are somewhat more resistant to erosion, butform steep slopes which are susceptible to rapid, shallow landsliding processes. 

### Plants andAnimals
The natural vegetation ofthe Redwood Creek watershed consists mostly ofconiferous forest, but also includes areas ofoak woodland and grasslandprairie. The distributionofplant communities depends primarily onwater availability and fire regime. Old-growth forest currently covers 24,315 acres inthe watershed, equivalent to 14% ofits total area. Nearthe coast, the most commonforest tree is the Sitka spruce. Most ofthe lowerbasin forest, however, is dominated by coastredwoods. Farther inland, where summer· temperatures are higher and fog is less frequent, Douglas fir is more commonthan redwood. Several hardwood species grow in association with bothredwood and Douglas fir, including bigleafmaple, red alder, tanbark oak, madrone, and bay. Prairies and oak woodlands occur on southandwest-facing ridgetops andhillslopes onthe east side ofRedwood Creek. Approximately 250 species ofwildlife (amphibians, reptiles, mammals, and birds) are knownto occupy habitats found inthe Redwood Creekwatershed. Thirty three species ofwildlife are identified as species ofspecial concern (threatened, endangered or sensitive to human activities, see RNP, 1997 for details). The Redwood Creek watershed provides aquatic habitat for a variety offish species. Anadromous and resident salmonids identified inRedwood Creek include steelhead andrainbow trout, coastal cutthroattrout, coho salmon, and chinook salmon. Otherfish identified orreported include the tidewater goby, Humboldt sucker, threespine stickleback, coast range sculpin, Pacific lamprey, and eulachon. Five species offish have been listed as species ofspecial concern, endangered species, or sensitive species by federal and state agencies. 

### Land Use and Sedimentation Issues Relations between floods, sediment, and land use have been central to the debate over resource protection inthe Redwood Creek watershed. Damage to forest resources, fish, and other resources coincided with both intensive land use and a series oflarge storms that were accompanied by widespread flooding and erosion. Erosion rates in northwestern California are 13naturally high, and land use has significantly increased erosion above natural levels associated with storms. The questionhas obvious practical importance because erosionrelated to land use potentially canbe prevented. In the Redwood Creek Watershed, the large number ofimproperly designed and maintained roads, landings and skid trails causes: 1) increased surface erosion and fine sedimentproduction and delivery and 2) an increased potential for stream diversions (stream channel capture), rill and gully erosion, androad related landslides with corresponding increases in sedimentproduction and delivery (See roads map, figure 3). Timber harvest operations onunstable slopes and removal ofriparian vegetation have also contributedto increased erosion and sediment production. 

### Water Quality Objectives
Water quality objectives (the term used bythe State ofCaliforniato refer to water quality standards) adopted for the Redwood Creek basin are contained inthe RWQCB BasinPlan. The beneficial uses ofwater for Redwood Creek are described inthe BasinPlan as either existing or potential. The water quality objectives are designed to protectthe most senSitive beneficial uses. The beneficial uses addressed inthe Redwood Creek TMDL include: cold freshwater habitat (COLD); migration ofaquatic organisms (MIGR); estuarine habitat (EST); uses ofwater for community, military, orindividual systems including, butnot limited to drinking water supply (MUN); uses ofwaterthat supporthabitats necessary, at least inpart, for the survival and successful maintenance ofplant or animal species established under state orfederal law as rare, threatened or endangered (RARE); and spawning, reproduction, and/or early development (SPAWN). The water quality objectives addressed include settleable material ("Water shall not contain substances that result in deposition ofmaterial that causes nuisance or adversely affect beneficial uses") and sediment ("The suspended sediment load and suspended sediment discharge rate ofsurface water shall not be altered in such a manner as to cause nuisance or adversely affect beneficial uses."). Discharges ofsediment are also addressedby a discharge prohibition. 

### Beneficial Use Issues Salmonids are borninfresh water streams where they spend one to several years oftheir lives feeding, growing, and hiding from predators. Once they are large enough, fresh water salmonids undergo a physiological change which allows them to swim outto the ocean where they then spendthe next one to several years. Salmonids return to the streams in which they were born to lay eggs and beginthe life cycle again. They require gravels free from excessive fine sediment to lay their eggs and for the eggs to develop into free-swimming fish. They also require deep pools for the young fish to feed and growwhile protected from predators. Redwood Creekis largely free ofthe effects ofnon-native aquatic species orhatchery stocks which might impactthe native fishery. Although numbers ofnative salmonid species present in Redwood Creek have declined substantially(by perhaps 90% bythe mid-1970s), remnantpopulations ofcoho, fall and summer chinook, winter and summer steelhead, and cutthroat trout are still present. Coho salmonwere listedunderthe federal Endangered Species Act as a threatened species onMay 6, 1997 by theNational Marine Fisheries Service. Redwood Creek is located within the Evolutionarily Significant Unit (ESU) known as the Southern Oregon/Northern California Coastwhere coho salmonwere listed. 14Redwood Creek's ability to support fish populations is determinedby habitat availability and quality. Habitat availability is limited by streamflow, stream gradients,. and physical barriers such as boulders and logjams. Habitat quality is limited by channel bottom composition, pool structure, water temperature, dissolved oxygen, food supply, and predation (RNP, 1997). However, the TMDL onlyaddresses habitat quality impacts associated with excessive sediment discharges. Thekey habitatproblems inRedwood Creek associated with sedimentation appearto be pool quality, gravel quality (for spawning and food production), and changes in channel structure which contribute to temperature elevation. Residents inthe upper Redwood Creekbasin commonly have instream domestic water intakes. These water supplies canbe adversely impacted by high sediment loads, but that beneficial use is not currently impaired. Excessive sediment mayresult in turbidity, adverse tastes, and nuisance condition dueto clogging offilters. Itis anticipated that implementation ofthe TMDL will also helpprotect drinking water. 

### Summary ofExisting Conditions
The Draft Redwood Creek Watershed Analysis (RNP, 1997) provides a summary analysis ofexisting stream conditions. In general, stream channels inthe Redwood Creekbasin are wider, shallower, and more homogeneous than is desirable orwere historically present. 1. Stream Channel Conditions andFishHabitat Impacts
Stream channel structure along the mainstem ofRedwood Creek and its tributary watersheds has changed substantially overthe last40 years. Key changes inthe mainstem of Redwood Creek include 

### (1) increases inthe volume ofstored sediment, (2) decreases inpool numbers and depth, (3) increases in stream width and decreases in stream depth, (4) reduced recruitment oflarge woody debris, (5) deposition ofhigh levels offine sediments onthe stream bottom, and (6) reduced volumes oflarge woody debris. Stored Sediment More sedimenthas been supplied to the low gradientreaches ofthe mainstem than it can effectively transport. Low gradient reaches ofthe mainstem Redwood Creekhave acted as long term repositories oferoded sedimentwhich originated in upstream areas. Although the creek is apparently beginning to downcut through aggraded sediments in its lower basinreaches, this stored sediment has the potential to affect channel structure and habitat values for centuries. In contrast, the higher gradientmainstem reaches inthe upper watershed have removed abouthalfthe sediment deposited by the 1964 flood within 20 years (RNP, 1997). Pool Distribution and Depth Most mainstem pools were filled by sediments bornprimarily by the 1964 flood, and to a lesser extent by otherhighmagnitude events between 1954 and 1975. Pool frequency and mean depth appeared to increase since 1975 as the creekbeganto move outpreviously deposited sediment loads, and pool recovery is more apparent in the upper basin. However, many pools were again filled by sediments following the moderate 1997 storm season. Reduced pool frequency and depth impairs rearing habitat byreducing availability ofcool water refuges and increasing predation. 15Channel Width and Depth Manyreaches ofRedwood Creekbecame substantially wider and shallower inresponse to excessive sediment inputs and destructive flood**flow~** which occurred between the mid 1950s and mid 1970s. Stream width increased and depth decreased in response to streambank erosion and channel aggradation. Although many reaches ofRedwood Creek have begunto downcutthrough aggraded sediments (especially in the middle and upper basins), stream widths have not decreased substantially. Fishhabitat impacts associated with increased width and decreased depth include increases inwatertemperature, decreased coverto hide from prey, and increased difficulty in moving up and downthe stream in search offood and cool water refugia. In addition, aggraded sediment deposits have formed "deltas" at the mouths ofmany tributaries which impede fish passage upstream into tributaries. Finally, as the creekhas widened and riparian timber has been harvested, canopy coverage ofthe stream has been reduced substantially, contributing to water temperature increases. Fine Sediments Although limited data are available concerning stream substrate composition inRedwood Creek, it appears thatthere is a slighttrend toward coarsening ofbed material since the 1970s. However, levels offine sediment (which canbe

### harmful to fish spawning success) appearto be higherthan desirable for successful fish spawning inmany reaches ofRedwood Creek, principally inthe lower basin. Large Woody Debris Large woody debris (L WD}inNorth Coast streams provides multiple functions which are key to the maintenance ofhealthy streamhabitat and the moderation ofsedimentation impacts on those streams. Presence ofadequate LWD is a key factor inpool formation, sediment storage, and nutrient loading inmany streams. Due to extensive harvesting ofriparian forests along Redwood Creek and its tributaries along with extensive streambank erosion, recruitment ofLWD is well belowhistoric levels needed to support healthy fish habitat and to moderate sediment transport. To summarize, fish populations inRedwood Creek are muchreduced incomparison to historic accounts. Habitat conditions are probably still quite degraded relative to pristine conditions, but are showing signs ofimprovement. Although channel deepening and pool development have been observed in all butthe lower few miles ofthe Creek, the mainstem generally lacks an adequate pool-riffle structure and cover. Coarse sediment deposited inthe mainstem allows a large proportion ofsummerbase flows to infiltrate and flow subsurface, thereby limiting the surface water available to fish and increasing surface watertemperatures. Large deltas in some tributaries block some tributary mouths and preventmigration offish. The lack ofsuitable rearing habitat inthe mainstem and tributaries has forcedjuvenile fish to the estuary, where they are subject to the impacts of uncontrolled breaching ofthe sand bar. Spawning habitat is improving slowly as gravels are cleaned offine sediment. Canopy closure along the upper reaches ofRedwood Creek is increasing, but is still far less than it was early this century. Tributary water temperatures are generally suitable for salmonids, but are suboptimal for fish along much ofthe mainstem. Recruitment oflarge woody debris and nutrients are probably well belowhistoric levels. This condition is likely to persist into the future as deciduous willows and alders take the place ofevergreen conifers along much ofthe mainstem and tributaries, and as large conifers along watercourses inthe upper basin are harvested (NPS, 1997). Willows and alders generally yield less durable LWD than conifers. 162. Hillslope Conditions Timberharvesting is the mostwidespread land use inRedwood Creekbasin. Over 85% of the basinupstream ofthe parkhas been logged, including about 30% whichwas logged between 1978-1992. About three-quarters ofthis recently logged areawas logged using intensive silvicultural methods whichremove all or almost all trees from the harvest area. Substantial areas ofthe park were intensively loggedprior to their inclusion inthe park. Harvested areas remain at greater risk ofincreased erosion (principally through landsliding) for at least a year or two following harvest, andpossibly for longerperiods oftime. Itis expected that timberharvesting of second growthtimber inthe upperbasin will continue inthe future, so erosionpotential associated with these harvests will need to be addressed throughthe TMDL.
Most ofthe likely future erosionpotential inthe basin caused byhuman activity is associated with logging roads and skid trails, although roads constructed for otherpurposes also pose significant erosionpotential. Roughly 1400 miles offorest roads and over 5000 miles ofskid trails have beenbuild within the basin, ofwhich about 445 miles ofroads and 3000 miles ofskid trails were included withinthe national parkboundaries. About halftlie roads and a very high percentage ofskid trails upstream ofthe park are notproperly maintained orhave been abandoned. The Redwood CreekWatershed Analysis contains a detailed analysis ofthe status and condition of existing roads, and concludes that remaining erosionpotential associated withpoorly designed and maintained roads remains the largest future erosion source inthe basin which can be controlled. Althoughthere has been somerecovery inthe Redwood Creek andtributary channels, it is expected that a very highpercentage ofimproperly constructed ormaintained roads will fail during the nexthigh magnitude storm. Unless correctedthrough road upgrading, maintenance, and/or decommissioning, such road failures are expected to cause substantial direct erosion (through crossing failures, stream diversions, etc.) and indirect erosionevents (e.g. gully formation and mass wasting events). Other continuing land uses inthe basinpose less substantial erosionpotential although potential impacts could be significant in local settings. Intensive timber harvesting, particularly using clearcutting and tractor logging in sensitive streamside areas may pose significant erosion potential inthe future. State and countyroads pose significant erosion potential in some locations. Ranching operations and residential property management may also have the potential to cause significant erosion, particularly in locations where livestock access contributes to bank erosion. 

### General Problem Statement TheRedwood Creekwatershed has experienced a reduction inthe quality and quantity of instream habitat whichis capable ofsupporting the cold water fishery, particularly that ofcoho salmon, chinook salmon, and steelhead. Controllable factors contributing to this habitat loss include the acceleration ofsedimentproduction and delivery due to land management activities, including existing roads, and the loss ofinstream channel structure necessary to maintain the system's capacity to efficiently store, sort, andtransport delivered sediment. Three factors are important in describing the issue ofsedimentation: sedimentproduction, delivery, and transport. Water quality concerns arise when sediment is delivered to the stream in amounts orto locations that overwhelmthe stream's capacity to transport it. Such is the case inthe 17Redwood Creek watershed. Habitat niches are filled by sediment and the stream channel is aggraded, in some places. Itis importantto note, though, thatthe aggradation ofthe upper mainstem and mosttributaries appears to bereversing-- an indicationthat the process ofrecovery has begun. Adequatepool riffle structure and stream cover are still absent inthe lower mainstem. Excessive sedimentation has also contributed to habitat degradation inthe estuary. For gravel-bed streams, such as the Redwood Creek, the presence ofchannel structure plays a crucial role in the efficient storage, sorting, and transport ofsediment through the river system. Channel structure takes the form oflarge woody debris, boulders, armoured stream banks, and other structural elements. For streams inthe Pacific Northwest, including northern California, large woody debris has been identified as a particularly important structural element. Thus, sediment delivery and instream channel structure, particularlylarge woody debris, are integral companions inthe problems (and solutions) related to sedimentation and the reduction inthe quality and quantity ofinstreamhabitat.
Instream Problem Statements



### 1. Fine Sediment in Spawning Gravels Spawning gravels ofthe Redwood Creek watershed are impacted and likely to suffer additional impacts by the delivery offine sedimentto the stream which fills the interstices ofthe framework particles: 1) cementing them inplace and reducing their viability as spawning substrate, 2) reducing the oxygen available to fish embryos, 3) reducing intragravel water velocities andthe delivery ofnutrients to and waste material from the interior ofthe redd (salmon nest), 4) and impairingthe ability ofyoung salmon to emerge as free-swimming fish. This statement relates to the SPAWN beneficial use and the potential for settleable material to affect spawning redds. 

### 2. ChannelAggradation Spawning gravels ofthe Redwood Creek watershed are impacted bythe delivery offine and coarse sediment to the stream which causes aggradation, the burial oflarge woody debris and other structural elements, a loss ofthe stream's ability to effectively sort gravel, and a potential reduction inthe dominant particle sizes. This statementrelates to the SPAWN and COLD beneficial uses and the potential for sediment and settleable material to adversely affect spawning substrate. 

### 3. Lackof suitablepools for RearingHabitat Pools ofthe Redwood Creek watershed potentially suitable as rearing habitat are impacted by the delivery offine and coarse sedimentto the stream which: 1) reduces the volume ofavailable rearing habitat by filling inpools and burying pool-forming structural elements such as large woody debris, 2) reduces pool depth and therefore the cool water refuge associated with temperature stratification, 3) reduces the availability offish cover as a result ofdecreased depths and the burial oflarge woody debris and other structural elements, and 4) causes loss ofsurface flow as pools are filled inresulting in less available habitat and protection from predators. This statement relates to the SPAWN and COLD beneficial uses and the potential for sediment and settleable material to impact rearing habitat. 

### 18

### 4. Stream ChannelInstability Increased sediment delivery to the Redwood Creekwatershed impacts stream channel stability by causing: 1) aggradation, stream channel widening, greater flood potential, and greater stream bank erosion, and 2) the burial ofchannel structural elements such as large woody debris with a reduction in sediment transport efficiency. This statement relates to the COLD and EST beneficial uses and the potential for sediment to impact stream channel stability andhabitat niches. 

### 5. PhysicalBarriers to Migration The migration ofanadromous fish inthe Redwood Creekwatershed from the ocean, within the basin, and backto the ocean is impacted by thepresence ofmigration barriers including shallow or dewatered stream segments due to aggradation (rising stream bed elevation). This statement relates to the MIGRbeneficial use and the potential for sediment inthe form of aggradation orroad fill to prevent the migration ofsalmonids. (Natural barriers, such as bedrock falls, are not addressed here since they are notpollutants for which TMDLs are needed. In addition, the TMDL does not address anthropogenic barriers associated with culverts because EPA does not consider culverts a pollutant for which TMDL preparation is needed (EPA, 1997a)). Hillslope Problem Statements
1. 

### Improperly DesignedorMaintainedRoads The large number ofimproperly designed and maintained roads, landings and skid trails in the Redwood Creek watershed causes: 1) increased surface erosion and fine sediment production and delivery and 2) an increased potential for stream diversions (stream channel capture), rill and gully erosion, and road related landslides with corresponding increases in sedimentproduction and delivery. This statement relates to the COLD beneficial use and the potential for sediment and settleable matterto impact stream channel stability and habitat niches. 

### 2. Sediment from UnstableAreas Timber harvest operations onunstable slopes (e.g., inner gorges, headwall swales, active or potentially active landslides, or steep slopes) inthe Redwood Creekwatershed cause increased landsliding and the production and delivery offine and coarse sediment. In addition, agricultural operations in streamside areas increase streambank erosion in localized settings. This statement relates to the COLD beneficial use and the potential for sediment and settleable matterto impact stream channel stability and habitat niches. 

