U.S. Department of the Interior

U.S. Geological Survey

Scientific Investigations Report 2010–5128

Prepared in cooperation with the Johnson County Stormwater Management Program

Effects of Urbanization, Construction Activity, 

Management Practices, and Impoundments on SuspendedSediment Transport in Johnson County, Northeast Kansas, 

February 2006 through November 2008
2 Report Title

Cover photographs.  Photographs taken after a storm in the headwaters of Clear Creek, Lenexa, Kansas, April through May 2007.

Photographs courtesy of Dale Clark, City of Lenexa.

Erosion from a residential 

construction site.

Gully formation near culvert.

Sediment deposition downstream 

from culvert
Effects of Urbanization, Construction Activity, 

Management Practices, and Impoundments 

on Suspended-Sediment Transport in 

Johnson County, Northeast Kansas, 

February 2006 through November 2008

By Casey J. Lee and Andrew C. Ziegler

Prepared in cooperation with the Johnson County Stormwater Management

Program

Scientific Investigations Report 2010–5128

U.S. Department of the Interior

U.S. Geological Survey
U.S. Department of the Interior

KEN SALAZAR, Secretary

U.S. Geological Survey

Marcia K. McNutt, Director

U.S. Geological Survey, Reston, Virginia: 2010

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reproduce any copyrighted materials contained within this report.

Suggested citation:

Lee, C.J., and Ziegler, A.C., 2010, Effects of urbanization, construction activity, management practices, and impoundments on suspended-sediment transport in Johnson County, northeast Kansas, February 2006 through November 

2008: U.S. Geological Survey Scientific Investigations Report 2010–5128, 54 p.
iii

Contents

Abstract...........................................................................................................................................................1

Introduction.....................................................................................................................................................2

Purpose and Scope ..............................................................................................................................2

Description of Study Area ...................................................................................................................4

Construction Sites .......................................................................................................................4

Land Use......................................................................................................................................10

Previous Studies .................................................................................................................................12

Methods.........................................................................................................................................................15

Data Collection and Analysis............................................................................................................15

Quality Assurance...............................................................................................................................16

Regression Models.............................................................................................................................16

Estimating Periods of Turbidity Truncation.....................................................................................18

Estimating Sediment Loading during Periods of Missing Turbidity Data...................................20

Sediment Transport in Johnson County, Kansas....................................................................................22

Total and Annual Rainfall, Streamflow, and Sediment Transport in Mill Creek from

2006 to 2008.............................................................................................................................22

Sediment Transport from Subbasins with Increased Construction Activity.............................26

Turbidity Levels Relative to U.S. Environmental Protection Agency Construction

Effluent Guidelines .......................................................................................................26

Sediment Transport in the Clear Creek Basin.......................................................................27

Sediment Transport in the Shawnee Mission Lake Basin ..................................................29

Frequency and Storm-by-Storm Analysis of Streamflow and Sediment Transport in the

Mill Creek Basin.....................................................................................................................33

Sediment Transport from Varying Storms..............................................................................37

Comparison of Sediment Loads Across Johnson County............................................................44

Summary and Conclusions.........................................................................................................................49

References Cited..........................................................................................................................................51
iv

Figures

1.  Map showing location of sampling sites, basin boundaries, roads, and structures in

Johnson County, northeast Kansas, 2008.................................................................................3

2.  Map showing location of basin boundaries, sampling sites, and land use in the Mill

Creek Basin, Johnson County, northeast Kansas, 2008 .........................................................6

3.  Aerial photograph showing location of City Center North construction site,

sampling sites, and selected best management practices, Lenexa, Kansas, 2008...........8

4.  Photographs showing A, destroyed mulch berm and rock check at City Center

North development, and B, turbid water entering Shawnee Mission Lake, Lenexa,

Kansas, March 30, 2007 ...............................................................................................................9

5.  Aerial photograph showing location of construction sites and sampling sites in the

headwaters of Clear Creek, Lenexa, Kansas, 2004 through 2008 .......................................11

6.  Photographs showing A, erosion from a residential construction site, B, gully

formation near culvert, and C, sediment deposition downstream from culvert after

a storm in the headwaters of Clear Creek, Lenexa, Kansas, April through May 2007 ....13

7.  Graphs showing percentage impervious surface area A, upstream from and

B, between sampling sites in Johnson County, northeast Kansas, 2003

through 2008 ................................................................................................................................14

8.  Graph showing linear fit between cross section median and in-stream turbidity

readings at sites in the Mill Creek Basin, Johnson County, northeast Kansas,

February 2006 through November 2008...................................................................................17

9.  Graphs showing regression relations between turbidity and suspended-sediment

concentration at A, 12 Mill Creek sites and B, 2 sites downstream from detention

basins near Shawnee Mission Lake, Johnson County, northeast Kansas, February

2006 through March 2009 ..........................................................................................................19

10.  Graphs showing relation between suspended-sediment yield from 2006 to 2008 and

increases in impervious surface A, from 2005 to 2006 and B, from 2006 to 2008, Mill

Creek sites, Johnson County, Kansas .....................................................................................25

11.  Photographs showing A, sediment deposition in the Clear Creek channel upstream

from site CL1a, October 2007, and B, deposition in the Clear Creek channel adjace

to Clare Road construction, Lenexa, Kansas, October 2008................................................28

12.  Graph showing stormflow volume and sediment load for selected large storms in

the Clear Creek Basin, Johnson County, Kansas, 2007 through 2008 ................................29

13.  Graph showing stormflow volume and sediment load for the 20 largest storms at

site SM1, Lenexa, Kansas, 2007 ...............................................................................................31

14.  Graph showing stormflow volume, sediment load, and average sediment

concentration for the 10 largest storms upstream from Shawnee Mission Lake,

Lenexa, Kansas, 2008 .................................................................................................................32
v

15.  Graphs showing streamflow exceedance for A, hourly streamflow values and

B, the top 10 percent of hourly streamflow values at Mill Creek at Johnson Drive,

Johnson County, northeast Kansas, 2003 through 2008.......................................................34

16.  Graphs showing duration statistics for A, streamflow and B, streamflow normalized

by subbasin area for Mill Creek sampling sites operated from February 2007

through November 2008, Johnson County, northeast Kansas ............................................35

17.  Graph showing duration statistics for suspended-sediment concentrations at Mill

Creek sampling sites, February 2007 through November 2008, Johnson County,

northeast Kansas........................................................................................................................36

18.  Graph showing flow-weighted suspended-sediment concentrations compared to

streamflow exceedance at Mill Creek sampling sites, Johnson County, northeast

Kansas, February 2007 ...............................................................................................................37

19.  Graphs showing streamflow and suspended-sediment loading at less than 1-percent

streamflow exceedance intervals and between 1- and 10-percent exceedance

intervals for three storms at site MI7, Johnson County, northeast Kansas, 2007

through 2008 ................................................................................................................................38

20.  Graph showing daily rainfall in the basin upstream from site MI7 and numbered

storms with more than 0.5 inch of rainfall, Johnson County, northeast Kansas,

February 2006 through November 2008...................................................................................40

