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Chapter 7. Hydromodification 1 

1 Chapter 7. Hydromodification 

1 

2 Contents 

3 1 Overview................................................................................................................................... 3 

4 1.1 Sources..............................................................................................................................3 

5 1.1.1 Streambank and Shoreline Erosion..........................................................................4 

6 1.1.2 Channelization .........................................................................................................4 

7 1.1.3 Dams and In-stream Structures................................................................................5 

8 1.1.4 Contribution .............................................................................................................5 

9 2. Chesapeake Bay Hydromodification Implementation Measures.............................................. 7 

10 2.1 General Principles and Goals............................................................................................7 

11 2.2 Implementation Measures.................................................................................................8 

12 2.2.1 Implementation Measure #1: Protect Streambanks and Shorelines from 

13 Erosion .....................................................................................................................9 

14 2.2.1.1 Existing Practices..................................................................................... 9 

15 2.2.1.2 Multi-Cell Culvert.................................................................................... 9 

16 2.2.1.3 Non-eroding Roadways ......................................................................... 10 

17 2.2.1.4 Riprap..................................................................................................... 13 

18 2.2.1.5 Toe Protection........................................................................................ 13 

19 2.2.2 Implementation Measure #2: Control Upland Sources of Sediment and 

20 Nutrients at Dams ..................................................................................................14 

21 2.2.2.1 Existing Practices................................................................................... 14 

22 2.2.3 Implementation Measure #3: Restore In-stream and Riparian Habitat 

23 Function .................................................................................................................15 

24 2.2.3.1 Existing Practices................................................................................... 16 

25 2.2.3.2 Shoreline Sensitivity Assessment .......................................................... 16 

26 2.2.3.3 Establish and Protect Stream Buffers .................................................... 17 

27 2.2.3.4 Riparian Improvements.......................................................................... 20 

28 2.2.3.5 Vegetated Buffers .................................................................................. 21 

29 2.2.3.6 Vegetated Filter Strips ........................................................................... 22 

30 2.2.4 Implementation Measure #4: Reduce Pollutant Sources through Operational 

31 and Design Management........................................................................................23 

32 2.2.4.1 Existing Practices................................................................................... 23 
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Chapter 7. Hydromodification 2 

1 2.2.4.2 Advanced Hydroelectric Turbines ......................................................... 24 

2 2.2.4.3 Flow Augmentation ............................................................................... 24 

3 2.2.4.4 Selective Withdrawal............................................................................. 26 

4 2.2.4.5 Turbine Operation.................................................................................. 27 

5 2.2.4.6 Turbine Venting..................................................................................... 27 

6 2.2.5 Implementation Measure #5: Restore Stream and Shoreline Physical 

7 Characteristics........................................................................................................28 

8 2.2.5.1 Existing practices................................................................................... 29 

9 2.2.5.2 Bank Shaping and Planting.................................................................... 30 

10 2.2.5.3 Brush Mattressing .................................................................................. 30 

11 2.2.5.4 Cross Vanes ........................................................................................... 31 

12 2.2.5.5 Joint Planting ......................................................................................... 32 

13 2.2.5.6 Legacy Effects of Dams and Dam Removal.......................................... 33 

14 2.2.5.7 Live Crib Walls...................................................................................... 38 

15 2.2.5.8 Live Fascines ......................................................................................... 39 

16 2.2.5.9 Live Staking........................................................................................... 41 

17 2.2.5.10 Log & Rock Check Dams...................................................................... 43

18 2.2.5.11 Marsh Creation and Restoration ............................................................ 44 

19 2.2.5.12 Revetments............................................................................................. 45 

20 2.2.5.13 Rock and Log Vanes.............................................................................. 46 

21 2.2.5.14 Rosgen’s Stream Classification Method................................................ 47 

22 2.2.5.15 Step Pools............................................................................................... 59 

23 2.2.5.16 Streambank Dewatering......................................................................... 60 

24 2.2.5.17 Vegetated Gabions................................................................................. 61 

25 2.2.5.18 Vegetated Geogrids................................................................................ 61 

26 2.2.5.19 Vegetated Reinforced Soil Slope (VRSS) ............................................. 62 

27 2.2.5.20 Weirs...................................................................................................... 62 

28 2.2.5.21 Wing Deflectors..................................................................................... 63 

29 3 References.................................................................................... Appendix A. Sources of Data

30 66 
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Chapter 7. Hydromodification 3 

1 1 Overview 

2 The Chesapeake Bay and its tributaries, representing the nation’s largest estuary, is a 

3 resourceresources of important economic, social and environmental significance. The 

4 Chesapeake Bay ecosystem, however, remains severely degraded primarily because of pollution 

5 from excess nitrogen (N), phosphorus (P), phosphorous, and sediment, which enters surface 

6 waters. Those pollutants come from multiple diverse sources within the Chesapeake Bay 

7 watershed, but the primary sources are agriculture, urban and suburban runoff, wastewater, and 

8 airborne contaminants (Chesapeake Bay ProgramCBP 2009). One source that has been identified 

9 as a contributor of pollutants to the Chesapeake Bay is hydromodification. EPA Region 3 states 

10 report that, of assessed waters—a cumulative total of 1,427 miles of assessed rivers and streams, 

11 1,687 acres of assessed lakes and reservoirs, and 1,916 square miles of assessed bays and 

12 estuaries—hydromodification is the probable source contributing to impairments. 

13 The term hydromodification as used in this guidance refers to the “alteration of the hydrologic 

14 characteristics of waterbodies, which in turn could cause degradation of water resources.” Many 

15 activities that are considered forms of hydromodification have been conducted and continue to 

16 be conducted because they are considered to be critical to human activities, such as dredging 

17 shipping channels for commerce or constructing culverts at stream crossings for transportation. 

18 Hydromodification can also refer to activities that are conducted in and adjacent to stream 

19 channels to maintain stream functions or reduce damage to streams or adjacent properties such as 

20 clearing of debris or armoring of streambanks. 

21 While hydromodification activities likely occurred within the Chesapeake Bay watershed before 

22 European settlement (e.g., fish traps, secondary effects from riparian agriculture) the scale and 

23 scope of hydromodification increased dramatically with the advent of European expansion on the 

24 east coast of North America. Early settlers constructed dams to harness hydropower and drained 

25 floodplain areas for farming (Walter and Merritts 2008; Schenk and Hupp 2009).(Walter et al.

26 2008; Schenk et al. 2009). As development accelerated through the colonial, post revolutionary 

27 and industrial periods hydromodification activities expanded to include dredging of natural and 

28 man-made waterways for commerce, construction of water supply, recreational and flood control 

29 dams, and channel straightening and dredging for flood control and agriculture. In more recent 

30 years, development of the built environment has resulted in secondary channel erosion within 

31 and downstream of urban centers. 

32 1.1 Sources 

33 Hydromodification activities are grouped into three general categories for the purposes of this 

34 document: (1) channelization and channel modification, (2) dams, and (3) streambank and 

35 shoreline erosion. Such broad categories are useful in that they provide a logical organization for 

36 hydromodification activities. However, as is described later in this document, implementation 

37 measures and practices can apply across these three activity categories. In addition certain 

38 hydromodification activities might not fit neatly within any of the three categories described 

39 below. 
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Chapter 7. Hydromodification 4 

1 1.1.1 Streambank and Shoreline Erosion 

2 Streambanks and shoreline erosion refers to the degradation of stream, estuary and lake shore 

3 areas resulting in loss of soil and other material landward of the bank along non-tidal streams and 

4 rivers. Streambank erosion occurs when the force of flowing water in a river exceeds the ability 

5 of soil and vegetation to hold the banks in place. Eroded material is carried downstream and re6 deposited in the channel bottom or in point bars located along bends in the waterway. Shoreline 

7 erosion occurs in large open waterbodies, such as larger lakes and the lower estuarine portion of 

8 the Chesapeake Bay, where waves and currents sort coarser sands and gravel from eroded bank 

9 materials and move them in both directions along the shore away from the area being eroded. 

10 While the underlying forces causing the erosion could be different for streambank and shoreline 

11 erosion, the results, erosion and its impacts, are usually similar. It is also important to note that 

12 streambank and shoreline erosion are natural processes and that natural background levels of 

13 erosion also exist and might be necessary to ensure the health of a particular stream. However, 

14 human activities along or adjacent to streambanks or shorelines can increase erosion and other 

15 nonpoint sources of pollution. 

16 1.1.2 Channelization 

17 Channelization and channel modification include activities such as straightening, widening, 

18 deepening, and clearing channels of debris and accumulated sediment. Examples of 

19 channelization and channel modification projects include flood control, infrastructure protection, 

20 channel and bank stabilization, habitat improvement/enhancement, recreation, and flow control 

21 for water supply (source). Channelization activities play an important role in nonpoint source 

22 pollution effect on the Chesapeake Bay by affecting the timing and delivery of pollutants that 

23 enter the water. Channelization can also be a cause of higher flows during storm events, which 

24 increases the risk of flooding. 

25 Historically, channelization occurred to reduce flooding, drain wet areas for agriculture and to 

26 allow for commerce among, other reasons. In recent years however regulatory requirements 

27 primarily driven by the Clean Water Act (USEPA 1972) have limited traditional 

28 hydromodification activities within stream channels and waterbodies. Simultaneously, water 

29 resource managers have recognized the critical role that healthy stable stream corridors play in 

30 the protection and improvement of water quality and living resources within the Chesapeake 

31 Bay. As a result many of the hydromodification activities occurring currently are those related to 

32 maintenance and restoration of channel corridors and shorelines. 

33 One type of hydromodification activity that is attracting increased attention by water resource 

34 professionals as a possible source of pollutants, and overall degraded health of stream benthic 

35 communities, is the erosion of streambanks in unstable streams particularly in urban and 

36 suburban areas. Previously researchers theorized that the principle predictor of stream health and 

37 instability in urbanizing watersheds was imperviousness. Furthermore, it was initially reported 

38 that channel instability and reduced benthic health generally occurred once imperviousness 

39 passed 10 percent (Schueler 1994). As a result of these findings many water resource protection 

40 agencies developed stormwater management regulations based on restrictions of imperviousness 

41 (need example). Subsequent research however has shown substantial effects on the stream health 

42 and stability across all levels of imperviousness (Booth et al. 2004). As a result many agencies 
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Chapter 7. Hydromodification 5 

1 are shifting the focus of stormwater management to those practices that control the causative 

2 factors of stream instability, namely changes in watershed hydrology. This topic is covered in the 

3 Urban chapter of this guidance. 

4 1.1.3 Dams and In-stream Structures 

5 Dams and in-stream structures are artificial barriers on waterbodies that control the flow of 

6 water. These structures can be built for a variety of purposes, including flood control, power 

7 generation, irrigation, navigation, and to create ponds, lakes and reservoirs for uses such as 

8 municipal water supply, fish farming and recreation. While these types of structures are 

9 constructed to provide benefits to society, they can contribute to nonpoint source pollution and 

10 effects on living resources. For example dams can alter flows whichwith ultimately can cause 

11 effects on water quality and roadway culverts can result in the scour of stream sediments at their 

12 outlet. While these structures were often built for purposes related to human needs in many cases 

13 that need is no longer present (e.g., small hydropower dams to support manufacturing). As a 

14 result water resource managers have conducted detailed cost benefit analysis at many dams and 

15 the result often show that the benefits of dam removal outweigh the benefits of continuing to 

16 maintain and operate the dam. 

17 An important development in the effect of dams in water quality is the increasing trend of 

18 agencies and dam removal within the Chesapeake Bay as dams reach their life expectancy and 

19 are removed for safety concerns or to restore the connectivity of aquatic ecosystems. This 

20 phenomenon is covered extensively in one of the practices recommended later in this document. 

21 1.1.4 Contribution 

22 The contribution of hydromodification activities to sediments and nutrient loads to the 

23 Chesapeake Bay is poorly defined in the current research literature. Traditionally land use 

24 managers and water resources professionals categorized these pollutant loadings based on 

25 specific land uses (such as agricultural, urban and silviculture). Contribution of specific 

26 hydromodification activities such as channel erosion or dams was less well defined. With recent 

27 research on the topic however increased attention and research activity has been focused on 

28 separating the contribution of specific activities such as stream corridor instability to overall 

29 pollutant loading of the bay. 

30 The interaction between pollutants from upland sources and those which originate within the 

31 stream corridor is a complex one. During the 1700s and 1800s eroding upland agricultural areas 

32 resulted in significant sediment storage within stream corridors typically called legacy sediment 

33 (USGSLangland and Cronin 2003). The construction of Mill dams duringwithin this same period 

34 resulted in the impoundment and storage of sediment behind tens of thousands of mill dams in 

35 the mid-Atlantic region (Merrit et al.2004). Subsequent removal of these dams during the late 

36 industrial period and urban and suburban development in the past 100 years has led to erosion of 

37 the deposited sediments as stream corridors have become instable and streambanks have eroded 

38 (USGS 20032005). 

39 Because of the intimate nature of hydromodification activities with the stream corridor there is 

40 understandably a close relationship between those activities and sediment delivery to surface 
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Chapter 7. Hydromodification 6 

1 waters. A summary of existing information of the impacts of stream hydromodification on the 

2 quality of the Chesapeake Bay is provided in Table 7-1. These studies demonstrate the 

3 importance of stream restoration and protection in achieving pollutant reduction in the 

4 Chesapeake Bay, particularly for sediment and the Pphosphorus that accompanies sediment 

5 loading. 

6 Table 7-1. Studies quantifying the impact of sediment loading from stream hydromodification on 

7 Chesapeake Bay water quality 

Study Findings 

A Summary Report of Sediment Processes in Chesapeake 

Bay and Watershed, USGS, Water-Resources 

Investigations Report 03-4123, 2003 

Summarizes the impacts and sources of 

sediment and notes that sediment yield 

from urbanized areas can remain high 

after active construction is complete 

because of increased stream corridor 

erosion due to altered hydrology 

Schueler, Thomas, et.al, The Practice of Watershed 

Protection, Technical Note #119 from Watershed 

Protection Techniques 3(3):729-734, Center for Watershed 

Protection, 2000. 

Stream enlargement, and the resulting 

transport of excess sediment, is caused by 

urban development 

U.S. Environmental Protection Agency. 2001. Protecting 

and Restoring America’s Watershed’s: Status, Trends, and 

Initiatives in Watershed Management, EPA 840-R-00-001. 

http://www.epa.gov/owow/nps/urbanm/pdf/urban_guidance

.pdf. 

Straighten and channelized streams carry 

more sediments and other pollutants to 

their receiving waters. Up to 75% of the 

transported sediment from the Pocomoke 

watershed on the Eastern Shore of 

Maryland was found to be erosion from 

within the stream corridor 

Gellis et al. Synthesis of U.S. Geological Survey Science 

for the Chesapeake Bay Ecosystem and Implications for 

Environmental Management, Chapter 6: Sources and 

Transport of Sediment in the Watershed. 2007, U.S. 

Geological Survey Circular 1316. 

Sediment sources are throughout the 

Chesapeake Bay watershed, with more in 

developed and steep areas 

Gellis et al. 2009, Sources, transport, and storage of 

sediment in the Chesapeake Bay Watershed: U.S. 

Geological Survey Scientific Investigations Report 2008–

5186 

In the Piedmont region, streambank 

erosion was a major source of sediment in 

developed Little Conestoga Creek; 30% of 

sediment from the Mattawoman 

Watershed on the Coastal Plain (flat land) 

is from streambanks 

Devereux et al. Suspended-sediment sources in an urban 

watershed, Northeast Branch Anacostia River, Maryland. 

Hydrological Processes, Accepted 2009. 

Streambank erosion was the primary 

source of sediment in the Northeast 

Branch Anacostia River 

8 

9 While the contribution of sediment from streambankStreambank erosion might be a significant 

10 source in many streams, the percentage of unstable streams within the Chesapeake Bay 

11 watershed is unknown (USGS 2003). 

12 The contribution of hydromodification to other pollutants of concern in the Chesapeake Bay is 

13 even less well documented. NNitrogen contribution throughout the watershed is primarily from 

14 agricultural, wastewater, and airborne sources. NNitrogen in its most commonly observed forms 

15 is present in very low levels within contributions from hydromodification sources. PPhosphorus

16 on the other hand, given its tendency to become soil and particulate bound is often present in the 

17 legacy sediments, which are significant contributors to eroding streams. 
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Chapter 7. Hydromodification 7 

1 2. Chesapeake Bay Hydromodification Implementation 

2 Measures 

3 In 2007 EPA published a guidance document titled National Management Measures to Control 

4 Non-point Source Pollution from Hydromodification (USEPA 2007) whose purpose was to 

5 provide background information on nonpoint source pollution and to offer a variety of solutions 

6 for reducing nonpoint source pollution resulting from hydromodification. Background 

7 information included a discussion of the sources of nonpoint source pollution and mechanisms 

8 for transport into the nation’s waters. The guidance further presented a series of Management 

9 Measures for use on a national scale to directly address the causative factors for nonpoint source 

10 pollution. Management measures as presented in the 2007 document establish performance 

11 expectations and where appropriate specific actions that can be taken to prevent or minimize 

12 nonpoint source pollution. 

13 A series of practices was also described for each management measure. Practices are specific 

14 actions taken to achieve, or help achieve aid in the achievement of a management measure. 

15 Practices are often termed best management practices (BMPs); however, the word best was 

16 dropped from the 2007 Hydromodification guidance and will not be used in this chapter 

17 becauseas the use of the adjective is too subjective. 

18 ThisWhile this document should not necessarily be considered an addendum or follow up to the 

19 2007 guidance; for more information,, EPA encourages the reader to see the earlier guidance for

20 more information. 

21 2.1 General Principles and Goals 

22 The purpose of this guidance document is to provide the user with background information on 

23 how hydromodification activities affect nutrient and sediment impacts within the Chesapeake 

24 Bay and to provide guidance on a range of practices that can be implemented to reduce the 

25 impact of hydromodification activities on bay water quality. While this document focuses on 

26 practices that are relevant to the Chesapeake Bay and its associated watershed specifically, the 

27 information provided herein is also widely relevant wherever hydromodification activities result 

28 in degradation of surface waters. 

29 While the primary focus of this document is on reducing loading of sediment, Nitrogen, and 

30 Phosphorous, it is important to note that there are often numerous secondary benefits to each 

31 specific practice detailed herein. To thatthis end where appropriate additional information is 

32 provided on secondary benefits such as those associated with living resources (and 

33 complementing the activities suggested in draft report 202(g) of Executive Order 13508). For 

34 example bioengineering techniques such as live staking and brush mattressing are typically 

35 applied to an eroding streambank principally to reduce sediment loading to the associated stream. 

36 However, the function of thosethese practices is based on establishing riparian vegetation, which 

37 is an important component in improving aquatic riparian habitat. 

38 For many hydromodification activities and their associated effects, a close relationship exists to 

39 other sections of this guidance series. In such cases, the reader might be directed to the 

40 associated section for additional guidance. For instance, increased rate and volume of stormwater 
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Chapter 7. Hydromodification 8 

1 runoff from urbanizing areas often leads to channel and streambank erosion. In that case, the 

2 causative factor of the effect (urbanization) is covered in the urban section of this document. 

3 Because streambank erosion is itself considered a form of hydromodification, the effect is 

4 described in detail and number of structural practices recommended to address the effect within 

5 the stream corridor. 

6 2.2 Implementation Measures 

7 To accomplish the goals set forth above, this document suggests using five implementation 

8 measures. The reader might use the measures to address the causative factors that result in 

9 sediment and nutrient loading to the Chesapeake Bay associated with hydromodification 

10 activities. 

11 

12 This document expands on the extensive resources provided in the 2007 document while 

13 focusing on the pollutants, sources, and practices considered important to the overall goal of 

14 restoring the health of the Chesapeake Bay. Implementation Measures (formerly management 

15 measures) presented are either the same or improved versions of those suggested in the 2007 

16 guidance. Where available, information on the application, design and performance of specific 

17 practices suitable for use in the Chesapeake Bay are provided. To support one of the key steps 

18 required by the Executive order 13508 to define next generation tools, a number of practices 

19 have been added to this document which exhibit proven capability to address the nonpoint source 

20 issues within the Chesapeake Bay. 

Implementation Measures

Implementation Measure #1 – Protect Streambanks and Shorelines from Erosion 

Implementation Measure #2 – Control Upland Sources of Sediment and Nutrients at Dams 

Implementation Measure #3 – Restore In-stream and Riparian Habitat Function 

Implementation Measure #4 – Reduce Pollutant Sources through Operational and Design 

Management 

Implementation Measure #5 – Restore Stream and Shoreline Physical Characteristics 
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Chapter 7. Hydromodification 9 

1 2.2.1 Implementation Measure #1: Protect Streambanks and Shorelines 

2 from Erosion 

Implementation Measure: The protection of streambanks and shorelines from erosion refers to 

the installation of structural or biological practices at or near the land water interface. This 

measure directly addresses one of the primary contributors of pollution from hydromodification 

activities. The primary goals of this implementation measure are the following:

1. Protect streambank and shoreline features with the potential to reduce nonpoint source 

pollution

2. Protect streambanks and shorelines from erosion from uses of either the shorelands or adjacent 

surface waters

3 The protection of streambanks and shorelines from erosion refers to the installation of structural 

4 or biological practices at or near the land water interface. This measure directly addresses one of 

5 the primary contributors of pollution from hydromodification activities. The primary goals of 

6 this implementation measure are the following:

7 1. Protect streambank and shoreline features with the potential to reduce nonpoint source

8 pollution.