### 3. Removal of Riparian Trees andLoss of Large Woody Debris The removal ofvegetation (particularly large conifers) from the riparian zone ofthe Redwood Creek watershed causes: 1) a loss ofstream bank stability and increased stream bank erosion, 2) a loss ofsediment filtering capacity and increases in sediment delivery, and 3) a reduction inthe potential for large woody debris recruitment to the stream and in the stream's sediment transport efficiency. This statement relates to the COLD beneficial use and the potential for sediment and settleable matter to impact stream channel stability and habitat niches. 19

## Section 3.2. Numeric Targets
Section 303(d)(l)(C) ofthe CleanWaterAct states that TMDLs "shall be established at a level necessary to implement the applicable water quality standards

...." The numeric targets developed for the Redwood Creek TMDL are intended to interpret the narrative water quality standards adopted in the BasinPlan (1994). EPA notes thatthe Regional Boardhas indicated that it does not intend to bring enforcement action based on instream numeric target exceedences.
Instream numeric targets, as included inthe TMDL, represent adequate streamhabitat conditions for salmonid reproductive success. Instream targets provide a vital set ofmeasures of whether, inthe long run, beneficial uses impacted by sedimentation are recovering. Hillslope numeric targets represent desired conditions for land management which are associated withproperly functioning erosional processes and erosion rates which are not excessively accelerated byhumaninfluences. Ifthese hillslope target conditions are attained, erosion rates and sediment delivery to streams should decline to levels which allowRedwood Creek streamhabitatto recover from the effects ofexcessive sedimentation which occured inthe past. EPA expects that recovery from these effects may take many years. Hillslope targets provide an immediately useful set ofmeasures ofwhether land uses knownto contribute much of the human-caused share ofsediment loading to Redwood Creek are being modified inways which will minimize future erosionpotential and sediment delivery. The numeric targets are based on scientific literature, available monitoring data for the basinandbestprofessionaljudgment. When implemented, the TMDL should fully meet these targets and, as a result, the WQS. Table 3 depicts the instream numeric targets, andtable 4 depicts the hillslope numeric targets

.. Numerictargets interpret existing narrative water quality objectives in orderto:

• describe physical conditions ofRedwood Creek and the hillslopes around the Creek which are associated with attainment ofthe narrative objectives and beneficial uses, • assist in estimating Redwood Creek's capacity to receive future sediment inputs and still support beneficial uses, • compare existing and target conditions for sediment related indicators, • provide an evaluationframework for analysing monitoring data collected inthe future and making changes inthe TMDL and/or Implementation Plan inresponse, and • assist in evaluating whether land management andrestoration actions are effective in adequately reducing erosion and subsequent sediment loading to the Creek. 

### Instream Numeric Targets The indicators for which EPAis establishing instream numeric targets include percent fmes <0.85 mm, percent fmes <6.5 mm, median surface particle size (d50), percent ofsurface fines <2 mm, percentage ofmainstem creek length in riffles, residual large woody debris, and meanresidual pool depth. Fine sedimenttargets are intendedto apply in fish bearing reaches ofgenerally low gradient (<3% slope). Separate pool depth targets are established for the mainstem and for tributaries to


### 20Redwood Creekto reflect the differences in stream sizes and related differences indesirable pool characteristics. In addition, the streamriffle target is being set only for the lower gradient part of Redwood Creek to reflect the fact that pool riffle structure may be substantially different 

### in higher gradient streams. Scientific literature suggests thatthese indicators are the most easily linkedto fish habitat conditions which support salmonids and can assist in evaluating long term impacts of hillslope erosion and erosion reduction efforts (Knopp, 1993, Chapman, 1988, Peterson, et.al. 1992, NMFS, 1997). The targets are monitoring and evaluation goals intended to represent the desired condition where sediment is not a limiting factor for salmonid production. Table3. Instream Numeric Targets for theRedwood CreekWatershed.
Parameter Numeric Targets (Desired Conditions) Percent fines <0.85 mm inriffle crests offish- <14% bearing streams2 Percent fmes <6.5 mm inriffle crests offish- <30% bearing streams Percent ofStream Length in Riffles3 < 25-30% ofstream reaches inriffles (reach gradient < 2%) Pool depth 

### inmainstem Redwood Creek the mean depth ofpools at lowflow exceeds reaches with pool-riffle morphology 2m Depths ofpools in 3rd and 4thorder the mean depth ofpools at lowflow exceeds tributaries withpool-riffle morphology4 1-1.5 m Medianparticle size diameter (d50) from riffle 

### 2:. 37 

### mm (minimum for a reach) crest surfaces 2::,69 

### mm (mean for a reach) Percent fmes < 2 mm atriffle crest surfaces in <10-20% fish-bearing streams Large Woody Debris in any watercourse Improving trend towards increased large capable oftransporting sediment to a higher woody debris order watercourse

1 Targets should be evaluated as ten yearrolling annual averages to avoid premature assessment oftrends

based on inadequate information. This approach addresses the variations in sediment loading and instream indicators which are characteristic ofRedwood Creek and which may not indicate management related effects. 2 Fish-Bearing Streams: Fishpresent seasonally oryear-round, or having fish habitat capable ofsupporting

fish. Fish habitat is the aquatic environment and the immediately surrounding terrestrial environment that, combined, afford the necessary biological and physical support systems required by fish species during various life history stages. 3 Riffle- low gradient: shallow stream channel areas with swiftly flowing turbulent water with some partially

exposed substrate. Gradient< 4 %, substrate is usually cobble dominated. The gradient is the general slope, or rate ofchange in vertical elevation per unit ofhorizontal distance, ofthe water surface ofa flowing stream; orthe rate ofchange ofany characteristic perunit oflength. 4 Stream order is the designation ofthe relative position ofstream segments in the drainage basin network.

For example, a first order stream is the smallest, unbranched, tributary which terminates atthe upper point. A second order stream is formed when two first order streamsjoin.

21Some ofthe selected indicators and target values are sensitiveto variations inconditions in different areas ofthe watershed which are influenced by differences in geology and stream morphology. However, the indicators and associated numeric targets are relatively insensitive to probable annual variations infuture sediment loading and impacts overtime. 

### Itwould be desirable to use more dynamic indicators which set erosion reduction and habitat improvement goals as· a function ofthe factors which determine year-to-year variations in sediment loading and stream responses. Ideally, the tMDL would include indicators which directly account for variations in precipitation and resultant runoffand flows. Use ofthis type ofindicator would enable analysts to distinguish changes in erosion and instream effects associated with land management actions from changes attributable to differences inrunoffintensity. This approach could make iteasierto evaluate the effectiveness ofthe TMDL based on limited data. Because such indicators couldnot be identified for this TMDL, most ofthe numeric targets are expressed as ten yearrolling averages. This approach helps ensure that conclusions concerning watershed responses to erosion control actions are not drawnprematurely. The drawback ofthis approach is that we must wait several years before we will be able to complete this critical evaluation ofTMDL effectiveness. 1. Percent Fines <0.85 mm

Once the eggs are laid and fertilized, the spawners coverthe redds withmaterial from upstream, including clean gravels and cobbles. The interstitial spaces between the particles allow for water to flow into the interior cavity where dissolved oxygen, needed bythe growing embryos, is replenished. Similarly, the interstitial spaces allowwater to flow out ofthe interiorcavity carrying away metabolic wastes. However, fine particles either delivered to the stream ormobilized by storm flow canintrude into those interstitial spaces, blocking the flow ofoxygen into the redd and the metabolic wastes out ofit. The reduced permeability into and out ofthe redd results in a reduction inthe rate ofembryo survival.

a. Numeric Target The numeric target for fines <.85mm for Redwood Creek is less than orequal to 14%. The target should be monitored at stream riffles inreaches around existing monumented cross sections to be selected during the design ofthe monitoring plan. EPA intends thatthis target indicator should be measured through the use ofbulk sampling ofthe surface and subsurface substrate layers (preferrably measuring dry weights). The target is selected as the midpoint between the percentages offines reported in unmanaged streams in the Peterson (1992) and Burns (1970) studies. Thetarget takes into account that the 11% fines <0.85 mm which was observed in unmanaged streams inthe Pacific Northwest (Peterson et al., 1992) is probably lower than would be expected in California. Onthe otherhand, the 17% fines <0.85 mm which was seen in unmanaged California streams beginning in 1967 (Burns, 1970) is probably too high giventhe huge sediment loads which were discharged to streams as a result ofthe 1964 storms. In addition, Tappel and Bjorn (1983) predictedthat 14% fines <0.85 mm in combination with about 30% fines <9.5mm would provide an average of50% survival to emergence for steelhead and an average of 70% survival to emergence for chinook salmon. These appear to be acceptable rates ofsurvival to emergence. The literature sources reviewed in setting the target generally support the 14%target level as reasonably protective. EPA recognizes that there will be spatial and temporal variability around the target level for instream indicators.



### 22b. Existing Conditions Fine sediment size fractions are difficult to measure accurately. The percentage offine sediment 

### in the channel bottom is often measured through various bulk sampling methods which gatherboth surface and subsurface sediments from the stream bottom. No bulk sampling datahas been published for Redwood Creek; however, the fraction offme sediments <2 mm commonly exceeds 20% (personal communicationwith Mary Ann Madej,**USGS~** June 1998). Levels ofvery fine sediments are believed to be relatively higher 

### in lower Redwood Creek than inthe middle and upperbasin (personal communication with Mary AnnMadej, USGS, June 1998). This is a reasonable expectation because (1) particles tend to break down as they move downstream, increasing thepercentage offines present, (2) lower Redwood Creek has a low gradient which would bemore suited for deposition offine sediments, and (3) lower Redwood Creek is still experiencing sediment aggradation associated withcatastrophic historic floods and sediment loads.

c. Comparison ofNumeric Target and Existing Conditions
A comparison ofthe numeric target and existing information helps provide information onthe extent ofthe problem as well as the sedimentreduction needed to meetwater quality standards. However, itwas infeasible to conduct a quantitative comparison ofthe numeric target and existing conditions because inadequate reliable data were available. Ifthe rough assessment that levels of fines often exceeds 20% is true, portions ofRedwood Creekprobably exceed the numeric target. 2. Percent fines <6.5 mm

After4 to 

### 6 weeks orlife, the embryos are ready to emerge from the gravel as fry (young swimming fish.) Thepresence offme sediment in the gravel interstices can impede fry emergence. However, the size offine particles likely to fill the interstices ofredds sufficientto blockpassage offry are larger thanthose likely to suffocate embryos. That is, particles ranging from 0.85 mmto 9.5 mm are capable ofblocking fry emergence, depending onthe sizes and angularity ofthe framework particles, while still allowing sufficient water flow through the gravels to support embryo development. Besides a correlation betweenpercent fines and the rate ofsurvival to emergence, there is also a correlationbetweenpercent fines and the length ofincubation; i.e., the amount oftime ittakes for the fry to emerge from the egg. Percent fines is also inversely related to the size ofemerging fry (Chapman, 1988). Each ofthese factors impact the ultimate survivability ofthe embryos and fry.

a. Numeric Target · The numeric target for fmes <6.5 mm is less than or equal to 30% for Redwood Creek. The lower basintarget should be monitored at stream riffles inreaches around existing monumented cross sections to be identified during the design ofthe monitoring program. EPA intends that this target indicator.should be measured through the use ofbulk sampling ofthe surface and subsurface substrate layers (preferrably measuring dry weights). The numeric target was selected based on a review ofliterature which evaluated the relationship between fines <6.5mm and survival to emergence rates for salmonids. Research results concerning the relationship between salmonid survival to emergence and levels offines <6.5mm are relatively consistent. Tappel and Bjorn (1983) predicted that 30% fines <9.5mm in combination with 14% fines< 0.85mm would provide 23an average of50% survival to emergence for steelhead. The same study predicted that 32% fines <9.5mm in combination with 14% fines< 0.85mm wouldprovide an average of70% survival to emergence for chinook salmon. Both steelhead and chinook are expected to have greater emergence success than coho salmon when redds are sedimented. Kondolf(unpublished data), evaluating data from other studies, concluded that ifone chooses a 50% survival to emergence rate, the data indicate that fines defined either as <3.35 or <6.5 mm should not comprise more than 30% ofsubstrate composition. Finally, Chapman (1988) reported data from several other studies concerning fine sediment levels in unlogged Oregonwatersheds whichvaried from 27-55%. The 30% target rate appears consistent withthe research fmdings concerning acceptable survival to emergence rates andthe levels offines found inunlogged watersheds. EPArecognizes thatthere will be spatial and temporal variability around thetarget level for instream indicators. b. Comparison ofNumeric Target andExisting Conditions Althoughno specific bulk sampling datahave beenpublished for Redwood Creek, the fraction of fine sediments <8 mm commonly exceeds 50% (personal communicationwith Mary

### Ann Madej, USGS, June, 1998).
Because data are so limited for fine sediment levels in Redwood Creek, itwas not feasible to make quantitative comparisons between existing andtarget conditions. Ifthe rough assessment ofthe amount ofsediments < 8mmmentioned above is correct, levels offine sediment in some reaches of Redwood Creekprobably exceed the numeric target. 3. Pool-Riffle Structure. and Percent Riffles

Juvenile coho require pools for both summer and overwintering rearing. In the summer, pools provide cool, quiet habitat where coho feed and hide from predators. During the winter, offchannel poolsprovide habitat in which coho and steelhead both can getout offlood flows to avoid being swept downriver and out to sea. Steelheadprefer riffles for rearing during their first summer, but make more regular summer uses ofpool habitat as they grow in size. Pool volumes are reduced either when a stream's hydrologic power is reduced (e.g., by increased sediment loading) or bythereduction ofpool-forming elements. The number ofpool-forming elements can bereduced by modification ofthe channel morphology (e.g., burial), physical removal (e.g., logjamremoval), reduction in supply (e.g., logging ofnear streamtrees), ora combination ofall three causes. Various pool measures havebeen used (e.g., pool, frequency, spacing, or area) but are oflimited value since the definition ofthe beginning and end ofa pool is quite subjective. It is generally easierto identify riffle locations. Although some riffles are vital to north coast streams, excessive riffle habitat indicates that deep water habitat is deficient. Therefore, because riffles are easierto measure and provide an indirect indicator ofpool abundance, this TMDL includes a target for the percentage ofcreek length inriffles (personal communication.with Mary Ann Madej, June, 1998).

a. Numeric Target The target for percent riffles is no more than 25-30% riffles for creek reaches less than 2% in gradient. This target is based onjudgment ofa Redwood Parkresearcher who is very familiar with
24

### the pool/riffle structure ofRedwood Creek and ofnorthcoastrivers with different habitat qualities (personal communication with Mary Ann

### Madej, June, 1998). The 25-30% level is believed to be consistent with the riffle patterns found in well-functioning north coast streams. This target only applies in the lower gradient sections ofthe creekbecause percent riffles may exceed the target level in steeper streams which support excellent habitat. Inthe long run, it may prove more effectiveto measure pool quality and distribution based on statistical analysis oflongitudinal profile data collected at monumented reaches ofRedwood Creek. This monitoring method has promise in providing a more discriminating indicator ofchannel roughness and variability, which canbe adjusted (normalized) to account for and allow comparisons between streams ofdifferent sizes. b. Existing Conditions and Comparison WithNumeric Targets Inthe 1970s and early 1980s, riffles comprised from 50 to 70% ofobserved reaches in study areas (personal communication with Mary Ann

### Madej, June, 1998). Bythe mid 1990s, riffles comprised 20to 40% ofobservedreaches 

### in study areas. Some reaches ofRedwood Creek are still characterized by excessive riffle and insufficientpool structure. 4. Pool Depth

Salmonids rely on deep, cool pools during the rearing stage for protection from predators and as refuges from hightemperature water. Pool depth is partly a function ofstream disturbance (and associated channel changes) and partly a function ofstream size. Pools in larger streams tend to be deeper, on average, than pools in smaller streams (assuming otherfactors are equal). Flosi and Reynolds (1994) concluded from the Department ofFish and Game's habitat typing data that better Californiacoastal coho streams (stream order 3 or 4) have pools with depths ofat least 3 feet.

a. Numeric Target The numeric target for low flow pool depth is >2 meters on average for the mainstem ofRedwood Creek. and 1-1.5 meter'for third and fourth order tributaries to Redwood Creek. This target is basedprincipally onthe results reported by Flosi and Reynolds (1994) and applies only inreaches which have pool-riffle morphology. The targets for the mainstem ofRedwood Creek are higher thanthe results reported by Flosi and Reynolds because Redwood Creek is a larger, higher order streamthanthe stream type referred to inthis study. Several commenters have reported the existence ofmany pools greater than 10 feet deep priorto the onset ofexcessive sediment loading to the stream more than 30 years ago. In addition, there is some evidencethat chinook salmon prefer deeper pools than coho. The targets are also consistent with the "species habitat needs matrix" developed by an interagency group in connection withresource management discussions with Pacific Lumber Company (NMFS, 1997). b. Existing Conditions and Comparison withNumeric Target Limited information is available concerning pool depths in Redwood Creek. The Redwood Creek Watershed Analysis (RNP,.1997) indicated that mean pool depths at three locations in Redwood Creek mainstem in 1986 were about 1.4-1.8 meters. Following the 1997 storm (11-yearrecurrence interval), pool recovery trends observed in previous monitoring were reversed (written comments 25

### ofRedwood National Park, November 18, 1998) These results are too limited to draw a meaningful comparison withthe numeric target levels for the mainstem and for tributaries. 5. Median Surface Particle Size Diameter (d5

### o).

The d50 

### is the median value ofthe size distribution in a sample ofsurface pebble counts. It

### is a measure ofthe central tendency ofthe whole sample, and thus is one ofseveral indicators ofhow "fine" or "coarse" the sample is overall. As discussed in the discussion for the percent fines targets, both amount and size offine and coarse sediments can impact salmonid lifestages. Various measures ofcentral tendency have been used by researchers (Young, et al. (1991) lists several). The d50 

### indicator is selected for Redwood Creek because it is easy to calculate based onresults from pebble counts. In a study that evaluated the relationship betweenhillslope disturbance and various instream indicators, Knopp (1993) found that cleartrend ofdecreasing particle sizes 

### inthe riffles was evident withincreasing hillslope disturbance. Moreover, Knopp found that a statistically significant difference in average and minimum d50 

### values when comparing reaches in undisturbed and less disturbed watersheds withreaches inmoderately andhighly disturbed watersheds. Therefore, the d50 

### levels identified in undisturbed and less disturbed locations are good candidates for numeric targets for Redwood Creek. Knopp also found that the moderately disturbed reaches were not statistically different from the highly disturbed reaches. This indicates that d50 

### results may take upwards of40 years before mitigation ofcurrent disturbance is positively reflected.

a. Numeric Targets The targets for d50 

### are means greater than or equal to 69 mm and a minimum ofgreater than or equal to 3 7 mm. The d50 

### indicator has two targets associated with it. The higher number >69 mm represents the optimumtarget, while the lower number ?..37 mm represents the minimum number that should be found. By setting two numbers, EPA recognizes that there may be annual variability in this target. These values are based on Knopp's findings (1993) concerning d50 

### levels innorth coast watersheds which were relatively undisturbed. Because Knopp found the d50 

### to be a discriminating indicator (that is, an indicator capable ofdistinguishing between watersheds which were more or less disturbed as a result ofprior management), the indicator and associated target levels identified in Knopp's study are appropriate. b. Existing Conditions Table 4 is a summary ofsurface d50 

### data collected by USGS and Redwood National Park in 1979 and again in 1994 at 8 monitoring sites along the mainstem ofRedwood Creek. It should be noted that these data were collected using a surface pebble count method. This method may notproduce reliable results regarding percentages ofvery fine sediments due to operator variability. In addition, monitoring was conducted at a relatively small number ofsites on only 2 occasions. For these reasons, firm conclusions concerning actual past orpresent conditions for fine sediment in Redwood Creek should not be drawn based onthis limited data set. However, the limited data are reported to provide some basis for comparing historical and target co.nditions.