21.  Graphs showing suspended-sediment load and yield for the 10 largest storms in

the Mill Creek Basin, Johnson County, northeast Kansas, February 2006 through

November 2008............................................................................................................................41

22.  Graphs showing stormflow-weighted suspended-sediment concentrations for

groups of storms in the A, Clear Creek, B, Little Mill Creek, and C, mainstem Mi

Creek subbasins, Johnson County, northeast Kansas, February 2006 through

November 2008............................................................................................................................42

23.  Graph showing stormflow-weighted suspended-sediment concentrations by year

for storm ranges at sites in the Little Mill Creek Basin, Johnson County, northeast

Kansas, February 2006 through November 2008 ...................................................................43

24.  Graph showing slope and y-intercept of log-log relations between streamflow and

sediment loading for storms at Mill Creek sampling sites, Johnson County,

northeast Kansas, February 2006 through November 2008 .................................................46

25.  Graph showing stormflow-weighted suspended-sediment concentrations during

different storm sizes at the five largest sites in Johnson County, northeast Kansas,

February 2006 through November 2008...................................................................................48

26.  Photographs showing A, high-water mark on golf course and B, area of

channel-bank failure after the 25-year storm on July 30, 2008, at Indian Creek,

Johnson County, northeast Kansas.........................................................................................50
vi

Tables

1.  Location and contributing drainage area of sampling sites in Johnson County,

northeast Kansas, February 2006 through November 2008 ...................................................5

2.  Land use, channel slope, and major impoundments upstream from sampling sites in

Johnson County, northeast Kansas, 2008.................................................................................7

3.  Active construction sites, construction area, and phasing in the basins upstream

from sites CL1a, CL1b, and SM1, Lenexa, Kansas, 2004 through 2008...............................12

4.  Suspended-sediment concentration and percent silt/clay for samples collected

at Mill Creek sampling sites, Johnson County, northeast Kansas, February 2006

through March 2009 ...................................................................................................................17

5.  Sediment-load estimates during periods of turbidity truncation for sampling sites in

the Mill Creek Basin, Johnson County, northeast Kansas, February 2007 through

November 2008............................................................................................................................20

6.  Periods of missing turbidity record, regressions used to estimate stormflowweighted suspended-sediment concentrations and sediment loading, and total

estimated suspended-sediment load for sampling sites in the Mill Creek Basin,

Johnson County, northeast Kansas, February 2007 through November 2008 ..................21

7.  Total rainfall, streamflow and stormflow volumes, and peak streamflow upstream

from and at Mill Creek sampling sites, Johnson County northeast Kansas, February

2006 through November 2008....................................................................................................23

8.  Total suspended-sediment load, yield, and stormflow-weighted suspended-sediment

concentrations at Mill Creek sampling sites, Johnson County, northeast Kansas,

February 2006 through November 2008...................................................................................24

9.  Streamflow and sediment transport during streamflow values exceeded less than

1and 10 percent of the time, Mill Creek, Johnson County, northeastern Kansas,

February 2007 through November 2008...................................................................................39

10.  Multiple regression relations between suspended-sediment load and stormflow

magnitude, rainfall intensity, and antecedent rainfall and sediment-load conditions

for Mill Creek sampling sites, Johnson County, northeast Kansas, February 2006

through November 2008.............................................................................................................45

11.  Annual stormflow, stormflow yield, suspended-sediment load and yield, and

stormflow-weighted suspended-sediment concentrations at sampling sites in

Johnson County, northeast Kansas, February 2006 through November 2008 ..................47
vii

Conversion Factors and Datums

Multiply By To obtain

Length

centimeter (cm) 0.3937 inch (in.)

inch (in.) 2.54 centimeter (cm)

foot (ft) 0.3048 meter (m)

micrometer (μm) 0.00003937 inch (in.)

mile (mi) 1.609 kilometer (km)

Area

acre 4,047 square meter (m2

)

square mile (mi2) 2.590 square kilometer (km2) 

Volume

gallon (gal) 3.785 liter (L) 

gallon (gal) 0.003785 cubic meter (m3

) 

acre-foot (acre-ft) 1,233 cubic meter (m3)

Flow rate

acre-foot per square mile (acreft/mi2

)

476.25 cubic meter per square kilometer 

(m3/km2)

cubic foot per second (ft3/s) 0.02832 cubic meter per second (m3/s)

cubic foot per second (ft3/s) 1.9835 acre-feet per day (acre-ft/d)

cubic foot per second per square 

mile [(ft3/s/mi2])

0.01093 cubic meter per second per square 

mile [m3/s)/km2]

foot per mile (ft/mi) 0.1894 meter per kilometer (m/km)

million gallons per day (Mgal/d) 0.04381 cubic meter per second (m3

/s)

inch per hour (in/h) 25.4 millimeter per hour (mm/h)

Mass

gram (g) 0.03527 ounce (oz)

pound per second (lb/s) 43.2 ton per day (ton/d)

ton 2,000 pound (lb)

Yield

ton per square mile (ton/mi2) 0.3503 tonne per square kilometer (tonne/

km2)

Density

pound per cubic foot (lb/ft3) 16.02 kilogram per cubic meter (kg/m3)

pound per cubic foot (lb/ft3) 0.01602 gram per cubic centimeter (g/

cm3)

Hydraulic gradient

foot per mile (ft/mi) 0.1894 meter per kilometer (m/km)

Temperature in degrees Fahrenheit (°F) may be converted to degrees Celsius (°C) as follow

          °C=(°F-32)/1.8

Vertical coordinate information is referenced to the North American Vertical Datum of 1988

(NAVD 88).
viii

Horizontal coordinate information is referenced to the North American Datum of 1983 (NAD 83).

Altitude, as used in this report, refers to distance above the vertical datum.

Suspended-sediment concentrations are reported in milligrams per liter (mg/L).

Suspended-sediment loads are reported in tons.
Effects of Urbanization, Construction Activity, 

Management Practices, and Impoundments on 

Suspended-Sediment Transport in Johnson County, 

Northeast Kansas, February 2006 through November 2008

By Casey J. Lee and Andrew C. Ziegler

Abstract

The U.S. Geological Survey, in cooperation with the 

Johnson County, Kansas, Stormwater Management Program, 

investigated the effects of urbanization, construction activity, 

management practices, and impoundments on suspended-sediment transport in Johnson County from February 2006 through 

November 2008. Streamgages and continuous turbidity sensors were operated at 15 sites within the urbanizing 57-squaremile Mill Creek Basin, and 4 sites downstream from the other 

largest basins (49 to 66 square miles) in Johnson County.