9 2. Protect streambanks and shorelines from erosion because of uses of either the shorelands or 

10 adjacent surface waters.

11 2.2.1.1 Existing Practices 

12 The National Management Measures to Control Nonpoint Sources Pollution from 

13 Hydromodification document (USEPApublished by EPA in 2007) provides information on the 

14 use of the following practices to protect streambanks and shorelines from erosion: 

15 • Breakwaters 

16 • Bulkheads and seawalls 

17 • Groins 

18 • Return Walls 

19 2.2.1.2 Multi-Cell Culvert 

20 Description 

21 Roadway crossing, typically of smaller streams, where the main culvert at the stream channel is 

22 sized for bankfull discharge and additional culverts are placed on the floodplain to convey 

23 overbank flow up to the design discharge. 

24 Application and Purpose 

25 The use of a multi-cell culvert distributes stream conveyance during larger storm events across a 

26 larger portion of the stream/floodplain cross-section than the traditional single culvert system 
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Chapter 7. Hydromodification 10 

1 resulting in reduced flow velocities and better floodplain connectivity, In addition the smaller 

2 primary culvert can increase flow depths during low flows enabling fish passage. 

3 Multi-cell culverts typically consists of a primary culvert installed inline with the stream channel 

4 and sized with a cross-sectional area equivalent to the stream at bankfull discharge. One or more 

5 secondary culverts are located at floodplain or bankful elevation at variable locations across the 

6 road crossing to provide passage of floodflow. Primary culvert inverts are often placed below the 

7 channel invert to allow water and sediments to pool within the culvert to enable fish passage. 

8 The placement and geometry of the primary culvert is intended to allow the natural transport of 

9 sediment in the stream channel and prevent scour of the streambed because ofdue to flow 

10 contraction (Rosgen 1996). The combined capacity of the primary and secondary culverts is the 

11 design flow. 

12 Multi-cell culverts might not be appropriate for streams that are incised or actively incising 

13 streams, exhibit high flow velocities, or streams that often carry a heavy debris load (Johnson 

14 and Brown 2000). Use of multi-cell culverts in such systems could result in perched culverts and 

15 debris jams, Rosgen (1996) type C or E channels might be most appropriate for use of multi-cell 

16 culverts (Maryland Waterways Construction Guidelines 2000) 

17 Performance 

18 Published data on the performance of multi-cell culverts is primarily limited to fish passage 

19 requirements and assessment of appropriate channels systems. Laboratory scale model 

20 experiments investigating the scour and flow depth characteristics of multi-cell culverts showed 

21 reduction in overall scour pool volume and culvert perching of 52 percent and 55 percent,

22 respectively (Wargo and Weisman 2006).(Wargo 2006).

23 Design Guidance and additional info 

24 Maryland Department of the Environment Water Management Administration, 2000. 

25 Maryland’s Waterway Construction Guidelines at. At

26 http://www.mde.state.md.us/assets/document/wetlandswaterways/mgwc.pdf. Accessed 

27 February 2010. 

28 2.2.1.3 Non-eroding Roadways 

29 Description 

30 Non-eroding roadways refer to practices that reduce the sediment load to receiving waterbodies 

31 from dirt and gravel roads. 

32 Application and Purpose 

33 The National Management Measures to Control Nonpoint Sources Pollution from 

34 Hydromodification document (USEPApublished by EPA in 2007) contains a chapter on the 

35 practice of Non-eroding Roadways. For additional information on the appropriate use and 

36 application of non-eroding roadways, see the 2007 guide. 

37 In addition to the information contained in the 2007 guide, the following practices are 

38 recommended to reduce the sediment load from dirt and gravel roads. 
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Chapter 7. Hydromodification 11 

1 Driving Surface Aggregate (DSA) 

2 DSA is a specific gradation of crushed stone developed by the Center for Dirt and Gravel Road 

3 Studies specifically for use as a surface wearing course for unpaved roads. DSA achieves 

4 sediment reductions by decreasing erosion and transport of fine material from the road surface. 

5 Sandstone- and limestone-derived aggregates are preferred. 

6 Raising the Road Profile 

7 Raising the road profile involves importing material to raise the elevation of an unpaved road. It 

8 is typically practiced on roads that have become entrenched (lower than surrounding terrain). 

9 Raising the elevation of the road is designed to restore natural drainage patterns by eliminating 

10 the downslope ditch and providing cover for pipes to drain the upslope ditch. Removing the 

11 downslope ditch will eliminate concentrated flow conveyed in the ditch and create sheet flow. 

12 Raising the road profileRoad Profile achieves sediment reduction by controlling and reducing the 

13 volume of road runoff. 

14 Raising the road profile involves importing fill material to raise the elevation of the roadway up 

15 to the elevation of the surrounding terrain. The road is filled to a sufficient depth as to eliminate 

16 the ditch on the downslope side of the road and encourage sheet flow. Shale and gravel are the 

17 most common fill materials for roads. Other potential recycled fill materials include ground 

18 glass, waste sand, automobile tires, clean concrete rubble, and the like. 

19 Grade Breaks 

20 Grade breaks are an intentional increase in road elevation on a downhill grade, which causes 

21 water to flow off of the road surface. It is designed to reduce erosion on the road surface by 

22 forcing water into the ditches or surrounding terrain. Erosion of the road surface is reduced by 

23 forcing runoff laterally off the road. In some cases, grade breaks are used to force water off the 

24 road entirely, serving as an additional drainage outlet. Sites where water is not forced off the 

25 road entirely convey the water into a roadside ditch. 

26 Drainage Outlets 

27 Drainage outlets are designed to capture water flowing in the roadside ditch and force it to leave 

28 the road area. There are two major types of drainage outlets. Turnouts (also called bleeders or 

29 cutouts) outlet water from the downslope road ditch. They usually consist of relatively simple 

30 cuts in the downslope road bank to funnel road drainage away from the road. Drainage that is 

31 carried by the upslope road ditch is usually outletted under the roadway by the use of a crosspipe 

32 (also called culvert, sluice pipe, or tile drain). Installing additional drainage outlets reduces 

33 concentrated flow, peak flow discharges and sediment transport and delivery from unpaved roads 

34 and ditches into streams, and can increase infiltration. It does not affect sediment generation 

35 from the road surface or deliver in the upslope ditch; thus, all data on sediment reductions in this 

36 document is for a downslope ditch only, unless otherwise noted. Drainage outlets are to be 

37 placed in locations that have the least likelihood of reaching streams. If a newly added outlet 

38 conveys sediment to the stream, little, if any, sediment reductions will be obtained. 

39 Berm Removal 

40 A berm is a mound of earthern material that runs parallel to the road on the downslope side. 

41 Berms can be formed by maintenance practices and road erosion that lowers the road elevation 
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Chapter 7. Hydromodification 12 

1 over time. In many cases, the berm is unnecessary and creates a ditch on the downslope side of 

2 the road. The berm can be removed to encourage sheet flow into surrounding land instead of 

3 concentrated flow in an unnecessary ditch. Restoring sheet flow results in decreased runoff and 

4 sediment transport along the roadway, increase infiltration, and reduced maintenance associated 

5 with the road drainage system. 

6 Efficiency Data 

7 The following total suspended solids (TSS) reduction efficiencies are estimated for each practice. 

Technique TSS effectiveness estimate 

Driving Surface Aggregate Limestone* 50% 

Sandstone 55% 

Raising the Road Profile 45% 

Grade Breaks 30% 

Additional Drainage Outlet 15% 

Berm Removal 35% 

8 

9 Total nitrogen (TN) and total phosphorus (Total phosphorous (TP) removal is minimal with dirt 

10 and gravel road sediment control. One reason is that dirt and gravel roads are not fertilized. The 

11 other is that the environmental benefit association with dirt roads is such that nitrogen (N) and 

12 phosphorus (P) reductions are not anticipated, nutrient reductions are not a component of the 

13 average function of dirt and gravel roads. If N and P reductions are associated with dirt and 

14 gravel roads, they should track sediment reductions should be tracked. 

15 Design Guidance and additional info 

16 For additional information on non-eroding roadways, see the following sources: 

17 Controlling Nonpoint Source Runoff Pollution from Roads, Highways, and Bridges 

18 http://www.epa.gov/owow/nps/roads.html

19 Erosion, Sediment, and Runoff Control for Roads and Highways 

20 http://www.epa.gov/owow/nps/education/runoff.html

21 Gravel Roads: Maintenance and Design Manual—the purpose of the manual is to provide clear 

22 and helpful information for doing a better job of maintaining gravel roads. The manual is 

23 designed for the benefit of elected officials, mangers, and grader operators who are responsible 

24 for designing and maintaining gravel roads. http://www.epa.gov/owow/nps/gravelroads

25 Low-Volume Roads Engineering Best Management Practices Field Guide 

26 http://zietlow.com/manual/gk1/web.doc

27 Massachusetts Unpaved Roads BMP Manual 

28 http://www.berkshireplanning.org/download/dirt_roads.pdf

29 Planning Considerations for Roads, Highways, and Bridges 

30 http://www.epa.gov/owow/nps/education/planroad.html
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Chapter 7. Hydromodification 13 

1 Pollution Control Programs for Roads, Highways, and Bridges 

2 http://www.epa.gov/owow/nps/education/control.html

3 Recommended Practices Manual: A Guideline for Maintenance and Service of Unpaved Roads 

4 http://www.epa.gov/owow/nps/unpavedroads.html

5 The Road Maintenance Video Set is a five-part video series developed for the U.S. Department 

6 of Agriculture– (USDA) Forest Service (USDA-FS) equipment operators that focuses on 

7 environmentally sensitive ways of maintaining low volume roads. 

8 http://www.epa.gov/owow/nps/maint_videoset.html

9 2.2.1.4 Riprap 

10 Description 

11 Riprap is a layer of appropriately sized stones designed to protect and stabilize areas subject to 

12 erosion, slopes subject to seepage, or areas with poor soil structure. 

13 Application and Purpose 

14 The National Management Measures to Control Nonpoint Sources Pollution from 

15 Hydromodification document (USEPApublished by EPA in 2007) contains a chapter on the 

16 practice of Riprap. At the time of this writing, no additional information is provided pertaining to 

17 this practice. For information on the appropriate use and application for riprap, see the 2007 

18 guide. 

19 Cost Data 

20 Riprap costs vary depending on the class of riprap, the location of the quarry, and installation 

21 practices. Prices typically range from $40 to $70 per ton. 

22 2.2.1.5 Toe Protection 

23 Description 

24 Toe protection refers to the installation of erosion resistant material, typically stone, near and at 

25 the water line along shorelines and streams to reduce wave reflection and scour of the land water 

26 interface. 

27 Application and Purpose 

28 The purpose of toe protection is to dissipate wave and scour energy at the land water interface of 

29 and therefore reduce shoreline and streambank erosion. 

30 The National Management Measures to Control Nonpoint Sources Pollution from 

31 Hydromodification document (USEPApublished by EPA in 2007) provides information on the use 

32 of tow protection to reduce shoreline erosion. While the installation techniques and methods differ 

33 slightly where toe protection is used to reduce streambank erosion the practice is principally the 

34 same. 
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Chapter 7. Hydromodification 14 

1 Efficiency Data 

2 Efficiency data on toe protection in streambanks is limited. However, recent research projects 

3 have shown reduced loss of streambank where toe protection is implemented on eroding 

4 channels. A modeling study in the Lake Tahoe basin using the Bank-Stability and Toe-Erosion 

5 Model (BSTEM) predicted that the application of a 1.0-m-high rock toe protection would reduce 

6 bank erosion by 69–100 percent (Simon et al. 2009). It was further noted that only 14 percent of 

7 the sediment loss in the streambank of the studied reach was from the toe region, the remaining 

8 sediment loss resulted from mass wasting of the overlying streambank indicating the importance 

9 of the land water interface in overall stream sediment dynamics. 

10 2.2.2 Implementation Measure #2: Control Upland Sources of Sediment and 

11 Nutrients at Dams 

Implementation Measure: The control of upland sources of nonpoint source pollutants at dams, 

as well as other hydromodification facilities, refers to the active implementation of pollutant 

control techniques and practices that minimize the source generation and reduce the transport of 

sediments and nutrients into the Chesapeake Bay and its watershed. This implementation

measure was well described in the 2007 guidance document (formerly titled Erosion and 

Sediment Control for Construction of New Dams and Maintenance of Existing Dams). The goals 

of this implementation measure are

1. Reduce the generation of sediment and nutrients during and after construction

2. Retain eroded sediment and nutrients on-site

3. Apply nutrients at rates necessary to establish and maintain vegetation without causing 

significant nutrient runoff to surface waters

12 The control of upland sources of nonpoint source pollutants at dams, as well as other 

13 hydromodification facilities, refers to the active implementation of pollutant control techniques 

14 and practices which minimize the source generation reduce the transport of sediments and 

15 nutrients into the Chesapeake bay and its watershed. This Implementation Measure was well 

16 described within the 2007 guidance document (formerly titled Erosion and Sediment Control for 

17 Construction of New Dams and Maintenance of Existing Dams). The goals of this 

18 implementation measure are

19 1. Reduce the generation of sediment and nutrients during and after construction.

20 2. Retain eroded sediment and nutrients onsite.

21 3. Apply nutrients at rates necessary to establish and maintain vegetation without causing 

22 significant nutrient runoff to surface waters.

23 2.2.2.1 Existing Practices 

24 The National Management Measures to Control Nonpoint Sources Pollution from 

25 Hydromodification Hydromodification document (USEPApublished by EPA in 2007) provides 
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Chapter 7. Hydromodification 15 

1 information on using the following practices to control upland sources of sediment and nutrients 

2 at dams: 

3 • Check Dams 

4 • Coconut Fiber Roll 

5 • Construction Runoff Intercepts 

6 • Construction Management 

7 • Erosion Control Blankets 

8 • Locate Potential Land Disturbing Activities Away from Critical Areas 

9 • Mulching 

10 • Preserve Onsite Vegetation 

11 • Phase Construction 

12 • Retaining walls 

13 • Revegetate 

14 • Project Scheduling 

15 • Sediment Basin/ Rock Dams 

16 • Sediment fences 

17 • Sediment traps 

18 • Seeding 

19 • Site Fingerprinting 

20 • Sodding 

21 • Soil Protection 

22 • Surface Roughening 

23 • Training ESC 

24 • Wildflower cover 

25 2.2.3 Implementation Measure #3: Restore In-stream and Riparian Habitat 

26 Function 

Implementation Measure: The restoration of in-stream and riparian habitat function refers to 

the direct implementation of practices which address functions of the aquatic environment. 

Because the practices recommended as part of this implementation measure often do not address 

the causative factors behind habitat degradation, other implementation measures described in this 

document should be considered for implementation. This implementation measure was well 

described in the 2007 guidance document (formerly titled Protection of Surface Watery Quality 

and In-stream and Riparian Habitat). The primary goal of this implementation measure is

1. Provide for safe passage of fish and other aquatic species upstream or downstream of dams 

and other structures
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Chapter 7. Hydromodification 16 

1 The restoration of in-stream and riparian habitat function refers to the direct implementation of 

2 practices which address functions of the aquatic environment. Since the practices recommended 

3 as part of this implementation measure often do not address the causative factors behind 

4 degradation of habitat, other implementation measures described in this guidance document 

5 should be considered for implementation. This Implementation Measure was well described 

6 within the 2007 guidance document (formerly titled Protection of Surface Watery Quality and 

7 In-stream and Riparian Habitat). The primary goal of this implementation measure is:

8 1. Provide for safe passage of fish and other aquatic species upstream or downstream of dams 

9 and other structures.

10 2.2.3.1 Existing Practices 

11 The National Management Measures to Control Nonpoint Sources Pollution from 

12 Hydromodification document (USEPApublished by EPA in 2007) provides information on using 

13 the following practices restore in-stream and riparian habitat function: 

14 • Behavioral Barriers 

15 • Collection Systems 

16 • Fish Ladders 

17 • Fish Lifts 

18 • Physical Barriers 

19 • Transfer of Fish Runs 

20 Note: Certain other practices as described in other chapters of this document might be 

21 appropriate for use in meeting the goals of this implementation measure. For instance the Legacy 

22 effects of Dams and Dam Removal practice is included in the Implementation Measure 5: 

23 Restore Stream and Shoreline Physical Characteristics. 

24 2.2.3.2 Shoreline Sensitivity Assessment 

25 Description 

26 Shoreline Sensitivity Assessments are methodologies that apply to shoreline areas and are used 

27 to evaluate, classify and assess stability and erosion vulnerabilities in various types of lakes, 

28 reservoirs, estuaries, and coasts. 

29 Application and Purpose 

30 Langendoen et al. (2009)Langendoen (2009) found that restoration projects could benefit from

31 using proven models of stream and riparian processes to guide restoration design and to evaluate 

32 indicators of ecological integrity. The USDA has developed two such models: the channel 

33 evolution computer model (CONCEPTS) and the Riparian Ecosystem Management Model 

34 (REMM). 
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Chapter 7. Hydromodification 17 

1 Efficiency Data 

2 The physical process modules of the channel evolution model CONCEPTS and the riparian 

3 ecosystem model REMM have been integrated to create a comprehensive stream-riparian 

4 corridor model that will be used to evaluate the effects of riparian buffer systems on in-stream 

5 environmental resources (Langendoen et al. 2009).(Langendoen 2009). The models have been 

6 integrated to evaluate the impact of edge-of-field and riparian conservation measures on stream 

7 morphology and water quality. The capability of REMM to dynamically simulate streambank 

8 hydrology and plant growth has been used to study the effectiveness of a deciduous tree stand 

9 and an eastern gamagrass buffer in controlling the stability of a streambank of an incised stream 

10 in northern Mississippi. 

11 2.2.3.3 Establish and Protect Stream Buffers 

12 Description 

13 Stream buffers can provide cost-effective, long-term pollutant removal without having to 

14 construct and maintain structural controls. Specific stream buffer practices include establishing a 

15 stream buffer ordinance, developing vegetative and use strategies within management zones, 

16 establishing provisions for stream buffer crossings, integration of structural runoff management 

17 practices where appropriate and developing stream buffer education and awareness programs. 

18 Application and Purpose 

19 Establishing and protecting these areas is important to water quality protection. Land acquisition 

20 programs help to preserve areas considered critical to maintaining surface water quality. Stream 

21 buffers can also protect and maintain near-stream vegetation that attenuates the release of 

22 sediment into stream channels. Stream buffers should be protected and preserved as a 

23 conservation area because they provide many important functions and benefits, including the 

24 following: 

25 • Providing a right-of-way for lateral movement 

26 • Conveying floodwaters 

27 • Protecting streambanks from erosion 

28 • Treating runoff and reducing drainage problems from adjacent areas 

29 • Providing nesting areas and other wildlife habitat functions 

30 • Mitigating stream warming 

31 • Protecting wetlands 

32 • Providing recreational opportunities and aesthetic benefits 

33 • Increasing adjacent property values 

34 Efficiency Data 

35 The biennial National Water Quality Inventory surveys shows no reduction in the percentage of 

36 degraded miles of streams since the early 1990s despite an exponential increase in river 

37 restoration projects to improve water quality, enhance in-stream habitat and manage the riparian 

38 zone (Langendoen et al. 2009).(Langendoen 2009). This might suggest that many river 
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Chapter 7. Hydromodification 18 

1 restoration projects fail to achieve their objectives. This was found to be partly due to a lack of 

2 understanding of the dynamics of the degraded riverine system and its interaction with the 

3 riparian zone. Vegetative riparian conservation measures are commonly used to stabilize failing 

4 streambanks. The shear strength of bank soils is greatly affected by the degree of saturation of 

5 the soils and root reinforcement provided by riparian vegetation. An integrated model was used 

6 to study the effectiveness of woody and herbaceous riparian buffers in controlling streambank 

7 erosion of an incised stream in northern Mississippi. Comparison of model results with 

8 observations showed that pore-water pressures are accurately predicted in the upper part of the 

9 streambank, away from the groundwater table. Simulated pore-water pressures deviate from 

10 those observed lower in the streambank near the phreatic surface. These discrepancies are mainly 

11 caused by differences in the simulated location of the phreatic surface and simulated 

12 evapotranspiration in case of the woody buffer. The modeling exercise further showed that a 

13 coarse rooting system, e.g., as provided by trees, significantly reduced bank erosion rates for this 

14 deeply incised stream. 

15 The impact of different management of similar riparian land uses was studied in two pasture 

16 subreaches by Zaimes et al. (2008),Zaimes et al. (2006), who found that total streambank soil 

17 loss can be estimated by using magnitude of bank erosion, soil bulk density, and severely eroded 

18 bank area. Significant seasonal and yearly differences in magnitude of bank erosion and total soil 

19 loss were partially attributed to differences in precipitation and associated discharges. Riparian 

20 forest buffers had significantly lower magnitude of streambank erosion and total soil loss than 

21 the other two riparian land uses. Establishment of riparian forest buffers along all of the 

22 nonbuffered subreaches would have reduced streambank soil loss by an estimated 77 to 97 

23 percent, significantly decreasing sediment in the stream. The pasture with cattle had consistently 

24 higher magnitudes of bank erosion than those for the pasture with horses for the entire study 

25 period. The pasture with cattle was also the only subreach to show an increase in eroding stream 

26 length (3 3 percent) and eroding area (10 percent) from 1998 to 2002. Riparian vegetation and 

27 land use are an integral part of streambank erosion, but high precipitation levels and associated 

28 high discharges can also influence the erosion process. Differences in the magnitude of bank 

29 erosion, severely eroded bank lengths and areas, and soil losses throughout this study are 

30 partially attributable to differences in precipitation that were associated with the occurrence of 

31 substantial discharge events. Other processes such freeze and thaw events and season, which 

32 impacted the density of the vegetation cover of the watershed, were also implicated. The 

33 variation in soil losses from streambank erosion over the entire study period also suggest that a 

34 dataset of many years is needed to get a good estimate of bank erosion contributions to stream 

35 sediment load. One-year datasets can be misleading in estimating the long term contributions of 

36 bank erosion to stream sediment loads. 