### 26Table 4: Summary ofExistingData for Median Particle Size (d50 ) Cross Section d50 (1979) d50 (1994) 

### 2 16 16 5 

### 8 

### 12 16 15 

### 27 17 9 12 20 11 

### 16 32 19 41 34 12 27 40 41 not available MEAN 

### 16 22 Source: Unpublished USGS and NPS data reported in RNP, 

### 1995.

c. Comparison ofNumeric Targets and Existing Conditions Quantitative comparisons ofhistorical andtarget conditions are infeasible due to the limitations in the available data. While definitive comparisons cannot be drawn, it appears that d50levels inthe watershed may notmeetthe numeric target, and that meanparticle sizes are higher inthe middle/upper watershed than inthe lower watershed. The numeric target for the meanparticle size diameter is setfor the watershed as awhole. However, particles tend to become finer as they are transported downstream due to streatn power and friction. The targets set for the meanparticle size diameter for the lowerportion ofthe watershed may behigher than needed for recovery of spawning habitat. As more informationbecomes available during instream monitoring, the numeric targets for the lower part ofthe watershed maybe adjusted during subsequent TMDL revisions.
6. Percent Surface Fines 

### < 2 mm

As discussed above, salmonid egg growth and emergence ofyoung fry are adversely affected when excessive levels offine sediments are present onthe stream bottom. In addition to the two measures offine sediment used above, which are based ondata for both surface and subsurface particle sizes collectedthroughbulk sampling methods, a numeric target is included based onfine sediment onthe surface ofstream riffies which canbe measured through the same pebble count method used to calculate the d50 particle size target established above. The target is being established for fines atthe 2 mm size because this is approximately the smallest size particle which canbe reliably identified through pebble count analysis. This indicator is being used because most past and expected future monitoring ofsubstrate composition inRedwood Creek basinrelies upon the pebble countmethod. In addition to providing a measure offine sediment levels whichmaybe associated with impacts to salmonid egg growth and emergence offry, the level offines onthe stream surface is also a useful measure ofthe degree to whichthe stream is experiencing sediment loading inexcess ofsediment transport capacity.



### 27a. Numeric Target The numeric target for surface fines <2mm for Redwood Creek is less than or equal to 10-20%. The target should be monitored through pebble counts inriffle crests located at monumented cross sections infish bearing streams, to be selected.during the design ofthe monitoring plan. The target is selectedbased on a review ofseveral literature sources, including Chapman and McLeod (1987) and Young, et.al. (1991). The target is set as a range to reflect (1) the relatively sparse research results regarding the levels ofsurface fines associated with good and poor quality salmonid habitats and (2) to reflect the significant variability which would be expected from year to year and in different locations withinthe watershed. ··EPA expects the target range to be exceeded in some years and is setting the target as a 10 yearrolling average to account for expected interannual variability. b. Existing Conditions Fine sediment size fractions are difficult to measure accurately. Thepercentage offine sediment in the channel bottom is often measured through various bulk sampling methods which gather both surface and subsurface sediments from the stream bottom. No bulk sampling data has been published for Redwood Creek; however, the fraction offine sediments <2 mm commonly exceeds 20% (personal communication with Mary AnnMadej, NPS, June 1998). Surfaceparticle size distributions can also be measured through the pebble count method. Table 5 is a summary of unpublished fine sedimentmonitoring data collectedby USGS and Redwood National Park in 1979 and again in 1994 at 8 monitoring sites along the mainstem oflower and middle Redwood Creek. Table 5 onthe following page reports data for the <2 mm size. It should be noted thatthe results are not reliable estimates for the stream as a whole or for the recent past. In addition, monitoring was conducted at a relatively small number ofsites ononly 2 occasions. Forthese reasons, firm conclusions concerning actual past orpresent conditions for fine sediment in Redwood Creek should not be drawn based onthis limited data set. These data are presented here to provide a general sense ofsubstrate surface particle sizes observed in 1979 and 1994. Because fines are often winnowed from the surface by stream flow, the fraction offine sediment is expected to be higher when subsurface fines are also measured, as is done throughbulk sampling methods (Lisle and Madej, 1992).

c. Comparison ofNumericTarget and Existing Conditions A comparison ofthe numeric target and existing information helps provide information onthe extent ofthe problem as well as the sedimentreduction needed to meet water quality standards. However, itwas infeasible to conduct a quantitative comparison ofthe numeric target and existing conditions because inadequate reliable data were available.

28

### Table 5: Summary ofExisting Data for Fine Sediment Sizes on the Channel Bottom Surface
Cross %fines<2mm %fines<2mm Section (1979) (1994) 2. 20 15 

### 5 14 12 16 3 6 17 9 22 20 4 28 32 3 13 

### 34 14 19 40 9 not available MEAN 10 

### 16
Source: RNP and USGS datareported in RNP (1995). 7.**Lar~e** 

### Woody Debris

The removal ofvegetation (particularly large conifers) from the riparian zone ofthe Redwood Creekwatershed causes: 1) a loss ofstream bank stability and increased stream bank erosion, 2) adverse effects on stream channel morphology, including pool formation, and channel geometry, 3) a loss ofsediment filtering capacity and increases in sediment delivery, and 4) a reduction inthe potential for large woody debris recruitment to the stream and inthe stream's sedimenttransport efficiency. This statementrelates to the COLD beneficial use and the potential for sediment and settleable matterto impact stream channel stability and habitat niches.

a. Numeric Target The numeric**tar~et** 

### for**lar~e** 

### woody debris is**increasin~** 

### trends in**lar~e** 

### woody debris. Insufficient data and information were available to support the delineation ofa specific numeric target. To assist in reviewing whether large woody debris conditions are approaching satisfactory levels, table 5 lists suggested large woody debris frequency and size for streams ofdifferent widths based on research conducted by Bilby and Ward (1989) concerning woody debris levels inforested watersheds dominated by old growth douglas fir. The suggested woody debris levels are most appropriately used for comparative purposes inparts ofRedwood Creekbasin inwhich douglas fir is the predominant conifer type (generally, inthe areas ofthe watershed upstream ofthe National Park). These suggested values are not being established as numeric targets for the TMDL because their applicability to Redwood Creek is not well understQod at this time.



### 29

### Table 5: Relationship between channelwidth and mean for debris diameter, length and volume and the number ofpieces ofdebris in old-growth Douglas-fir streams. ChannelWidth Debris/100 ft Geometric mean Geometric mean Mean debris

(ft) debris diameter debris length piece volume (inches) (ft) (cubic feet) 15 16 14 18 13 20 12 16 20 26 25 9 17 22 38 30 7 18 25 51 40 5 21 29 75 50 4 23 33 100 55 4 25 35 113 60 3 26 37 125 65 3 27 40 137 Source: Adapted from Btlby and Ward (1989).

b. Existing Conditions and Comparison withNumeric Target Limited information is available concerning large woody debris withintheriparian management zone inRedwood Creek. In a study byPitlick (1982), 16 tributaries inRedwood CreekBasinwere evaluated for percentage ofsediment storedby large woody debris. Values ranged from a low of 13 percent to a high of94 percent. On average, greater than40 percent ofthe sediment volume was stored by large woody debris. 

### Hillslope Numeric Targets
As described above, numeric targets are designed to interpret narrative State water quality standards in effect for Redwood Creek and identify the desired condition for the watershed with respect to sedimentation. The suite ofinstream numeric targets included inthe TMDL are intended to identify key characteristics ofthe instream environment which, ifattained, are expected to be adequate to ensure recovery ofaquatic habitat health. To account for temporal variability 

### in conditions, the instreamtargets are expressed as ten yearrolling averages (i.e., they are not expected to yield reliable diagnostic results inperiods ofless thanten years). The drawback ofthis approach is that it does notprovide indicators which are capable ofguiding shorter term evaluation ofwhetherthe watershed is moving toward recovery ofconditions whichwill support all beneficial uses ofconcern which were affected by excessive sediment delivery. Hillslope numeric targets are included inthe TMDL to describe desired conditions with respect to several land management uses which are ongoing inthe watershed and which are expected to continue to pose significant erosionpotential in the future. Hillslope targets are being established to identify appropriate road design, location, inspection, and maintenance patterns 

### 30along with appropriate silvicultural practices in sensitive areas. Ifattained, these hillslope targets are expectedto result in the reduction oferosionpotential and future sediment delivery to streams to levels which will allowrecovery ofinstreamhabitat from sediment impacts overthe coming decades. Therefore, hillslope targets supplement instreamtargets by providing measureable goals which are not subject to the variability associated with water year type. They have the advantatge to the individual landownerthat they canbe converted directly into implementation plans and management practices whichcanbe evaluated more frequently than the 10 year rolling average. While inadequate information was available for this TMDL to support development of hillslope targets to address all potentially significant sediment sources (e.g. livestockimpacts on streambanks), EPA believes the hillslope targets collectively describe the attributes ofa wellfunctioning watershed which supports both healthy aquatic habitat and ongoing road use and logging. EPA also believes these hillslope targets are consistent withthe proposed implementation provisions inthe State's TMDL and implementationplan draft datedNovember 10, 1998. 

### As additional information is collected inthe future regarding the effectiveness oferosionprevention and control methods and associated stream habitat recovery trends, itmay be appropriate to review andrevise these hillslope targets accordingly. Table 6 onthe following page summarizes the hillslope targets, which are discussed in detail below. 8. Road stream crossings with diversion potential

A key source ofcontinuing erosionpotential inRedwood Creek watershed is the existence ofmany road crossings with diversionpotential (i.e., the tendency to divert stream flow out ofthe channel and along and across the road surface) (RNP, 1997, Hagans and Weaver, 1987). Diversion offlow is associated withmajorroad surface erosion and creation ofdebris flows and othermass wasting events. The potential for diversion is eliminated in well-designed crossings throughthe use of rolling dips or othermeasures which ensure that ifthe crossing fails, the flow remains inthe channel.

a. Numeric Target The numeric target is that no crossings have diversion potential (i.e

.. all crossings are reconfigured permanently to assure that no diversion will occur). This target is selected based on recommendations from RedwoodNational Park and USGS scientists (see comments from RNP and M. Madej, USGS) and EPA's review ofliterature sources concerning the potential for eliminating road-related erosion potential (Weaver and Hagans, 1994 and 1996; Spence et.al. 1996). b. Existing Conditions and Comparison with Numeric Target Although specific data concerning diversion potential ofroads in Redwood Creek were not available to EPA for this TMDL, Redwood National Parkresearchers have estimated that about 55% ofthe approximately 1400 miles ofroads in the basin are not maintained and are therefore more likely to fail during a storm thanmaintained roads. There are several thousand crossings associated with these roads. Therefore, itis likely thathundreds ifnot thousands ofcrossings continue to have diversion potential. 31

### Table 6· Hillslope Numeric Targets for theRedwood CreekWatershed 

# . . Parameter Numeric Targets (Desired Conditions) Road stream crossings with No crossings have diversion potential (i.e., all crossings are

diversion potential reconfigured permanently to assure that no diversion will occur). Road culvert/crossing sizing All culverts and crossings are sized to pass the 50 year flood and associated sediment and debris. In addition, crossings and culverts inthe snow zone (generally, upstream ofHighway 299, are sized large enough to accommodate flows and associated sediment and debris caused byprecipitation and snow melt runoff. Landing and road fill stability All landings and road fills (e.g., sidecasts) on slopes >50% and which could potentially deliver sedimentto a water course are pulled back and stabilized. Road surfacing and drainage All roads have surfacing and drainage facilities or structures which are appropriate to their patterns and intensity ofuse. Road inspection, maintenance, All roads are inspected and maintained annually or decommissioned.

and decommissioning Decommissioned roads (roads which are closed, abandoned, or obliterated) are hydrologically maintenance free. 1 Road location in inner gorge or Roads are not located in steep inner gorge orunstable headwall areas

unstable headwall areas except where alternative road locations are unavailable? Use ofclearcut and/or tractor Clearcut and/or tractor yarding harvest methods are not used in steep

yardingtimber harvest inner gorge, unstable, or streamside areas unless a detailed methods geological assessment is performed which shows there is no potential for increased sediment delivery to watercourses as a result ofusing these methods. 3 1 Hydrologically mamtenance free means that:

-drainage in the road area mimics natural hydrology,

- all drainage is dispersed to the slope through use, as appropriate, ofoutsloping or cross-road drains,

- all culverts and associated fill material is removed from crossing areas,

- all potentially unstable road fill and landing sidecasts are pulled back, and

- excavated spoils are placed in locations where they will not enter a water course. 2 This target is intended to address roads located adjacent to water courses with inner gorge topography or

which cross steep, unstable headwall areas, and is not intended to apply to road crossings ofinner gorge areas. Steep inner gorge areas generally exceed 65% in slope and are located adjacent to class 1 and 2 water courses. Characteristics ofsteep unstable headwall areas generally include the following:

- slopes greaterthan 50%,

- erosive or incompetent soil types orunderlying geology,

- concave slope shape,

- convergent groundwater present, and/or

- evidence ofpast movement is present 3 Characteristics ofsteep inner gorge, unstable, or streamside areas generally include a the following:

- slopes greater than 50%, -located within 300 feet ofa Class 1, 2, or 3 watercourse,

- erosive or incompetent soil types orunderlying geology,

- concave slope shape,

- convergent groundwater present, and/or

- evidence ofpast movement is present 

### 32 i9. Road culvert/crossing sizing A second important source ofcontinuing erosionpotential in Redwood Creek watershed is the existence ofmany road crossings with inadequately sized culverts or drainage structures. When culverts orcrossings are blocked with debris during runoffevents, the crossing may be fail, triggering debris flows which can scour downstream channels and deliver massive amounts offill and scoured material to stream channels (RNP, 1997, RNP, 1998c, Hagans and Weaver, 1987). The potential for crossing failure is minimized when culverts ordrainage structures are sized to handle the flow and associated debris and sediment load associated with infrequent butpotentially destructive storms.

a. Numeric Target The numeric target is that all culverts and crossings are sized to pass the 50 year flood and associated sediment and debris. In addition. crossings and culverts inthe snow zone (generally; upstream ofHighway 299. are sized large enough to accommodate flows and associated sediment and debris caused byprecipitation and snow meltrunoff.. This target is selected based on recommendations from Redwood National Park and USGS scientists (see comments from RNP and M. Madej, USGS) and EPA's review ofliterature sources concerning the potential for eliminating road-related erosionpotential (Weaver and Hagans, 1994 and 1996; Spence et.al. 1996). b. Existing Conditions and Comparison with Numeric Target 

### Ithas been estimated that onthe basis ofroad maintenance status, hillslope gradient, geology, and soil types, stream crossing failures are likely to occur on about one third ofthe 1110 road miles upstream ofthe park during a large storm (RNP, 1998c). About 55% ofthe approximately 1400 miles ofroads in the basin are not maintained and are therefore more likelyto fail during a storm than maintained roads. 10. Landing and road fill stability

A third source ofcontinuing erosionpotential in Redwood Creek watershed is the existence of landings androads which containperched, unstable fill on steep slopes. Unstable fill is vulnerable to failure in response to major storm runoffand stream diversions from channels, which may cause large-scale debris torrents and sediment delivery to streams. (RNP, 1997, RNP, 1998c ). The potential for failure oflanding and road fills crossing failure is minimized when landings and road fills are properly located (e.g., not onexcessively steep, unstable slopes) when inuse and properly pulled back (i.e., excavated) following use.

a. Numeric Target The numeric target is that all landings and road fills (e.g

.. sidecasts) on slopes >50% which could potentially deliver sediment to a water course are pulled back and stabilized. This target is selected based onrecommendations from Redwood National Park and USGS scientists (see comments from RNP and M. Madej, USGS) and EPA's review ofliterature sources concerning the potential for eliminating road-related erosionpotential (Weaver and Hagans, 1994, 1996; Spence et.al. 1996). 33