The largest sediment yields in Johnson County were 

observed downstream from basins with increased construction activity. Sediment yields attributed to the largest (68 acre) 

active construction site in the study area were 9,300 tons per 

square mile in 2007 and 12,200 tons per square mile in 2008; 

5 to 55 times larger than yields observed at other sampling 

sites. However, given erodible soils and steep slopes at this site, 

sediment yields were relatively small compared to the range 

in historic values from construction sites without erosion and 

sediment controls in the United States (2,300 to 140,000 tons 

per square mile). Downstream from this construction site, 

a sediment forebay and wetland were constructed in series 

upstream from Shawnee Mission Lake, a 120-acre reservoir 

within Shawnee Mission Park. Although the original intent of 

the sediment forebay and constructed wetland were unrelated to 

upstream construction, they were nonetheless evaluated in 2008 

to characterize sediment removal before stream entry into the 

lake. The sediment forebay was estimated to reduce 33 percent 

of sediment transported to the lake, whereas the wetland did 

not appear to decrease downstream sediment transport. Comparisons of time-series data and relations between turbidity and 

sediment concentration indicate that larger silt-sized particles 

were deposited within the sediment forebay, whereas smaller silt 

and clay-sized sediments were transported through the wetland 

and into the lake. Data collected at sites up and downstream 

from the constructed wetland indicated that hydraulic retention 

alone did not substantially reduce sediment loading to Shawnee 

Mission Lake.

Mean-daily turbidity values at sampling sites downstream from basins with increased construction activity were 

compared to U.S. Environmental Protection Agency turbidity criteria designed to reduce discharge of pollutants from 

construction sites. The U.S. Environmental Protection Agency 

numeric turbidity criteria specifies that effluent from construction sites greater than 20 acres not exceed a mean-daily 

turbidity value of 280 nephelometric turbidity units beginning 

in 2011; this criteria will apply to sites greater than 10 acres 

beginning in 2014. Although numeric criteria would not have 

been applicable to data from sampling sites in Johnson County 

because they were not directly downstream from construction 

sites and because individual states still have to determine additional details as to how this criteria will be enforced, comparisons were made to characterize the potential of construction 

site effluent in Johnson County to exceed U.S. Environmental 

Protection Agency Criteria, even under extensive erosion and 

sediment controls. Numeric criteria were exceeded at sampling 

sites downstream from basins with increased construction 

activity for multiple days during the study period, potentially 

indicating the need for additional erosion and sediment controls and (or) treatment to bring discharges from construction 

sites into compliance with future numeric turbidity criteria.

Among sampling sites in the Mill Creek Basin, sediment yields from the urbanizing Clear Creek Basin were 

approximately 2 to 3 times those from older, more stable 

urban or rural basins. Sediments eroded from construction 

sites adjacent to or surrounding streams appear to be more 

readily transported downstream, whereas sediments eroded 

from construction sites in headwater areas are more likely 

to be deposited locally on land surfaces or within the stream 

network. Comparison of sediment yields among headwater 

and downstream sites in the Clear Creek Basin indicated that 

factors such as site and stream slope, the current phase of 

construction, management practices, and site location relative 

to streams affect the amount and length of time it takes eroded 
2 Effects on Suspended-Sediment Transport in Johnson County, Northeast Kansas, February 2006 through November 2008

sediment to be transported downstream. Sediment concentrations in Mill Creek tributaries downstream from increased 

construction activity were larger than other sites for a much 

longer period of time, likely decreasing light penetration and 

increasing fine sediment deposition on streambeds. Subbasins 

partially regulated by impoundments and those with stable 

urban land use had the smallest sediment concentrations and 

loads in the Mill Creek Basin.

The most extreme streamflows transported the most 

sediment throughout the Mill Creek Basin. Streamflows that 

occurred less than 1 percent of the time transported 73 to 

91 percent of sediment loads, whereas streamflows that 

occurred less than 10 percent of the time transported 93 to 

100 percent of sediment loads. Multiple regression analysis of 

the factors affecting sediment transport indicated the largest, 

most intense storms transport substantially larger sediment 

loads at all sampling sites. Large storms decreased sediment 

supplies available for transport by subsequent storms.

Contrary to results observed from smaller subbasins 

within the Mill Creek Basin, sediment yields from the predominantly mature, urban Indian Creek Basin were more 

than double those from other large urbanizing and rural (49 to 

66 square miles) basins in Johnson County from 2006 through 

2008. Larger sediment loads in the Indian Creek Basin likely 

originate from frequent stormflows that erode streambed and 

streambank sediments. Variation in sediment yields among 

other large basins in Johnson County are likely related to differences in the number and location of large impoundments 

and the magnitude and location of urban construction.

Introduction

Urban development causes substantial change to the 

form, flow, and ecology of streams. The removal of surface 

vegetation and excavation of soils for building and road foundations increase soil erosion during rainfall events (Wolman 

and Schick, 1967). These soils are transported downgradient and can be redeposited on land surfaces, floodplains, and 

streambeds. When the construction phase is finished, impervious surfaces route rainwater directly to streams, resulting 

in larger, faster streamflows that can transport deposited 

sediments and incise or widen stream channels (Wolman, 

1967; Wolman and Schick, 1967; Leopold and others, 2005). 

Changes to natural streams as a result of urbanization can 

result in property loss, reduction in biological diversity (Wood 

and Armitage, 1997), siltation of downstream reservoirs 

(Morris and Fan, 1997), and increased water treatment costs 

(Osterkamp and others, 1998).

Urban growth has negatively affected streams in Johnson 

County, located in the southwest corner of the Kansas City 

metropolitan area (fig. 1). Sampling sites downstream from 

urban areas of the county have decreased macroinvertebrate 

diversity (Poulton and others, 2007; Rasmussen and others, 

2009b) and transport more water, sediment, nutrients, and 

bacteria than streams draining rural areas (Rasmussen and 

others, 2008). Streambed sediments in urbanized basins have 

among the largest concentrations of selected metals, polycyclic aromatic hydrocarbons, phthalates, and other organic 

compounds (Lee and others, 2005). All of these negative 

effects can, in part, be related to changes in streamflow and 

sediment transport resulting from urbanization. Nutrients, 

indicator bacteria, trace elements, and organic contaminants 

often are transported while adsorbed to sediment. Increased 

water routing to streams from impervious surfaces in urban 

basins facilitates the transport of sediments (and associated 

contaminants) downstream. Increased sediment deposition and 

(or) changes to natural streamflow conditions have been linked 

to decreased diversity of macroinvertebrate and fish communities (Walters and others, 2003; Freeman and Schorr, 2004; 

Poff and others, 2006).

To improve the understanding of the effects of urbanization on streamflow and sediment transport, from 2006 to 2007 

the U.S. Geological Survey (USGS) in cooperation with the 

Johnson County Stormwater Management Program, studied 

streamflow and sediment transport at nine sampling sites 

with varying upstream land use in the urbanizing Mill Creek 

Basin, and at four sampling sites in larger basins throughout 

Johnson County (Lee and others, 2009). That study reported 

increased sediment transport from subbasins with more active 

construction sites, and decreased sediment transport from 

smaller, completely urbanized basins within the Mill Creek 

Basin. Continued study of streamflow and sediment transport 

conducted by the USGS and the Johnson County Stormwater 

Management Program involved data collection at previously 

studied sampling sites (through November 2008), and new 

data collection at sampling sites more directly downstream 

from active construction sites, as well as from one sampling 

site downstream from a small, undisturbed “reference” basin 

with grassland/forest cover. New sampling sites were installed 

to better quantify sediment loading downstream from differently sized construction sites with varied erosion and sediment 

controls, and to better understand how these sediments are 

transported downstream.