37 A partnership involving more than a dozen organizations, agencies and businesses joined forces 

38 to construct a 800-foot living shoreline that rebuilt the barrier between the creek and the cove 

39 with natural materials, which was then planted with native plants to provide more stability 

40 (Blankenship 2009)(Alliance for the Chesapeake Bay, Blankenship, ed., November 2009). The 

41 project relied on volunteers and multiple funders and was the first project in the Chesapeake Bay 

42 that involved the Corporate Wetland Restoration Partnership, which brings together government 

43 on environmental projects. This type of restoration project was envisioned in the draft habitat 

44 report that responded to President Barack Obama’s Chesapeake Bay Executive Order of May of 
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Chapter 7. Hydromodification 19 

1 2009. The report calls for using partnerships to build strategically placed “largescale, 

2 multifaceted restoration [projects] targeted at improving living resources.” 

3 Besides the living shoreline, curved rock structures were built at both ends of the cove to protect 

4 it from waves and to trap sand that will serve as beach habitat. The project included the 

5 construction of an oyster reef, which serves as habitat and buffers the shoreline from waves. 

6 Shallow water habitats, which had largely eroded away, were rebuilt and planted with marsh 

7 grasses. Reestablishing shallow water habitat, including oyster beds and mussel beds, will serve 

8 as foraging grounds for sea ducks, which should keep Hail Creek as one of the top five 

9 waterfowl habitats for years to come. 

10 Langendoen et al. (2009)Langendoen (2009) found that restoration projects could benefit from

11 using proven models of stream and riparian processes to guide restoration design and to evaluate 

12 indicators of ecological integrity. The USDA has developed two such models: CONCEPTS and 

13 REMM. Those models have been integrated to evaluate the impact of edge-of-field and riparian 

14 conservation measures on stream morphology and water quality. The physical process modules 

15 of the channel evolution model CONCEPTS and the riparian ecosystem model REMM have 

16 been integrated to create a comprehensive, stream-riparian corridor model that will be used to 

17 evaluate the effects of riparian buffer systems on in-stream environmental resources. The 

18 capability of REMM to dynamically simulate streambank hydrology and plant growth has been 

19 used to study the effectiveness of a deciduous tree stand and an eastern gamagrass buffer in 

20 controlling the stability of a streambank of an incised stream in northern Mississippi. 

21 Cost Data 

22 A study of cost-effectiveness analysis of vegetative filter strips and in-stream half-logs as tools 

23 for recovering scores on a fish index of biotic integrity (IBI) in the upper Wabash River in 

24 Indiana provided baseline data and a framework for planning and determining the cost of stream 

25 restoration (Frimpong et al. 2006).(Frimpong et al. 2006). The authors found that costs per unit 

26 increase in IBI score with vegetative filter strips as the method of restoring stream health 

27 decreases with increasing stream order and decreasing recovery time and that vegetative filter 

28 strips is likely a useful method, given cost considerations, for recovering lost IBI scores in an 

29 agricultural watershed. Three assumptions were made about recovery time for IBI scores (5, 15, 

30 and 30 years) and social discount rates (1, 3, and 5 percent), which were tested for sensitivity of 

31 the estimated cost-effectiveness ratios. The effectiveness of vegetative filter strips was estimated 

32 using fish IBIs and riparian forest cover from 49 first-order to fifth-order stream reaches. Half33 log structures had been installed for approximately 2 years in the watershed before the study and 

34 provided a basis for estimates of cost and maintenance. Cost-effectiveness ratios for vegetated 

35 filter strips decreased from $387 to $277 per 100 meters for a 1 percent increase in IBI scores 

36 from first- to fifth-order streams with 3 percent discount and 30-year recovery. This cost 

37 weighted by proportion of stream orders was $360 per 110 meters. On the basis of installation 

38 costs and an assumption of equal recovery rates, half-logs were two-thirds to one-half as cost39 effective as vegetative filter strips. Half-logs would be a cost-effective supplement to filter strips

40 in low-order streams if they can be proven to recover IBI scores faster than using filter strips 

41 alone. 
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Chapter 7. Hydromodification 20 

1 Design Guidance and additional info 

2 Maryland Department of the Environment Water Management Administration, 2000. Maryland’s 

3 Waterway Construction Guidelines at. At

4 http://www.mde.state.md.us/assets/document/wetlandswaterways/mgwc.pdf. Accessed 

5 February 2010. 

6 2.2.3.4 Riparian Improvements 

7 Description 

8 Riparian improvements are strategies used to restore or maintain aquatic and riparian habitat 

9 around reservoir impoundments or along the waterways both upstream of and downstream from 

10 dams and include reducing sediment loading in the downstream watershed, improving riparian 

11 vegetation, eliminating barriers to fish migration, providing greater in-stream and riparian habitat 

12 diversity and reducing flow-related effects on dams. 

13 Application and Purpose 

14 Maintaining and improving riparian areas upstream of and downstream from dams is an 

15 important consideration. Riparian improvements might be necessary along smaller-order streams 

16 if their ability to detain and absorb floodwater and stormwater has been impaired—often the 

17 result of removing forest cover or increasing watershed imperviousness. Cumulative effects on 

18 riparian areas of smaller streams include increased discharge volumes and velocities of water, 

19 which then result in more severe downstream flooding and increased storm damage or 

20 maintenance to existing structures, including dams. Information on techniques to mitigate effects 

21 on smaller streams can is also in the Urban Section of this guidance (Chapter 3). 

22 Design Guidance and additional info 

23 The Iowa Department of Natural Resources (no date) recommends that the property owner or 

24 developer estimate the amount of time, materials, equipment, and labor necessary to complete 

25 the work as compared to those personally available. This is a subjective decision based on time, 

26 knowledge, and resource constraints. 

27 a. Construction activities should be conducted during periods of low flow. 

28 b. Construction equipment, activities, and materials should be kept out of the water to the 

29 maximum extent possible. 

30 c. All construction debris should be disposed of on land in such a manner that it cannot 

31 enter a waterway or wetland. 

32 d. Equipment for handling and conveying materials during construction should be operated 

33 to prevent dumping or spilling the material into waterbodies, streams, or wetlands. 

34 e. Care should be taken to prevent any petroleum products, chemicals, or other deleterious 

35 materials from entering waterbodies, streams, or wetlands. 

36 f. Clearing of vegetation, including trees located in or immediately adjacent to waters of the 

37 state, should be limited to that which is absolutely necessary for construction of the 
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Chapter 7. Hydromodification 21 

1 project. All vegetative clearing material shall be removed to an upland, non-wetland 

2 disposal site. 

3 Each of the methods described in the manual requires observation and maintenance of the 

4 streambank erosion control practices over time. Observations should be made regularly before 

5 and after major stream flow events. Maintenance activities should include the following: 

6 • Remove any debris that becomes entangled in the erosion control material and could 

7 damage the bank materials. 

8 • Replace missing or damaged erosion control materials during times of low stream flow. 

9 • Apply fertilizer to plant materials to enhance their growth each year. 

10 • Apply fertilizer and weed control to buffer strip vegetation. 

11 • Restrict livestock from steep banks and the areas containing the erosion control measures. 

12 Riparian Buffers 

13 Riparian buffers are described in Chapter 5 of this document. 

14 2.2.3.5 Vegetated Buffers 

15 Description 

16 Vegetated buffers are a naturally occurring, composed of vegetative areas that provide physical 

17 separation between a waterbody and adjacent land uses. 

18 Application and Purpose 

19 Vegetated buffers remove nutrients and other pollutants from runoff, trap sediments, and shade 

20 the waterbody to optimize light and temperature conditions for aquatic plants and animals. 

21 Efficiency Data 

22 Protection or restoration of modest-sized patches of living shoreline can provide adequate prime 

23 waterfowl habitat (Blankenship 2009).(Alliance for the Chesapeake Bay, Blankenship, ed.,

24 November 2009). Hail Creek, a tiny waterway at the tip of a peninsula that is separated by a 

25 narrow swath of land from the Chester River, is shorter than a half-mile long, but despite its 

26 diminutive size, the creek and its surrounding marshes, part of the Eastern Neck National 

27 Wildlife Refuge, are one of the top five waterfowl habitats in Maryland, with large 

28 concentrations of bufflehead and scaup, as well as black ducks, Canada geese, and other species. 

29 The creek contains about 100 acres of underwater grasses, in contrast with nearby areas where 

30 grasses have been declining. Those habitats have faced increasing danger in recent years from 

31 rising water levels that have been eating away at a narrow barrier of land that separates the 

32 upstream end of the creek from Hail Cove along the Chester River. If breached, the sheltered 

33 creek habitats and adjoining wetlands would suddenly be subjected to highly erosive waves. 

34 Besides the living shoreline, curved rock structures were built at both ends of the cove to protect 

35 it from waves and to trap sand that will serve as beach habitat. The project included constructing 

36 an oyster reef, which serves as habitat and buffers the shoreline from waves. Shallow water 

37 habitats, which had largely eroded away, were rebuilt and planted with marsh grasses. 
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Chapter 7. Hydromodification 22 

1 Reestablishing shallow water habitat, including oyster beds and mussel beds, will serve as 

2 foraging grounds for sea ducks, which should keep Hail Creek as one of the top five waterfowl 

3 habitats for years to come. 

4 Cost Data 

5 A partnership involving more than a dozen organizations, agencies and businesses joined forces 

6 to construct a 800-foot living shoreline that rebuilt the barrier between the creek and the cove 

7 with natural materials, which was then planted with native plants to provide more stability. The 

8 project relied on volunteers and multiple funders and was the first project in the Chesapeake that 

9 involved the Corporate Wetland Restoration Partnership, which brings together government on 

10 environmental projects. This type of restoration project was envisioned in the draft habitat report 

11 that responded to President Barack Obama’s Executive Order of May 2009 that calls for using 

12 partnerships to build strategically placed “largescale, multifaceted restoration [projects] targeted 

13 at improving living resources.” 

14 2.2.3.6 Vegetated Filter Strips 

15 Description 

16 Vegetated filter strips are low-gradient vegetated areas that filter overland sheet flow. Runoff 

17 must be evenly distributed across the filter strip and channelized flows decrease their 

18 effectiveness. 

19 Application and Purpose 

20 Vegetated filter strips should have relatively low slopes and adequate length to provide optimal 

21 sediment control and should be planted with erosion-resistant plant species. The main factors that 

22 influence the removal efficiency are the vegetation type, soil infiltration rate, and flow depth and 

23 travel time. These factors are dependent on the contributing drainage area, slope of strip, degree 

24 and type of vegetative cover, and strip length. Maintenance requirements for vegetated filter 

25 strips include sediment removal and inspections to ensure that dense, vigorous vegetation is 

26 established and concentrated flows do not occur. 

27 Efficiency Data 

28 A study of cost-effectiveness analysis of vegetative filter strips and in-stream half-logs as tools 

29 for recovering scores on a fish IBI in the upper Wabash River in Indiana provided baseline data 

30 and a framework for planning and determining the cost of stream restoration (Frimpong et al. 

31 2006).(Frimpong et al. 2006). Three assumptions were made about recovery time for IBI scores 

32 (5, 15, and 30 years) and social discount rates (1, 3, and 5 percent), which were tested for 

33 sensitivity of the estimated cost-effectiveness ratios. The effectiveness of vegetative filter strips 

34 was estimated using fish IBIs and riparian forest cover from 49 first-order to fifth-order stream 

35 reaches. Half-log structures had been installed for approximately two years in the watershed 

36 before the study and provided a basis for estimates of cost and maintenance. 

37 Cost Data 

38 Frimpong et al. (2006)(2006) found that costs per unit increase in IBI score with vegetative filter 

39 strips as the method of restoring stream health decreases with increasing stream order and 
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Chapter 7. Hydromodification 23 

1 decreasing recovery time and that vegetative filter strips is likely a useful method, given cost 

2 considerations, for recovering lost IBI scores in an agricultural watershed. Cost-effectiveness 

3 ratios for vegetated filter strips decreased from $387 to $277 per 100 meters for a 1 percent 

4 increase in IBI scores from first- to fifth order streams with 3 percent discount and 30-year 

5 recovery. This cost weighted by proportion of stream orders was $360 per 110 meters. Based on 

6 installation costs and an assumption of equal recovery rates, half-logs were two-thirds to one-half 

7 as cost-effective as vegetative filter strips. Half-logs would be a cost-effective supplement to 

8 filter strips in low order streams if they can be proven to recover IBI scores faster than using 

9 filter strips alone. 

10 2.2.4 Implementation Measure #4: Reduce Pollutant Sources through 

11 Operational and Design Management 

Implementation Measure: Reduction of pollutant sources through operational and design 

management of dams refers to the design and management of dams so as to minimize the source 

generation and reduce the transport of sediments and nutrients into the Chesapeake Bay and its 

watershed. This implementation measure was well described in the 2007 guidance document 

(formerly titled Erosion and Sediment Control for Construction of New Dams and Maintenance 

of Existing Dams). The goals of this implementation measure are

1. Reduce pollutant generation and impact on living resources through programmatic dam 

management

2. Design structures to limit pollutant generation

12 Reduction of pollutant sources through operational and design management of dams refers to the 

13 design and management of dams so that minimize the source generation reduce the transport of 

14 sediments and nutrients into the Chesapeake Bay and its watershed. This Implementation 

15 Measure was well described within the 2007 guidance document (formerly titled Erosion and 

16 Sediment Control for Construction of New Dams and Maintenance of Existing Dams). The goals 

17 of this implementation measure are

18 1. Reduce pollutant generation and impact on living resources though programmatic dam 

19 management.

20 2. Design structures to limit pollutant generation

21 2.2.4.1 Existing Practices 

22 The National Management Measures to Control Nonpoint Sources Pollution from 

23 Hydromodification document (USEPApublished by EPA in 2007) provides information on using 

24 the following practices to reduce pollutant sources through design and operational management: 
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Chapter 7. Hydromodification 24 

1 2.2.4.2 Advanced Hydroelectric Turbines 

2 Description 

3 Advanced hydroelectric turbines are the result of engineering studies of how the hydraulic 

4 components interact with biota and optimization of turbine operations designed to reduce effects 

5 on juvenile fish passing through the turbine as it operates. 

6 Application and Purpose 

7 Most research on advanced hydroelectric turbines has been conducted by electric power 

8 producers in the western United States. Improving the survival of juvenile fish by encouraging 

9 development of low impact turbines is also being pursued on a national scale by the U.S. 

10 Department of Energy and the U.S. Army Corps of Engineers. Research includes biological 

11 studies of turbine passage at field sites and hydraulic model investigations leading to innovative 

12 concepts for turbine design that will have environmental benefits and maintain efficient electrical 

13 generation. 

14 Efficiency Data 

15 Previous field studies have shown that improvements in the design of turbines have increased the 

16 survival of juvenile fish and researchers continue to examine the causes and extent of injuries 

17 from turbine systems, as well as the significance of indirect mortality and the effects of turbine 

18 passage on adult fish. Ongoing research is continuing to assess improvements in turbine design 

19 and operation as well as modeling to assess turbine-passage survival. 

20 2.2.4.3 Flow Augmentation 

21 Description 

22 Flow augmentation is the term used to describe operational procedures such as flow regulation, 

23 flood releases, or fluctuating flow releases that all have the potential for detrimental impacts on 

24 downstream aquatic and riparian habitat. Several options exist for creating minimum flows in the 

25 tailwaters below dams. Sluicing is the practice of releasing water through the sluice gate rather 

26 than through the turbines. For portions of the waterway immediately below the dam, the steady 

27 release of water by sluicing provides minimum flows with the least amount of water expenditure. 

28 Turbine pulsing is a practice involving the release of water through the turbines at regular 

29 intervals to improve minimum flows. In the absence of turbine pulsing, water is released from 

30 large hydropower dams only when the turbines are operating, which is typically when the 

31 demand for power is high. 

32 Application and Purpose 

33 The downstream impacts that can be mitigated through the use of flow augmentation are highly 

34 variable as each impounded system is unique. The location of a dam within a river system, its 

35 age, depth and surface area, the hydraulic residence time, the regional climate, operation of the 

36 dam, and chemistry of the inflowing waters all influence how impoundments affects downstream 

37 water quality. Hydropower producers are faced with two environmental problems that can affect 

38 the water quality in areas downstream from dams (i.e., tailwaters). These are low concentrations 

39 of dissolved oxygen in the water released through the dam during generation and dry riverbeds 
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Chapter 7. Hydromodification 25 

1 that result when hydropower generation is shut off. The selection of any particular technique as 

2 the most cost-effective is site-specific and depends on several factors including adequate 

3 performance to achieve the desired in-stream and riparian habitat characteristic, compatibility 

4 with other requirements for operation of the hydropower facility, availability of materials, and 

5 cost. 

6 Efficiency Data 

7 Numerous studies have examined the effects of flow regulation on water quantity and quality by 

8 comparing an impounded system with an adjacent unimpounded system. Mitigation techniques 

9 to improve ecosystem health downstream of impoundments rely on the restoration of a more 

10 natural flow regime by creating and implementing site-specific dam management plans. 

11 A study by Ahearn et al. (2005)Ahern (2005) examined the effects of flow regulation on water 

12 quantity and quality by comparing an impounded system with an adjacent unimpounded system 

13 in California. The study found that a strong seasonal cycle for total suspended solids, NO3-N, 

14 TNtotal nitrogen, PO4-P, TPtotal phosphorus, dissolved silicon, specific conductivity and flow

15 into reservoirs in the lower Mokelumne River was attenuated by physical and chemical 

16 fluctuations creating a weak seasonal pattern. Dissolved silicon and total suspended solids were 

17 the two constituents most efficiently sequestered by the reservoirs. While the reservoirs acted as 

18 traps for most constituents, NO3-N and PO4-P were produced during the drier years of the study, 

19 2001 and 2002. In contrast, the unimpounded reference reach in the Cosumnes River was an 

20 annual source for all constituents measured. The Cosumnes delivers its highest NO3-N 

21 concentrations during the winter months (December–April), while peak concentrations in the 

22 Mokelumne occur during the snowmelt (May–July) and baseflow (August–November) seasons. 

23 Because of downstream N-limitation, this temporal shift in NO3-N export might be contributing 

24 to accelerated algal growth in the reach immediately downstream and eventually to algal biomass 

25 loading to the downstream Sacramento–San Joaquin Delta. 

26 In 2003 the Housatonic Valley Association (HVA) partnered with The Massachusetts Riverways 

27 Program (in the Department of Fish & Game) to begin measuring streamflow on several rivers 

28 below recreational reservoirs. The measurements indicated unnatural variations in streamflow at 

29 several sites that are detrimental to downstream aquatic life and habitat. A more natural flow 

30 regime is being reestablished in these streams to improve their ecological condition. The HVA 

31 has been meeting with Conservation Commissions, Lake Associations, and other stakeholders to 

32 develop guidelines for managing flows out of reservoirs. The goal is to improve ecosystem 

33 health downstream of impoundments through the restoration of a more natural flow regime by 

34 creating site-specific dam management plans in the form of monthly flow recommendations 

35 using a methodology jointly developed by the U.S. Geological Survey (USGS) and the 

36 Massachusetts Department of Conservation and Recreation (DCR). The long-term goal is to 

37 develop guidance for Conservation Commissions throughout the Commonwealth to help them 

38 craft Orders of Conditions for dam projects that include specific requirements to provide a year39 round flow regime appropriate to the natural variability of the ecosystem downstream of the 

40 impoundment. 
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Chapter 7. Hydromodification 26 

1 Cost Data 

2 Since the early 1990s, the Tennessee Valley Authority (TVA) has spent about $60 million to 

3 address dissolved oxygen problems, including the installation of equipment to increase dissolved 

4 oxygen concentrations below 16 dams and operational changes and installation of additional 

5 equipment to ensure minimum water flows through all its dams. TVA has since completed a 

6 second round of improvements by installing or enhancing oxygen systems at nine projects and 

7 two new autoventing turbines have been installed at the Boone Dam. The additional oxygenation 

8 capacity will help offset the increased oxygen demands associated with delaying the seasonal 

9 drawdown of TVA reservoirs. 

10 References

11 Ahearn, D.S., R. Sheibley and R. Dalhlgren. Effects of River Regulation on water QWuality in 

12 the Lower Mokelumne River, California. In River Res. Applic. 21: 651–670 (2005).