### b. Existing Conditions and Comparison withNumeric Target Specific estimates ofthe number ofunstable landings and fills are unavailable. As described above, about 55% ofthe approximately 1400 miles ofroads inthe basin are not maintained and are therefore more likely to fail during a storm than maintained roads. About 80% ofthe roads inthe basin were constructed before 1978, when lower road construction standards were generally in effect (RNP, 1998c ). This suggests that several hundred to several thousand unstable landings and fills may exist in the basin. The percentage ofthese unstable fills and landings withpotential to contribute sedimentto watercourses is unknown, but is expected to be significant. Ofthe 50 miles ofroads constructed on steep inner gorge slopes inthe middle and upperbasinupstream from the park, over 43 miles hadbeen effectively abandoned by 1992 (RNP,1998c). 11. Road surfacing and drainage

A very highpercentage ofroads inRedwood Creek are dirt surfaced roads withminimal or inadequate road surface drainage structures. Large quantities ofsediments erode from road surfaces inresponse to storms, which can contribute to fluvial erosion and mass wasting on sites belowroads 

### (RNP, 1997, 

### RNP, 1998c). The potential for excessive road surface erosion is minimized when roads are properly surfaced and have appropriate drainage structures. For example, roads which are used during wet weather periods shouldberocked orpaved, depending upon intensity ofuse. All roads should have appropriate drainage structures which disperse drainage across slopes and do not contribute to hillslope fluvial erosion ormass wasting.

a. Numeric Target The numeric target is that all roads have surfacing and drainage facilities or structures which are appropriate to their patterns and intensity ofuse. This target is selected based onrecommendations from RedwoodNational Park and USGS scientists (see comments from RNP and M. Madej, USGS) and EPA's review ofliterature sources concerning the potential for eliminating road-related erosionpotential (Weaver and Hagans, 1994 and 1996; Spence et.al. 1996). b. Existing Conditions and Comparison withNumeric Target About 80% ofthe roads inthe basin were constructed before 1978, when lower road construction standards were generally in effect (RNP, 1998c). These roads are less likely thanrecently constructed roads to have appropriate surfacing and drainage facilities. It

### is likely that road surfacing and drainage facilities have been upgraded on some roads atthe time recent timber harvesting activities required the use ofolder roads in some parts ofthe basin. However, Redwood National Park researchers estimate that about 55% ofthe roads in the basin are notmaintained (RNP, 1998c). These roads are therefore more likely to have degraded road surfaces orfailing drainage structures. This suggests that several hundred miles ofroads in the basin may have inadequate road surfacing and drainage facilities. 12. Road inspection. maintenance. and decommissioning

A very highpercentage ofroads in Redwood Creek are dirt surfaced roads with minimal or inadequate road surface drainage structures. Large quantities ofsediments erode from road 34surfaces inresponse to storms, whichcancontribute to fluvial erosion and mass wasting on sites belowroads (RNP, 1997, RNP, 1998c ). The potential for excessive road surface erosion is minimized whenroads are properly surfaced and have appropriate drainage structures. For example, roads which are used during wetweatherperiods should be rocked orpaved, depending upon intensity ofuse. All roads should have appropriate drainage structures which disperse drainage across slopes and do not contribute to hillslope fluvial erosion ormass wasting.

a. Numeric Target Ihe numeric target is that all roads are inspected and maintained annually or decommissioned. Decommissioned roads (roads which are closed. abandoned. or obliterated) are hydrologically maintenance free. This target is selectedbased onrecommendations from Redwood National Park and USGS scientists (see comments from RNP and M. Madej, USGS) and EPA's review of literature sources concerning thepotential for eliminating road-related erosionpotential (Weaver and Hagans, 1994 and 1996). EPA intends that annual road inspections need not involve intensive analysis ofroad conditions, andthatthistarget would be attained ifall roads are driven annually and inspected visually. The visual inspection may identifyroad-related problems whichcause an increase in erosionpotential, including, but not limited to culvert plugging, cracking or gullying of road fills and landings, and failures ofdrainage structures. These problems shouldbe promptly corrected before the potential erosion and sediment delivery can occur. This road inspection and maintenance target would complement the initial, more intensive road inventory proposed inthe State's draftTMDL implementationplan datedNovember 10, 1998.
Roads which cannot be inspected and maintained annually should be decommissioned in a manner which assures that erosionpotential is prevented andthe roads are hydrologically maintenance free. Hydrologically maintenance free means that:

- drainage in the road area mimics natural hydrology,

- all drainage is dispersed to the slope through use, as appropriate, ofoutsloping or crossroad drains, -all culverts and associated fill material are removed from crossing areas,

- all potentially unstable road fill and landing sidecasts are pulled back, and

- excavated spoils are placed inlocations where they will not enter a water course. b. Existing Conditions and ComparisonwithNumeric Target
No information aboutroad inspection activity inRedwood Creek was available for this TMDL; however, Redwood National Parkresearchers estimate that about 55% ofthe roads inthe basinare not maintained on a regular basis (RNP, 1998c). RedwoodNational Park has decommissioned many roads since the parkwas established, and several private landowners have decommissioned roads which are no longerused. Underthe park's proposed future management alternative, 155 miles ofroads within the parkwould be decommissioned and over 900 miles ofroads upstream from the park onprivate land would be decommissioned orupgraded (RNP, 1998a). Attainment of this target is likely to require increases in annual road inspection and maintenance activity on private lands, while decommissioning activity may be consistent with the park managementplan preferred alternative.

3513. Road location in inner gorfie orunstable headwall areas Roads in inner gorge areas are particularlyprone to failures·which canintroduce substantial quantities ofsediment into water courses. Roads in unstable headwall areas are also prone to failure, which may cause debris torrents which can transport large volumes ofsediments to some watercourses (RNP, 1997, RNP, 1998c). Itis difficult to engineerroads 

### in these areas in a manner which assures that erosionpotential is minimal; therefore, it is most appropriate that roads be eliminated inthese areas. However, EPA recognizes that in some areas ofthe basin, there may be no alternative means ofaccess ifsuch roads are eliminated. Inthese situations, itmay be appropriate for the roads to remain inplace ifa geological and engineering reviewis conducted which ensures that no erosionpotential exists associated withthe roads. In general, newroads should not bebuilt in steep inner gorge orunstable headwall areas.

a. Numeric Target The numeric target is thatroads are not located in steep inner gorfje or unstable headwall areas except where alternative road locations are unavailable. This target is intended to address roads located adjacent to water courses with steep inner gorge topography orwhich cross steep, unstable headwall areas, and is not intended to apply to road crossings ofinner gorge areas. Steep inner gorge areas generally exceed 65% in slope and are located adjacent to class 1 and 2 water courses. Characteristics ofsteep unstable headwall areas generally include a combination ofthe following:

- slopes greater than 50%, -erosive or incompetent soil types orunderlying geology,

- concave slope shape, -convergentgroundwater present, and/or

- evidence ofpast movement is present. This target is selected based onrecommendations from Redwood National Park and USGS scientists (see comments from RNP and M. Madej, USGS) andEPA's review ofliterature sources concerning the potential for eliminating road-related erosionpotential (Weaver and Hagans, 1994 and 1996). b. Existing Conditions and Comparison withNumeric Target Approximately 50 miles ofroads inRedwood Creekbasin above thepark are located in steep inner gorge areas (RNP, 1998c), and an unknown butprobably significantnumber ofroads cross unstable headwall areas inthe basin. About 85% ofthese inner gorge roads had been effectively abandoned by 1992, and 64% were no longer drivable. Therefore, it appears likely that most of these inner gorge roads above the park could be decommissioned without impairing access. Most ifnot all inner gorge roads inthe parkhave been decommissioned. The number ofroads crossing unstable headwall areas inthe park is unknown, but EPA understands that suchroads have been targeted for decommissioning work in the past. 14. Use ofclearcut and/or tractor yarding timber harvest methods

Timber harvesting is expected to remain the primary land use onprivate lands upstream ofthe park. Most futtire harvesting is expected to occur in areas ofsecond growth forests. Reentry and 36harvesting ofsecond growth forests may cause excessive sediment loading unless more protective harvesting and yarding methods are used. Steep inner gorge, unstable, and streamside areas are most vulnerable to the effects ofthese more intensive harvesting and yarding methods because sediment from landslides and bare ground erosion is more likely to reach watercourses and cause adverse impacts to fish habitat. Studies inthe lower Eel River basin suggestthat landslides inrecently harvested second growth areas underlain by Franciscan geology (similar to that found inRedwood Creek) are larger and more commonthanthose in areas ofunharvested second growth (PW A, 1998). In Redwood Creek basin, Pitlick (1982) found that slides inharvested inner gorge areas were no more commonbut were much largerthan those inuncut inner gorge slopes. Clearcut logging and tractor yarding were byfar the most common methods used inRedwood Creekbasinbefore the 1980s. Clearcut logging and tractor logging are significantly more disruptive ofnatural watershed processes including soil erosionthan are other logging andyarding methods which do not cause as much ground surface disturbance (Spence, et.al, 1996). Although alternative silvicultural methods are increasingly in use inRedwood Creek, use ofclearcut logging andtractor yarding methods is expectedto continue inthe future. In orderto minimize the erosionpotential associated withuse ofthese methods, the TMDL includes a numeric target which focuses onthe most vulnerable geologically unstable areas and streamside zones. Thetarget articulates a future desired condition that clearcutting andtractor methods are not used ininner**gorge~** unstable or streamside areas except in cases where a thorough geological investigation shows that use ofthese methods will result in no increase in sediment loading to streams compared

### to pre-logging conditions. Attainment ofthis target is expected to reduce logging related erosion inunstable or streamside areas to acceptable levels.

a. Numerictarget

The numeric target is that clearcut and/or tractor yarding harvest methods are not used in steep inner gorge. unstable. or streamside areas unless a detailed geological assessment is performed which shows there is no potential for increased sediment delivery to water courses as a result of using these methods. This target is selected based on recommendations from RedwoodNational Park and USGS scientists (see comments from 

### RNP and M. Madej, USGS) and EPA's review of literature sources concerning the potential for minimizing logging-related erosionpotential in inner gorge, unstable, and streamside areas (Spence, et.al., 1996, Reid, 1996 and 1998). Characteristics ofsteep inner gorge, unstable, or streamside areas generally include a combination ofthe following:

- slopes greater than50%,

- located within 300 feet ofa Class 1, 2, or 3 watercourse,

- erosive or incompetent soil types orunderlying geology,

- concave slope shape,

- convergent groundwaterpresent, and/or

- evidence ofpast movement is present. b. Comparison ofExisting Conditions and Numeric Targets
Pastharvesting practices inRedwood Creek basin consisted almost entirely oflarge scale clearcuts using tractor yarding (RNP, 1998c). Between 1978-1995, about 30% ofthe area logged was 37clearcut (RNP, 1998c). During this period, tractor yarding was still the preferred method for removing logs. The extentto which streamside forest areas were harvested and the methods used for suchharvesting in recent years is unknown, although California Forest Practice Rules specify watershed and lake protection zones which must be adhered to inpreparation oftimber harvest plans. Additionally, current Forest Practice Rules require planreviewby a certified geologist under some conditions. Attainment ofthis target could require modification ofharvest andyarding methods in a significantportion ofthe middle and upper basinwhich are managedprimarily for timberharvesting. 

### Conclusion The numeric targets are intended to interpret and apply the narrative water quality objectives. They were developed to support a goal ofsalmonid recovery whichis a conservative approach. A variety ofinstream indicators were selected because no single indicatorprovides a truly effective, discriminating measure ofthe relationship between sediment loading and instream sediment impacts. The instreamnumeric targets are expressed as ten year rolling average values to account for interannual variability. It should benoted that very useful monitoring information isbeing collectedthrough the park's ongoing monitoring ofmonumented cross sections and associated thalweg (lowflow channel) profiles. Although it was infeasible to derive specific indicators and numerictarget values for these monitoring methods for this TMDL, researchers are currently developing indicators which could serve this purpose inthe future. Cross section and thalweg measures shouldprove effective inthe future as indicators ofchannel stability and change overtime. Other new measures are also being developed (e.g., substratepermeability andturbidity measures) which could prove more effective than some ofthe indicators used inthis TMDL. Infuture TMDL revisions, itmay be appropriate to consider inclusion ofindicators based onthese and other new monitoring approaches as they become available in the future. Hillslope indicators were also included in order to articulate desired conditions with respect to key landuses which are associated with future erosion potentiaL The best information available to EPA suggests that attainment ofthese targets would be an indicator that a managed watershed is capable ofreturning to an acceptable erosionregime and supporting recovery and maintenance of healthy instream habitat conditions. As additional information concerning these indicators becomes available through ongoing monitoring efforts bythe State, Redwood National Park, landowners, and other stakeholders, these indicators and targets will be revisited and revised ifnecessary to provide the most discriminating set ofindicators possible.
Itis recognized that no indicators were selected to address the issues ofold growth redwood risks inthepark or impairment ofestuarine habitat nearthe mouth ofRedwood Creek. EPA expects that ifsediment reductions result in attainment ofthe numeric targets established in this TMDL, future risks to remaining streamside groves ofold growth redwoods and sedimentrelated estuary impairments will be substantially reduced. However, some ofthe problems in the estuary apparently are associated with levee structures which the TMDL is not designed to address.

38

## Section 3.3 Source Analysis
The purpose ofthe Source Analysis is to demonstrate that all pollutant sources have been considered, and significant sources estimated, in order to help determine the degree ofloading reductions neededto meet numeric targets and allocation ofloading allowances among sources. 40 CFR 130.2 defmes a TMDL as the sum ofindividual wasteload allocations, load allocations and natural background. The TMDL mustnot exceed the loading capacity ofthe receiving water for thepollutant ofconcern (inthis case, sediment). In orderto estimate the loading capacity of Redwood Creek and develop individual load allocations, existing and potential sources must ;first be characterized. This section provides three types ofinformation:

• an estimate ofaverage annual sediment loads per square mile for the entire Redwood Creek watershed, • estimates ofaverage annual sediment loads per square mile for three "reference"tributary watersheds withinthe Redwood Creek basin, and • estimates ofhistorical sediment loading rates from all the significant sources ofsediment inthe Redwood Creekbasin, organized byerosional process categories.
ForRedwood Creek, two general types ofsediment source information are available from geomorphic research and monitoring programs ofthe National Park Service and the U.S. Geological Survey."" These are: 1) measurements oferosional processes withinthe watershed, and 2) records of sedimenttransport inRedwood Creek and some tributaries. The first type ofinformation was used primarilyto estimate the relative contributions ofdifferent source categories to overall sediment loading, and as the basis for allocating sediment source reductions and resulting TMDL load allocations. The second type ofinformation was used to estimate overall sediment loading rates for the Redwood Creek basin and localized loading rates for three tributaries. The overall loading rate informationprovides the baseline against which TMDL-related sediment reductions are calculated. The localized tributary loading rate information assists in estimating the future loading capacity of Redwood Creek basin and the overall sediment discharge reductions heeded to protectbeneficial uses. Long Term Estimates ofTotal Sediment Loading An estimate oflong term annual average sediment loading per square mile was determined for the Redwood Creek gauging station at Orick, nearthe downstream end ofthe basin. Data reported inthe Redwood Creek Watershed Analysis, supplemented by data furnished by Redwood National Parkresearchers, were analysed to develop long term annual average sediment output rates for the period 1954-1997. This is the amount ofsediment which actually moves out ofthe basin past the Orick gauging station. During the 1954-1997 period, there was a substantial increase ininstream storage ofsediment delivered to Redwood Creek and its tributaries. Most ofthis increase in instream storage was the result ofa few major discharge and flood events ofwhich the 1964 flood was most important (RNP, 1997). The sedimentbudget calculated for the Redwood Creek Watershed Analysis estimates that there was a net increase in the volume ofsediments added to instream storage which was onthe order of23% ofthe total sediment output from the basin (RNP, 1997). Most ofthe stored sediments

39are either inthe mainstem ofRedwood Creek or atthe bottoms oftributary streams. Ithas been estimated that stored sediments may take several decades to be remobilised, move downstream, and eventually discharge from thebasin. This huge increase in stored sediment inRedwood Creek caused major adverse impacts to the stream channel and to aquatic habitat as a result The Watershed Analysis discusses these impacts in detaiL The long term restoration ofaquatic habitat in ·Redwood Creek depends, to a significant degree, onthe ability ofthe system to erode and move out these excessive deposits ofstored sediment
Forthe loading estimates developed for this section, sediment storage was notincluded as a specific factor inthe analysis for several reasons. It was infeasible to calculate a reliable estimate of changes in instream stored sediment for this period. Second, additions to stored sediment have caused significantdamage to aquatic habitat inRedwood Creek. Ifinstream storage were added to the loading estimate as a sediment sink, the overall estimate ofsedimentloading from 1954-1997 would be increased substantially. By including instream storage in the analysis, it could create the impressionthat continuing increases in instream storage inthe future are acceptable. This is notthe case; to the contrary, decreases in instream stored sediment are needed. Third, the esti_mates of sedimentreductions needed inthe basin were made through comparisons with "reference" watershed sediment loading rates for three tributary watersheds in Redwood Creekbasin. The Watershed Analysis indicates that 60-80% offlood-related instream sediment deposits are flushed out of tributary watersheds within 10 years, in contrast to the mainstem. In orderto more fairly compare loading rates for the tributary "reference" watersheds andthe loading rates for the entire Redwood Creek basin, itis appropriate to exclude instream storage from the loading estimates for the Redwood Creek mainstem. This analysis treats instream channel storage ofsediment as a potentially long term, but still temporary sink for sedimentwhich is associated with substantial adverse impacts to beneficial uses and which is generally not amenable to control after ithas occurred. 