Purpose and Scope

The purpose of this report is to describe the effects of 

urbanization, construction activity, management practices, 

and impoundments on sediment transport in Johnson County, 

Kansas, based on data collected from February 2006 through 

November 2008. This report describes data collected using 

continuously recording stage and water-quality sensors at 

nine sites previously monitored within the urbanizing Mill 

Creek Basin, and at the outlets of the four other largest basins 

in Johnson County. Six additional sites were operated within 

the Mill Creek Basin from February 2007 to December 2008 

to assess sediment transport from active construction sites, 

through a sediment forebay, and a constructed wetland 

upstream from one of Johnson County’s largest reservoirs 
Introduction 3

CL1a

Blue River

Captain Creek

Kill Creek

Cedar

Creek

Big Bull Creek

Litt e Bull Creek

Mi ll

Clear Cr

Coon Cr

Turkey

Creek

Brush Cree

Ro

k

ck Creek

Indian

Creek

Tomahawk Creek

Coffee Creek

Wolf Creek

Camp Branch

Branch

Little Mill

Creek

t

s

e

e

f

l

Dykes

Kansas

River

Creek

SM1

SM1a

SM1b

SM2

CL1a

CL1b

KANSAS MISSOURI

CL1

CE6

MI7

IN6

BL5

LM1

KI6b

CL2

LM2

MI4

MI3

CO1

MI5

MI7

0 1 2 3 4 5 MILES

0 1 2 3 4 5 KILOMETERS

Physiographic sections from Schoewe (1949)

Osage Plains

Kansas City

metropolitan area Johnson County

Dissected Till Plains

Index map

KANSAS MISSOURI

Indian Creek

Basin

Mill Creek

Basin

Kill Creek

Basin

Cedar Creek

Basin

Olathe

Gardner

Blue River

Basin

Base map from U.S. Geological Survey digital data, 1994, 1:2,000,000

Albers Equal-Area Conic projection,

Standard parallels 29°30' and 45°30', central meridian 96°

Horizontal coordinate information is referenced to the

North American Datum of 1983 (NAD 83)

EXPLANATION

Basin boundary

Roads and structures built before 2003

Roads and structures built between 

 2003 and 2005

Roads and structures built between 

 2005 and 2006

Roads and structures built between 

 2006 and 2008

Sampling site and identifier operational before 2007 (Lee and others, 2009)

New sampling site and identifier operated in 2007 and (or) 2008

Data from Johnson County Automated Mapping System, written commun., 2009

I R

U

OSSI M

KANSAS

50’

38°45’

39°

95° 94°55’

50’

45’ 94°40’

55’

Miami County

yt nuo Csal guo D

Leavenworth County

Wyandotte County

Johnson County

yt nuo Cssa C yt nuo Cnos kcaJ

Figure 1. Location of sampling sites, basin boundaries, roads, and structures in Johnson County, northeast Kansas, 2008.
4 Effects on Suspended-Sediment Transport in Johnson County, Northeast Kansas, February 2006 through November 2008

(Shawnee Mission Lake), and from a small, undeveloped 

basin. Data collected from this study can be used by local officials to help develop effective strategies to mitigate sedimentrelated impairments. These results support Federal, state, and 

local efforts to improve water quality and identify processes 

affecting the transport of fluvial sediment.

Description of Study Area

Johnson County, Kansas, consists of 477 square miles 

(mi2) of surface area located in the western part of the Kansas 

City metropolitan area (U.S. Census Bureau, 2008). Sites were 

located at the most feasible downstream point in the 5 largest 

basins (Blue River, Cedar Creek, Indian Creek, Kill Creek, 

and Mill Creek) in Johnson County and at 14 additional sites 

(during various times) within the urbanizing Mill Creek Basin 

(fig. 1; table 1). Physiographic regions of Johnson County 

include the Osage Plains in the central and southern parts of 

the county and the Dissected Till Plains along the northern part 

of the county (fig. 1) (Schoewe, 1949). The county is underlain by sedimentary rock characterized by alternating layers 

of limestone and shale, and smaller amounts of fine-grained 

sandstone. Soils primarily consist of loess, and to a lesser 

degree, glacial till (Evans, 2003).

The Mill Creek Basin is located in the north-central part 

of the county and includes a large percentage of the cities of 

Lenexa, Olathe, and Shawnee (fig. 2). One municipal wastewater-treatment facility (Mill Creek Regional) discharges to 

Mill Creek, directly upstream from sampling site MI3 (fig. 2). 

Percolation of rainfall to groundwater is limited because of 

relatively impermeable limestone and shale bedrock. Wells in 

the county commonly yield less than 10 gallons per minute 

(gal/min) (O’Connor, 1971). Because of limited groundwater capacity, most of the streamflow likely originates from 

overland or shallow subsurface flow. Most of Mill Creek and 

its tributaries flow through alternating layers of limestone and 

shale; streambeds primarily are composed of gravel, cobble, 

rock, and bedrock. Entrainment of large-grained streambed 

material is not considered a substantial part of the streamsediment load. Soils and stream-channel banks within the Mill 

Creek Basin generally consist of erosive to moderately erosive 

silt and silty-clay loams; channel-banks have occasional limestone and shale outcrops (Evans, 2003).

Channel slope was determined upstream from and among 

sites using methods described in Lee and others (2008). Among 

large basins in the county, slopes were steepest among north 

flowing streams [Cedar Creek, 14.6 feet per mile (ft/mi); Kill 

Creek, 17.1 ft/mi; and Mill Creek, 14.6 ft/mi] relative to eastflowing streams (Blue River, 9.6 ft/mi; Indian Creek, 11.8 ft/mi). 

Among Mill Creek sampling sites, channel slope was steepest among headwater sampling sites (SM2, 210 ft/mi; SM1, 

112 ft/mi; SM1a, 102 ft/mi; SM1b, 96.0 ft/mi; CL1a, 53.7 ft/mi; 

table 2) and decreased downstream. Channel slope was smallest 

between downstream sites MI5 and MI7 (5.9 ft/mi), sites MI4 

and MI5 (13.1 ft/mi), and sites CL1 and CL2 (17.6 ft/mi).

The mean annual temperature (1931–2008) in Olathe, 

Kansas (located in the center of the county; fig. 1), is 

55.2 degrees Fahrenheit (°F), with a mean monthly range of 

29.4°F in January to 78.8°F in July (National Oceanic and 

Atmospheric Administration, 2009). Mean annual rainfall 

(1931–2008) is 39.0 inches (in.), with 68 percent of the rainfall occurring during the growing season from April through 

September (National Oceanic and Atmospheric Administration, 2009). Storms with more than 1 in. of rainfall occur an 

average of 10.7 days per year (1948–2008; National Oceanic 

and Atmospheric Administration, 2009).