13 Published online 8 June 2005 in Wiley InterScience (www.interscience.wiley.com). DOI: 

14 10.1002/rra.853

15 Tennessee Valley Authority, No Date. Tailwater Improvements: Improving Water Quality Below 

16 TVA Hydropower Dams

17 2.2.4.4 Selective Withdrawal 

18 Description 

19 Selective withdrawal from a reservoir describes the use of intake structures on reservoirsdams

20 that are capable of releasing waters from specific locations within a stratifiedof different

21 temperatures to provide cooler or warmer water column to addresstemperatures downstream 

22 water quality objectives. at times that are critical for other in-stream resources.

23 Application and Purpose 

24 Selective withdrawalTemperature control in reservoir releases depends on the volume of water 

25 storage in the reservoir, the timing of the release relative to storage time, and the level from 

26 which the water is withdrawn. Selective withdrawal takes advantage of the phenomenon of 

27 reservoir stratification, in which the water column exhibits various quality characteristics 

28 respective to water depth. Multilevel intake devices in storage reservoirs allow selective 

29 withdrawal of water based on temperature, and DO levels or other stratified water quality 

30 characteristics. These can be particularly useful in stratified reservoirs so that they can be 

31 operated to meet downstream water quality temperature objectives such as to enhance a cold32 water or warm-water fishery or to maintain downstream temperature conditions or minimize the 

33 turbidity of discharge waters. While most selective withdrawal intakes structures are built during 

34 initial reservoir construction, release structures can be successfully modified to incorporate 

35 selective withdrawal as a retrofit, although this may be costly. .
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Chapter 7. Hydromodification 27 

1 2.2.4.5 Turbine Operation 

2 Description 

3 Turbine operations include implementation of changes in the turbine start-up procedures that can 

4 enlarge the zone of withdrawal to include more of the epilimnetic waters in the downstream 

5 releases. 

6 Application and Purpose 

7 In an improvement effort that included changes in turbine operation, the Tennessee valley 

8 Authority (TVA) made operational changes and installed additional equipment to ensure 

9 minimum water flows through its dams. 

10 Cost Data 

11 Since the early 1990s, the TVA has spent about $60 million to address DO problems below 

12 dams, including turbine operation. 

13 Reference 

14 Tennessee Valley Authority, No Date. Tailwater Improvements: Improving Water Quality Below 

15 TVA Hydropower Dams. 

16 2.2.4.6 Turbine Venting 

17 Description 

18 Turbine venting is the practice of injecting air into water as it passes through a turbine. If vents 

19 are provided inside the turbine chamber, the turbine will aspirate air from the atmosphere and 

20 mix it with water passing through the turbine as part of its normal operation. Autoventing 

21 turbines are constructed with hub baffles, or deflector plates placed on the turbine hub upstream 

22 of the vent holes to enhance the low-pressure zone in the vicinity of the vent and thereby 

23 increase the amount of air aspirated through the venting system. 

24 Application and Purpose 

25 Developments in turbine venting technology show potential for aspirating air with no resulting 

26 decrease in turbine efficiency, however, the application of turbine venting technologies is site27 specific and outcomes will vary considerably. 

28 Efficiency Data 

29 Turbine efficiency relates to the amount of energy output from a turbine per unit of water passing 

30 through the turbine. Efficiency decreases as less power is produced for the same volume of 

31 water. In systems where the water is aerated before passing through the turbine, part of the water 

32 volume is displaced by the air, thus leading to decreased efficiency. 
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Chapter 7. Hydromodification 28 

1 2.2.5 Implementation Measure #5: Restore Stream and Shoreline Physical 

2 Characteristics 

Implementation Measure: The restoration of stream and shoreline physical characteristics is 

important to restoring predevelopment hydrology and reducing loading from larger and scouring 

flows. Degraded streams can themselves become a source of downstream pollution, such as 

when phosphorus-laden sediments are mobilized during high flow events. In such cases, stream 

restoration can be a useful strategy to improve downstream water quality. However, it is 

important to keep in mind that the elevated flows causing sediment mobilization must also be 

addressed (see the Urban chapter). Stream stabilization requires restoration of the stream’s 

energy signature. The predevelopment hydrology of the watershed must be restored to regain the 

predevelopment character of the stream; however, in existing urban areas, that might be a longerterm goal. The primary goal of this implementation measure is to

1. Restore stable relationship between watershed hydrology and stream and shoreline geometry. 

Where streambank or shoreline erosion is a nonpoint source pollution problem, streambanks 

and shorelines should be stabilized. Vegetative methods are strongly preferred unless 

structural methods are more effective, considering the severity of stream flow discharge, wave 

and wind erosion, offshore bathymetry, and the potential adverse effect on other streambanks, 

shorelines, and offshore areas.

3 Stream restoration can help to restore the natural ecosystem function of N removal that occurs in 

4 streams. Studies that evaluate the N removal ability of restored streams are summarized in Table 

5 7-2.

6 Table 7-2. Studies evaluating the N removal ability of restored streams in the chesapeake bay 

7 watershed

8 The restoration of stream and shoreline physical characteristics is important to restoring 

9 predevelopment hydrology and reducing loading from larger and scouring flows. Degraded 

10 streams can themselves become a source of downstream pollution, such as when phosphorus11 laden sediments are mobilized during high flow events. In such cases, stream restoration can be a 

12 useful strategy to improve downstream water quality. However, it is important to keep in mind 

13 that the elevated flows causing sediment mobilization must also be addressed (see urban 

14 chapter). Stream stabilization requires restoration of the stream’s energy signature. The 

15 predevelopment hydrology of the watershed must be restored to regain the predevelopment 

16 character of the stream; however, in existing urban areas, that might be a longer term goal. The 

17 primary goal of this implementation measure is to

18 1. Restore stable relationship between watershed hydrology and stream and shoreline geometry. 

19 Where streambank or shoreline erosion is a nonpoint source pollution problem, streambanks 

20 and shorelines should be stabilized. Vegetative methods are strongly preferred unless 

21 structural methods are more effective, considering the severity of stream flow discharge, wave 

22 and wind erosion, offshore bathymetry, and the potential adverse effect on other streambanks, 

23 shorelines, and offshore areas.
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Chapter 7. Hydromodification 29 

1 Stream restoration can help to restore the natural ecosystem function of nitrogen removal that 

2 occurs in streams. Studies that evaluate the nitrogen removal ability of restored streams are 

3 summarized in Table 7-2.

4 Table 7-2. Studies Evaluating the Nitrogen Removal Ability of Restored Streams in the 

5 Chesapeake Bay Watershed

Study Finding 

Kausal, Sujay S., et.al. Effects of Stream 

Restoration on Denitrification in an Urbanizing 

Watershed. Ecological Applications, 18(3), 2008, 

pp. 789-804. 

Streams with ecological functions intact remove 

Nnitrogen at a much higher rate than degraded 

urban streams, and stream restoration practices 

can restore this Nnitrogen removal function 

Klocker et al. Nitrogen uptake and denitrification in 

restored and unrestored streams in urban 

Maryland, USA. Aquatic Sciences, Accepted 

October 2009. 

Degraded urban streams, deeply eroded and 

disconnected from their floodplain have 

substantially lower rates of Nnitrogen removal that 

than streams hydraulically connected to their 

riparian banks via low slopes, and reconnecting 

the stream to the floodplain can increase 

6 In addition to the water quality improvements that can be achieved through stream restoration, 

7 the flood management community has become increasingly aware of the benefits of restoration 

8 in preventing flood damages. The Association of State Floodplain Managers (ASFPM) has 

9 prepared a white paper called Natural and Beneficial Floodplain Functions: Floodplain 

10 Management— More than Flood Loss Reduction (http://www.floods.org), which emphasizes the 

11 multiple benefits of protecting and restoring streams and their associated floodplains. 

12 Techniques for stream and floodplain restoration are also described in the Riparian Section of 

13 this guidance document. Example references for stream restoration, and for information on the 

14 impacts of urban runoff to stream ecosystems, are provided in Table 7-3. 

15 Table 7-3. References on urban stormwater effects on streams with emphasis on restoration and 

16 habitat

USDA Natural Resources Conservation Service, Part 654 Stream Restoration Design National 

Engineering Handbook, 210–VI–NEH, August 2007 

Federal Interagency Stream Restoration Working Group (FISRWG) (1998). Stream Corridor 

Restoration: Principles, Processes, and Practices, ISBN-0-934213-60-7, Distributed by the National 

Technical Information Service at 1-800-533-6847.

Infiltration vs. Surface Water Discharge: Guidance for Stormwater Managers, Final Report. 03-SW-4, 

Water Environment Research Federation (WERF 2006) Appendix B. Assessment of Existing 

Watershed Conditions: Effects on Habitat. 

17 2.2.5.1 Existing practices 

18 The National Management Measures to Control Nonpoint Sources Pollution from 

19 Hydromodification document (USEPApublished by EPA in 2007) provides information on using 

20 the following practices to restore stream and shoreline physical characteristics: 

21 • Branch Packing 

22 • Brush Layering 
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Chapter 7. Hydromodification 30 

1 • Dormant Post Plantings 

2 • Root Wad Revetments 

3 • Tree Revetments 

4 2.2.5.2 Bank Shaping and Planting 

5 Description 

6 Bank shaping and planting involves regrading a streambank to establish a stable slope angle, 

7 placing topsoil and other material needed for plant growth on the streambank, and selecting and 

8 installing appropriate plant species on the streambank. 

9 Application and Purpose 

10 Bank shaping and planting is most successful on streambanks where moderate erosion and 

11 channel migration are anticipated. Reinforcement at the toe of the bank is often required, 

12 particularly where flow velocities exceed the tolerance range for plantings and where erosion 

13 occurs below base flows. 

14 Efficiency Data 

15 Nearly 400 rock riprap grade-control structures (hereafter GCS) were recently placed in streams 

16 of western Iowa, to reduce streambank erosion and protect bridge infrastructure and farmland. In 

17 that region, streams are characterized by channelized reaches, highly incised banks, and silt and 

18 sand substrates that normally support low macroinvertebrate abundance and diversity. Therefore, 

19 GCS composed of riprap provide the majority of coarse substrate habitat for benthic 

20 macroinvertebrates in these streams. Litvan et al. (2008) sampled 20 sites on Walnut Creek, 

21 Montgomery County, Iowa, to quantify macroinvertebrate assemblage characteristics (1) on GCS 

22 riprap, (2) at sites 5–50 m upstream of GCS, (3) at sites 5–50 m downstream of GCS and (4) at 

23 sites at least 1 km from any GCS (five sites each). Macroinvertebrate biomass, numerical 

24 densities and diversity were greatest at sites with coarse substrates, including GCS sites and one 

25 natural riffle site and relatively low at remaining sites with soft substrates. Densities of 

26 macroinvertebrates in the orders Ephemeroptera, Trichoptera, Diptera, Coleoptera and 

27 Acariformes were abundant on GCS riprap. Increases in macroinvertebrate biomass, density, and 

28 diversity at GCS might improve local efficiency of breakdown of organic matter and nutrient and 

29 energy flow, and provide enhanced food resources for aquatic vertebrates. However, lack of 

30 positive macroinvertebrate responses immediately upstream and downstream of GCS suggest 

31 that positive effects might be restricted to the small areas of streambed covered by GCS. 

32 Improved understanding of GCS effects at both local and ecosystem scales is essential for stream 

33 management when these structures are present. 

34 2.2.5.3 Brush Mattressing 

35 Description 

36 A brush mattress is a layer (mattress) of interlaced live branches placed on a bank face, often 

37 with a live fascine and/or rock at the base. This mat is then secured to the bank by live and/or 

38 dead stakes and partially covered with fill soil to initiate growth of the cuttings. 
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Chapter 7. Hydromodification 31 

1 Application and Purpose 

2 Brush mattressing is commonly used in Europe for streambank protection. It involves digging a 

3 slight depression on the bank and creating a mat or mattress from woven wire or single strands of 

4 wire and live, freshly cut branches from sprouting trees or shrubs. Branches approximately one 

5 inch in diameter are normally cut 6 to 9 feet long (the height of the bank to be covered) and laid 

6 in criss-cross layers with the butts in alternating directions to create a uniform mattress with few 

7 voids. The mattress is then covered with wire secured with wooden stakes 2.5 to 4 feet long. It is 

8 then covered with soil and watered repeatedly to fill voids with soil and facilitate sprouting; 

9 however, some branches should be left partially exposed on the surface. The structure might 

10 require protection from undercutting by placement of stones or burial of the lower edge. Brush 

11 mattresses are generally resistant to waves and currents and provide protection from the digging 

12 out of plants by animals. Disadvantages include possible burial with sediment in some situations 

13 and difficulty in making later plantings through the mattress. 

14 Brush mattresses can restore riparian vegetation and habitat and enhance conditions for 

15 colonization of native plants. They reduce soil erosion and intercept sediment flowing down the 

16 streambank. After vegetation reaches a height of a few feet, it can improve fish habitat by 

17 shading the stream, lowering water temperatures and offering protection from predators (Allen 

18 and Fischenich 2000). Brush mattresses are also useful on steep, fast-flowing streams. 

19 Cost Data 

20 Costs for brush mattresses range between $3 and $14 per square foot (Allen and Fischenich 

21 2000). Costs can be reduced by using free material from donation sites and volunteer labor. 

22 Costs related to project permitting or planning are not included in the estimate. 

23 Design Guidance and additional info 

24 Installation guidelines are available from the USDA-FS Soil Bioengineering Guide (USDA-FS 

25 2002). Under the Ecosystem Management and Restoration Research Program (EMRRP), the 

26 USACE has presented research on brush mattresses in a technical note (Brush Mattresses for 

27 Streambank Erosion Control). 

28 2.2.5.4 Cross Vanes 

29 Description 

30 A rock cross vane is a stone structure consisting of footer and vane rocks constructed in a way 

31 that provides grade control and reduces bank erosion. The vane is composed of a center section 

32 perpendicular to the streambanks joined to two arms that extend into the streambank at the 

33 channel flow height. The rock cross vane accumulates sediment behind the vane arms, directs 

34 flow over the cross vane, and creates a scour pool downstream of the structure. 

35 Application and Purpose 

36 Low profile in-stream structures, such as cross vanes, are primarily used to create aquatic habitat 

37 in the form of scour pools and for grade control on incising streams and rivers. Additionally, they 

38 are well-suited for channeling flow away from unstable banks. Cross vanes are typically suited 

39 for use in moderate to high gradient streams. When constructed and spaced properly, cross vanes 
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Chapter 7. Hydromodification 32 

1 can simulate the natural pattern of pools and riffles occurring in undisturbed streams while 

2 forming gravel deposits which fish use as spawning grounds. Cross vanes can also be used to 

3 stabilize banks when designed properly. Cross vanes should be avoided in channels with bedrock 

4 beds or unstable bed substrates, and streams with naturally well developed pool-riffle sequences. 

5 Cross Vanes are appropriate for the following: 

6 • Stabilization of a vertically unstable stream bed requires grade control 

7 • To direct erosional forces away from the streambanks and to the center of the channel 

8 • When fish habitat enhancement and grade control are both desired 

9 • For bridge protection. Cross vanes provide grade controls, prevent lateral migration of 

10 channels, increase sediment transport capacity and competence, and reduce footer scour 

11 • To enhance or create recreational paddling opportunities 

12 • Most suitable for rapid-dominated stream systems with gravel/cobble substrate 

13 Cost Data 

14 Construction costs for cross vanes are highly variable, depending on the design, size of the stone, 

15 availability of materials, and site constraints. 

16 2.2.5.5 Joint Planting 

17 Description 

18 Joint planting involves tamping live stakes of rootable plant material or rooted cuttings into soil 

19 in the interstices of porous revetments, riprap, or other retaining structures. 

20 Joint planting is useful where rock riprap is required or already in place. It is successful 30 to 50 

21 percent of the time, with first year irrigation improving survival rates. Live cuttings must have 

22 side branches removed and bark intact. They should range from 0.5 to 1.5 inches in diameter and 

23 be long enough to extend well into the soil, reaching into the dry season water level. 

24 Application and Purpose 

25 Joint planting can improve aquatic habitat by providing food and cover in the riparian zone and 

26 over the water when they are used in close proximity to the edge of the stream. Stone used at the 

27 base of the joint planting produces substrates suited for an array of aquatic organisms. Some of 

28 these organisms adapt to living on and within the rocks and some attach to the leaves and stems. 

29 The leaves and stems can also become food for shredders. 

30 Species for joint planting systems can be selected to provide color, texture, and other attributes 

31 that add a pleasant, natural landscape appearance. Such plants for these systems include willow 

32 (Salix spp.), which tends to be the best from an adventitious rooting perspective and is normally 

33 an excellent choice. However other species such as poplar (Populus spp.), Viburnum spp., 

34 Hibiscus spp., shrub dogwood (Cornus spp.) and buttonbush (Cephalanthus), also work well. 

35 After establishment, joint planting system can reduce non-point pollution by intercepting 

36 sediment and attached pollutants that otherwise enter the stream from overbank flow areas. 
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Chapter 7. Hydromodification 33 

1 Cost Data 

2 Joint planting ranges in cost between $1 to $5 per square foot (Gray 1996).(Gray and Sotir 

3 1996). Costs do not include riprap and assumes a spacing of 4 cuttings per square yard. 

4 Design Guidance and additional info 

5 Installation guidelines are available from the USDA FS Soil Bioengineering Guide (USDA-FS 

6 2002) and the USDA NRCS Engineering Field Handbook, Chapter 18 (USDA-NRCS 1992). 

7 2.2.5.6 Legacy Effects of Dams and Dam Removal 

8 Description 

9 Dam removal is the process of dismantling and removing unsafe, unwanted or obsolete dams and 

10 restoring the original stream gradient to the extent possible. 

11 Application and Purpose 

12 Dams serve a variety of important social and environmental purposes, including water supply, 

13 flood control, power generation, wildlife habitat and recreation (USEPA 2007). Dam removal is 

14 undertaken either by owners of the dam or by public agencies and might become necessary for 

15 various reasons. These include most notably the physical or structural deterioration of the dam 

16 resulting in a public safety risk, sediment accumulation in the impoundment/reservoir behind the 

17 dam and corresponding deleterious effects on the quality and quantity of water supplies. There 

18 are many things to consider when removing a dam, one of which is the function(s) of the dam 

19 and the status of that function (active vs. inactive). Sometimes the need for the dam is no longer 

20 be as important as it once was, usually because of economic considerations. Finally, ecological 

21 concerns sometimes drive the need for dam removal. For example, migratory fish passage 

22 throughout United States rivers and streams is obstructed by over 2 million dams and many other 

23 barriers such as blocked, collapsed, and perched culverts (USEPA 2007). Because dams are 

24 capital intensive, long-term ventures, the opportunity for dam removal typically occurs 

25 infrequently, often corresponding to their periodic licensing renewal. 

26 Efficiency Data 

27 Many rivers and streams of the Mid-Atlantic Region, United States have been altered by 

28 postcolonial floodplain sedimentation (legacy sediment) associated with numerous milldams. 

29 Little Conestoga Creek, Pennsylvania, a tributary to the Susquehanna River and the Chesapeake 

30 Bay, is one of these streams. Floodplain sedimentation rates, bank erosion rates, and channel 

31 morphology were measured annually during 2004-2007 at five sites along a 28-km length of 

32 Little Conestoga Creek with nine colonial era milldams (one dam was still in place in 2007). A 

33 study by Schenk and Hupp (2009)Schenk et al. (2009) was part of a larger cooperative effort to 

34 quantify floodplain sedimentation, bank erosion, and channel morphology in a high sediment 

35 yielding region of the Chesapeake Bay watershed. 

36 Data from the five sites were used to estimate the annual volume and mass of sediment stored on 

37 the floodplain and eroded from the banks for 14 segments along the 28-km length of creek. A 

38 bank and floodplain reach based sediment budget (sediment budget) was constructed for the 28 

39 km by summing the net volume of sediment deposited and eroded from each segment. Mean 
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Chapter 7. Hydromodification 34 

1 floodplain sedimentation rates for Little Conestoga Creek were variable, with erosion at one 

2 upstream site (5 mm⁄ year) to deposition at the other four sites (the highest was 11 mm⁄ year) 

3 despite over a meter of floodplain aggradation from postcolonial sedimentation. Mean bank 

4 erosion rates range between 29 and 163 mm⁄ year among the five sites. Bank height increased 1 1 

5 m for every 10.6 m of channel width, from upstream to downstream (R2 = 0.79, p < 0.0001) 

6 resulting in progressively lowered hydraulic connectivity between the channel and the 

7 floodplain. 