### Itis not expectedthat following the sediment loading reductions called for in the TMDL, there will be significant increases to instream storage exceptin response to very infrequent, high magnitude events. For these reasons, the simplifying assumption was made that inthe long term, sediment inputs equal sediment outputs inproperly functioning streams. In other words, the total sediment loading estimate does not separately account for instream storage as a sink or a source ofsediment outputs at Orick. Table 7 provides summaries ofannual sediment loading per square mile at Orickbased on estimates inthe Watershed Analysis for the periods 1954-1980 and 197 4-1992 along with loading estimates calculated for this report for the period 1981-1997 based on sediment loading data provided by Redwood National Park. Table 7 also provides an estimate ofannual loading per square mile at Orick for the period 1954-1997 which is used as the baseline for calculating the TMDL and associated allocations. As discussed in Appendix C ofthe Watershed Analysis, the 1954-80 estimate is based on actual data collected by U.S. Geological Survey since 1971 along with an estimate of probable sedimentyields from 1954-1971 by Knott (USGS, 1981, cited in RNP, 1997). The 1974- 1992 estimate is based on USGS and NPS data collected at Orick and is reported inRNP, 1997. The 1981-1997 estimate is based onUSGS and NPS data provided in RNP, 1997.
Forthe 1981-1997 estimate, where bedload data were not reported, it was assumed that bedload equals 25% oftotal sediment transport inthe Redwood Creek system. This assumption is based on comparison ofsuspended and bedload sediment loading rates from 1974-1992 and is 40consistent withthe Watershed Analysis, whichreports that bedload accounts for roughly 20-25% of total sediment load, and with findings ofother researchers (e.g. Lisle and Madej, 1992, whichreports that bedload constitutes 10-30% oftotalload). The 1954-1997 loading estimate was calculated as follows: [(54-80 av. loading rate)*(# ofyears 54-80) 

### + (81-97 av. loading rate)*(# ofyears 81-97)] (number ofyears 1954-1997) which is: [(5995*27) 

### + (2769*17)] = 4749 tons/square mile/year 44 

### Table 6· Summaries ofAnnualAverage SedimentLoading PerSquareMile at Orick 

# . Time Period AnnualAverage Load Source (tons/mi2 

### /year) 1954-1980 5995 Redwood Creek Watershed Analysis, AppendixC 1974-1992 3120 Watershed Analysis 1981-1997 2769 calculated from Watershed Analysis and RNPdata 1954-1997 4749 calculated from Watershed Analysis and RNPdata
Because the TMDL is presented interms ofaverage annual sediment loading per square mile to be measured as ten yearrolling averages, table 7 provides a summary of 10 yearrolling average sediment yields at Orick, which canbe compared with the TMDL of 1900 tons/square mile/year. 

### Table 7: Ten YearRolling Average Sediment Yields at Orick Time Period Average SedimentYield (Wateryears) (tons/square mile) 1980-89 2880 1981-90 2649 1982-91 2539 1983-92 1955 1984-93 1517 1985-94 1225 1986-95 1412 1987-96 1481 1988-97 2251
41Figure 2 provides these 10 year rolling average dataingraphform. 

### Figure 2: Rolling 10 Year**A~** SedimentYield atOrick**~,--------------------------------------------- zmT;~--~--~----------------------------------** 

1981-90 1983-92**198~4** 1987.Q6 1980-89' 1982-91 1984-93 1986-95 1988-97 

### Estimates ofAnnual Loadingfor "Reference" Tributaries Annual average sediment loads per square mile were calculated for three tributaries of Redwood Creekwhicharebelievedto be inrelatively good condition 

### interms oferosionpotential and which, as a result, may serve as "reference streams" for purposes ofcomparing localizederosion rates with erosion rates ofthe.basinas a whole. They have received relatively little disturbance through timberharvesting, road building, and other landmanagement activities inrecent decades when comparedto most ofRedwood Creekwatershed, and arereasonablyrepresentative ofthe major geological formations present inthe basin. This type ofcomparison assists 

### inevaluating 1MDLgoals or desired conditions withrespect to sediment loading rates and in estimatingthe basin's loading capacity for sediment inputs. The

### first two tributary basins may becharacterized as moderately vulnerable to erosiondue to land management impacts: Panther Creek is located onthe west side ofthe valley and has experienced moderate logging during the pastdecade. Most ofPanther Creekbasin was also harvested several decades ago, although increased logging has resumed inthe last 2 years (personal communicationwith Greg Bundros,RNP, June, 1998). Panther Creek

### was selectedpartly because itis underlainby Redwood Creek schist, the most commonrocktype west ofRedwood Creek. Lacks Creek is a larger tributary onthe east side ofthe valley whichhas experienced relatively little timberharvesting during the past decade and nowhosts extensive mature second growth forest (personal communication with Greg Bundros, RNP, June 1998). Lacks Creek 

### is underlainby a combination ofrocktypes-- principally the CoherentUnit ofLacks Creek (mostly less erosive sandstones) and the Incoherent Unit ofCoyote Creek (more erosive silt and mudstones)-- and is believed to be generally representative ofthe geology ofthe east side ofthe valley.

Sediment TMDLfor Redwood Creek, CA 

### 42Little Lost Man Creek is tributary to Prairie Creek, the largest tributary to Redwood Creek, and has experienced no significant logging orland management disturbance (personal communicationwith Randy Klein, RNP, June 1998). Itis underlain by a third majorrocktype which characterizes the Prairie Creek subwatershed. Little Lost Man Creek (and Prairie Creek as a whole) are not representative ofthe rest ofRedwood Creek basin because they are less steep, are underlain by a generally less erosive rock type, and are much less intensively managed.

Note that although these three tributary watersheds are appropriate for examination as historical reference watersheds, they are not assumed to be appropriate as future reference streams for comparative analysis. It is quite possible that Panther Creek and Lacks Creek will be subjectto intensive future management which may result inunacceptably large increases in loading rates. Additional work would beneeded to evaluate whetherthey are appropriate reference streams for the purpose ofcomparing future erosionrates with erosionrates for the entire Redwood Creek watershed. Sedimenttransport datawere collected at gauging stations near the mouths ofthe three tributaries discussed above: Panther Creek, Lacks Creek, and Little Lost Man Creek. Table 8 presents estimates for annual average loading rates per square mile for each ofthese locations. Because bedload data were not generally available after 1992, the estimates were based onthe assumption thatbedload equals 25% oftotal sediment loads (see above discussion for rationale).
In order to facilitate comparisons between loadingrates for these locations and for the Redwood Creek watershed as a whole (as calculated for Orick from 1954-1997), Table 

### 8 also presents adjusted loading rate estimates for each ofthese locations. The annual average loading rates were adjusted to account for different time periods covered by the datarecord in each location. The adjustments are based onthe assumption that percentage differences inthe average annual loading rates for the entire watershed betweenthe 1954-1980 period andthe 1981-1997 period also were experiencedinthe tributary watersheds. Itis recognized that this assumption is not well validated; however, it is reasonable to assume that loading rates inthe "reference" tributaries and for the watershed as a whole would vary inproportion to each otherovertime.
For Panther Creek, and Lacks Creek, data were generally available for 1981-1997 (although datafor 1989-91 were missing). ForLittle Lost Man Creek, data were only available for 1993-1997.
For Redwood Creek at Orick, the annual loading rate for 1954-1997 was 172% ofthe loading rate at that location from 1981-1997. The adjusted estimated loading rates for Redwood Creek at Okane, Panther Creek, and Lacks Creek are equal to 172% ofthe estimated 1981-97loadingrates to account for the higher loading rates assumed to have occurred before 1981. ForLittle Lost Man Creek, data were only available for 1993-1997. For Redwood Creek at Orick, the annual loading rate for 1954-1997 was 127% ofthe loading rate at the same location from 1993-1997. The adjusted estimated loading rate for Little Lost Man Creek is equal to 127% ofthe estimated 1993-97 loading rates to account for the higher loading rates assumed to have occurred before 1993.

43

### Table 8: EstimatedAverage Annual Sediment LoadingForUpper Basin and Tributaries
Location Unadjusted Average Annual Load AdjustedAverage (area) (tons/mF1year) Annual Load (1954- 

# *

Panther Creek 1119 (6.07 mF) (1980-97) Lacks Creek 1467 (16.9 mF) (1981-97) Little Lost Man Creek 238 (1993-97) *source: Redwood National Park and USGS Unpublished Data (RNP, 1998b) 1results were rounded to the nearest ten 

### Specific Source Estimates 97) (tons/mF'year) 1
1930
2520
300

Sediment loading associated with specific sediment source categories was estimated based primarily on analysis ofthe sedimentbudget inthe Redwood Creek Watershed Analysis (RNP, 1997, Appendix C). A sediment budget quantifies sediment sources (inputs), by each erosional process, as well as changes inthe amount ofchannel stored sediment, and sediment outputs as measured at gauging stations over a designated time frame (Reid and Dunne, 1996). The Redwo.od Creek sediment budgetprovides rough estimates oftotal erosion from all the significant source categories (erosional processes) for the period 1954-1980 along with estimates ofinstream sediment storage and sediment outputs at Orick. The results are notbelieved to be highly accurate (RNP, 1997). The individual source estimates for this TMDL were calculated by multiplying the percentage oftotal load associated with each individual source category by the total sediment load estimated above for the period 1954-1997. This approach assumes that future loading rates from different source categories will be proportional to historical loading rates for these categories. This assumption is reasonable giventhat the main erosionprocesses ofinterest (and their causes) have not changed substantially in the watershed. There continue to be a large number ofpoorly designed and maintained roads and skid trails inthe basin, and intensive timber harvesting activities continue. What has changed is spatial distribution ofthese land management activities. Road construction and logging have decreased in the lower watershed and increased inthe upper watershed (RNP, 1997). Quantifying sediment sources involves determining the volume ofsediment delivered to stream channels bythe variety oferosional processes operating within the watershed. Forthe Redwood Creek watershed, these canbe divided into 2 general processes or sediment delivery mechanisms: 1) mass movement (ofwhich landslides are most important) and 2) fluvial erosion (road and skid trail crossing failures, gullies, and surface or sheetwash erosion, and stream bank erosion). Erosional processes in the watershed range from the removal ofindividual soil particles by raindrops to extensive landslides that cover entire hillslopes. In general, erosion caused by obvious large-scale earth movement has been better documented than erosion caused by dispersed small44scaleprocesses. The smaller-scale processes, however, may also be ofgreat importance in generating sediment because they are more widespread. Past studies indicate that streamside landsliding and fluvial hillslope erosionmaybe the most importantprocesses delivering sedimentto Redwood Creek (Harden and others, 1978; 1995; Kelsey and others, 198la; 198lb, cited in RNP, 1997). The Watershed Analysis discusses different erosional processes ofinterest inRedwood Creek in detail; a briefsummary ofthose processes is presented here. 

### Landslides Streamside landslides are clearly an important source ofsediment inthe Redwood Creek watershed, because oftheir number and volume, and because they deliver sediment directly to channels. Streamside landslides include debris slides, debris avalanches, and earthflows; however, debris slides account for most ofthe streamside landslide volume (Kelsey and others, 1995, cited in RNP, 1997). Streamside landslides maybe caused inpartbychannel aggradation (Janda and others, 1975, cited inRNP, 1997). Sediment deposited inthe channel raises water levels during storms, resulting inundercutting ofhillslopes that subsequently fail as debris slides.
Most streamside landslides identified for the 1954-97period occurred between 1962 and 1966. Between 1970 and 1976, the number ofnew streamside landslides decreased inthe upper basin, butincreased inthe middle and lower basins. Few streamside landslides have been initiated during the relatively dry period since 1975, although the 1997 storm activated a substantial number ofnew slides. Themost aerially extensive mass movement features inthe watershed are earthflows; however, they contribute relatively little sediment to Redwood Creek (RNP, 1997). Landslides other than streamside landslides include debris avalanches and debris, slumps, forested block slides, and some large and relatively inactive earthflows. These landslides are much less significant as sediment sources than are streamside landslides. 

### Fluvial Hillslope 

### Erosion
Fluvial hillslope erosion inthe Redwood Creekwatershed is apparent in bothnatural and disturbed settings. Onunlogged forested hillslopes, fluvial erosion is related to interactions between subsurface piping through root channels and gully and rill. On logged hillslopes, extensive networks ofrills and gullies have developed from streamflow diversions and washouts atroad and skid trail stream crossings, from ditches and cutbanks, and from interception ofsubsurface flow along roads andtrails. Surface erosion oflogged areas may also have increased as a result ofdecreased interception ofrainfall bythe forest canopy following harvest. Prairies are particularly susceptible to gully erosion, and road runoffhas carvednumerous large gullies inthe BaldHills area, near Berry Summit on Highway 299, and other areas withinthe watershed. Previous studies have documented large increases influvial erosion on lands where timber has beenharvested or where roads have been constructed (Janda and others, 1975; Nolan and others, 1976; Walter, 1985; Hagans and Weaver, 1987, cited in RNP, 1997).

45Channel Storage Massive amounts ofcoarse sediment were deposited intributaries and the upper and middle reaches ofthe mainstem during the flood of 1964. During subsequent floods, particularly in 1972 and 1975, coarse sediment was scoured from tributaries and the upper mainstem and re-deposited in lowerreaches. Sediment stored within the channel system continues to move inwave-like fashion downstream (Madej and Ozaki, 1996). As of 1990, peak aggradation was about 

### 5 miles downstream from the Tall Trees Grove and about 4 miles upstream ofOrick (fig. 3-5). Channel cross section surveys in 1995 indicated that, for the first time since measurements began in 1973, the channel bed betweenthe Tall Trees Grove and Orick was scoUring. However, cross section surveys from 1996- 97 document continued channel aggradation orinfilling for several miles belowthe Tall Trees Grove (public comments ofRedwood National Park, November 18, 1998). Itseems clearthat sediment discharged into Redwood Creekduring major storm runoffevents remains in storage for decades or longer. High flow events canremobilize these stored sediments and cause adverse impacts through channel modification and sediment redeposit in downstream habitat areas: Sediment Budget Adjustments Sediment budget estimates oftributary streamside landslides were further subdivided for the TMD L in orderto reflect different likely causative mechanisms. Pitlick's study oflandslide associations withpre-failure site conditions (Pitlick, 1982) provides information which can beused to estimate the relationship between landslides and land uses. Pitlick showed that for Redwood Creek tributaries, 40 percent ofstream side slope failures intributary canyons were logging related, and 80 percent ofthetotal landslide volume came from slopes loggedprior to failure. Based on Pitlick's analysis, tributary streamside landslides were divided into three categories: natural (corresponding to Pitlick's unlogged category), road- related (corresponding to Pitlick's road-related failures category) and harvest-related (corresponding to Pitlick's clear cutand selection cut categories). Landslides were divided based on the percent oftotal inventoried slide mass measured by Pitlick for each category. This approach assumes that the distribution oflandslidevolumes associated with roads, harvesting, and natural conditions for the basin as a whole is the same as measured inPitlick's sample ofseveral hundred landslides.
A 1980 study ofsediment sources and sedimenttransport inRedwood Creek evaluated 586 mainstem landslides. The study revealed that approximately 50 

### % ofthe slides had one ormore associated roads (Kelsey, et. al., 1981) The evaluation ofmainstem landslides recognizes thatthe volume ofeach slide may be variable. However, the volume ofmainstem landslides associated with roads, or othermanagement activities may represent more than 50 percent ofthe total load. Table 9 reports the results ofthe modified sedimentbudget. Annual average loading rates were estimated by calculating the percentage ofthe total estimated loads associated with each source mechanism, then multiplying that percentage by the estimated total average annual sediment load for 1954-1997, as discussed above.

46

### Table 9: Sediment Source Category Estimates 

### a 

### b 

### c 1

2



### 3


### 4 5 6 

### 7 8 9 10 11



### 12 Source Mechanism 54-97 Average Percentage ofTotal Annual Sediment Load Estimate

Load (t/mF/yr) Roads and Skid Trails 690 14.6% ( Including silvicultural activities, agriculture, andpublic roads.) Gully Erosion 1020 21.4% (Mostly roadrelated) Bare Ground Erosion 400 8.4% Stream BankErosion 590 12.4% Tributary Landslides: Natural 210 4.4% Tributary Landslides: Road Related 360 7.6% Tributary Landslides: Harvest Related 390 8.3% Mainstem Landslides 810 17.0% Debris Torrents 100 2.2% Other Mass Movements: 180 3.7%

- earthflows

- block slides TOTAL ESTIMATED LOADS 4750 100%

Note: CalculatiOns are rounded to the nearest 10. Average annual loads are calculated by multiplying the percentage in column c by 4750, the total estimated annual loading rate for the watershed between 1954-97. Source: Percentages oftotal loads in column care derived from Redwood Creek Watershed Analysis, 1997, Appendix C. 

### Explanation ofSedimentBudget About 54% ofthe overall budget was from fluvial and surface erosion, and about 46% ofthe budget is associated with mass wasting processes. Road-related erosionprocesses account for approximately 50% ofthe total budget, including significantproportions ofthe loadings associated with both fluvial and mass movement processes. It

### is difficult to estimatethe proportion oftotal loading associated with timber harvesting (road-related impacts aside), butit probably exceeds 10% ofthe total. Natural background erosion accounts for roughly 30-40% ofthe total loadings. As discussed above, it is assumed that approximately 10% ofaverage annual sediment loads were stored instream during the period 1954-97. This sediment budget is expected to be accurate within a factor ofabout+/- 40%. As such, it should be adequate for purposes ofestimating the relative share ofloadings from different source categories and establishing a baseline loading level for purposes ofcalculating needed load reductions. EPA expects that opportunities will arise in the future to evaluate the accuracy ofthe sediment budget and associated TMDL loading allocations, and make adjustments as necessary.