Construction Sites

Active construction sites in the study area typically 

undergo three phases before completion. Grading consists of 

excavation (cut) and filling of soils to provide level, stable 

foundations for buildings and roads. This phase is likely to 

produce the most surface erosion because of widespread 

destabilization of surface soils and removal of surface vegetation. Roads and storm sewer construction typically succeed cut 

and fill activities, followed by building construction. Phase II 

National Pollution Discharge Elimination System regulations 

require operators of separate municipal storm sewer systems 

to enforce best management practices (BMPs) during and after 

construction activities at sites disturbing greater than 1 acre 

of land (U.S. Environmental Protection Agency, 2005). These 

BMPs include erosion controls (early seeding, erosion control 

blankets/mats) and sediment controls (mulch/earth berms, silt 

fences, rock checks, swales, and settling basins).

Sampling sites SM1, SM1a, and SM1b were installed 

to assess sediment transport from a large, 68-acre multi-use 

construction site (City Center North; City of Lenexa) and 

through a sediment forebay and constructed wetland to Shawnee Mission Lake (fig. 3). Shawnee Mission Lake is a 150-acre 

reservoir constructed in 1962, and primarily is used for swimming, boating, and fishing. The basin upstream from the lake 

has had some residential development from 2000 to 2006, but 

remained primarily undeveloped until the City Center North 

construction site broke ground in March 2007. At the City 

Center North construction site, steep slopes required extensive 

cut and fill to bring the site to final grade (R. Beilfuss, City of 

Lenexa, written commun., 2008). Mulch berms and silt fences 

(not visible on aerial photography) were installed in series 

along each slope, along with three rock checks in the central 

channel (fig. 3). Silt fences also were installed around fill piles 

on site. After a 1.2-in. rain on March 29, 2007 (slightly larger 

than the average storm in terms of amount and intensity), 

inspections conducted by the City of Lenexa indicated that 

storm runoff had compromised perimeter mulch berms and a 

rock check, runoff from the central stream eroded beneath rock 

checks, sediment-laden water was discharging from the main 

settling basin, and a large sediment plume was observed leaving the site and entering Shawnee Mission Lake (fig. 4). After 

this event, existing sediment-control practices were strength-
Table 1.  Location and contributing drainage area of sampling sites in Johnson County, northeast Kansas, February 2006 through November 2[mi2, square mile; mm, month; yr, year]

Sampling 

site

(fig. 1)

U.S. Geological 

Survey

identification 

number

Site name

Contributing 

drainage 

area 

(mi2)

Latitude

(degrees,

minutes,

seconds)

Longitude 

(degrees, 

minutes, 

seconds)

P

Mill Creek sites

CL1a 385818094520300 Clear Creek at 86th Terrace, Lenexa 0.7 38°58'18" 94°52'03" CL1b 385922094485500 Clear Creek at 79th Street, Lenexa 2.8 38°59'22" 94°48'55" CL1 390051094522200 Clear Creek at Clare Road, Shawnee 5.5 39°00'51" 94°52'22" CL2 390056094493200 Clear Creek at Woodland Road, Shawnee 10.9 39°00'56" 94°49'32" CO1 385826094491700 Coon Creek at Woodland Road, Lenexa 5.1 38°58'26" 94°49'17" LM1 385952094454000 Little Mill Creek at Lackman Road, Shawnee 8.8 38°59'52" 94°45'40" LM2 390010094482100 Little Mill Creek at Warwick Lane, Shawnee 12.1 39°00'10" 94°48'21" MI3 385404094485800 Mill Creek at Woodland Road, Olathe 2.8 38°54'04" 94°48'58" MI4 385800094485300 Mill Creek at 87th Street Lane, Lenexa 19.7 38°58'00" 94°48'53" MI5 390026094485800 Mill Creek upstream from Shawnee Mission Parkway, Shawnee 31.7 39°00'26" 94°48'58" MI7 06892513 Mill Creek at Johnson Drive, Shawnee 57.4 39°01'46" 94°49'03" SM1 385835094471300 Unnamed tributary at Barkley Drive, Lenexa .6 38°58'35" 94°47'13" SM1a 385910094474400 Unnamed tributary into Shawnee Mission Lake Wetland 1.3 38°59'10" 94°47'44" SM1b 385859094473700 Unnamed tributary into Shawnee Mission Lake, Lenexa 1.4 38°58'59" 94°47'37" SM2 385922094485500 Unnamed tributary near Shawnee Mission Lake, Lenexa .2 38°59'22" 94°48'55" 

Additional Johnson County sites monitored during study period

BL5 06893100 Blue River at Kenneth Road, Overland Park 65.7 38°50'32" 94°36'44" CE6 06892495 Cedar Creek near DeSoto 58.5 38°58'41" 94°55'20" IN6 06893390 Indian Creek at State Line Road, Leawood 63.1 38°56'15" 94°36'30" KI6b 06892360 Kill Creek at 95th Street near DeSoto 48.6 38°57'28" 94°58'30" 
6 Effects on Suspended-Sediment Transport in Johnson County, Northeast Kansas, February 2006 through November 2008

Mill Creek

Regional

wastewatertreatment

facility 

Creek

94°50' 94°45'

39°

38°55'

Lenexa

Olathe

Shawnee

Wyandotte County

Johnson County

10

7

0 1 2 3 MILES

0 1 2 3 KILOMETERS

Base map from U.S. Geological Survey digital data, 1994, 1:2,000,000

Albers Equal-Area Conic projection

Standard parallels 29°30' and 45°30', central meridian 96°

Horizontal coordinate information is referenced to the

North American Datum of 1983 (NAD 83)

CL1

CL1a

Boundary of Mill Creek Basin

Boundary of Mill Creek subasin

Sampling site and identifier operated since 2006 

 (Lee and others, 2009)

Land use in Mill Creek Basin

Commercial

Industrial

Parks

Residential

Surface water

Undeveloped

Other

EXPLANATION

Land use from Johnson County Automated

Mapping System, written commun., 2009

New sampling site and identifier operated in 2007 

 and (or) 2008

Mill Creek

Mill Creek

Creek

Cedar

Clear

Creek

Mill Little

Coon Creek

Shawnee

Mission Lake

Creek

Mill

Indian Creek

Turkey Creek

Kansas River

Lake

Lenexa

Waterworks

Lakes

Lake Quivira

Lake

Olathe

Shadow

Lake

Creek

§ ̈¦35

§ ̈¦435

§ ̈¦435

MI5 LM2

LM1

CL2

CL1

MI4

CO1

MI3

MI7

SM1

SM1a

SM1b

SM2

CL1a

CL1b

Figure 2. Location of basin boundaries, sampling sites, and land use in the Mill Creek Basin, Johnson County, northeast

Kansas, 2008.
Table 2.  Land use, channel slope, and major impoundments upstream from sampling sites in Johnson County, northeast Kansas, 2008.[mi2, square mile; ft/mi, foot per mile; --, not applicable; data from S. Porter, Johnson County Automated Information Mapping System, written commun., 2009]