8 A knickpoint approximately 9 km upstream of the dam has produced a net erosional environment 

9 in the upstream two river segments. The floodplain experienced short periods of inundation 

10 nearly annually at the USGS streamgage, between the knickpoint and the dam, despite the 

11 heightened banks from postcolonial sedimentation and subsequent dam removals. Sediment 

12 trapping was recorded at four of the five study sites, indicating that the aggraded Little 

13 Conestoga Creek floodplain still functions as a sediment sink. 

14 The study concluded that dam removals have many benefits, but they come with the cost of 

15 remobilizing large amounts of sediment. Managers and policy makers in the Northeast and Mid16 Atlantic states will have the additional burden of managing the storage and transport of legacy 

17 sediment. Dam removals in these regions can lead to large and sustained sediment pulses as 

18 legacy sediment is remobilized and transported further downstream, where increased 

19 sedimentation is a critical concern for imperiled estuarine resources, in this case the Susquehanna 

20 River and the Chesapeake Bay. 

21 Gravel-bedded streams are thought to have a characteristic meandering form bordered by a self 

22 formed, fine-grained floodplain. This ideal guides a multibillion-dollar stream restoration 

23 industry. Walter and Merritts (2008)Walter et al. (2008) mapped and dated many of the deposits 

24 along mid-Atlantic streams that formed the basis for this widely accepted model. These data, as 

25 well as historical maps and records, show instead that before European settlement, the streams 

26 were small anabranching channels within extensive vegetated wetlands that accumulated little 

27 sediment but stored substantial organic carbon. Subsequently, 1 to 5 meters of slackwater 

28 sedimentation, behind tens of thousands of 17th- to 19th-century milldams, buried the 

29 presettlement wetlands with fine sediment. These findings show that most floodplains along mid30 Atlantic streams are actually fill terraces, and historically incised channels are not natural 

31 archetypes for meandering streams. The study concludes that fluvial aggradation and degradation 

32 in the eastern United States were caused by human-induced base level changes from the 

33 following processes: 

34 • Widespread milldam construction that inundated presettlement valleys and converted 

35 them into a series of linked slackwater ponds, coupled with deforestation and agricultural 

36 practices that increased sediment supply 

37 • Sedimentation in ubiquitous millponds that gradually converted these ponds to sediment38 filled reservoirs 

39 • Subsequent dam breaching that resulted in channel incision through postsettlement 

40 alluvium and accelerated bank erosion by meandering streams 

41 • The formation of an abandoned valleyflat terrace and a lower inset floodplain, which 

42 explains why so many eastern streams have bankfull (discharge) heights that are much 
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Chapter 7. Hydromodification 35 

1 lower than actual bank heights (note that assessments of bankfull discharge are crucial to 

2 estimates of flood potential and to design criteria for stream restoration). 

3 Most research to date has considered western and eastern streams in the United States to have 

4 similar origins and forms, however, western streams are in a more tectonically active region, 

5 generally have high stream gradients, and carry substantial bed-load fractions, whereas eastern 

6 Piedmont streams are in a tectonically quiescent region, have low stream gradients, and largely 

7 did not carry gravel (or even much fine sediment) during the Holocene before formation of 

8 modern incised channels. Formation of gravel bars in the wake of eroding, meandering channels, 

9 followed by overbank deposition of fine sediment, was not the natural process of floodplain 

10 formation in the eastern United States before mill damming and subsequent channel incision 

11 after dam breaching. Valley bottoms along eastern streams were characterized by laterally 

12 extensive, wetland-dominated systems of forested meadows with stable vegetated islands and 

13 multiple small channels during recent geologic time (Holocene). These findings are consistent 

14 with research on streams in the Pacific Northwest, which revealed that large, woody debris from 

15 forested, riverine areas was critical to geomorphic processes and habitat before logging, channel 

16 clearing, and ditching during the late 1800s to early 1900s. In particular, logjams blocked 

17 channels and led to the formation of side channels and floodplain sloughs, producing multiple 

18 anabranching channels and riverine wetlands that are in stark contrast to the large, single 

19 channels that exist in these streams today. 

20 Results of this study explain the unusually thick deposits of fine sediment in streambanks relative 

21 to the limited amount of modern overbank deposition and the lack of levees on mid-Atlantic 

22 streams. Also explained are the great contrast between fine stream-bank and coarse stream-bed 

23 material; the observation that eastern (incised) streams, in comparison with western streams, 

24 change little in width as discharge increases at a station and the anomalously high suspended 

25 sediment and nutrient loads measured in Piedmont streams. Postsettlement milldam construction 

26 and millpond sedimentation were rapid and pervasive. This process inundated, buried, and 

27 sequestered presettlement wetlands and altered regional stream functions probably within two 

28 generations of settlement. Our field and historical research shows that stream valleys were once 

29 lined with millponds, which then silted in to form broad, flat bottom lands. Modern, incised, 

30 meandering streams are an artifact of the rise and fall of Mid-Atlantic streams in response to 

31 human manipulation of stream valleys for water power. Our results indicate that a substantial 

32 portion of modern suspended sediment and nutrient loads could be due to dam breaching and 

33 erosion of reservoir sediment, which is consistent with studies of recent dam removals elsewhere 

34 in the United States. These conclusions change the interpretation of hydraulic geometry in 

35 eastern United States streams that is based on the archetype of an “ideal meandering river form” 

36 and imply the need to reconsider current procedures for stream restoration that rely on reference 

37 reach conditions and the assumption that eroding channel banks are natural and replenishable. 

38 The current condition of single gravel-bedded channels with high, fine-grained banks and 

39 relatively dry valley-flat surfaces disconnected from groundwater is in stark contrast to the 

40 presettlement condition of swampy meadows (shrub-scrub) and shallow anabranching streams 

41 described here might have been the result of mill damming. 

42 Stanley and Doyle (2002)Stanley et al. (2002) presented a geomorphic perspective on nutrient 

43 retention following dam removal from streams and rivers in Wisconsin reflecting the influence 

44 of more than 100 years of human activity. In addition to dam construction these systems have 
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Chapter 7. Hydromodification 36 

1 been subjected to upland and channel alterations that include deforestation, wetland drainage, 

2 soil inputs from poor farming practices, and nutrient enrichment from point and nonpoint 

3 sources. There are approximately 3700 dams, or 1 dam every 14 kilometers of river in Wisconsin 

4 Department of Natural Resources (WDNR ) (1995). Although there is a healthy representation of 

large dams (structures > 2 meters [m] that impound ≥ 62,000 m35 , or structures > 7.6 m that 

6 impound 18,500 m3; USACE 1998), state waterways are more commonly populated by high 

7 densities of small, run-of-river structures, many of which are well over 80 years old. (Run-of8 river structures are dams that create reservoirs with small storage capacity and do not alter the 

9 river’s flow regime.) The abundance of dams can be traced back to the Milldam Act of 1840, 

10 which encouraged using hydropower to fuel the state’s burgeoning economy (Martini 1998). 

11 Unfortunately, many of these structures are no longer economically viable, represent a safety 

12 risk, and compromise the quality of the aquatic resource (Born et al. 1998). Under these 

13 circumstances, dam removal is a logical management option, and more than 50 dams have been 

14 removed under the supervision of the WDNR over the past three decades. To date, and reflective 

15 of the national trend (Doyle et al. 2005)(Doyle et al. 2000), most dams that have been removed 

16 within the state were relatively small structures. 

17 The growing interest and occurrence of dam removal underscores the inextricable link between 

18 agriculture and river modification in the Midwest. Dams were often built for milling of 

19 agricultural products, and the sediment-trapping ability of reservoirs means that topsoil and 

20 nutrients lost from farm fields are now stored behind dams. Given the growing concerns about 

21 nutrient enrichment and the potential for dam removal to affect nutrient dynamics, understanding 

22 the effects of dam removal on nutrient processes should be a research and management priority. 

23 The study draws from the context of agriculturally dominated watersheds in Wisconsin to 

24 explore how dam removal could influence the movement of N and P in rivers, considering 

25 nutrient transport in rivers and how reservoirs can affect nutrient processes. Changes in nutrient 

26 dynamics following dam removal are considered with respect to geomorphic adjustments and 

27 ecosystem responses caused by the removal. 

28 The major theme emphasized in the study is that changes in nutrient retention caused by dam 

29 removal are expected to be shaped by geomorphic channel adjustments. Although the specific 

30 way in which channels adjust to dam removal will vary from region to region, the change in the 

31 physical template will strongly influence the ecological responses to dam removal. Changes in 

32 nutrient retention following dam removal should be complex, reflecting a balance between the 

33 dynamics of channel adjustment and the relative influence of different channel stages on N and P 

34 processing. Following dam removal, affected sections of a river can consist of a series of reaches 

35 that have distinct and potentially contrasting influences on the form and amount of nutrients 

36 being transported downstream. 

37 Dam removal represents an extreme example of the influence of channel morphology on nutrient 

38 dynamics in streams and rivers. While it is impossible to ignore the dramatic and relatively rapid 

39 geomorphic changes when studying dam removal, streams and rivers are dynamic physical 

40 systems subject to short- and long-term changes in channel form. Yet channel geomorphology is 

41 usually treated as a fixed or constant attribute in ecological studies. As channels change over 

42 time or from site to site in a stream, the extent of sediment– water contact or the rate of sediment 

43 transport will also vary. For example, the transition from a narrow and deep incised channel to a 

44 broader, shallow channel under conditions of constant discharge will be accompanied by a 
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Chapter 7. Hydromodification 37 

1 decline in water velocity, an increase in wetted perimeter, and probably an increase in the 

2 amount of interstitial flow. Because geomorphic adjustments can alter sediment transport and the 

3 extent of sediment–water contact, changing channel form alone has the potential to affect uptake 

4 lengths and rates of biologically important elements such as N and P. Although the general 

5 importance of channel form on a range of ecosystem processes, including nutrient cycling, is 

6 well established (Brussock et al. 1985, Frissell et al. 1986, D’Angelo et al. 1997), specific 

7 geomorphic attributes constrain nutrient dynamics in lotic systems are just beginning to be 

8 understood. Dam removal can be used as an experiment for testing predictions or quantifying 

9 relationships between the dynamics of channel form and nutrient retention and thus represents a 

10 rare opportunity to gain valuable insights into the transport and transformation of nutrients as 

11 they move through watersheds. 

12 A study by Skalak et al. (2009)Skalak et al. (2009) demonstrated that the effects of dams on 

13 downstream channel morphology are minor. No significant differences in the water surface slope 

14 upstream and downstream of dams were observed. The study found that although monitoring 

15 studies of dam removals are becoming more common (Wildman and MacBroom; Bushaw16 Newton et al. 2002; Doyle et al. 2003; Chang 2008)Bushaw-Newton et al. 2002; Doyle et al. 

17 2003; Wildman and McBroom 2005; Cheng and Granata 2007), empirical knowledge of the 

18 effects of dam removal is still limited and most observations and conceptual models tend to 

19 focus on the transient effects of dam removal, the shorter-term patterns of upstream sediment 

20 mobilization and downstream sediment storage. 

21 Very little research has been conducted on the long-term effects of dam removal, although Graf 

22 (20062005) suggests that one of the most important unanswered questions involves the likely 

23 course of channel change following dam removal. The Skalak suggests that the results of their 

24 study can provide some useful estimates of the long-term effects of dam removal on downstream 

25 channels because the reaches upstream of existing dams provide a useful surrogate for the 

26 channel downstream before dam construction. If the dam is removed, the following scenario is 

27 likely to occur. For an initial period of adjustment, sediment will be eroded from reservoir 

28 deposits upstream, and a transient sediment pulse will likely pass into and through the reach 

29 below the dam (Pizzuto 2002). During this period, changes in channel morphology and bed 

30 composition might be expected. However, after the new channel within the reservoir reach has 

31 stabilized, the supply of sediment and distribution of discharges should approach predam levels, 

32 and the channel will slowly stabilize. We argue that the reach upstream of the dam has already 

33 adjusted to these conditions, and therefore we use the characteristics of the upstream channels to 

34 represent the equilibrium channel that will develop downstream of the dams long after dam 

35 removal. 

36 Following this approach, the results can be directly applied as predictions of downstream channel 

37 characteristics long after dam removal and the study proposes that long after dam removal, the 

38 water surface width, slope, percent exposed bedrock, and percent boulders will be unchanged. 

39 The median grain diameter will decrease slightly, but it will remain in the pebble size fraction. 

40 The results of the study also have important implications for channel changes that could persist 

41 long after the removal of the dams within the Chesapeake Bay watershed because the authors 

42 argue that after an initial period of transient adjustment as sediment eroded from upstream 

43 reservoirs passes through downstream channels, changes in channel geomorphic characteristics 

44 will be limited to increases in the percentages of silt and clay, sand, and granules, and that 
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Chapter 7. Hydromodification 38 

1 changes in the other geomorphic characteristics measured during this study will not be 

2 detectable. Thus, dam removal projects in streams similar to those of our study area should not 

3 cause significant long-term geomorphic changes to stream channels downstream. 

4 Cost Data 

5 Costs of dam removal is site-specific and can vary from tens of thousands of dollars to hundreds 

6 of millions of dollars, depending on the size and location of the dam (USEPA 2007). 

7 2.2.5.7 Live Crib Walls 

8 Description 

9 Live crib walls are hollow, box-like frameworks of untreated logs or timbers filled with riprap 

10 and alternating layers of suitable backfill and live branch layers and are used for slope, 

11 streambank, and shoreline protection. 

12 Application and Purpose 

13 Live crib walls are constructed to protect the toes and banks of eroding stream reaches against 

14 scour and 

15 undermining, particularly at the outsides of meander bends where strong river currents are 

16 present. The log frameworks provide immediate protection from erosion while the live branch 

17 cuttings contribute long-term durability and ultimately replace the decaying logs. Additionally, 

18 live crib walls are effective in areas where encroachment into the stream channel should be 

19 avoided. When considering these structures as a stream restoration technique, the following 

20 limitations should be considered: 

21 • Live crib walls should not be used where the channel bed is severely eroded or where 

22 undercutting is likely to occur (e.g., where the terrain is rocky or where narrow channels 

23 are bounded by high banks). 

24 • Live crib walls are not intended to resist large lateral earth stresses, therefore their heights 

25 should be limited accordingly (as noted in the installation specifications). 

26 • Live crib walls promote siltation and retain large amounts of bed material; therefore they 

27 require continual monitoring for adverse streamflow patterns. 

28 When choosing and preparing logs and woody cuttings for live crib walls, the following 

29 guidelines should be followed: 

30 • Crib frameworks should be constructed from stripped logs or untreated lumber 4 to 6 

31 inches (10 to 15 centimeters) in diameter. 

32 • Live branches should be cut from fresh, green, healthy parent plants which are adapted to 

33 the site conditions whenever possible. 

34 1. Live branches should be 0.5 to 2.5 inches (1.3 to 6 centimeters) in diameter and 

35 should be long enough to reach the soil at the back of the wooden crib structure while 

36 projecting slightly from the crib face. 
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Chapter 7. Hydromodification 39 

1 2. Commonly used woody plants for this measure include willow, poplar, and alder 

2 since they are versatile and have high growth rates with shrubby habits, fibrous root 

3 systems, and high transpiration rates especially when in leaf. 

4 3. Live branch cuttings should be kept covered and moist at all times and should be 

5 placed in cold storage if more than a few hours elapse before installation. 

6 • Fill soil should be native to the site, when possible, and should contain enough fine 

7 material to allow for the live branches to root and grow readily. 

8 Cost Data 

9 Live crib walls range in cost between $13 to $33 per square foot (Gray 1996)(Gray and Sotir 

10 1996).

11 Design Guidance and additional info 

12 Installation guidelines are available from the USDA-FS Soil Bioengineering Guide (USDA-FS 

13 2002) and the USDA NRCS Engineering Field Handbook, Chapter 18 (USDA-NRCS 1992). 

14 Additional Resources 

15 FISRWG (Federal Interagency Stream Restoration Working Group). 1998. Stream Corridor 

16 Restoration: Principles, Processes, and Practices. Federal Interagency Stream Restoration 

17 Working Group. 

18 http://www.nrcs.usda.gov/technical/stream_restoration/PDFFILES/APPENDIX.pdf.

19 ISU (Iowa State University). 2006. How to Control Streambank Erosion: Live Cribwall. Iowa 

20 State University. http://www.ctre.iastate.edu/erosion/manuals/streambank/live_cribwall.pdf.

21 Mississippi State University, Center for Sustainable Design. 1999. Water Related Best 

22 Management Practices in the Landscape: Live Cribwall. Prepared for the U.S. Department 

23 of Agriculture, Natural Resource Conservation Service, Watershed Science Institute. 

24 http://www.abe.msstate.edu/csd/NRCS-BMPs/pdf/streams/bank/livecribwall.pdf.

25 Ohio DNR (Department of Natural Resources). No date. Ohio Stream Management Guide: Live 

26 Cribwalls. Ohio Department of Natural Resources. 

27 http://www.ohiodnr.com/water/pubs/fs_st/stfs17.htm.

28 2.2.5.8 Live Fascines 

29 Description 

30 A form of soil bioengineering which uses long bundles of live branch cuttings bound together in 

31 long rows and placed in shallow trenches following the contour on dry slopes, and at an angle on 

32 wet slopes. 

33 Application and Purpose 

34 Live fascines are suited to steep, rocky slopes, where digging is difficult (USDA-NRCS 1992). 

35 When cut from appropriate species (e.g., young willows or shrub dogwoods) that root easily and 

36 have long straight branches, and when properly installed, they immediately begin to stabilize 
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Chapter 7. Hydromodification 40 

1 slopes. Willow, alder, and dogwood cuttings are well suited for use in live fascines. Fascine 

2 bundles can range from 5 to 30 feet (1.5 to 9 meters) in length, depending upon handling and 

3 transportation limitations, with diameters ranging from 4 to 10 inches (10 to 25 cm). Untreated 

4 twine or wire used to tie the bundles should be at least 2 millimeters thick. If inert (dead) stakes 

5 are employed to secure the bundles, they should be made from 2 by 4 inch (5 by 10 cm) lumber 

6 cut on the diagonal with lengths of 2.5 feet (0.8 meters) for cut slopes and 3 feet (0.9 meters) for 

7 fill slopes.The goal is for natural recruitment to follow once slopes are secured. Live fascines 

8 should be placed in shallow contour trenches on dry slopes and at an angle on wet slopes to 

9 reduce erosion and shallow face sliding. Live fascines should be applied above ordinary high10 water mark or bankfull level except on very small drainage area sites. In arid climates, they 

11 should be used between the high and low water marks on the bank. This system, installed by a 

12 trained crew, does not cause much site disturbance.

13 Establishing Establishment of live fascines, also known as wattles, consists of the following: 

14 • Preparing sausage-shaped bundles of live, woody plant cuttings 

15 • Anchoring the bundles in shallow ditches in a slope or streambank with live and/or inert 

16 stout stakes 

17 • Partially burying the fascines to promote growth 

18 As with other bioengineering measures, live fascines are an economical method when materials 

19 are locally available. Additionally, live fascines are often an effective measure when employed 

20 to 

21 • Reduce runoff energy, and hence surface erosion, by braking a slope into a series of 

22 shorter slopes 

23 • Protect other bioengineering measures from washout and undercutting 

24 • Replace brush layers on suitable cut slopes (since they are easier to install) 

25 • Protect streambanks from washout and seepage, particularly at toes where water levels 

26 fluctuate only moderately 

27 • Stabilize or protect streambanks 

28 • Provide habitat 

29 • Reduce overland sediment loading 

30 Cost Data 

31 Live fascine costs range from $10 to $30 per foot for 6- to 8-in.bundles. Prices include securing 

32 devices for installation, twine (for fabrication), harvesting, transportation, handling, fabrication, 

33 and storage of the live-cut branch materials, excavation, backfill, and compaction. Costs vary 

34 with design, access, time of year, and labor rates.

35 Design Guidance and additional info 

36 Installation guidelines are available from the USDA-FS Soil Bioengineering Guide (USDA-FS 

37 2002) and the USDA NRCS Engineering Field Handbook, Chapter 18 (USDA-NRCS 1992). 

38 Under their Ecosystem Management and Restoration Research Program (EMRRP), the U.S. 
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Chapter 7. Hydromodification 41 

1 Army Corps of Engineers presents research on live fascines in a technical note (Live and Inert 

2 Fascine Streambank Erosion Control). 

3 Additional Resources 

4 Massachusetts DEP. 2006. Massachusetts Nonpoint Source Pollution Management Manual: Live 

5 Fascines. Massachusetts Department of Environmental Protection, Boston, MA. 

6 http://projects.geosyntec.com/NPSManual/Fact%20Sheets/Live%20Fascines.pdf.

7 Greene County Soil & Water Conservation District. No date. Construction Specification VS-01: 

8 Live Fascines. http://www.gcswcd.com/stream/library/pdfdocs/vs-01.pdf.

9 ISU (Iowa State University). 2006. How to Control Streambank Erosion: Live Fascine. Iowa 

10 State University. http://www.ctre.iastate.edu/erosion/manuals/streambank/live_fascine.pdf.

11 Mississippi State University, Center for Sustainable Design. 1999. Water Related Best 

12 Management Practices in the Landscape: Live Fascine. Prepared for the U.S. Department 

13 of Agriculture, Natural Resource Conservation Service, Watershed Science Institute. 

14 http://abe.msstate.edu/csd/NRCS-BMPs/pdf/streams/bank/livefacine.pdf.

15 Ohio DNR. No date. Ohio Stream Management Guide: Live Fascines. Ohio Department of 

16 Natural Resources. http://www.ohiodnr.com/water/pubs/fs_st/stfs14.pdf.

17 2.2.5.9 Live Staking 

18 Description 

19 Live staking is used to reestablish streambank vegetation and help stabilize selected slope areas. 

20 This form of soil bioengineering involves the planting of live cuttings from shrubs or trees along 

21 the streambank and is also known as woody cuttings, posts, poles or stubs. Stakings provide 

22 long-term streambank stabilization with delayed initial onset and are best used as part of a 

23 system which includes immediate means of buffering banks from erosive flows (e.g., tree 

24 revetments, which can actually accrue sediments), a component to deter undercutting at the 

25 bed/bank interface (e.g., riprap or gabions) and a means of reducing the energy of incoming 

26 flows at their source. 