47

### Conclusion For the period 1954-1997, long term average annual sedimentproduction rate for the entire basin is estimated to be approximately 4750 tons/mF/yr. Approximately halfwas from mass wasting and halffrom fluvial erosion sources, including surface erosionprocesses. About halfthe sediment production was associated withroads and skid trails and roughly 10%-20% was associated with timber harvesting (not including harvestrelated roads and skid trails). Perhaps 30%-40% oftotal loads were naturally occurring, or at least were not associated with specific land management causes. Itis importantto emphasize that average annual loading rates provide useful information for planning only when a long term monitoring and analysis horizon is applied. Evaluation ofsediment loading dynamics over shorttime periods (e.g., less than 10 ormore years) is unlikely to yield reliable results, giventhat Redwood Creek sedimentloading is dominated by infrequent, high magnitude events. For example, the key sediment loading events ofthe past40 years were believed to be storms expected to occurperhaps once every 25-50 years. Just as important, stream recovery from high magnitude sediment loading events may take decades or longer to occur. Although average annual sediment loading rates for theperiod 1981-97 were substantially lower than the period 1954-1980, it is not clearthat the recent lower loading rates indicate thatthe sediment loading problems in the basin are a thing ofthe past. The 1980s and early 1990s were marked by lower than normal precipitation and relatively few high magnitude events. Thus sources onthe hillslope couldbe triggered by future highrainfalVflow events. However, the lower loading rates may be also be attributable, to some extent, to improvements intimber harvest practices. This period coincided with a tightening ofCaliforniaForest Practice Rules and the use ofmore protective harvest practices; however the amount oflogging inthe basin has not declined during the period since Redwood National Parkwas established. Rather, logging has been moved upstream into the middle and upper parts ofthe basin. Analysis offuture loadings and associated land management practices will be needed to evaluate the degree to which lower loading rates for the 1980-97 period were associated with improvements in forest practices. The early analysis ofthe effects ofthe 1997 "New Year's" storm (approximately an 11 year storm) indicates that a large amount ofunaddressed erosion potential remains (NPS 1997 and written comments by Redwood National Park, November 18, 1998). Over 100 large landslides were triggered orreactivated, and multiple road failures occurred both within the Park and on lands outsidethe park. It was estimatedthat over 900,000 tons ofsediments were discharged into Redwood Creek or its tributaries, ormoved into unstable hillslope positions and are perchedto fail. The erosionresponse to this storm indicates that additional action is needed to prevent ongoing, destructive sediment loading inthe basin.

48

## Section 3.4. Loading Capacity Linkage Analysis
In orderto determine the TMDL, it is important to assess the magnitude ofinstream sediment problems and the associated levels ofsediment source reductions needed to address instream problems. Theresult ofthis assessment is anestimate of"loading capacity"

-- the amount of sedimentthe Creek can assimilate and still meet its water quality standards. This section assesses the degree to which sediment reductions are needed from sources inthe Redwood Creek watershed to alleviate the instream sediment problems discussed inthe Problem Statement section and quantified inthe Numeric Targets section. The analysis is based ontwo methods ofcomparing existing and desired conditions for the watershed: 1. quantitative comparison ofaverage sediment loading rates per square mile inmore highly impacted and relatively unimpaired areas ofRedwood Creek watershed, and 2. qualitative comparison ofexisting and historical conditions withtarget levels for the instream indicators selected inthe numeric targets section. Itis recognized that inferring linkages between prospective hillslope erosionsources and instream impacts based onthese methods will produce uncertain results. However, itis necessary to estimate the level ofsediment reductions needed inthe future to meet water quality standards. Because there are no reliable direct linkages to evaluate (i.e., the sediment-impactrelationships tend to be separated intime and space) and no reliable methods for modeling those linkages, it is necessary to rely onthese less certain inferential methods. EPA believes that through future monitoring and evaluation, it willprove more feasible to evaluate these cause-effect linkages with greater certainty than was feasible for this TMDL. Comparison ofSedimentLoads in Redwood Creekto Reference Streams As discussed inthe preceding sections, Lacks Creek, Panther Creek, and Little Lost Man Creekprovide the best local candidates for estimating historical reference watershed loading rates. Adjusted average annual loading rates were estimated for each ofthese tributaries (see Source Analysis chapter for details), and the results are reported along withthe average annual loading rates estimated for Redwood Creek at Orick.
To allow a comparison ofhistorical loading rates for the Redwood Creek watershed as a whole with "reference watershed" loading rates, it was necessary to weightthe loading rates for the reference watersheds in accordance with howrepresentative their underlying geologies are ofthe entire basin. Forthis adjustment, it was assumed that Panther Creek loading rates would be representative of"reference" loading rates for all ofthebasin area underlain by schist-- about 42% of the basin. Itwas further assumed that Little Lost Man Creek loading rates were representative of "reference" loading rates for the Prairie Creek area-- about 14% ofthe basin. Finally, it was assumed that Lacks Creek loading rates were representative of"reference" loading rates for the remainder ofthe basin-- about 44% ofthe basin. The Lacks Creek assumption is reasonable because that tributary is underlain by both ofthe most common remaining geologic types present inthe basin, a combination ofresistant sandstones and less resistant mudstones and siltstones.



### 49The weightings were calculated as follows to yield a single estimated reference loading rate for the entire Redwood Creek basin (see table 1 0). First, the sediment loading rates for each reference stream (columnb) were multiplied bythe corresponding percentage (expressed as a decimal, i.e., 42% becomes 0.42) ofthe whole basin underlainby the reference stream geologic type (column c) to yield loading rate factors for each reference. The three loading rate factors were added together to yield the overall estimated loading for the entire basin. The weighting ofthe "reference" loadings yields an overall composite estimate ofloadings associated with reasonably well functioning watersheds which are not experiencing excessive human-caused erosion. This calculationyields an estimate for a basin-wide reference loading rate of 1962 tons/square mile, which is 59% lower than the estimated basin loading rate for 1954-1997 of4750 tons/square mile. While considering the assumptions made oncalculating the reference loading rate, the result suggests that a reduction ofapproximately 60-% mightbe needed in orderto achieve "reference watershed" conditions over a longtime horizon. 

### Table 10: Reference Stream Comparison Loading Information 

### a b 

### c I

2 

### 3 4 5 Reference Stream

Panther Creek Lacks Creek Little Lost Man Creek Estimated Reference Loading Rate for Redwood CreekBasin Estimated Sediment Loading Rate (t/sq milyr) 

## * 1925 2520 301 (weighted loading value= 1960)

*RedwoodCreek Watershed Analysis, RNP,1997 % ofWatershed Representative ofReference Stream Geology
42% 44% 14% 100%

Although some land management activity was occurring inPanther Creek and Lacks Creek several decades ago, this average annual loading estimate (1960 t/sq milyr) based uponreference streams is considered conservative because it includes the use ofLittle LostMan Creek- a nearly pristine tributary

-- as a reference stream for 14% ofthe basin. EPA does not expect that itwould be necessary to attain the near pristine levels ofsediment loading associated with Little Lost Man Creek in order to restore a functioning aquatic habitat inthe watershed as a whole. 

### Qualitative Analysis ofInstream and Hillslope Conditions Linkages between sediment sources inthe watershed and instream conditions are generally indirect and highly variable. However, over the long term, reductions in sediment inputs to the stream system are expected to result in reduction in sediment distributions inthe channel. Over time, the instream indicators identified in the Numeric Targets section should reflect changes in response to reduced sediment loading and transport. Because ofhistorical data limitations, itwas infeasible to prepare a quantitative comparisonbetween historical and target conditions for instream indicators. However, Table 11 summarizes the qualitative comparisons reported inthe Numeric Targets section. This qualitative comparison appears to indicate that instream conditions remain inadequate to support healthy habitat, but that conditions may be improving. Recently observed
50improvements inconditions may be associated with improved land management or with lower sediment loading rates during a relatively dry period. Significant continued sediment loading reductions appear to benecessary to address the instream problems associated with sediment. Large storm events ofthe magnitude seenprior to 1980 have not occurred since. When such events occur, higher sediment loading rates mayresult and consequently reveal deterioration ofinstream target conditions. Table 

### 11· Comparison ofExisting/HistoricalLevels for lnstream Indicatorswith Target Levels 

# . Indicator Qualitative Comparison Fines <0.85mm historical levels may exceed target levels to moderate extent; may be improving inupper watershed Fines <6.5mm historical levels may exceedtarget levels to moderate extent; may be improving inupper watershed Median surface particle size historical levels appear lowerthan target (d50) levels indicate elevated fine sediment; some improvement in upper basin Surface fines <2 mm maybe approaching target range, butno data post-1984 available PercentRiffles riffle percentage exceeds target inmany locations but appears to be improving Pool Depth possibly nearing target levels inmainstem
Conclusion: Estimate ofSedimentLoading Capacity in Redwood Creek Boththe reference stream analysis and instream indicator analysis indicate that some sedimentreductions and reductions infuture erosionpotential are necessary. In EPA'sjudgement, reductions should be based primarily onthe quantitative results ofthe reference stream analysis as this provides a more rigorous basis for estimating loading capacity. EPA estimates that reductions of about 60% are needed in order for Redwood Creek to meet water quality standards for sediment in the future. This suggests that allowable loading capacity is onthe order of40% ofhistoricalloading rates. This figure also compares with the estimation from the sediment budgetthat natural background erosion accounts for roughly 30-40% ofthe total estimated load for the period 1954- 1997. By multiplying the historical average annual loading rate (4750 tons/square mile) bythe 40% allowable annual loadings, it yields an overall loading capacity estimate at Orick of 1900 tons/square mile/year. The Loading Capacity meets the regulatory definition at 40 CFR 130.2(f) which states that the loading capacity is "the greatest amount ofloading that a water can receive without violating water quality standards." In addition, the Load Allocations meet the regulatory requirements at 40 CFR 130.2(g) inthatthey are "best estimates ofthe loading, which may range from reasonably accurate estimates to gross allotments

..."

51

## Section 3.5. Total Maximum Daily Loads and Allocations
The requirements ofa TMDL are described in40 CFR 130.2 and 130.7 and Section 303( d) of the CleanWater Act, as well as in various guidance documents. A TMDL is defined as the sum of the individual wasteload allocations for point sources, and load allocations for nonpoint sources and natural background pollutants, such that the loading capacity ofthe receiving water isnot exceeded. The allocations indicate the amount ofpollutant reduction from individual source categories that is required to attain water quality objectives. Allocations may be assignedbased onland use, land 'area, orerosional process. In addition, the regulations at 40 CFR 130.2(g) state that "Load allocations are best estimates ofthe loading, which mayrange from reasonably accurate estimates to gross allotments, depending onthe availability ofdata and appropnatetechniques for predicting the loading." The Redwood Creek allocations have been developed for erosionprocesses (associated with land use activities where feasible) based onthe source analysis ofthe various erosional processes. The load allocations have been developed as long term annual average loads per square mile at the basin-wide scale. As discussed inthe source analysis chapter, sediment storage was not factored into the TMDL, loading capacity, and allocation calculations. Total Maximum Daily Load Calculation The TMDL for Redwood Creek is being expressed as long term annual average sediment loading per square mile, as applied at the Orick gauging station atthe downstream end ofthe watershed. This meets the regulatory definition that "TMDLs canbe expressedinterms ofeither mass pertime, toxicity, or other appropriate measure." (40 CFR 130.2) This annual TMDL couldbe converted into daily loads, butexpressing the TMDL as an annual average yield better reflects the dynamic nature ofsediment movement throughout a watershed overtime. The annual average loading rate for this TMDL will be measured interms of 10 year rolling annual averages. The longer term annual average timestep is an appropriate approach to account for the large interannual variability in sediment loading and the longterm timeframe in which beneficial use impacts occur and change. This annual average loading per square mile will bereferred to as the TMDL for Redwood Creek. The TMDL is calculated by applying the loading capacity range from the previous section, which was estimated at 1900 tons/square mile/year (rounded). The TMDL for Redwood Creekis therefore estimated to be 

### 1900 tons/square mile/year. expressed as 

### 10 yearrolling annual averages. Load Allocations and Wasteload Allocations The following are the load allocations (column e inTable 12 onthe following page). The wasteload allocation for Redwood Creek is zero as there are no permittedpoint sources ofsediment discharge to the watershed. Explanation is provided below under Explanation ofAllocations and Calculations.

52Table 12: Summary ofTMDL and Allocations for the Redwood Creekwatershed.

a b 

### c d e Historic Percent Controllable Remaining Load Source Mechanism Sediment Load1 Controllable2 Load3 (Allocationt (t/mi2 /yr) (t/mi2 /yr) (t/mi2 /yr) 

### Roads, Landings and Skid 690 85% 580 

### llO Trails erosion Gully Erosion 1020 85% 870 150 (**~90%** 

### road related) Bare Ground Erosion 400 85% 340 60 StreamBankErosion 590 35% 210 380 Tributary Landslides: 210 0% 0 210 Naturally Occurring Tributary Landslides: 360 80% 290 70 Road Related Tributary Landslides: 390 50% 190 200 Harvest Related Mainstem Landslides 810 40% 320 490 (Human Induced and Naturally Occurring) Debris Torrents 100 50% 50 50 Other Mass Movements 180 0% 0 180 (Naturally Occurring): -earthflows

- block slides Totals 4750 2850 1900

1 The estimated historic sediment load for each source. 2 The percent ofthat historic loadthat is estimated as controllable. Controllable discharges are those discharges resulting

from human activities thatcan influence the quality ofthe waters ofthe State and that can be reasonably controlled. 3 The load that is estimated as controllable (the percent controllable multiplied bythe historic load), rounded to the

nearest 10. 4 The difference between the historic load estimate and the controllable load estimate, rounded to the nearest 10. This is

the estimated load atwhich sahnonids in the Redwood Creek watershed would no longerbe limited by sediment Explanation ofAllocations 

### The Allocations divide the TMDL among key source categories, including natural background sources. (The method for addressing natural background is discussed below.) The allocations are derived from the adjusted sediment budget presented inthe source analysis section, which was based primarily onthe sediment budget inthe Redwood Creek watershed analysis.

53The individual load allocations are based onEPA's assessment ofthe degree to which loadings from different source categories can actually be controlled orprevented. The controllable fraction oftotal loads from each source category was estimated, and the remaining loads by category were summed and compared with the TMDL. This analysis found that application ofreasonable practices to control and prevent future loading would result inreductions adequate to meetthe TMDL. "Controllable" sources ofsediment are defined as those which are associated withhuman activity 

### andwill respond to mitigation, altered land management, orrestoration. Thepercentages are based on anunderstanding ofthe available mitigation, land management and/or restoration measures whichhave beendeveloped for a variety ofsituations. The percentages reflectprofessional judgmentofhow successful the various best managementpractices (BMPs) generally are in controlling these sources. These assessments ofsource control potential are generally consistent withthose used for the Garcia River sediment TMDL established in 1998. Estimates ofcontrollable percentage ofloads for road-related sources are derived from field work inbasin and nearby basins by Weaver and Hagans (see, e.g., Weaver and Hagans, 1994). The estimate that about 90% ofgully erosion is road-related comes from Hagans, et al., 1986 and RNP, 1997). Estimates ofcontrollablepercentage ofloads from bare ground were derived from a conservative reading ofresults ofbare ground sediment control practices in Redwood Creekbasin documented in Kveton, et al. (1983) andHagens, et.al. (1986). Estimates ofcontrollablepercentage for streambank erosion were based onEPA'sjudgment summarized as follows: A significantportion ofbank erosion is believed to be associated with higher flow elevations caused by changes in channel shape, which in

### turn are associated with sediment loads which exceed the stream's natural transport capacity (Rosgen, 1996). As sediment loading is reduced inthe future, it is assumed thatthe frequency and magnitude ofbank erosion will decline, and thatthe volume oferoded bank sediments will decline as well. In addition, it is expected that some streambank erosion will be addressed through stream restorationprojects in some parts ofthe basin. Finally, it is expected that somereduction inbank erosion will occur in response to improvements inlivestockmanagement practices and, potentially, timber harvesting practices in riparian zones. Estimates ofcontrollable percentage ofharvest related mass wasting are based on Pitlick, 1982, EPA and Regional Board staff judgment and experience, and are consistent with control rates estimated for the Garcia River sediment TMDL. The available analysis concerning associations betweenlandslides and roaded, harvested, or unlogged areas focused uponlandslides intributaries (Pitlick, 1982). Becausethe patterns and causes, and associated ability to prevent landslides along the mainstem ofRedwood Creek are not well understood, this analysis assumed that mainstem landslides would notbe as amenable to control as tributary landslides. Following this reasoning, itis estimated that about 40% ofloads from mainstem landslides could be prevented, about halfthe amount ofload prevention which could be expected for tributary landslides which are road related.

54The sedimentbudget description inferred thatmost debris torrents are road-related. Because road-related debris torrents canusually be avoided throughproperroad siting and maintenance (e.g., through avoidance ofside-casting), the estimated 50% control level is realistic. Natural background is addressed inthe allocations intwo ways. First, explicit estimates of natural background loading levels are provided for different mass wasting processes, and it was assumed these sources are not controllable. Second, it is inferred that a portion offluvial erosion would be naturally occurring, although the proportion ofuncontrollable loads for the fluvial erosion categories which are related to natural sources versus uncontrollable anthropogenic sources is not distinguished. Control percentages for these sources are more modest as a result. Allocations for road-related sediment applies to all landuse activities including roads for timber, agricultural, residential, andpark management activities as well as state and countyroads. 

### Calculations
Table 12 summarizes the information used to calculate the individual allocations. The total historical loads estimated for each category (column a) are provided in column b. Column c provides data onthe percent ofthe total loads for informational purposes. The estimate of controllable load in column d was calculated by multiplying the loads from columnb bythe controllable percentages in column c. Column e is the remaining load, calculated by subtracting the controllable load (column d) from the historical load (columnb). Thus column e becomes the load allocation. There are no point sources inthe watershed; nor are any expected to be proposed inthe near future. Therefore, the wasteload allocation for point sources is zero. AI¢ culture
As noted above, the allocation for road related sediment applies to all land use activities including agriculture (principally ranching in Redwood Creekbasin). In addition, the allocations for the following categories also apply to agricultural activity: gully erosion, bare ground.erosion, streambank erosion, mainstem landslides, and debris torrents. The sediment budgetprepared by RedwoodNational Park does not separately estimate erosion associated with agriculture, although the existing categories account for agriculture related erosion to some degree. Overall, this approach is acceptable because agriculture-related erosion is notbelieved to be a major source inRedwood Creekwatershed. Separate Load allocations are onlyrequired for significant source categories. If subsequent erosion source inventories find that agriculture-related sources are significant, itmaybe appropriate to revise the allocations accordingly inthe future. 