Sites

immediately 

upstream 

(fig. 1)

Downstream 

sites

(fig. 1)

Estimated 

drainage 

area

(mi2)

Percentage of 

basin area affected by 

impoundments

Channel 

slope

(ft/mi)

Percentage land use 

Residential Commercial Industrial Right of way Parks Water Undevelopeda No d

Basin upstream from sampling sites

-- CL1a 0.7 -- 53.7 9.8 3.3 0.6 1.3 6.7 0.5 68.4 9.-- CL1b 2.8 -- 39.5 16 4.3 14.5 4.7 4.3 .4 47.7 8.-- CL1 5.5 -- 28.3 18.6 3.1 7.8 2.6 2.6 1.0 58.5 5.-- CL2 10.9 -- 20.0 19.9 5.5 4.8 4.3 5.6 1.1 51.5 7.-- CO1 5.1 40 (Lake Lenexa) 43.1 23.2 1.6 2.1 8 13.5 1.5 44 6.-- LM1 8.8 -- 29.2 52.6 9.9 7.3 2.4 7.3 .8 3.5 16-- LM2 12.1 -- 22.8 51 9.7 5.5 4.6 9.8 1.0 4.3 14-- MI3 2.8 36 (Waterworks Lakes) 22.9 37.6 11.6 13.0 9.2 1.3 2.4 7.4 17-- MI4 19.7 5 21.6 21.5 7.9 15.2 8.9 4.1 1.6 29.8 11-- MI5 31.7 19 18.2 22.1 5.8 10.6 8.7 12.9 2.2 28.1 9.-- MI7 57.4 10 14.6 27.8 6.3 8.2 6.9 10.7 1.7 28.5 9.-- SM1 .6 -- 112 15.6 5.0 .1 16.9 5.5 .5 46.6 9.-- SM1a 1.3 -- 102 27.2 3.9 .1 13.1 21.8 .4 23.5 10-- SM1b 1.4 -- 96.0 25.7 3.7 .1 12.4 26.0 .4 22.2 9.-- SM2 .2 -- 210 18.7 0 0 0 81.0 .3 0 0 

Basins between sampling sites

CL1a CL1b 2.1 -- 27.1 18.3 4.7 19.4 5.9 3.5 .3 40.3 7.

CL1b CL1 2.7 -- 22.2 21.1 1.8 1.3 .5 .8 1.5 68.9 4.

CL1 CL2 5.4 -- 17.6 21.3 8.1 1.7 6.1 8.9 1.2 44.2 8.

LM1 LM2 3.3 -- 23.1 41.5 8.0 .1 10.2 15.5 1.5 15.8 7.

MI3 MI4 16.9 -- 24.0 18.5 7.3 15.6 8.8 4.6 1.5 33.9 9.

CO1, MI3, MI4 MI5 5.3 42 (Shawnee Mission Lake) 13.1 12.5 .6 3.9 2.3 33.4 5.1 38.2 7.

CL2, LM2, MI5 MI7 2.7 -- 5.9 26.2 1.3 4.9 5.9 8.8 2.4 45.5 5.

SM1 SM1a .7 -- 77.5 37.7 2.9 .1 9.7 36.5 .4 2.7 10

SM1a SM1b .1 -- 63.6 0 0 0 0 96.6 .6 0 2.

Other monitored basins in Johnson County (Rasmussen and others, 2008)

-- BL5 65.7 -- 9.6 15.7 2.2 3.1 2.0 5.0 2.2 65.5 4.-- CE6 58.5 18 (Olathe Lake) 14.6 12.5 2.8 8.4 3.5 4.0 2.1 61.6 5.-- IN6 63.1 -- 11.8 45.0 15.3 2.4 4.4 8.3 1.0 8.5 15-- KI6b 48.6 11 (Gardner City Lake) 17.1 6.7 2.4 5.2 .7 3.6 1.9 76.8 2.

a Undeveloped land use includes agricultural land use and land not under production.b No data land use includes untaxed land uses (such as government property and public roads).
8 Effects on Suspended-Sediment Transport in Johnson County, Northeast Kansas, February 2006 through November 2008

tributarytributary

UnnamedUnnamed

94°48'30" 94°48' 94°47'30" 94°47'

38°59'

38°58'30"

0 0.25 MILE

0 0.25 KILOMETER

Sediment-control

ponds

Rock checks

Rock check

87th Street

Shawnee Mission

Lake

Constructed 

wetland

Sediment

forebay

87th Street

Renner Road

SM1b

SM1

SM1a

Sediment-control

ponds

Rock checks

Rock check

Constructed 

wetland

Sediment

forebay

City Center North Development

87th Street

87th Street

Renner Road

SM1b

SM1

SM1

SM1a

Shawnee Mission

Lake

Sampling site and identifier (table 1)

County defined drainage line

Horizontal coordinate information is referenced to the

North American Datum of 1983 (NAD 83)

EXPLANATION

Aerial photography taken March 2008

(Johnson County Automated Information Mapping System, 

written commun., 2009)

Data from Johnson County Automated Information Mapping System,

written commun., 2009

Figure 3. Location of City Center North construction site, sampling sites, and selected best management practices, Lenexa, Kansas, 2008.
Introduction 9

A

B

Figure 4. A, Destroyed mulch berm and rock check at City Center North development, and B, turbid

water entering Shawnee Mission Lake, Lenexa, Kansas, March 30, 2007. Photographs by Dale Clark,

City of Lenexa.
10 Effects on Suspended-Sediment Transport in Johnson County, Northeast Kansas, February 2006 through November 2008

ened, and two main sedimentation basins were added in early 

June 2007.

A constructed wetland and sediment forebay were completed in February 2008 immediately upstream from Shawnee 

Mission Lake and downstream from the City Center construction site (fig. 3). The wetland was constructed to augment a 

wetland that was naturally developing on the southeast arm of 

the lake, with the goal of increasing habitat diversity, providing educational opportunities to local citizens, and improving the water quality of Shawnee Mission Lake (T. Stanton, 

Olsson Associates, written commun., 2009). A 1.8-acre-foot 

(acre-ft) sediment forebay was installed upstream to maintain 

and extend the life of the wetland. Wetland/forebay construction was initiated in response to lake-water quality concerns 

present before City Center North construction, and thus were 

not implemented to specifically reduce sediment accumulation as a result of these projects. The wetland was designed 

to facilitate flow (as well as fish and canoes) into the lake, 

and thus was not constructed to maximize hydraulic retention for the purpose of reducing sediment accumulation in the 

lake. Additionally, although the construction of the sediment 

forebay and wetland were completed before site installation 

in 2008, wetland vegetation will not be fully established (and 

thus best able to filter sediment) for 3 to 4 years (T. Stanton, 

Olsson Associates, written commun., 2009). Nonetheless, 

sediment sampling was initiated to assess the ability of the 

forebay/wetland to reduce sediment accumulation in Shawnee 

Mission Lake.