27 Application and Purpose 

28 Live staking is an economical method when local supplies of woody cuttings are readily 

29 available since the implementation of this measure requires minimal labor. When used 

30 effectively, live stakes can do the following: 

31 • Act to trap soil particles in sediment laden water resulting from the erosion of adjacent 

32 land 

33 • Slow water velocities, trap sediment, and control erosion when organized in clustered 

34 arrays along the sides of gullies 

35 • Repair small earth slips and slumps which are frequently wet 

36 • Help control shallow mass movement when placed in rows across slopes

37 • Promote bank stabilization 
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Chapter 7. Hydromodification 42 

1 Live staking is a preventative measure and should be employed before severe erosion problems 

2 occur. Additionally, to be effective, live stakes should be 

3 • Planted only on streams with low to moderate flow fluctuations 

4 • Established in the original bank soil on moderate slopes of 4:1(h:v) or less 

5 • Planted where appropriate lighting exists 

6 • Used jointly with other restoration techniques especially on slopes with high erosion rates 

7 and incidents of mass wasting 

8 When choosing and preparing woody material for live stakes, managers should follow these 

9 guidelines: 

10 • Live stakes should be cut from fresh, green, healthy, dormant parent plants which are 

11 adapted to the site conditions whenever possible. Commonly used woody plants for this 

12 measure include willow, poplar, and alder since they are versatile and have high growth 

13 rates with shrubby habits, fibrous root systems, and high transpiration rates, especially 

14 when in leaf. 

15 • Live stakes should have a diameter between 0.75 and 1.5 inches (2 to 4 cm) and should 

16 be long enough to reach below the groundwater table so that a strong root system can 

17 quickly develop. At least 1 foot (0.3 m) should be exposed to sunlight. Live woody posts 

18 with diameters up to 10 inches (0.25 m) and lengths ranging from 4 to 6 feet (1.2 to 1.8 8 

19 m) can also be used at the discretion of the project manager. 

20 • Live stakes should be kept covered and moist at all times and should be placed in cold 

21 storage if more than a few hours elapse between the cutting and replanting times. 

22 • Vegetation selected should be able to withstand the degree of anticipated inundation, 

23 provide year round protection, have the capacity to become well established under 

24 sometimes adverse soil conditions, and have root, stem, and branch systems capable of 

25 resisting erosive flows. 

26 • Specific site requirements and available cutting source will determine size. 

27 Cost Data 

28 The installed cost of Live Stakes typically ranges from $1 to $2 per stake, depending on local 

29 labor rates, proximity of harvesting area to site, and other site variables. 

30 Design Guidance and additional info 

31 Installation guidelines are available from the USDA-FS Soil Bioengineering Guide (USDA-FS 

32 2002) and the USDA NRCS Engineering Field Handbook, Chapter 18 (USDA-NRCS 1992). 

33 Additional Resources 

34 ISU (Iowa State University). 2006. How to Control Streambank Erosion: Live Stakes. Iowa State 

35 University. http://www.ctre.iastate.edu/erosion/manuals/streambank/live_stakes.pdf. 
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Chapter 7. Hydromodification 43 

1 Myers, R.D. 1993. Slope Stabilization and Erosion Control Using Vegetation: A Manual of 

2 Practice for Coastal Property Owners. Live Staking. Publication 93-30. Washington 

3 Department of Ecology, Shorelands and Coastal Zone Management Program, Washington 

4 Department of Ecology. Olympia, WA. Publication 93-30. 

5 http://www.ecy.wa.gov/programs/sea/pubs/93-30/livestaking.html. 

6 Walter, J., D. Hughes, and N.J. Moore. 2005. Streambank Revegetation and Protection: A Guide 

7 for Alaska. Revegetation Techniques: Live Staking. Revised Edition. Alaska Department of 

8 Fish and Game, Division of Sport Fish. 

9 http://www.sf.adfg.state.ak.us/SARR/restoration/techniques/livestake.cfm. 

10 2.2.5.10 Log & Rock Check Dams 

11 Description 

12 Check dams are low structures built across a stream perpendicular to the flow. The most 

13 common use for check dams is to decrease the slope and velocity of a stream to control erosion. 

14 Application and Purpose 

15 The plunge pool below a check dam provides excellent fish habitat, and the downstream gravel 

16 bar often associated with the dam makes an excellent spawning bed. When used to enhance fish 

17 habitat, check dams should be placed far enough apart to insure that the pool below a dam is 

18 above the backwater of the next dam downstream. That will reduce the possibility that the habitat 

19 pool of the upper dam can fill with deposits. 

20 When constructed and spaced properly, check dams can simulate the natural pattern of pools and 

21 riffles occurring in undisturbed streams while forming gravel deposits that fish use as spawning 

22 grounds. 

23 Check dams have also been used to prevent the movement of fine sediments into the mainstream 

24 channel, to aerate water, and to raise water levels past culvert invert elevations, thereby allowing 

25 fish passage. 

26 Check dams should be avoided in the following areas: 

27 • Channels with bedrock beds or unstable bed substrates 

28 • Channels without well developed, stable banks 

29 • Streams with high bedload transport 

30 • Streams with naturally well developed pools-riffle sequences 

31 • Reaches where the water temperature regime is negatively impacted when the current is 

32 slowed 

33 Cost Data 

34 Check dams vary widely in cost depending on the design, availability and selection of materials, 

35 and site conditions. 
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Chapter 7. Hydromodification 44 

1 Design Guidance and additional info 

2 The following document provide design information and guidance for check dams. 

3 Maryland Department of the Environment Water Management Administration. 2000. Maryland’s 

4 Waterway Construction Guidelines. 

5 http://www.mde.state.md.us/assets/document/wetlandswaterways/mgwc.pdf.

6 2.2.5.11 Marsh Creation and Restoration 

7 Description 

8 Marsh creation and restoration is a useful vegetative technique that can address problems with 

9 erosion of shorelines. For shoreline sites that are highly sheltered from the effects of wind, 

10 waves, or boat wakes, the fill material is usually stabilized with small structures, similar to 

11 groins, which extend out into the water from the land. For shorelines with higher levels of wave 

12 energy, the newly planted marsh can be protected with an offshore installation of stone that is 

13 built either in a continuous configuration or in a series of breakwaters. 

14 Application and Purpose 

15 The exposed stems of marsh plants form a flexible mass that dissipates wave energy. As wave 

16 energy is diminished, the offshore transport and longshore transport of sediment are reduced. 

17 Ideally, dense stands of marsh vegetation can create a depositional environment, causing 

18 accretion of sediments along the intertidal zone rather than continued shore erosion. Marsh plants 

19 also form a dense mat of roots, which can add stability to the shoreline sediments. The basic 

20 approach for marsh creation is to plant a shoreline area in the vicinity of the tide line with 

21 appropriate marsh grass species. 

22 Efficiency Data 

23 Despite rapid growth in river restoration, few projects receive the necessary evaluation and 

24 reporting to determine their success or failure and to learn from experience. As part of the 

25 National River Restoration Science Synthesis, Alexander and Allan (2006)Alexander and Allan

26 (2007) interviewed 39 project contacts from a database of 1,345 restoration projects in Michigan, 

27 Wisconsin, and Ohio to (1) verify project information; (2) gather data on project design, 

28 implementation, and coordination; (3) assess the extent of monitoring; and (4) evaluate success 

29 and the factors that can influence it. Projects were selected randomly within the four most 

30 common project goals from a national database: in-stream habitat improvement, channel 

31 reconfiguration, riparian management, and water-quality improvement. About half of the 

32 projects were implemented as part of a watershed management plan and had some advisory 

33 group. Monitoring occurred in 79 79 percent of projects but often was minimal and seldom 

34 documented biological improvements. Baseline data for evaluation often relied on previous data 

35 obtained under regional monitoring programs using state protocols. Although 89 percent of 

36 project contacts reported success, only 11 11 percent of the projects were considered successful 

37 because of the response of a specific ecological indicator, and monitoring data were underused in 

38 project assessment. Estimates of ecological success, using three criteria from Palmer and others 

39 (2005), indicated that half or fewer of the projects were ecologically successful, markedly below 

40 the success level that project contacts self-reported, and sent a strong signal of the need for well41 designed evaluation programs that can document ecological enhancements. 
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Chapter 7. Hydromodification 45 

1 2.2.5.12 Revetments 

2 Description 

3 Revetments are the stabilization of eroding streambanks and for shoreline protection by using 

4 designed structural measures, such as rock riprap, gabions, pre-cast concrete wall units and grid 

5 pavers. 

6 Application and Purpose 

7 The purpose of revetments is to protect exposed or eroded streambanks from the erosive forces 

8 of flowing water. They are generally applicable where flow velocities exceed 6 feet per second 

9 or where vegetative streambank protection is inappropriate and necessary where excessive flows 

10 have created an erosive condition on a streambank. 

11 Because each channel is unique, measures for structural streambank should be installed 

12 according to a design according to specific site conditions. Develop designs according to the 

13 following principles: 

14 • Make protective measures compatible with other channel modifications planned or being 

15 carried out in the channel reaches. 

16 • Use the design velocity of the peak discharge of the 10-year storm or bankfull discharge, 

17 whichever is less. Structural measures should be capable of withstanding greater flows 

18 without serious damage. 

19 • Ensure that the channel bottom is stable or stabilized by structural means before installing 

20 any permanent bank protection. 

21 • Streambank protection should begin at a stable location and end at a stable point along 

22 the bank. 

23 • Changes in alignment should not be done without a complete analysis of effects on the 

24 rest of the stream system for both environmental and stability effects. 

25 • Provisions should be made to maintain and improve fish and wildlife habitat. For 

26 example, restoring lost vegetation will provide valuable shade, food, and/or cover. 

27 • Ensure that all requirements of state law and all permit requirements of local, state, and 

28 federal agencies are met. 

29 Typical materials used for revetments are as follows: 

30 Riprap. Riprap is the most commonly used material to structurally stabilize a streambank. While 

31 riprap will provide the structural stabilization necessary, the bank can be enhanced with 

32 vegetative material to slow the velocity of water, filter debris, and enhance habitat. 

33 Gabions. Gabions are rectangular, stone-filled wire baskets. They are somewhat flexible in 

34 armoring channel bottoms and banks. They can withstand significantly higher velocities for the 

35 size stone they contain because of the basket structure. They also stack vertically to act as a 

36 retaining wall for constrained areas. 
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Chapter 7. Hydromodification 46 

1 Reinforced Concrete. Reinforced concrete can be used to armor eroding sections of streambank 

2 by constructing walls, bulk heads, or bank linings. Provide positive drainage behind these 

3 structures to relieve uplift pressures. 

4 Grid Pavers. Grid pavers are modular concrete units with or without void areas can be used to 

5 stabilize streambanks. Units with void areas can allow the establishment of vegetation. Such 

6 structures can be obtained in a variety of shapes or they can be formed and poured in place. 

7 Maintain design and installation in accordance with manufacturer’s instructions. 

8 Modular Pre-Cast Units. Interlocking modular precast units of different sizes, shapes, heights, 

9 and depths, have been developed for a wide variety of applications. These units serve in the same 

10 manner as gabions. They provide vertical support in tight areas as well as durability. Many types 

11 are available with textured surfaces. They also act as gravity retaining walls. They should be 

12 designed and installed in accordance with the manufacturers recommendations. Openings within 

13 the units provide drainage and allow vegetation to grow through the blocks. Vegetation roots add 

14 additional strength to the bank. 

15 The National Management Measures to Control Nonpoint Sources Pollution from 

16 Hydromodification document (USEPApublished by EPA in 2007) provides various examples of 

17 types of revetments. 

18 Design Guidance and additional info 

19 Ohio DNR. No date. Ohio Stream Management Guide: Riprap Revetments. Ohio Department of 

20 Natural Resources. http://www.ohiodnr.com/water/pubs/fs_st/stfs16.pdf.

21 2.2.5.13 Rock and Log Vanes 

22 Description 

23 Rock and log vanes are single-arm structures which are partially embedded in the streambed 

24 such that they are submerged even during low flows.

25 Application and Purpose 

26 Rock and log vanes induce secondary circulation of the flow thereby promoting the development 

27 of scour pools. Vanes can also be paired and positioned in a channel reach to initiate meander 

28 development or migration. They essentially mimic the effect of a tree partially falling into the 

29 stream. They are usually placed along the streambank where erosion is occurring along the toe of 

30 the slope. The purpose of vanes is to reduce erosion along the streambank by redirecting the 

31 stream flow toward the center of the stream. In addition, they tend to create scour pools on the 

32 downstream side. 

33 Vanes can be made of rock or log. They grade down from the bankfull elevation at the 

34 streambank to the channel invert at their terminus in the stream. Vanes generally extend out from 

35 the streambank one-third of the bankfull width and are angled upstream from the bank at a 20 to 

36 30 degree angle. They should be carefully located and installed so as not to produce additional 

37 erosion on the upstream side where they meet the bank (eddy scour) or allow flows to outflank 

38 them, exacerbating existing bank erosion problems. The only difference between the log vane 

39 and the rock vane is the material used. The J-hook vane is basically the same as a rock vane with 
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Chapter 7. Hydromodification 47 

1 the exception that it curls around at the end in the shape of a “J.” The curved end portion serves 

2 to enhance downstream scour pool formation. 

3 The following limitations apply to vanes: 

4 • Vanes should not be used in unstable streams unless measures have been taken to 

5 promote stream stability so that it can retain a constant planform and dimension without 

6 signs of migration or incision. 

7 • Vanes are ineffective in bedrock channels since minimal bed scouring occurs. 

8 Conversely, streams with fine sand, silt, or otherwise unstable substrate should be 

9 avoided since significant undercutting can destroy these measures. 

10 • Vanes should not be used in stream reaches that exceed a 3 percent gradient. 

11 • Vanes should not be used in streams with large sediment or debris loads. 

12 • Banks opposite thethese structures should be monitored for excessive erosion. 

13 Cost Data 

14 Rock and log vanes vary greatly in cost depending on the design, availability and selection of 

15 materials, and site conditions. 

16 Design Guidance and additional info 

17 The following documents provide design information and guidance for vanes. 

18 Stream Restoration: A Natural Channel Design Handbook, prepared by the North Carolina 

19 Stream Restoration Institute and North Carolina Sea Grant. 

20 http://www.bae.ncsu.edu/programs/extension/wqg/srp/sr_guidebook.pdf

21 The Virginia Stream Restoration & Stabilization Best Management Practices Guide, Department 

22 of Conservation and Recreation, Division of Soil and Water Conservation. 2004. 

23 http://www.dcr.virginia.gov/soil_and_water/documents/streamguide.pdf

24 2.2.5.14 Rosgen’s Stream Classification Method 

25 Description 

26 Rosgen’s stream channel stability method provides a sequence of steps for the field practitioner 

27 to use in reaching final conclusions and making recommendations for management, stream 

28 design, or restoration. 

29 Application and Purpose 

30 Field practitioners use field-measured variables to assess the following: 

31 • Stream state or channel condition variables 

32 • Vertical stability (degradation/aggradation) 

33 • Lateral stability 

34 • Channel patterns 
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Chapter 7. Hydromodification 48 

1 • Stream profile and bed features 

2 • Channel dimension factor 

3 • Channel scour/deposition (with competence calculations of field verified critical 

4 dimensionless shear stress and change in bed and bar material size distribution) 

5 • Stability ratings adjusted by stream type 

6 • Dimensionless ratio sediment rating curves by stream type and stability ratings 

7 • Selection of position in stream type evolutionary scenario as quantified by morphological 

8 variables by stream type to determine state and potential of stream reach. 

9 Stability assessments are conducted on a reference reach and a departure analysis is performed 

10 when compared to an unstable reach of the same stream type. Changes in the variables 

11 controlling river channel form, primarily streamflow, sediment regime, riparian vegetation, and 

12 direct physical modifications can cause stream channel instability. Separating the differences 

13 between anthropogenic versus geologic processes in channel adjustment is a key to prevention, 

14 mitigation, and restoration of disturbed systems. 

15 Efficiency Data 

16 Restoration activities intended to improve the condition of streams and rivers are widespread 

17 throughout the country but little information exists regarding types of activities and their 

18 effectiveness. Alexander and Allan (2006)Alexander and Allan (2006) developed a database of 

19 1,345 stream restoration projects implemented from the years 1970 to 2004 for the states of 

20 Michigan, Ohio, and Wisconsin to analyze regional trends in goals, presence of monitoring, 

21 spatial distribution, size, and cost of river restoration projects. They found that data on individual

22 projects were fragmented across multiple federal, state, and county agencies, as well as nonprofit 

23 groups and consulting firms. The most common restoration goals reported for this region were 

24 in-stream habitat improvement, bank stabilization, water-quality management, and dam removal. 

25 In a subsequent study, the National River Restoration Science Synthesis (Alexander and Allan 

26 2007)(Alexander and Allan 2007) they found that despite rapid growth in river restoration, few 

27 projects receive the necessary evaluation and reporting to determine their success or failure and 

28 to learn from experience. In this study, 39 project contacts from a database of 1,345 restoration 

29 projects were interviewed to (1) verify project information; (2) gather data on project design, 

30 implementation, and coordination; (3) assess the extent of monitoring; and (4) evaluate success 

31 and the factors that can influence it. Projects were selected randomly within the four most 

32 common project goals from the national database: in-stream habitat improvement, channel 

33 reconfiguration, riparian management, and water-quality improvement. 

34 About half of the projects were implemented as part of a watershed management plan and had 

35 some advisory group. Monitoring occurred in 79 percent of projects but often was minimal and 

36 seldom documented biological improvements. Baseline data for evaluation often relied on 

37 previous data obtained under regional monitoring programs using state protocols. Although 89 

38 percent of project contacts reported success, only 11 percent of the projects were considered 

39 successful because of the response of a specific ecological indicator, and monitoring data were 

40 underused in project assessment. Estimates of ecological success, using three criteria from 

41 Palmer and others (2005), indicated that half or fewer of the projects were ecologically 
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Chapter 7. Hydromodification 49 

1 successful, markedly below the success level that project contacts self-reported, and sent a strong 

2 signal of the need for well-designed evaluation programs that can document ecological success. 

3 The importance of stream restoration to address the degradation of aquatic ecosystems is not in 

4 doubt. However, based on this assessment of stream restoration practices in the upper midwest, 

5 many aspects of stream restoration could be improved. Project planning and implementation 

6 should be cognizant of restoration needs and activities throughout the watershed to further their 

7 understanding of the cumulative and interactive effects of dispersed restoration projects. In 

8 addition, projects should be implemented with a formal understanding of the larger landscape9 scale processes influencing the stream ecosystem. 

10 Monitoring protocols for similar types of projects and reporting results should be standardized 

11 regionally and nationally to allow for meaningful comparisons of results. Project designs that 

12 state success criteria based on the ecological performance of the project rather than project 

13 implementation would also aid in comparing the success of similar projects. The most critical 

14 need is for monitoring programs that collect pre-project and post-project data for extended 

15 periods of time. Granting agencies need to allocate money to monitoring and allow for 

16 disbursement of monitoring support during a long period of time (at least 10 years). Such an 

17 arrangement would also facilitate the implementation of restoration projects at the watershed 

18 scale. The present study and a companion study Alexander and Allan (2006)(Alexander and 

19 Allan 2006) confirm what has long been speculated. A great deal of stream restoration is 

20 occurring, at considerable expense, and few projects are being monitored to effectively evaluate 

21 ecological success. More detailed and standardized reporting restoration project outcomes is a 

22 critical need to further the science of ecological stream restoration in the upper midwest region 

23 and worldwide. 

24 He et al. (2009)He et al. (2009) applied a depth-averaged two-dimensional model to simulate the 

25 effect of large wood structures (LWS) on flow, sediment transport, bed change, and fish habitat 

26 in a deeply incised sharp bend in the Little Topashaw Creek, North Central Mississippi. 

27 Hydrodynamic simulations showed that the flow was retarded by the large wood matrices along 

28 the outer bank and accelerated in the main channel, thus causing deposition along the outer bank 

29 and erosion in the main channel, consistent with field observations. Effects on fish habitat were 

30 quantified using two approaches. Habitat evaluations using kinetic energy and circulation metrics 

31 indicated that LWS only slightly increased the diversity of physical conditions. Weighted usable 

32 areas (WUA) for two fish species, blacktail shiner (Cyprinella venusta) and largemouth bass 

33 (Micropterus salmoides), were computed using hydrodynamic simulations of three discharges 

34 before and after the LWS construction and habitat preference curves for depth and velocity. The 

35 results show that the values of WUA for both fish species were increased after LWS installation 

36 at all three discharges. Application of LWS improved the quantity and quality of fish habitats. 

37 Habitat evaluations based on computation of WUA were more sensitive to the influence of LWS 

38 than metrics based on velocity gradients. 