### Conclusion
The Loading Capacity and Allocations ofLoads are developed for all major sources of sediment in Redwood Creek. As part ofthe supporting documentation, all sources were considered. Certain sources were not quantified including sedimentrelated to certain agricultural activities. These were accounted for inthe margin ofsafety. The sum ofthe load allocations plus the natural background is less than or equal to the estimated loading capacity and associated TMDL.

55

## Section 3.6. Margin ofSafety
Section 303(d) ofthe Clean Water Act and the regulations at 40 CFR 130.7 require that TMDLs shall be established at levels necessary to attain and maintain the applicable narrative and numerical water quality standards with seasonal variations and a margin ofsafety which takes into account any lack ofknowledge concerning the relationship between effluent limitations and water quality. The margin of safety can either be incorporated into conservative assumptions used to develop the TMDL or added as a separate component ofthe TMDL (EPA, 1991}. In every one of the components used to develop the TMDL, assumptions were made where sufficient data was lacking. Conservative assumptions have generally been made ineach case as a way of addressing the uncertainty associated with the data. EPA has identified these conservative assumptions more specifically to fully account for the implicit margin of safety. Selection ofInstream Numeric Target Levels The relationship between physical measures ofcold water aquatic habitat characteristics and the actual future health ofsalmonid populations is poorly understood. Available research results, which provide the information base from which target values are selected, vary widely with respect to the physical characteristics believed to be associated with well-functioning cold water aquatic habitats. No specific information concerning the relationship between physical measures ofaquatic habitat and aquatic ecosystem health was available for Redwood Creek watershed. Instream numeric targets were selected for the Redwood Creek TMDL based on a review of available literature sources which evaluate the relationship between salmonid health and various physical habitat measures. Target values for each measure were generally established at levels which were associated with successful salmonid reproduction and survival in carefully designed research settings, or which were associated with actual stream ecosystems which support healthy cold water aquatic habitat. Where available research results report a range ofpossibly acceptable levels ofdifferent physical habitat characteristics, values were selected for numeric target levels for the TMDL which were associated with higher salmonid survival rates or with stream conditions more favorable for healthy cold water ecosystem function. In the case ofmeasures of fine sediment in stream riffles, target values were set at levels associated with high levels of salmonid reproductive success in streams in the Pacific Northwest. Salmonids in California may have adapted to be 

### able to thrive in settings where fme sediment levels are higher than found in comparable settings in Washington, Oregon, Alaska, or British Columbia. However, because this possibility has not been fully verified through reliable research results based on work in California streams, the target levels for fine sediments used in the TMDL were set at lower levels associated with research results from other locations in the Pacific Northwest. This is a conservative assumption because the numeric targets for fine sediments were set closer to the low end ofthe range of "acceptable" fine sediment levels reported in the literature.

56

### Use ofHillslQPe Targets It will take a substantial period oftime (at least 10 years) before it will be appropriate to assess whether instream targets and associated water quality standards are being attained. During the period before this assessment can be conducted, significant uncertainty will remain concerngint the effectiveness ofthe TMDL and associated implementation actions. In addition to instream targets, the TMDL includes hillslope targets which identify desired conditions with respect to key

.land use management practices which could contribute to unacceptable increases in sediment loading rates. It will be possible to monitor whether these hillslope targets are being attained over short periods oftime (i.e., less than 10 years). If

### it is determined that the hillslope targets are not being attained, it will be possible to evaluate whether the TMDL and/or implementation plan require immediate revision. Provision ofhillslope factors provides an additional margin ofsafety to account for the lag time between establishment and implementation ofthe TMDL and evaluation ofits effectivness. Proportion ofBedload in Total Sediment Load Total sediment load is comprised of suspended load and bedload. Much ofthe sediment data for Redwood Creek in recent years is available for suspended sediment only. It 

### was important to used these data in the TMDL analysis to evaluate recent trends in sediment loading. In order to make recent data comparable with historical data for total sediment loading, it was necessary to assume the bedload fraction oftotal sediment loading in Redwood Creek. The loading analysis assumes a bedload proportion at the high end ofthe range (25%) estimated for the basin in available literature sources. (10-30%). Sediment Storage in Mainstem ofRedwood Creek After sediment is discharged into North Coast California streams, it may be deposited in the stream bottom or floodplain, causing stream aggradation. It may take decades for excessive sediment loads deposited in the stream to be remobilized and transported out ofthe basin. The stream itselfmay therefore act as both a sink for sediments (a temporary storage location) and a source for sediment (through resuspension and transport ofpreviously discharged sediments). Streams may have some capaCity to absorb excess sediment loadings without impairing beneficial uses under some circumstances; however, this "buffering" effect is poorly understood. Moreover, in streams such as Redwood Creek which experienced massive discharges of sediment following major stoims over the past 40 years, the stream may be unable to absorb temporary discharges ofexcessive sediment in this manner. Therefore, the TMDL was developed through a conservative approach which gives no "credit" for instream storage as 

### a consideration in TMDL determination since current excessive levels of instream stored sediment are significantly impairing beneficial uses. The TMDL is approximately 10-25% lower than would be the case if instream storage credit were provided. Comparison of Sediment Loading from Reference Streams with Redwood Creek as a Whole The analysis of loading rates from three "reference" tributaries found that historical sediment loading rates were about 59% lower than for the Redwood Creek watershed as a whole. Some researchers and commenters have observed that, other factors being equal, sediment loading 57

### rates per unit ofarea appear to increase as watershed size increases. In comparing the loading rates from the smaller reference tributaries to the whole watershed, EPA made the conservative assumption that the loading rates could be compared directly, without attempting to compensate for scale differences which could explain (to some degree) why sediment loading rates from the watershed as a whole were much higher than for the reference tributaries. The Redwood Creek TMDL contains no compensating corrections to account for this phenomenon because it is poorly understood and because it was infeasible to evaluate the extent to which it actually exists in Redwood Creek watershed. This is a conservative assumption which may result in an overestimate ofamount of sediment loading reductions needed to address sediment problems in Redwood Creek as a whole. Association ofHillslQPe Sources With Human Causes Where possible, the source analysis distinguishes human-caused sediment discharge sources from naturally occurring sources. Available research provides information on several types ofhillslope sediment sources which are "associated" with land management activities. The TMDL source analysis makes the conservative assumption that hillslope sources identified as "associated" with land management activities are 

### causedby the associated land management activities. This assumption results a higher estimate ofhuman-caused discharges which are amenable to some degree ofcontrol or avoidance, and lower TMDL and associated load allocations as a result. Estimation of**Loadin~** 

### Capacity The estimate of sediment loading capacity in the TMDL was based on a quantitative comparison ofhistorical sediment loading rates in "reference" tributaries with the watershed as a whole, and a qualitative comparison ofobserved values for instream habitat indicators with the target values for those indicators. The quantitative comparison indicated that "reference" loading rates were about 40% ofthe loading rates for the watershed as a whole (suggesting that significant load reductions would be needed in the watershed as a whole). The qualitative comparison of instream parameters indicated that instream conditions may be improving, particularly in the upper watershed (implying that the system is recovering and may not require significant sediment discharge reductions. However, rather than raising the loading capacity estimate to account for the possible improvements in instream conditions, the TMDL makes the conservative assumption that the potential improvements in instream conditions have not been verified by adequate monitoring over an adequate monitoring period. This assumption results in the establishment ofa lower loading capacity estimate which is more protective ofaquatic habitat. Conclusion As the margin of safety discussion points out, there are a number ofuncertainties associated with the supporting documentation, most notably in the source analysis and linkage analysis to estimate loading capacity. Given these uncertainties, conservative assumptions have been made regarding the amount ofloading reductions that are needed to attain water quality objectives

. This approach is warranted and meets the statutory requirements that a margin of safety take into account any lack ofknowledge concerning the relationship between the effluent limitations and water quality. 

### 58Collection of site-specific data in the future will help to reduce the uncertainty associated with the current assessment and will therefore allow for a reduction inthe degree ofconservatism associated with the current assumptions. Thus, it is possible, depending on the quality and quantity ofthe site-specific data which is collected over time, that adjustments to the TMDL in the future will result in less stringent allocations as the margin of safety is reduced. 

## Section 3.7. Seasonal Variation
There is inherent annual and seasonal variation inthe delivery ofsediment to stream systems. Surface erosion occurs on an annual basis, butprimarily as a result ofwinter rains. Fluvial erosion and mass wasting, onthe otherhand, occur as a result ofbig storms and thus may not be significantly active processes every year. Forthis reason, the allocations are designed to apply to the sources ofsediment, themselves, notthe movement ofsediment across the landscape ordelivery of sediment directly to the stream channel. Ifimplemented as envisioned, potential and existing sediment delivery sites will be identified and the quantity ofsediment associated with each site measured or estimated. Then, as a result ofmitigation or altered land management, the amount of potential sediment saved from delivery to receiving water State will be measured orestimated. The relationship between the original measurement orestimate ofpotential sediment delivery and the amount savedby mitigation will indicatethe degree to which the allocation has been achieved. It is difficultto accurately predict specific impacts ofsediment loading atparticular times and places onparticular salmonid life stages given spatial and temporal lag time between sediment delivery andthe occurrence ofsedimentrelated impacts onbeneficial uses. Inaddition, itis infeasible topredict orcontrol sources at fine spatial and temporal scales inmany cases. Therefore, the approach inthis TMDL is to select indicators to interpret narrative waterquality objectives which are believed to provide a good compositepicture ofinstream sediment-related conditions and changes over time. Then, targets and associated TMDLs are set at levels believed to beprotective of beneficial uses atkey life stages taking into account the lag time effects. In addition, the numeric targets generally represent summer flow conditions. This TMDL accounts for seasonal variation throughthe careful articulation oflikely cause and effect relationships between sediment loadings and effects on salmonidhabitat at different key life stages, and its consideration oflag time effects. Normal winter rains and larger storms will nonetheless have an effect onthe assessment of allocations. Storm events which occur after mitigations have been achieved willprovide a test ofthe success ofthe mitigation. Forthis reason, the monitoring plan will propose follow-up inventories of hillslope sources which will help assess post-mitigation success. 

## Section 3.8. Critical Conditions
The regulations at 40 CFR 130.7 state that TMDLs shall take into account critical conditions for stream flow, loading and water quality parameters. This TMDL does not explicitly estimate critical flow conditions for several reasons. First, unlike many pollutants (e.g. acutely toxic chemicals) sedimentimpacts onbeneficial uses may occur long after sediment is discharged, often at locations far downstream from the point ofdischarge. Second, sediment impacts are rarely correlated closely with flow over short timeperiods. Third, it is impractical to accurately measure sediment loading, transport, and shortterm effects during high magnitude flow events which usually
59 /'produce most sediment loading and channel modification in systems such as Redwood Creek. Therefore, the approach used inthis TMDL to account for critical conditions is to use indicators which are reflective ofthe net long term effects ofsediment loading, transport, deposition, and associated receivil).g water flows. These indicators may be effectively measured at lower flow conditions atroughly annual intervals. Inclusion ofa large margin ofsafety helps to ensure that the TMDL will result inbeneficial use protectionduring and after critical flowperiods associated with maximum sedimentation events. Critical conditions concerning stream habitat status and recovery may change substantially following major storms (e.g., storms with a recurrence interval ofapproximately 50 years ormore). Such storms and the associated floods and huge sediment loads canhave the effect of "recallibrating" the stream channel morphology for decades to follow. Itmay be appropriate to reconsider the TMDL and associated allocations following such an event. 

## Se<;tion 4. Public Participation
Federal regulations require that TMDLsbe subjectto public review (40 CFR 130.7). The State and EPA haveprovided for publicparticipationthrough several mechanisms. The State has held several formal and informal public workshops during 1998 to discuss the State's TMDL and implementationplanproposals. EPAhas participated intwo ofthese workshops. The State and EPA have worked together to assure that the EPATMDL for Redwood Creek is very similar to the TMDL proposed bythe State.
EPA invitedpublic comment onthe EPA draft TMDL in a public notice dated October 19, 1998. Thatpublic notice was published in several North Coast newspapers and was mailed out to a mailing list ofinterested parties providedto EPAbythe RWQCB. EPA hosted a public hearing on the Redwood Creek and South Fork Trinity RiverTMDLs inEureka, CA onNovember 19, 1998. EPAreviewedpublic comments received inwriting during the commentperiod as well as oral comments made atthe public hearing inreaching its final decision onthe TMDL. EPAhas prepared a commentresponsiveness summary which shows howEPA considered public comments in its final decision. The fmal TMDL incorporates changes inthe following areas:

- clarification ofinstream numeric targets

- addition ofhillslope numeric targets -minorclarifications ofthe source analysis, linkage analysis, TMDL, and allocations

- restructuring ofthe margin ofsafety discussion, and

- additional detail inthe implementation and monitoring recommendations. 

## Section 5. Implementation and Monitoring Recommendations
Federal regulations require the Stateto identifY measures needed to implement TMDLs in the state water quality managementplan (40 CPR 130.6). EPA has established policies whiCh emphasized the importance oftimely implementation ofmeasures to implement TMDLs which address nonpoint source discharges ( EPA, 1997b ). EPA expects the State to promptly develop implementation measures and ensure the implementation ofsource control and erosion prevention measures which are adequate to achieve the allocations in the TMDL. •

60EPA expects that the State will incorporate the TMDL and associated implementation measures inthe State water quality management plan (in California, the RWQCB Basin Plan) upon approval by EPA , as required 40 CFR 130.6. This requirement may be metthrough EPA's approval ofthe TMDL and implementationplans already added to the BasinPlanbythe State, orthrough incorporation ofan EPA-established TMDL and State-adopted implementation measures inthe Basin Plan following EPA's establishment ofthe TMDL. Implementation Plan Recommendations Concurrentwith its effortto develop the Redwood Creek TMDL, the RWQCB has drafted an Implementation Plan (Plan) for the TMDL (November 10, 1998) and is continuingto refine the Plan inconsultation with interested stakeholders. EPA strongly supports the draft Implementation Plan and offers the following recommendations to further strengthen thatPlan:
L Promote and facilitate cooperative public-private implementation and monitoring efforts. The draft Plan recognizes that measures developed under the auspices ofotherplanning mechanisms may berecognized by the Regional Board ifthey contain all the required elements ofthe erosioncontrol plans. AnMOU between the park and interested private landowners provides a potential existing mechanism for planning implementation actions and monitoring programs at a scale broaderthan individual ownerships. The Regional Board Plan would be improved ifit more activelypromoted cooperative efforts by Redwood National Park and interested private landowners to inventory roads and otherpotential erosion sites, plan erosion control and prevention actions, carry outthose actions, and conduct instream and hillslope monitoring activities. The Plan shouldurge agencies andprivate landowners to share all data concerning instream water quality and hillslope practices with the State to assist infuture review ofthe TMDL. The Plan should also note that significant funding for implementationplanning and action as well as monitoring may be available from outside sources (e.g., President's Forest Plan funds, Clean Water Act Section 319 nonpoint source and Clean Water Action Plan grant funds, NRCS cost share funds, andpossibly state funding sources). Ifthe park and local landowners are interested in obtaining such funds, the Regional Board should actively facilitate efforts to do so. EPArecommends that if outside funding is obtained to support implementation activities in the basin, preference for spending these funds should be targeted to smaller landowners who may be less able to carry out the necessary planning and implementation activities. 2. Clarify focus onpotential erosion sites as well as existing sites. Although the text ofthe Plan indicates that landowner inventories should address both potential and active erosion sites, the Plan should be clarified to place greater focus ondetection ofpotential erosion sites and implementation ofmeasures to prevent activation oferosionfrom these sites. Itis often cost-prohibitive to address erosion sites which have already begun to erode. In addition, ifinitial erosion site inventories are designed to identify all sites with future erosionpotential based onthe presence ofcharacteristics indicating instability orvulnerability, it may prove unnecessary to conduct repeated detailed inventories every few years as proposed. Ifdone well the first time, it may be necessary to follow-up these detailed initial inventories only with periodic cursory inspections ofpotential erosion sites and erosion control practices and structures.



### 613. ClarifY the 10 year implementation timeframe and urge quicker implementation. ThePlancalls for implementation ofneeded erosionprevention and control measures within 10 years after the baseline inventory is developed. The baseline inventory is scheduled for submission by 2003. EPA supports the 10 year implementationtimeframe. However, the State should considerrequiring submission ofthe baseline inventory and initiation ofthe 10 year implementationtimeframe sooner than 2003. 