Sampling site SM1 was located 1,400 feet (ft) downstream from the City Center North construction site and operated from February 2007 through November 2008 to estimate 

the amount of sediment transported from the site (fig. 3). Sites 

SM1a and SM1b were operated from February 2008 through 

November 2008 after construction of a sediment forebay and 

constructed wetland. Site SM1a was installed directly downstream from the forebay; site SM1b was installed downstream 

from the constructed wetland to characterize sediment transport from the subbasin containing the construction site through 

the forebay and wetland into Shawnee Mission Lake.

Site SM2 was operated from February through November 2007 and was downstream from undeveloped parkland. 

Site SM2 was discontinued in November 2007 and equipment 

was relocated to monitor sediment removal at the sediment 

forebay and constructed wetland.

Because the headwaters of the Clear Creek Basin 

[upstream from site CL1, (fig. 1)] transported the most sediment to Mill Creek (per unit area) from February 2006 through 

June 2007 (Lee and others, 2009), sampling sites CL1a and 

CL1b were installed in the headwaters of the Clear Creek 

Basin to better characterize predominant sediment-source 

areas (fig. 5). Site CL1a was operated from February 2007 

through November 2008; site CL1b was operated from February through November 2007. Site CL1b was discontinued 

in December 2007, and equipment was relocated to monitor sediment removal at a sediment forebay and constructed 

wetland during 2008. Several construction sites were active 

in the Clear Creek Basin during and immediately before the 

study period (fig. 5; table 3), including several large housing developments, a school, and road construction. Sediment 

controls at construction sites generally consisted of silt fences 

and rock checks at locations where flows were concentrated. 

Although City of Lenexa erosion control inspections generally 

documented that on-site erosion controls were functioning correctly, examples of their failure were documented (fig. 6).

Land Use

Property tax data were used to distinguish land use 

among various types [residential, commercial, industrial, right 

of way, parks, water, undeveloped, and “no data” (S. Porter, 

Johnson County Automated Information Mapping System, 

written commun., 2009)]. The “no data” category consists 

of untaxed land-use parcels. Among the five large basins in 

Johnson County, Indian Creek is almost completely urbanized 

(as defined by residential, commercial, and industrial land use; 

fig. 1; table 2), Mill Creek is mixed between urban and rural, 

and Blue River, Cedar Creek, and Kill Creek predominantly 

are rural. The amount of urban construction (defined by the 

change in percentage of impervious surface from 2006 to 

2008; table 2) were largest in the Indian (1.3 percent) and Mill 

Creek (1.0 percent) basins and much less (0.5 to 0.6 percent) 

in the other large basins (table 2). Urbanization in the northeast part of Johnson County is beginning to expand into the 

predominantly rural Blue River and Cedar Creek Basins.

Urbanization in the Mill Creek Basin has been concentrated in the eastern and northern sections of the basin (fig. 1; 

table 2). Subbasins upstream from site LM1 (City of Lenexa) 

and site MI3 (City of Olathe) were the only subbasins with 

more than 60 percent (72 and 71 percent, respectively) urban 

land use (residential, commercial, industry, and right of way) 

and greater than 30 percent impervious surface (30.7 and 

35.1 percent, respectively). These basins also had the smallest amount of land classified as parks or as undeveloped 

(10.8 and 8.7 percent, respectively). Undeveloped areas (such 

as agricultural land, forests, and grassland) and parks are the 

predominant land use in the central and western parts of the 

basin, primarily in the Clear Creek and north-central Mill 

Creek subbasins (table 2).

Because property tax data indicate the primary use of 

a parcel of land rather than the actual building or road area, 

these data may not accurately characterize the effects of land 

use on streams. For this reason, changes in impervious surface 

(defined as building and pavement area obtained from aerial 

photography) are used to define changes for various periods 

from 2003 to 2008 (fig. 7). Subbasins upstream from sampling sites LM1 and LM2 had relatively small increases in 

impervious surfaces (table 2), indicating relatively little new 

urban construction (fig. 1). The largest increases in impervious surface from 2003 to 2008 generally occurred upstream 

from sites CL1, CL2, MI3, MI4, and SM1, indicating that 

new urban construction primarily is occurring in the central 

and western parts of the Mill Creek Basin (Clear Creek and 
Introduction 11

Creek

Clear

94°52'30" 94°52' 94°51'30" 94°51'

38°58'30"

38°57'30"

38°59'

38°58'

0

0

0.3

0.3

0.6 MILE

0.6 KILOMETER

S2

S3

R3

S4

R4

R1 R2

R5

S1

S2

S3

R3

S4

R4

R4

R1 R2

R5

S1

Aerial photography taken March 2008 (Johnson County Automated Information Mapping System, written commun., 2009) Data from Johnson County Automated Information Mapping System, written commun., 2009

R3

R1

R1

R2

Highway 7

79th Street

83th Street

CL1b

CL1a

Clare Road

Highway 7

CL1b

CL1a

Construction site boundary Sampling site and identifier (table 1)

Subbasin boundary Construction site and identifier (table 3)

County defined drainage line

CL1b

EXPLANATION

Figure 5. Location of construction sites and sampling sites in the headwaters of Clear Creek, Lenexa, Kansas, 2004 through 2008.
12 Effects on Suspended-Sediment Transport in Johnson County, Northeast Kansas, February 2006 through November 2008

central Mill Creek subbasins). Parking lot and building construction in the far southern, industrial part of the urbanized 

basin upstream from sampling site MI3 caused a substantial 

increase (32.9 to 35.1 percent) in impervious surface from 

2006 to 2008 (table 2); however, these developments were 

upstream from a series of impoundments (Waterworks Lakes), 

and thus may not affect sediment transport at downstream 

sampling sites.

Three, relatively large (greater than 30-acre) surfacewater impoundments are present within the Mill Creek Basin. 

The largest impoundment (in terms of surface area—impoundment volumes generally are unknown) is Shawnee Mission 

Lake, which has a surface area of 120 acres, an estimated contributing drainage area of approximately 2.9 mi2

, and affects 

42 percent of the basin area between sampling sites MI4 and 

MI5 (fig. 2). Waterworks Lakes have a combined surface area 

of 32 acres (volume unknown), an estimated contributing 

drainage area of 1.0 mi2, and affect 36 percent of the basin 

area upstream from site MI3 (fig. 2; table 2). Lake Lenexa is 

a 30-acre, 550-acre-ft, impoundment constructed from 2005 

to 2006, which has an estimated contributing drainage area 

of 2.0 mi2, and affects 40 percent of the basin area upstream 

from site CO1 (R. Beilfuss, City of Lenexa, written commun., 2007). Large impoundments generally retain incoming 

stormflows longer, allowing more time for sediment to deposit 

to the impoundment bottom, thus decreasing 

sediment loads at downstream sampling sites. 

Smaller farm ponds and sediment-control structures present in the Mill Creek Basin and other 

basins (fig. 2) also likely remove suspended sediment from fluvial transport (Renwick and others, 

2005).