39 The effects of upland disturbance and in-stream restoration on hydrodynamics and ammonium 

40 uptake in headwater streams was studied by Roberts et al. (2007)Roberts (2007), who found that 

41 the delivery of water, sediments, nutrients, and organic matter to stream ecosystems was strongly 

42 influenced by the catchment of the stream and can be altered greatly by upland soil and 

43 vegetation disturbance. Upland disturbance did not appear to influence stream hydrodynamics 

44 strongly, but it caused significant decreases in in-stream nutrient uptake. In October 2003, coarse 
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Chapter 7. Hydromodification 50 

1 woody debris (CWD) was added to one-half of the study streams (spanning the disturbance 

2 gradient) in an attempt to increase hydrodynamic and structural complexity, with the goals of 

3 enhancing biotic habitat and increasing nutrient uptake rates. CWD additions had positive short4 term (within 1 mo) effects on hydrodynamic complexity (water velocity decreased and transient 

5 storage zone cross-sectional area, relative size of the transient storage zone, fraction of the 

6 median travel time attributable to transient storage over a standardized length of 200 m, and the 

7 hydraulic retention factor increased) and nutrient uptake (NH4 þ uptake rates increased). The 

8 results of this study suggest that water quality in streams with intense upland disturbances can be 

9 improved by enhancing in-stream biotic nutrient uptake capacity through measures such as 

10 restoring stream CWD. 

11 Mulholland et al. (2008) found that on a per area basis, nitrogen (N) removal is important both in 

12 stream channels and riparian buffers. Because N removal rates are site and time specific, it is 

13 difficult to predict the effectiveness of different restoration approaches. This study also suggests 

14 that clarifying how stream restoration influences N removal will require an evaluation of 

15 restoration projects within different landscape contexts that employs the approaches they 

16 suggest, both alone and in concert. Approaches should therefore be implemented as adaptive 

17 management experiments rather than as solutions to N loading issues, until the actual N removal 

18 capacity of such projects can be ascertained. Moreover, evaluating the ability of current methods 

19 to measure the effectiveness of restoration, along with conceptualizing and implementing new 

20 methods, is critical to understanding of how restoration affects N removal. 

21 The degradation of inland aquatic habitats caused by decades of human activities has led to 

22 worldwide efforts to rehabilitate freshwater habitats for fisheries and aquatic resources. Roni et 

23 al. (2008)Roni et al. (2008) reviewed published evaluations of stream rehabilitation techniques 

24 from throughout the world, including studies on road improvement, riparian rehabilitation, 

25 floodplain connectivity and rehabilitation, in-stream habitat improvement, nutrient addition, and 

26 other, less-common techniques. They summarize current knowledge about the effectiveness of 

27 these techniques for improving physical habitat and water quality and increasing fish and biotic 

28 production. Their review of 345 papers on effectiveness of stream rehabilitation techniques 

29 indicates that some techniques, such as reconnection of isolated habitats, rehabilitation of 

30 floodplains, and placement of in-stream structures, have proven to be effective for improving 

31 habitat and increasing local fish abundance under many circumstances. Techniques for restoring 

32 the natural processes that create and maintain habitats, such as riparian rehabilitation, sediment 

33 reduction methods (road improvements), dam removal, and restoration of floods, have also 

34 produced encouraging results, but it might take years or decades before a change in fish or other 

35 biota is evident, and little or no long-term monitoring of these techniques has been conducted. 

36 Their review emphasizes the need for adequate assessment of watershed processes and factors 

37 limiting biotic production, consideration of upstream or watershed-scale factors that influence 

38 the outcome of reach-scale or localized rehabilitation projects, and monitoring and evaluation of 

39 adequate temporal and spatial scales. 

40 Despite locating 345 studies on effectiveness of stream rehabilitation, firm conclusions about 

41 many specific techniques were difficult to make because of the limited information provided on 

42 physical habitat, water quality, and biota and because of the short duration and limited scope of 

43 most published evaluations (Roni et al. 2008).(Roni et al. 2008). Reconnection of isolated 

44 habitats, floodplain rehabilitation, and in-stream habitat improvement have, however, proven 
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Chapter 7. Hydromodification 51 

1 effective for improving habitat and increasing local fish abundance under many circumstances. 

2 Techniques such as riparian rehabilitation, road improvements (sediment reduction), dam 

3 removal, and restoration of natural flood regimes have shown promise for restoring natural 

4 processes that create and maintain habitats, but no long-term studies documenting their success 

5 have yet been published. Their review demonstrates that the failure of many rehabilitation 

6 projects to achieve objectives is attributable to inadequate assessment of historic conditions and 

7 factors limiting biotic production; poor understanding of watershed-scale processes that 

8 influence localized projects; and monitoring at inappropriate spatial and temporal scales. They 

9 suggest an interim approach to sequencing rehabilitation projects that partially addresses these 

10 needs through protecting high-quality habitats and restoring connectivity and watershed 

11 processes before implementing in-stream habitat improvement projects. 

12 Key research and monitoring priorities include examination of most techniques in areas other 

13 than the United States and Canada, where most research has occurred. Additional research on in14 stream habitat enhancement structures is needed in other parts of the world, but such techniques 

15 have been extensively examined in the western and midwestern United States and in Canada. 

16 Examination of the effectiveness of riparian, road, and floodplain rehabilitation techniques in 

17 restoring watershed processes (i.e., delivery of wood, water, and sediment) and biota is needed in 

18 all geographic areas. Finally, few studies have conducted examinations at a sufficiently broad 

19 scale for determining effects of individual or multiple projects on an entire watershed or fish 

20 population. This is clearly one of the most pressing research needs and is probably attainable 

21 with recent technological advances in remote sensing and fish tagging. 

22 Stream restoration, or more properly rehabilitation, is the return of a degraded stream ecosystem 

23 to a close approximation of its remaining natural potential. Many types of practices (dam 

24 removal, levee breaching, modified flow control, vegetative methods for streambank erosion 

25 control, and such) are useful, but Shields et al. (2003)Shields et al. (2003) focuses on channel 

26 reconstruction. A tension exists between restoring natural fluvial processes and ensuring stability 

27 of the completed project. Sedimentation analyses are a key aspect of design since many projects 

28 fail because of erosion or sedimentation. Existing design approaches range from relatively 

29 simple ones based on stream classification and regional hydraulic geometry relations to more 

30 complex two- and three-dimensional numerical models. Herein an intermediate approach 

31 featuring application of hydraulic engineering tools for assessment of watershed geomorphology, 

32 channel forming discharge analysis, and hydraulic analysis in the form of one-dimensional flow 

33 and sediment transport computations is described. 

34 Although the number and scope of stream restoration projects are increasing, designs for these 

35 projects are often weak in hydraulic engineering. This paper represents an attempt to outline 

36 acceptable standards for hydraulic design for channel reconstructions. All stream restoration 

37 projects require some level of sedimentation analysis to reduce the risk of undesirable outcomes. 

38 More powerful, user-friendly software tools are needed for this type of work. Sensitivity analysis 

39 and expert advice should be integral parts of such software. More accurate and robust flow 

40 resistance and sediment transport relations are needed. Ideally, tools for analyzing habitat issues 

41 should smoothly interface with those for flow and sediment transport. Because of the unorthodox 

42 nature and relatively high level of uncertainty surrounding stream restoration projects, 

43 involvement by the hydraulic designer should continue through the implementation phase, and a 

44 monitoring program should be included in project plans. 
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Chapter 7. Hydromodification 52 

1 Streambank erosion is often the dominant source of sediment leaving modified watersheds. Mass 

2 failure of high, steep banks is one of the most serious forms of streambank erosion. The risk of a 

3 given bank experiencing mass failure is a function of bank height, angle, and soil strength, which 

4 is governed by soil moisture. Two methods for bank dewatering were tested by Shields et al. 

5 (2009)Shields et al. (2009) in adjacent sections of streambank bordering a deeply incised channel 

6 in northern Mississippi: a low-cost pump system and subsurface horizontal drains. Pore water 

7 pressures (both positive and negative pressures, or matric suction) were continuously monitored 

8 for 2 years at the pumped site, at an adjacent untreated control section, and for 1 year at the site 

9 stabilized with horizontal drains. Resulting data were used to calculate a time series of the factor 

10 of safety using a computer model. Over the course of two wet seasons, average bank retreats for 

11 the control and pumped plots were 0D43 and 0D21 m, respectively. More limited monitoring 

12 revealed that the site with passive drains retreated about 0D23 m. At the pumped site pore water 

13 pressure was 3–4 kPa lower than at the control site during the most critical periods. Accordingly, 

14 computed factors of safety were above the failure threshold at the pumped site, but fell below 

15 unity at the control site on 11 occasions over the period of observation. Similarly, the drained site 

16 displayed generally lower pore water pressure and higher safety factors except for two events 

17 when drains were evidently overwhelmed with the volume of local surface and subsurface flows. 

18 These results suggest, but do not prove, that bank dewatering promoted lower rates of bank 

19 retreat and higher levels of stability since the three sites had slight differences in soils, geometry

20 and boundary conditions. Initial cost of the dewatering treatments were significantly less than 

21 orthodox bank stabilization measures, but operation and maintenance requirements could be 

22 greater. 

23 Observed bank retreat was much greater during the first wet season than during the second, even 

24 though more rainfall occurred during the second wet season (Pezeshki et al. 2007). During the 

25 first wet season, which was colder as well as drier, freeze–thaw action might have primed the 

26 bank for subsequent mass failure by opening vertical cracks extending from the floodplain 

27 surface into the upper bank. Sloughing associated with freeze–thaw and mass failures during the 

28 first year produced material that accumulated at the bank toes, reducing the bank angles and 

29 perhaps increasing stability. For stability modelingmodelling, the initial bank profiles were used 

30 for the entire 2-year simulation, leading to an underestimation of stability in the second year. 

31 Evidently freeze–thaw processes play a role in bank stability even in the relatively mild climate 

32 of northern Mississippi, and these processes are partially addressed by dewatering. The 

33 effectiveness of freeze–thaw cycling depends on an adequate moisture supply to form ice 

34 crystals and thus dewatering should retard freeze–thaw to some degree. Also, because of the high 

35 specific heat capacity of water, changes in soil moisture affect how rapidly soil temperature 

36 changes. 

37 Differences in the volume of water discharged by the drains and pumps as well as the differences 

38 among the four pumps suggest that movement of groundwater through the site was 

39 heterogeneous, probably as a result of the lenses of coarser and finer bed material that compose 

40 the bank materials and the presence of macropores (Wilson et al. 2008).(Wilson et al. 2007). As 

41 noted above, the local topography and a shallow waterway directed more surface runoff toward 

42 the drained site than the other two sites. Differences in surface soil were also observed, 

43 particularly in regard to dry season pore water pressure at a depth of 0D30 m. They ascribe these 

44 differences primarily to differences in soils and local hydrology instead of dewatering treatment 

45 because pumps and drains likely had little impact on soil moisture this far above the water table. 
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Chapter 7. Hydromodification 53 

1 In addition, at 0D30 m both plots responded to near-surface fluxes of rainfall, drainage and 

2 evapotranspiration rather than movements of water deeper in the bank profile. Clearly, precise 

3 comparison of the two methods of bank dewatering is not possible because of the site-specific 

4 conditions at each plot, but this is typical of field demonstrations as opposed to carefully 

5 controlled but less realistic laboratory experiments. 

6 Because shallow soil moisture (0D30 m) was not responsive to pumping, and since pumping 

7 occurred during the wetter winter and early spring months when vegetation was dormant, 

8 impacts of bank dewatering on vegetation were likely slight, and none were visually observed. 

9 Bank vegetation is desirable at most sites for aesthetic, environmental and stability reasons and 

10 impacts of dewatering on vegetation should be considered when such a project is planned. Site 

11 soils, hydrology and geometry will interact with the local plant community in site-specific ways. 

12 However, the main effects of correctly designed bank dewatering will generally be beneath the 

13 root zone, as for their site. 

14 The dewatered plots experienced bank retreat rates that were about half as great as the control 

15 plot rate. However, definite linkage between dewatering and bank retreat suppression would 

16 require multiple study sites and careful accounting for site differences in soils, groundwater 

17 movement, bank geometry and chemistry. Lack of replication was a fundamental limitation of 

18 this study. Bank retreat rates show great spatial variation when measured at smaller scales, and 

19 more sites would be required to address this source of variation. For example, Shields et al. 

20 (2004) reported results of surveys of 38 cross-sections along a 2 km reach of Little Topashaw 

21 Creek that encompassed the sites studied herein. The standard deviation of bank retreat for a 

22 given year was 1D5 to 3D0 times the annual mean. Retreat rates for the plots are comparable if 

23 site characteristics are carefully considered. Although the plots were located at different 

24 positions along the outside of the creek meander bend (Figure 2), removal of failed material from 

25 bank toes by fluvial action was not a significant erosion driver during the study period—in fact, 

26 there was some deposition in the toe areas adjacent to the plots as revealed in crosssection 

27 surveys summarized by Shields et al. (2004). Higher safety factors observed for the drained site 

28 were partially due to more gradual bank slope there, and the lack of pre-treatment data for that 

29 site made it impossible to conduct the kind of statistical tests that were done for the pumped site. 

30 Therefore use of passive drains was not shown to have an effect on bank retreat, although there 

31 were promising indications that drainage could improve bank stability under some conditions. It 

32 is notable that the failure events detected by the time series of computed safety factor (Figure 4E, 

33 Table IV) show lower minima for the drained plot than for the other treatments. These minima 

34 suggest that during certain hydrologic conditions the drains were simply overwhelmed with 

35 surface and subsurface flow, greatly increasing pore water pressure at key depths. 

36 Performance of the drains could have been improved by modifying drain design parameters 

37 (depth and spacing) using better information regarding soil permeability and hydrologic loading 

38 than we had available. Both dewatering treatments were relatively inexpensive compared with 

39 other methods of bank stabilization; total initial costs were $1200 and $370 for the pumped and 

40 drained plots, respectively (year 2000 dollars). Each plot stabilized about 30 m of bank at a cost 

41 of $40 per meter for the pumped plot and $12 per meter for the drained plot. This compares with 

42 costs of approximately $300/m for stabilization using re-grading and riprap, though there are 

43 recurrent costs associated with maintenance for both dewatering systems. Bank dewatering can 
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Chapter 7. Hydromodification 54 

1 be practical to protect critical infrastructure and provides a potential means of temporarily 

2 stabilizing a bank while vegetation is becoming established. 

3 The WVCA project manager designed and installed a 1.5-acre buffer along Links Run. The 

4 buffer was designed to enhance wildlife and demonstrated the feasibility of allowing the 

5 landowner to plant the trees himself while using the cost-share rate for larger and better tree 

6 stock. Two-hundred linear feet of streambank was protected with this plan. Nutrient management 

7 planning was a component of this project as well. In March the finishing touch was put on the 

8 first streambank stabilization demonstration project completed in 2008 with the establishment of 

9 a six acre woody buffer. Over twelve-hundred willows, dogwoods and other appropriate 

10 streamside trees and shrubs were planted at the site. BEHI surveys showed that 24 tons of 

11 sediment are being eroded from the site post construction. This is contrary to the 793 tons being 

12 lost annually before implementation. 

13 Lost River load reductions Wildlife Buffer Plan (WBP) vs. implemented

Pollutant WBP reductions Estimated reductions % Reductions

Nitrogen (lbs/yr) 29,954 1,230 4.11%

Phosphorus (lbs/yr) 2,700 4,739 175.54%

Sediment (tons/yr) 5,300 769 14.51%

Fecal coliform CFUs/yr 2.39E+17 2.14E+14 0.09%

14 

15 

16 A second bioengineering streambank stabilization project was completed. In it, 250 feet of 

17 eroding streambank was stabilized using bank-sloping, bio-engineering products and stabilizing 

18 toe of slope with rock. The intent of this project was to use low-cost stream restoration 

19 techniques versus more costly natural stream restoration or riprap. After stabilization, 

20 streambank exclusion and pasture division fencing was installed allowing 22 livestock rotation, 

21 the estimated fecal reduction is 5.62 x 10^14 cfu/year. A nutrient management plan was 

22 developed that managed 1,230.3 pounds of N and 4,739,128 pounds of P. 

23 In addition to the WVCA streambank projects, NRCS has installed 11,840 feet of stream 

24 exclusion fencing. Over 3000 feet of the fencing was used to protect 6.3 acres of new woody 
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Chapter 7. Hydromodification 55 

1 riparian buffers. Outreach is an important component of the project, presentations were made to 

2 reach 78 people and site tours were given for the director of the Chesapeake Bay Program, 

3 representatives of Senator Robert Byrd and 23 other agricultural officials. Working with the 

4 Baker High School, an Earth Team Volunteers group was established to support the efforts. 

5 These volunteers joined with West VirginiaWV Division of Natural Resources, Baker Run 

6 Conservation Society, and USDA NRCS to electroshock in Bear’s Hell Run for biomass and 

7 species present. 

8 Lost River WBP implementation

BMP Units

Units 

planned

Units 

installed

%

Goal

Land retirement Acres 500 0.0%

Animal waste facility Structures 13 1 7.7%

Tree planting Acres 50 0.0%

Nutrient management Acres 500 0.0%

Off-stream watering w/ fencing Units 10 3 30.0%

Off-stream watering w/ fencing and rotational grazing Units 20 1 5.0%

Riparian buffers Acres 100 28 28.0%

Natural stream restoration Linear feet 10,000 1,750 17.5%

Totals 11,193 1,783 15.9%

9 

10 
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Chapter 7. Hydromodification 56 

1 The Mill Creek watershed headwaters are in Virginia, but most of Mill Creek is in the 

2 southeastern part of Berkeley County. It is 14.5 miles long (one mile of which is in Virginia), 

3 and its watershed covers 29.75 square miles. Mill Creek and Torytown Run are on the 303(d) list 

4 for biological impairment, with organic enrichment and sedimentation determined to be the 

5 biological stressors. These two streams are listed for fecal coliform impairment as well. 

6 Therefore, Mill Creek and Torytown Run received TMDL allocations for sediment and fecal 

7 coliform. Sylvan Run is listed for biological impairment only, and the biological stressor is 

8 sedimentation. Therefore, Sylvan Run received a sediment TMDL. Two projects are focusing on 

9 Mill Creek, the Conley Natural Stream Design Project funded from FY 2006 319 funds and the 

10 Mill Creek Project using FY 2009 319 funds. Only the FY 06 funds were actually available 

11 during FY 2009; therefore, only the Conley Project was implemented. 

12 Bukaveckas (2007)Bukaveckas (2007) studied the interplay between hydrogeomorphic features 

13 and ecosystem processes within designed channels. Water velocity, transient storage, and 

14 nutrient uptake were measured in channelized (prerestoration) and naturalized (postrestoration) 

15 reaches of a 1-km segment of Wilson Creek (Kentucky) to assess the effects of restoration on 

16 mechanisms of nutrient retention. Stream restoration decreased flow velocity and reduced the 

17 downstream transport of nutrients. Median travel time was 50 percent greater in the restored 

18 channel because of lower reachscale water velocity and the longer length of the meandering 

19 channel. Transient storage and the influence of transient storage on travel time were largely 

20 unaffected except in segments where backwater areas were created. First order uptake rate 

21 coefficients for N and P were 30- and 3-fold higher (respectively) within the restored channel 

22 relative to its channelized state. Changes in uptake velocities were comparatively small, 

23 suggesting that restoration had little effect on biochemical demand. Results from this study 

24 suggest that channel naturalization enhances nutrient uptake by slowing water velocity. 

25 Klocker et al. (2009)Klocker et al. (2009) quantified nitrate uptake in two restored and two 

26 unrestored streams in Baltimore, Maryland, using nitrate additions, denitrification enzyme 

27 assays, and a 15N isotope tracer addition in one of the urban restored streams, Minebank Run. 

28 Restoration included either incorporation of stormwater ponds below a storm drain and catch 

29 basins to attenuate flow or hydrologic reconnection of a stream channel to its floodplain. Stream 

30 restoration was conducted for restoring aging sanitary and bridge infrastructure and introducing 

31 some stormwater management in watersheds developed before current regulations. 

32 Denitrification potential in sediments was variable across streams, whereas nitrate uptake length 

33 appeared to be significantly correlated to surface water velocity, which was low in the restored 

34 streams during summer baseflow conditions. 

35 Schwartz and Herricks (2007)Schwartz et al. (2007) evaluated pool-riffle naturalization 

36 structures on habitat complexity and the fish community in an urban Illinois stream. A 0.62-km 

37 reach of the North Branch of the Chicago River in Northbrook, Illinois. Initial surveys of channel 

38 morphology, habitat and biota identified poor pool-riffle bed structure and fish biodiversity, 

39 which became the basis for research and development of a pool-riffle structure specifically 

40 designed for constrained, low-gradient channels. Habitat and fish surveys were conducted pre41 and post-construction. The project improved mesohabitat structure, and fish abundance, and 

42 biomass and diversity were greater for 2 years following construction (2002–2003) compared to 

43 3 years before construction (1999–2001). However, the improved fish metrics were in the low 

44 range when compared to rural streams in the same ecoregion, and the fish community consisted 
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Chapter 7. Hydromodification 57 

1 primarily of tolerant, slow-water species. Absent were intolerant and riffle dwelling species, such 

2 as insectivorous cyprinids and darters. Assessing pre- and post-project ecological condition and 

3 using species information provided a basis for ecologically informed design and expanded our 

4 understanding of the limitations to restoring urban streams. 