### It should not have to take landowners 

### 5 years to complete the inventory. EPA recommends a tighter timeframe for submission ofthe baseline inventory-- perhaps 2-3 years from the date ofTMDL adoption. Ifthe 2003 submission schedule is retained, the Plan should strongly encourage the implementation oferosionprevention and control measures as soonas is practicable, beginning now. 4. Improve protection ofClass 3 watercourses. Existing forest practice rules appearto provide inadequate measures to protect Class 3 watercourses from disturbances whichcantrigger significant erosion and sediment delivery to Class 1 and 2 watercourses. The Regional Boardplan should explicitly require inventories and action plans to address potential erosion sites near Class 3 watercourses. Monitoring Recommendations EPA guidance concerning the development ofTMDLs through the phased approach emphasizes the importance ofestablishing rigorous monitoring and evaluationplans and associated schedules which will guide the review andpotential revision ofthe TMDLs and implementation activities (EPA, 

### 1991). The State should establish a monitoring and evaluationplan which identifies parties responsible for implementation andtimeframes for RWQCB review ofmonitoring results. The monitoring plan should describe how and when monitoring results will be reviewed to evaluate the need for TMDL or implementation planrevisions. Finally, the monitoring plan should provide for data sharing among landowners, agencies, and interested stakeholders. The Regional Board Plan should describe a more detailed approach to developing a comprehensive monitoring plan. EPA recommends the following monitoring provisions: 1. Actively lead the development ofa comprehensive monitoring plan. EPA commends the State for its. plan to work with other agencies and landowners to develop the monitoring plan, we suggest that the Regional Board develop a specific agreement withRedwood National Park (andperhaps with other agencies) tojointly lead the development ofthis plan. The Plan should recognize the opportunities to dovetail TMDL monitoring activities with ongoing monitoring conductedby Redwood National Park, USGS, other agencies, and private landowners. The Regional Board and Redwood National Park should describe a specific mechanism through which interested agencies and landowners can work together to develop and implementthis monitoring plan. As discussed above, it maybe appropriate for the Regional Boardto facilitate acquisition ofoutside funds to support future monitoring efforts. 2. Distinguish monitoring needs in different stream types and hillslope locations. Different monitoring approaches will be appropriate in different locations. With respect to instream monitoring, it would be appropriateto establish monumented monitoring sites distributed throughout the mainstem and lowerportions ofkey tributary watersheds. Priorities for monitoring tributaries and mainstem reaches which include potential spawning/rearing habitat include (in priority order): 

### 62- pebble counts atriffle crests,

- large woody debris inventories,

- thalweg and cross section measures which facilitate measurement ofpool indicators,

- suspended sediment and possibly bedload sediment at mouths ofkeytributaries, including Lacks Creek, Prairie Creek, Panther Creek, Coyote Creek, Bridge Creek, and Little Lost Man Creek, and

- bulk sampling ofsubstrate composition atriffle crests in a subset ofestablished monitoring sites. Priorities for monitoring inthe larger portions ofRedwood Creek should include the following:

- thalweg profiles and cross sections,

- large woody debris inventories,

- suspended and bedload sediment loads at Orick and Okane. Additional indicators which should be considered for addition to monitoringprograms include: -substratepermeability,

- turbidity, and -bed mobility measures (e.g. scour chains) Hillslope monitoring will also be an important component ofthe monitoring plan. In addition to the implementationmonitoring and reporting requirements inthe Plan, the hillslope monitoring plan shouldprovide for information collection adequate to update the sediment budget about once every 10-15 years. EPArecommends the use ofrapid sedimentbudgeting methods described in Reid and Dunne (1996). All monitoring plans should include specific descriptions ofthe monitoring protocols and data management efforts to be followed inadequate detail to guide monitoring and datarecording by different field workers. Agreement at the outset onmonitoring protocols and data management methods is crucial to ensure that data collected at differenttimes and locations by different parties will be comparable inthe future. Iffeasible, provision should be made to record and report datain electronic formats.



### 63

## Section 6. Glossary Aggradation: To fill and raise the elevation ofthe stream channel by deposition ofsediment. Agricultural facility: Any building, corral, pen, pasture, field, trail, or other feature onthe landscape which is attributable to or associated with agricultural operations Anadromous: Refers to aquatic species which migrate up rivers from the seato breed in fresh water. Areas ofinstability: Locations on the landscape where land forms are present which·have the ability to discharge sedimentto a watercourse. Baseline data: Dataderived from field based monitoring orinventories used to characterize existing conditions and used to establish a database for planning or future comparisons. Beneficial Use: Uses ofwaters ofthe state that may be protected against quality degradation including, but not limited to, domestic, municipal, agricultural and industrial supply; power generation; recreation; aesthetic enjoyment; navigation; and the preservation and enhancement of**fish~** 

### wildlife and other aquatic resources orpreserves. Class I: Watercourses which contain domestic water supplies, including springs, on site and/or within 100 feet downstream ofthe operation area and/or have fish always or seasonally present onsite, including habitat to sustain fish migration and spawning. Class I streams include historically fish-bearing streams. Class II: Watercourses which have fish always or seasonally present offsite within 1000 feet downstream; and/or contain aquatic habitat for non-fish aquatic species. Class II waters do not include Class III waters that are directly tributary to Class I waters. Class III: Watercourses which do not have aquatic life present, but show evidence ofbeing capable ofsedimenttransport to Class I and II waters under normal high flow conditions during and after completion ofland management activities. Class IV: Human-made watercourses, which usually supply downstream established domestic, agricultural, hydroelectric supply or other beneficial uses. Controllable source: Any soti.rce ofsediment with the potential to enter a water ofthe State which is caused by human activity and will respond to mitigation, restoration, or altered land management. Debris torrents: Long stretches ofbare, generally unstable stream channel banks scoured and eroded bythe extremely rapid movement ofwater-ladened debris, commonly caused by debris sliding or road stream crossing failure in the upper part ofa drainage during an intense storm. Deep seated landslide: Landslides involving deep regolith, weathered rock, and/or bedrock, as well as surficial soil. Deep seated landslides commonly include large (acres to hundreds ofacres) slope features and are associated with geologic materials and structures.


### 64Drainage structure: A structure orfacility constructed to control road runoff. These structures include but are not limited to fords, inside ditches, water bars, outsloping, rolling dips, culverts or ditch drains. Flood event: Flood frequency analysis defines the event which can be expected once every 

### "Y" years, onthe average. This does not imply that a 

### "Y -year event" will occur regularly every 

### "Y" years. Return periods, as well as flood magnitudes, are subject to analysis. For example, there is a two percent chance that a 50-year event will occur I any one year. Flooding: The overflowing ofwater onto land that is normally dry. Fry: 

### A youngjuvenile salmon after ithas absorbed its egg sac and emerged from the redd. Headwater swale: The swale ordip inthe natural topography that is upslope from a stream, atits headwater. There may or may not be evidence ofoverland or surface flow ofwater inthe headwater swale. Interstices: The space betweenparticles (e.g. space between sand grains).
Inner gorge: 

### A geomorphic feature formed by coalescing scars originating from mass wasting and erosional process caused by active stream erosion. The feature is identified as that area ofstream bank situated immediately adjacent to the stream, having a slope generally over 65% and being situated belowthe first break in slope above the channeL Inside ditch: The ditch on the inside ofthe road, usually at the foot ofthe cutbank. Landslide: Any mass movement process characterized by downslope transport ofsoil and rock, under gravitational stress by sliding over a discrete failure surface-- orthe resultant landform. Large woody debris: A piece of woody material having a diameter greaterthan 30 em (12 inches) and a length greater than 2m (6 feet) that is located in a position where it may enter the watercourse channel.
Mass wasting: Downslope movement ofsoil mass under force ofgravity-- often used synonymously with "landslide." Commontypes ifmass soil movement include rock falls, soil creep, slumps, earthflows, debris avalanches, debris slides and debris torrents. Numeric targets: A numerical expression ofthe desired instream environment. For each stressor orpollutant addressed in the problem statement ofthe Strategy, a numeric target is developed based onthe numeric or narrative State water quality standards which are needed to recovered the impaired beneficial use. Permanent drainage: A road drainage structure designed and constructed to remain inplace following active structure land management activities while allowing year round access on a road. Planning Watershed: The uniform designation and boundaries ofsub basins within a larger watershed (designated by the California Department ofForestry as Cal Water Watersheds). 65Redd: A gravel nest ordepression inthe stream substrate formed by a female salmonid inwhich eggs are laid, fertilized and incubated. Sediment: Fragmented material that originates from weathering ofrocks and decomposed organic material that is transported by, suspended in, and eventually deposited bywater or air. Sediment budget: An accounting ofthe sources, movement, storage and deposition ofsediment produced by a variety oferosional processes, from its origin to its exit from a basin. Sediment delivery: Material (usually referring to sediment) which is delivered to a watercourse channel bywind, water ordirect placement. Sediment discharge: The mass or volume ofsediment passing a point inthe stream in a unit of time. Sediment erosion: The group of processes whereby sediment (earthen or rock material) is loosened, dissolved and removed from the landscape surface. It includes weathering, solubilization andtransportation. Sediment source: The physical location onthe landscape where earthen material resides which has ormay have the ability to discharge into a watercourse. Sediment yield: The sediment yield consists ofdissolved, suspended and bed loads ofa watercourse channel through a given cross-section in a given period oftime. Shallow seated landslide: A landslide produced bythe failure ofthe soil mantle (typically to a depth of 1-2 meters, sometimes includes some weathered bedrock), on a steep slope. 

### Itincludes debris slides, soil slips and failure ofroad cut-slopes and sidecast. The debris moves quickly (commonly breaking up and developing into a debris flow) leaving an elongated, concave scar. Skid trail: Constructed trails or established paths used by tractors orother vehicles for skidding logs. Also known as tractor roads. Smolt: A young salmon atthe stage at which 

### itmigrates from fresh water to the sea. Steep slope: A hillslope, generally greater than 50% that leads without a significant break in slope to a watercourse. A significant break in slope is onethat is wide enough to allow the deposition of sediment carried by runoffprior to reaching the downslope watercourse. Stream: See watercourse. Stream class: The classification ofwaters ofthe state, based onbeneficial uses, as required by the Department ofForestry in Timber Harvest Plan development. See definitions for Class I, Class II, Class III, and Class IV for more specific definitions. Stream order: The designation (1,2,3, etc.) ofthe relative position ofstream segments inthe drainage basin network. For example, a first order stream is the smallest, unbranched, perennial 

### 66

### tributary whichterminates at the upper point. A second order stream is formed whentwo first order streamsjoin, and so forth. Sub basin: A subset or division ofa watershed into smallerhydrologically meaningful Watersheds. For example, the North Fork Redwood Creek is a sub basin ofthe larger Redwood Creekwatershed. Swale: A channel-like linear depression orlow spot on a hillslope whichrarely carries runoffexcept during extreme rainfall events. Some swales may no longer carry surface flow under the present climatic conditions. Thalweg: The deepestpart ofa stream channel at any given cross section. Thalweg profile: Change in elevation ofthe thalweg as surveyed in anupstream-downstream direction against a fixed elevation. Unstable areas: Characterized by slide areas, gullies, eroding stream banks, orunstable soils. Slide areas include shallow and deep seated landslides, debris flows, debris slides, debris torrents, earthflows and inner gorges and hummocky ground. Unstable soils include unconsolidated, noncohesive soils and colluvial debris. Watercourse: Any well-defined channel with a distinguishable bed and bank showing evidence of having contained flowing water indicated by deposit ofrock, sand, gravel, or soiL Watershed: Total land area draining to any point in a watercourse, as measured on a map, aerial photo or otherhorizontal plane. Also called a basin, drainage area, orcatchment area. Water quality objective: Limits on or level ofwater quality constituents or characteristics which are established for the reasonable protection ofbeneficial uses ofwater orthe prevention ofnuisance within a specific area. Water quality standard: Consist ofthe beneficial uses ofwater and the water quality objectives as described in the Water Quality Control Plan for the North Coast Region.



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## Section 7. References Bilby, R.E. and J.W. Ward. 1989. Changes in characteristics and function ofwoody debris with increasing size ofstreams in western Washington. Transactions ofthe American Fisheries Society. 118:363-378. Burns, 

### J.W. 1970. Spawning bed sedimentation studies in north California streams. Pages 253-279 

### in California Fish and Game 56(4). Cederholm, C.J., L.M. Reid, and E.O. Salo. 1980. Cumulative Effects ofLogging Road Sediment on Salmonid Populations inthe Clearwater River, Jefferson County, Washington. In SalmonSpawning Gravel Conference Procedings, 1980. Chapman, D. W. 1988. Critical review ofvariables used to define effects offines inreds oflarge salmonids. In: Transactions ofthe American Fisheries Society 117. Pages 1-25 Chapman, D.W. and K.P. McLeod. 1987. Development ofCriteria for Fine Sediment inthe North American Rockies Ecoregion. EPA 910/9-87-162, April, 1987. Flosi, G. And F.L. Reynolds. 1994. California salmonid stream habitat restoration manuaL Inland Fisheries Division, California Department ofFishand Game, The Resources Agency. Hagans, D. K., W. E. Weaver and M.A. Madej. 1986. Long-term on-site and off-site effects of logging and erosion inthe Redwood Creek basin, northern California. In: Papers presented at Amer. Geophys. Unionmeeting oncumulative effects (9-13 Dec. 1985, San Francisco, Ca.). Tech. Bull. 490, pp. 38-66, National Council ofthe Paper Industry (NCASI), New York, New York. Hagans, D.K. andW.E. Weaver. 1987. Magnitude, cause andbasinresponse to fluvial erosion, Redwood Creek basin, northern California. Erosion and Sedimentation inthe Pacific Rim (Proceedings ofthe Corvallis Symposium, August 1987). Keller, E. A., andW. N. Melhorn. 1995. Rhythmic spacing and origin ofpools and riffles. In: Geological Society ofAmerica Bulletin, v. 89. Doc. no. 80509. Pages 723-730 Kelsey, H., et. al. 1981. Sediment Sources and Sediment Transport inthe Redwood Creek Basin: A Progress Report, National Park Service, Redwood National Park, Arcata, California. Knopp, C. 1993. Testing indices for cold water fish habitat. Final Report for the North Coast Regional Water Quality Control Board. Kondolf, G. Mathias, M. 

### J. Sale, M.G. Wolman. 1993. Modification ofFluvial Gravel Size by Spawning Salmonids. Water Resources Research, Vol. 29, No.7, 2265-2274, July 1993.

68Kveton, K.J., et aL 1983. Comparison ofSlope Treatments for Reducing SurfaceErosionof Disturbed Sites at Redwood National Park. Redwood National Park. In Proceedings ofthe first biennial conference ofresearch 

### in California's National Parks. September 9-10, 1982, University of California, Davis. Lisle, T. 

### E. and M.A. Madej. 1992. Spatial Variation in Armoring in a Channel with High Sediment Supply. Dynamics ofGravel BedRivers. John Wiley and Sons Ltd., 1992. Madej, Mary Ann and Vicki Ozaki. 1996. Channel Response to Sediment Wave Propagation and Movement, Redwood Creek, California USA. Earth Surface Processes and Landforms, Vol. 21, 911-927 (1996). National Marine Fisheries Service. 1997. Aquatic Properly Functioning ConditionMatrix. NMFS, SouthwestRegion, March 20, 1997. Peterson, N.P., A. Hendry, and T.P. Quinn. 1992. Assessment ofcumulative effects on salmonid habitat; some suggested parameters and targets conditions. Timber, Fish and Wildlife. TFW-F3-92- 

### 00l. Pitlick, John. 1982. Sedimentrouting 

### in tributaries ofRedwood Creek basin,Northwestern California, RedwoodNational Park, Arcata, California. RedwoodNational and State Parks, 1995. Draft Redwood Creek Watershed Analysis. June 2, 1995. RedwoodNational and State Parks, 1997. DraftRedwood CreekWatershed Analysis. March, 1997. RedwoodNational and State Parks, 1998a. Draft Redwood National and State Park General Management Plan/General Plan and Draft EIS/EIR, 1998•

. Redwood National and State Parks, 1998b. Unpublished Sediment DataForRedwood Creek and

Tributaries, 1998. RedwoodNational and State Parks, 1998c. Redwood Creek Watershed Information. 1998. Regional Water Quality Control Board. 1994. Water Quality Control Planfor the North Coast Region, SantaRosa, CA. Regional Water Quality Control Board. 1998. StaffReport for the Proposed Redwood CreekWater Quality Attainment Strategy for Sediment (Total Maximum Daily Loads and ImplementationPlan), November 10, 1998. Reid, L.M. 1996. Evaluating Timber ManagementEffects onLand Uses and Values inNorthwest California. Draft, December 3, 1996. Reid, L.M. 1998. Review ofthe Sustained Yield Plan/Habitat Conservation Plan for the properties ofthe Pacific Lumber Company, Scotia Pacific Holding Company, and Salmon Creek Corporation.

69Reid, L.M. andT. Dunne. 1996. Rapid Evaluation ofSediment Budgets. CATENA VERLAG GMBH, 35447 Reiskirchen, Germany. Rosgen, D. 1996. Applied River Morphology. Wildland Hydrology, Pagosa Springs, Colorado. Spence, B.C., G.A. Lornnicky, R.M. Hughes, and R.P. Novitzki. 1996. An ecosystem approach to salmonid conservation. TR-4501-96-6057. ManTech Environmental Research Services Corp., Corvalis OR. Tappe!, P.D. and T.C. Bjomn. 1983. A new method ofrelating size ofspawning gravel to salmonid embryo survival. North AmericanJournal ofFisheries Management 3:123-135. U.S. Environmental Protection Agency. 1991. Guidance for Water Quality-based Decisions: The TMDL Process, EPA440/4-91-001. U.S. Environmental Protection Agency. 1997a. National Clarifying Guidance for 1998 State and Territory Section 303(d) Listing Decisions. Memo from Robert Wayland to Water Division Directors, August 27, 1997. U.S. Environmental ProtectionAgency. 1997b. NewPolicies for Establishing and Implementing Total MaximumDaily Loads (TMDLs). Memo from Robert Perciasepe to Regional Administrators and Regional Water Division Directors, August 8, 1997. U.S. Environmental Protection Agency. 1998a. Records ofTelephone Communications With R. Klein, M.A. Madej, G. Bundros, and V. Ozaki. · U.S. Environmental ProtectionAgency. 1998b. Description ofBasis for Sediment Source Estimates in Redwood Creek TMDL. E-Mail message from David Smith, USEPA to Bruce Gwynne, North Coast Regional Water Quality Control Board, August 20, 1998. U.S. Environmental Protection Agency. 1998c. Total Maximum Daily Loads for SedimentRedwood Creek, California. Public Review Draft, October 19, 1998.
Weaver W. E. and D. 

### K. Hagans. 1994. Handbook for Forest and Ranch Roads: a guide for planning, designing, constructing, reconstructing, maintaining and closing wildland roads. Prepared for the Mendocino County Resource Conservation District, Ukiah, CA in cooperation with the California Department ofForestry and Fire Protection and the USDA Soil Conservation Setvice. 149 pages 

### + appendices. Weaver, W. and D. Hagans. 1996. Sediment Treatments and Road Restoration: Protecting and Restoring Watersheds and Restoring Watersheds from Sediment-Related Impacts. InHealing the Watershed: A Guide to the Restoration ofWatersheds and Native Fish in the West. Pacific Rivers Council, Inc., July, 1996. Young, Michael K., W.A. Hubert, and T.A. Wesche.1991. Selection ofMeasures ofSubstrate Composition to Estimate Survival to Emergence ofSalmonids and to Detect Changes in Stream Substrates. North American Journal ofFisheries Management 11:339-346. 70