5 The pre-design assessment of habitat and fish identified an urban channel with limited deep pool 

6 habitat consisting mostly of glide-riffle mesohabitat structure, and poor fish community 

7 structure. Identification of the single area of high fish abundance and biomass at Shermer Road 

8 suggested that increasing the number and depth of pools was a critical design criterion for the 

9 project. Pre-project assessments for habitat and biota have been shown useful for overall project 

10 appraisal (Charbonneau and Resh 1992; Purcell et al. 2002). However, pre-design assessments in 

11 these projects relied on qualitative habitat surveys and did not specifically guide the in-channel 

12 design analysis supports the view that a broader examination of the stream ecosystem and 

13 watershed-derived stressors is necessary to advance our restoration science. Important research 

14 questions on improving the biological integrity of urban streams remain, such as (1) can critical 

15 ecological processes be restored by in-channel, reach-scale projects and (2) how can watershed16 scale restoration be achieved by multiple reach-scale projects. The second question should 

17 consider what type of habitat enhancement, how many structures and where they are placed in 

18 the watershed. But more importantly, it must acknowledge or address the persistent hydrological 

19 and ecological stressors. Restoration practitioners and academics alike are interested in better 

20 understanding the ecological limitations to restoring urban watersheds (Palmer et al. 2005; 

21 Gillilan et al. 2005), and how to rehabilitate the lost ecological processes (Jannsson et al. 2005). 

22 The availability of quality mesohabitat structure will be a key element to any restoration 

23 initiative, as suggested by the more robust fish community developed after constructing the 

24 Northbrook project. However, improvements in watershed-scale restoration initiatives that better 

25 integrate stormwater programs with in-channel projects are seriously needed (Urbonas 2001). 

26 Restoration challenges are many in urban streams, with streams physically constrained by 

27 development and biota impaired by multiple stressors, but advances in restoration approaches 

28 can be achieved by baseline habitat and biota assessments, new design development integrated 

29 with assessments, effective project monitoring and improved watershed management. 

30 Kuhnle et al. (2008)Kuhnle (2008) studied the effects of conservation practices, such as enrolling 

31 erodible lands in the Conservation Reserve Program and in-stream grade stabilization structures 

32 in the Goodwin Creek Experimental Watershed in north Mississippi. The study found that mean 

33 sediments yields would increase from 15 percent to over 200 percent depending on location in 

34 the watershed, if in-channel structures were not present. The combined effect of the grade35 control structures and the change of lands because of CRP-enrollment was a reduction in 

36 sediment yields by 78 percent near the outlet of the watershed. 

37 Increased delivery of Nnitrogen because of urbanization and stream ecosystem degradation is 

38 contributing to eutrophication in coastal regions of the eastern United States according to 

39 Kaushal et al. (2008) who tested whether geomorphic restoration involving hydrologic 

40 reconnection of a stream to its floodplain could increase rates of denitrification at the riparian41 zone–stream interface of an urban stream in Baltimore, Maryland. Rates of denitrification 

42 measured using in situ 15N tracer additions were spatially variable across sites and years and 

43 ranged from undetectable to .200 lg N (kg sediment). Concentrations of nitrate-N in groundwater 

44 and stream water in the restored reach were also significantly lower than in the unrestored reach, 
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Chapter 7. Hydromodification 58 

1 but this might have also been associated with differences in sources and hydrologic flow paths. 

2 Riparian areas with low, hydrologically connected streambanks designed to promote flooding 

3 and dissipation of erosive force for storm water management had substantially higher rates of 

4 denitrification than restored high nonconnected banks and both unrestored low and high banks. 

5 Coupled measurements of hyporheic groundwater flow and in situ denitrification rates indicated 

6 that up to 1.16 mg NO3-N could be removed per liter of groundwater flow through one cubic 

7 meter of sediment at the riparian-zone–stream interface over a mean residence time of 4.97 d in 

8 the unrestored reach, and estimates of mass removal of nitrate-N in the restored reach were also 

9 considerable. Mass removal of nitrate-N appeared to be strongly influenced by hydrologic 

10 residence time in unrestored and restored reaches. Results of the study suggest that stream 

11 restoration designed to reconnect stream channels with floodplains can increase denitrification 

12 rates, that there can be substantial variability in the efficacy of stream restoration designs, and 

13 that more work is necessary to elucidate which designs can be effective in conjunction with 

14 watershed strategies to reduce nitrate-N sources to streams. 

15 Cost Data 

16 The most common restoration activities found by Alexander and Allan (2006) were the use of 

17 sand traps and riprap, and other common activities were related to the improvement of fish 

18 habitat. The median cost was $12,957 for projects with cost data, and total expenditures since 

19 1990 were estimated at $444 million. Over time, the cost of individual projects has increased, 

20 whereas the median size has decreased, suggesting that restoration resources are being spent on 

21 smaller, more localized, and more expensive projects. Only 11 percent of data records indicated 

22 that monitoring was performed, and more expensive projects were more likely to be monitored. 

23 Standardization of monitoring and record keeping and dissemination of findings are urgently 

24 needed to ensure that dollars are well spent and restoration effectiveness is maximized. 

25 Implications for practicePractice

26 • Stream restoration in the Midwest is increasing; yet, lack of project documentation and 

27 monitoring have inhibited the learning cycle. 

28 • Since the early 1990s, total expenditures on stream restoration in the upperUpper

29 Midwest region are approximately $444 million. 

30 • Project goals have emphasized improvements in in-stream habitat, riparian and bank 

31 condition, and water quality. 

32 • Standardizing Standardization of monitoring and record keeping and dissemination of 

33 findings are urgently needed to ensure that dollars are well spent and restoration 

34 effectiveness is maximized. 

35 Design Guidance and additional info 

36 Rosgen, D. 1996. Applied River Morphology. Wildland Hydrology, Pagosa Springs, CO. 
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Chapter 7. Hydromodification 59 

1 2.2.5.15 Step Pools 

2 Description 

3 Step pools are rock grade-control structures constructed in the stream channel that recreate 

4 natural step-pool channel morphology. 

5 Application and Purpose 

6 Step-pool channels are characterized by a succession of channel-spanning steps formed by large, 

7 grouped boulders called clasts that separate pools containing finer bed sediments. They are 

8 constructed in higher gradient channels where a fixed-bed elevation is required. Step pools are 

9 built in series and allow for stepping down the channel over a series of drops. The steps are 

10 constructed of large rock with the pools containing smaller rock material. As flow tumbles over 

11 the step, energy is dissipated into the plunge pool. 

12 Step-pools can be used to backwater a culvert, providing improved fish passage and can be used 

13 to connect two reaches with different elevations. 

14 Step-pool morphologies are typically associated with well-confined, high-gradient channels with 

15 slopes greater than 3 percent, having small width-depth ratios and bed material dominated by 

16 cobbles and boulders. Step pools generally function as grade-control structures and aquatic 

17 habitat features by reducing channel gradients and promoting flow diversity. At slopes greater 

18 than roughly 6.5 percent, similar morphologic units termed cascades spanning only a portion of 

19 the channel width are formed in these channel conditions. 

20 Step pools are not generally considered a habitat enhancement practice. The enhancement 

21 potential is in the form of maintaining fish passage and expanding the total amount of habitat 

22 available for fish. 

23 Cost Data 

24 Construction costs for step pools are highly variable, depending on the design, size of the stone, 

25 availability of materials, and site constraints. 

26 Design Guidance and additional info 

27 The following documents provide design information and guidance for vanes. 

28 Stream Restoration: A Natural Channel Design Handbook, prepared by the North Carolina 

29 Stream Restoration Institute and North Carolina Sea Grant. 

30 http://www.bae.ncsu.edu/programs/extension/wqg/srp/sr_guidebook.pdf

31 The Virginia Stream Restoration & Stabilization Best Management Practices Guide, Department 

32 of Conservation and Recreation, Division of Soil and Water Conservation 2004. 

33 http://www.dcr.virginia.gov/soil_and_water/documents/streamguide.pdf
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Chapter 7. Hydromodification 60 

1 2.2.5.16 Streambank Dewatering 

2 Description 

3 Using groundwater level management adjacent to an eroding streambank to lower static water 

4 pressure on bank and reduce erosion potential.

5 Application and Purpose 

6 Streambank dewatering is the practice of actively or passively reducing the static water level 

7 immediately adjacent to a streambank with erosion potential for the purposes of reducing poor 

8 water pressure within the streambank. The reduced pore pressure improves the shear strength of 

9 bank soils. As shear strength is one of several governing factors for bank failure, a reduction in 

10 bank failure rates and potential is expected. 

11 Dewatering systems can take several forms. Specific designs which are discussed in the research 

12 literature are vertical groundwater wells managed by an active pumping system and installing 

13 horizontal tile drains, which provide passive drainage for the riparian zone. While other 

14 dewatering system designs might be possible, no published information on additional methods 

15 are available. The location, depth, capacity, and configuration of the dewatering systems vary 

16 depending on local conditions, and no published guidance on streambank dewatering is 

17 available. 

18 Using streambank dewatering is not widespread. A number of alternative practices are available 

19 that might be more suitable for a particular application. Dewatering systems that rely on 

20 pumping systems have an inherent long-term maintenance and operational cost. For those, 

21 reasons streambank dewatering might be most appropriate for short-term use or in areas where 

22 grading and practice installation along the bank are not possible (such as because of utility 

23 conflicts, access constraints, and the like). In addition, it is important to note that streambank 

24 dewatering can affect riparian habitat condition and available groundwater for riparian habitat. 

25 Where wetlands are present adjacent to the stream, dewatering could affect the wetland 

26 condition. 

27 Performance 

28 Shields et al. (2009)Shields et al. (2009) reported that streambank dewatering resulted in reduced 

29 rates of bank erosion on a deeply incised channel in northern Mississippi (2009). Pumped and 

30 passive drain systems exhibited bank erosion of 0.21 m and 0.23 m, respectively, over a 2-period 

31 of two wet seasons, while a streambank without dewatering exhibited erosion of 0.43 m. While 

32 reduced bank erosion was observed where streambank dewatering was used, the researches note 

33 that at some individual monitoring stations, bank erosion exceeded control values. 

34 Cost Effectiveness 

35 While no published cost information is available, Shields et al. (2009)Sheild et al. (2009) report 

36 that initial costs of dewatering systems was significantly lower than more orthodox bank 

37 stabilization measures, while it was acknowledged that long term pumping and maintenance 

38 costs were neglected. 
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Chapter 7. Hydromodification 61 

1 2.2.5.17 Vegetated Gabions 

2 Description 

3 A gabion is a rectangular basket made of heavily galvanized wire mesh filled with small to 

4 medium size rock. The gabions are laced together and installed at the base of a bank to form a 

5 structural toe or sidewall. Vegetation can be incorporated by placing live branches between each 

6 layer of rock filled baskets. The branches take root inside the gabions and in the soil behind the 

7 structures. Their roots eventually consolidate the structure and bind it to the slope. 

8 Application and Purpose 

9 The National Management Measures to Control Nonpoint Sources Pollution from 

10 Hydromodification document (USEPApublished by EPA in 2007) contains a chapter on the 

11 practice of vegetated gabions. At the time of this writing no additional information is provided 

12 pertaining to this practice. For information on the appropriate use and application for vegetated 

13 gabions, see the 2007 guide. 

14 Cost Effectiveness 

15 Vegetated gabions are comparable to vegetated geogrids and vegetated reinforced soil slope, 

16 ranging from $15 to $40 per square foot. Construction costs vary with the structure’s design 

17 (materials, depth into the streambed, height and width, and such), site access, time of year, 

18 degree and type of associated channel redefinition, and equipment and labor rates. 

19 2.2.5.18 Vegetated Geogrids 

20 Description 

21 Vegetated geogrids are the covering of soil with erosion control fabric (geotextile) on the slope 

22 of the bank. The erosion control fabric is secured by tucking it into the slope. Live cuttings are 

23 placed between the geogrids, and a root structure is established to bind the soil within and behind 

24 the geogrids. The toe of the bank is stabilized by layers of rock on top of the same geotextile 

25 fabric. 

26 Application and Purpose 

27 The National Management Measures to Control Nonpoint Sources Pollution from 

28 Hydromodification document (USEPApublished by EPA in 2007) contains a chapter on the 

29 practice of Vegetated Geogrids. At the time of this writing no additional information is provided 

30 pertaining to this practice. For information on the appropriate use and application for vegetated 

31 geogrids, see the 2007 guide. 

32 Cost Data 

33 Vegetated geogrids range in cost from $20 to $40 per square foot depending on the design and 

34 construction techniques (Sotir and Fischenich 2003). 
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Chapter 7. Hydromodification 62 

1 2.2.5.19 Vegetated Reinforced Soil Slope (VRSS) 

2 Description 

3 The vegetated reinforced soil slope (VRSS) soil system is an earthen structure constructed from 

4 living, rootable, live-cut, woody plant material branches, bare root, tubling or container plant 

5 stock, along with rock, geosynthetics, geogrids, and/or geocomposites. 

6 Application and Purpose 

7 The National Management Measures to Control Nonpoint Sources Pollution from 

8 Hydromodification document (USEPApublished by EPA in 2007) contains a chapter on the 

9 practice of Vegetated Reinforced Soil Slopes. At the time of this writing, no additional 

10 information is provided pertaining to this practice. For information on the appropriate use and 

11 application for vegetated reinforced soil slopes, see the 2007 guide. 

12 Cost Data 

13 Vegetated reinforced soil slopes structure costs typically range from $15 to $35 per square face 

14 foot. These prices do not include design, which can be extensive because of the required 

15 geotechnical data collection and analysis. Harvesting, transportation, handling, and storage of the 

16 live-cut branch materials or rooted plants can significantly influence cost, and are included in the 

17 above range. 

18 Construction costs also vary with the structure’s design (materials, depth into the streambed, 

19 height and width, etc.), site access, time of year, degree and type of associated channel 

20 redefinition, and equipment and labor rates. Installation is relatively complex, as it can require 

21 large earth-moving machinery. Installation, excavation, and soil replacement costs are usually 

22 high. 

23 2.2.5.20 Weirs 

24 Description 

25 This is a technique in which boulders or logs are laced across the channel and anchored to the 

26 channel bank and/or bed to check the water and raise its level for diversion purposes; they are 

27 designed to allow overtopping. 

28 Application and Purpose 

29 Low profile in-stream structures such as vortex rock weirs and w-weirs are primarily used to 

30 create aquatic habitat in the form of scour pools and for grade control on incising streams and 

31 rivers. Additionally, they are well-suited for channeling flow away from unstable banks. Weirs 

32 are used to collect and retain gravel for spawning habitat, to deepen existing resting/jumping 

33 pools; to create new pools above or below the structure, to trap sediment, to aerate the water, and 

34 to promote deposition of organic debris. 

35 There are several types of weirs, but the two most common types for stream restoration are the 

36 W-weir and the rock vortex weir. Both types provide grade control and reduce bank erosion. The 

37 weirs accumulate sediment behind the weir arms and create a scour pool downstream of the 

38 structure. A rock W-weir is a stone structure composed of footer and vane rocks and consists of 
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Chapter 7. Hydromodification 63 

1 four weir arms arranged in a W fashion across the channel. A rock vortex weir consists of footer 

2 and vane rocks, and the form of the rock vortex weir is parabolic and spans the channel width. 

3 The rock vortex weir accumulates sediment behind the weir arms and creates a scour pool 

4 downstream of the structure. 

5 Weirs are typically suited for use in moderate to high gradient streams. W-weirs are best used in 

6 rivers with bankfull widths greater than 40 feet (12 meters). Weirs should be avoided in channels 

7 with bedrock beds or unstable bed substrates, and streams with naturally well-developed, pool8 riffle sequences. 

9 Cost Data 

10 Construction costs for weirs are highly variable, depending on width of the channel, size of the 

11 stone, availability of materials, and site constraints. 

12 Design Guidance and additional info 

13 The following documents provide design information and guidance for vanes. 

14 Stream Restoration: A Natural Channel Design Handbook, prepared by the North Carolina 

15 Stream Restoration Institute and North Carolina Sea Grant. 

16 http://www.bae.ncsu.edu/programs/extension/wqg/srp/sr_guidebook.pdf

17 2.2.5.21 Wing Deflectors 

18 Description 

19 Wing deflectors are devices made of a variety of materials that project outward into the channel 

20 from one or both streambanks but do not extend entirely across the channel. Wing deflectors are 

21 especially effective in wide, shallow, low gradient streams to create pools and cover.

22 Application and Purpose 

23 Wing deflectors are designed to deflect flows away from the bank and create scour pools by 

24 constricting the channel and accelerating flow. The structures can be installed in series on 

25 alternative streambanks to produce a meandering thalweg and stream diversity. The most 

26 common design is a rock and rock-filled log crib deflector structure. The design bases the size of 

27 the structure on anticipated scour. These structures need to be installed far enough downstream 

28 from riffle areas to avoid backwater effects that could drown out or damage the riffle. This 

29 design should be employed in streams with low physical habitat diversity, particularly channels 

30 that lack pool habitats. Construction on a sand bed stream can be susceptible to failure and 

31 should be constructed with the use a filter layer or geotextile fabric beneath the wing deflector 

32 structure (FISRWG 1998). 

33 When two wing deflectors are placed opposite each other they serve to narrow or constrict the 

34 flow of water. The double wing deflector is more often used in urban applications as it forces the 

35 water toward the center of the channel and deepens the baseflow channel. Double wing 

36 deflectors also create an area of increased velocity between them, enhancing riffle habitat 

37 between and just upstream of the structure. This increased velocity also creates an area of scour, 

38 creating pool habitat downstream of the structure. The construction is the same as a single wing 
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Chapter 7. Hydromodification 64 

1 deflector except that in some instances, a rock sill at the stream invert can connect the two 

2 structures. 

3 Both single and double wing deflectors have significant habitat enhancement potential. These 

4 structures enhance habitat through pool formation, the narrowing and deepening of the baseflow 

5 channel, and the enhancement of riffle habitat. Deflectors protect the bank in the immediate area 

6 and provide desirable changes to the stream flow patterns. They are relatively easy to construct, 

7 inexpensive, easily modified to suit on-site conditions, and are adaptable for use with other 

8 treatments. They are significantly cheaper to install than dam-type structures. They are effective 

9 in sections of streams where the banks are too low or too wide for dams. 

10 The following limitations apply to stream deflectors: 

11 • Deflectors should not be used in unstable streams which do not retain a constant planform 

12 or are actively incising at a moderate to high rate. 

13 • Deflectors are ineffective in bedrock channels since minimal bed scouring occurs. 

14 Conversely, streams with fine sand, silt, or otherwise unstable substrate should be 

15 avoided since significant undercutting can destroy these measures. 

16 • Deflectors should not be used in stream reaches which exceed a 3 percent gradient. 

17 • Deflectors should not be used in streams with large sediment or debris loads. 

18 • Banks opposite these structures should be monitored for excessive erosion. 

19 Design Guidance and additional info 

20 Additional Resources 

21 FISRWG (Federal Interagency Stream Restoration Working Group). 1998. Stream Corridor 

22 Restoration: Principles, Processes, and Practices. Federal Interagency Stream Restoration 

23 Working Group. 

24 http://www.nrcs.usda.gov/technical/stream_restoration/PDFFILES/APPENDIX.pdf. 

25 Massachusetts DEP. 2006. Massachusetts Nonpoint Source Pollution Management Manual: 

26 Wing Deflectors. Massachusetts Department of Environmental Protection, Boston, MA. 

27 http://projects.geosyntec.com/NPSManual/Fact%20Sheets/Wing%20Deflectors.pdf. 

28 Mississippi State University, Center for Sustainable Design. 1999. Water Related Best 

29 Management Practices in the Landscape: Single Wing Deflector. Prepared for the U.S. 

30 Department of Agriculture, Natural Resource Conservation Service, Watershed Science 

31 Institute. http://www.abe.msstate.edu/csd/NRCS-BMPs/pdf/streams/bank/singlewing.pdf. 

32 Mississippi State University, Center for Sustainable Design. 1999. Water Related Best 

33 Management Practices in the Landscape: Double Wing Deflector. Prepared for the U.S. 

34 Department of Agriculture, Natural Resource Conservation Service, Watershed Science 

35 Institute. http://abe.msstate.edu/csd/NRCS-BMPs/pdf/streams/bank/doublewing.pdf. 

36 Ohio DNR (Department of Natural Resources). No date. Ohio Stream Management Guide: 

37 Deflectors. Ohio Department of Natural Resources. 

38 http://www.ohiodnr.com/water/pubs/fs_st/stfs19.pdf. 
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Chapter 7. Hydromodification 65 

1 SMRC (Stormwater Manager’s Resource Center). No date. Stream Restoration: Flow 

2 Deflection/Concentration Practices. The Stormwater Manager’s Resource Center. 

3 http://www.stormwatercenter.net/Assorted%20Fact%20Sheets/Restoration/flow_deflection

4 .htm. 
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Chapter 7. Hydromodification 66 

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5 Alexander, G.G., and J.D. Allan 2006). Stream restoration in the Upper Midwest, USA. 

6 Restoration Ecology 14(4):595–604.

7 Alexander, G.G., and J.D. Allan 2007). Ecological success in stream restoration: Case studies 

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9 Allen, H., and C. Fischenich. 2000. Coir Geotextile Roll and Wetland Plants for Streambank 

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31 Hydraulic Engineering-ASCE 134(3):295–302.

32 Charbonneau, R., and V.H. Resh. 1992. Strawberry creek on the University of California, 

33 Berkeley campus: A case history of urban stream restoration. Aquatic Conservation: 

34 Marine and Freshwater Ecosystems 2(4):293–307.
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1 Chesapeake Bay Program. 2009. Bay Barometer: A Health and Restoration Assessment of the 

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1 Kaushal, S.S., P.M. Groffman, P.M. Mayer, E. Striz, and A.J. Gold. 2008. Effects of stream 

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