Previous Studies

Rasmussen and others (2008) used continuous water-quality monitoring to estimate 

constituent concentrations and loads in the five 

largest Johnson County streams, including Mill 

Creek. That study determined that most streamflow and sediment were transported from the 

most urbanized basin (Indian Creek; Rasmussen 

and others, 2008). Suspended-sediment yields 

from Mill Creek were smaller than yields from 

Indian Creek, but larger than those from the 

more rural Cedar and Kill Creeks (fig. 1).

A report on sediment sources and transport 

in the Mill Creek Basin from February 2006 

through June 2007 was published in 2009 (Lee 

and others, 2009). That report described streamflow and sediment transport at nine sites in the 

Mill Creek Basin and four sites at the outlet 

of the other largest basins in Johnson County. 

The initial study determined that construction 

sites were the largest source of sediment to Mill 

Creek, whereas mature, urban subbasins within 

the Mill Creek Basin had substantially smaller sediment 

yields. These findings served as the impetus for continued 

study described in this report focusing on sediment transport 

with respect to construction sites. Slightly smaller sediment 

yields in larger basins were attributed to sediment deposition in larger, less sloping stream channels. Streamflow and 

sediment transport were enumerated for individual storms 

and analyzed in relation to measurements of storm intensity, 

antecedent rainfall, and sediment transport conditions. Storms 

with increased rainfall intensity resulted in increased sediment 

transport at eight of the nine sampling sites, whereas storms 

that follow periods of increased sediment loading transported 

substantially less sediment at two of the nine sampling sites. 

Methods of data collection and analysis from the study by 

Lee and others (2009) are used as a template for those in this 

report. This study served as the impetus for continued monitoring and further focus on sediment transport with respect to 

construction sites.

Construction has been shown to cause substantial 

sediment deposition in stream channels resulting in erosion 

of channel banks, obstruction of flow and increased flooding, blanketing of stream life, changes in light transmission 

through the water column, and alteration of fish species (Wolman and Schick, 1967; Guy, 1970). Several, primarily older 

(1960s to 1980s) studies have characterized the effect of urban 

Table 3.  Active construction sites, construction area, and phasing in the

basins upstream from sites CL1a, CL1b, and SM1, Lenexa, Kansas, 2004

through 2008.

[mi2; square mile]

Site

designation

(fig. 5)

Area

(mi2)

Sampling 

site identifier

immediately 

downstream

Phases and timing of construction 

(D. Clark, City of Lenexa, 

written commun., 2009)

Residential construction sites

R1 0.34 CL1a/CL1b Mass graded in 2004, houses built 

through 2008.

R2 .04 CL1a Mass graded in 2005, paved in 

2006, houses built through 2008.

R3 .12 CL1b Construction from 2004 to 2008.

R4 .06 CL1 Construction from 2004 to 2008.

R5 .11 CL1b Mass graded and paved in 2006, 

houses built through 2008.

Road/School/Commercial construction sites

S1 (Public school) 0.05 CL1b/CL1 Building construction through 2006.

S2 (Prairie Star Parkway) .02 CL1a Graded in 2007, paved in 2008.

S3 (Clare Rd) .02 CL1a/CL1b Mass graded and storm drainage 

began in spring 2008.

S4 (Private school) .06 CL1a Completed in 2005.

City Center North .11 SM1 Grading from spring-summer 

2007, storm sewers and roads in 

fall 2007, building construction 

through 2008.
Introduction 13

A

B

C

Figure 6. A, Erosion from a residential construction site, B, gully formation near culvert, and C, sediment deposition

downstream from culvert after a storm in the headwaters of Clear Creek, Lenexa, Kansas, April through May 2007.

Photographs by Dale Clark, City of Lenexa.
14 Effects on Suspended-Sediment Transport in Johnson County, Northeast Kansas, February 2006 through November 2008

0

5

10

15

20

25

30

35

40

CL1a CL1b CL1 CL2 CO1 LM1 LM2 MI3 MI4 MI5 MI7 SM1 SM1a SM1b SM2 BL5 CE6 IN6 KI6b

PERCENTAGE IMPERVIOUS SURFACE UPSTREAM FROM SAMPLING SITE

2003

2005

2006

2008

0

5

10

15

20

25

30

35

40

CL1a CL1b CL1 CL2 CO1 LM1 LM2 MI3 MI4 MI5 MI7 SM1 SM1a SM1b SM2 BL5 CE6 IN6 KI6b

PERCENTAGE IMPERVIOUS SURFACE BETWEEN SAMPLING SITE 

AND NEXT UPSTREAM SAMPLING SITE

2003

2005

2006

2008

Data from Johnson County Automated Mapping System, written commun., 2009

B

A

Figure 7. Percentage impervious surface area A, upstream from and B, between sampling sites in Johnson

County, northeast Kansas, 2003 through 2008.
Methods 15

construction on sediment transport in the United States. These 

studies indicated widespread erosion and sediment transport 

during urban construction relative to agricultural, urban, or 

undisturbed land. Historical sediment yields from construction 

sites without sediment-control measures ranged from 2,300 to 

140,000 tons per square mile per year (tons/mi2/yr), compared 

to agricultural (420 to 2,750 tons/mi2/yr) or forest land (15 to 

110 tons/mi2/yr; Wolman and Schick, 1967; Vice and others, 

1969; Guy, 1970; Walling and Gregory, 1970; Yorke and Herb, 

1978; Helsel, 1984; and Owens and others, 2000). The principal factors affecting the transport of sediment from sites are 

basin size, soil type, rainfall amount and intensity, length of 

time the sites were unvegetated, slope, site proximity to stream 

channels, soil compaction from heavy equipment, and the 

use of erosion and sediment-control measures (Wolman and 

Schick, 1967; Yorke and Herb, 1978). Erosion and sedimentcontrol measures at construction sites have been shown to 

decrease sediment yields by 60 to 80 percent (Yorke and Herb, 

1978).

Methods

Data Collection and Analysis

Eight sampling sites were installed in the Mill Creek 

Basin in February 2006 (in addition to site MI7, operated 

since October 2002). Four additional sites were installed in 

February 2007 (CL1a, CL1b, SM1, SM2), two of these sites 

(CL1b, SM2) were removed in December 2007 and equipment 

reinstalled to monitor sediment removal at a sediment forebay 

and constructed wetland at sites SM1a and SM1b in February 2008. All monitors in the Mill Creek Basin were removed 

from November 30 to December 1, 2008 (table 1). YSI Incorporated (YSI) water-quality monitors equipped with specific 

conductance, water temperature, and model 6136 turbidity 

sensors were operated at each site. Suspended-sediment concentration (SSC) and the percentages of sediment greater and 

less than 63 micrometers (μm) in diameter were determined 

at the USGS Sediment Laboratory in Iowa City, Iowa, using 

methods from Guy (1969).

YSI water-quality monitors were installed in streams and 

were housed in polyvinyl chloride pipes with holes drilled 

to facilitate flow through the installation. Monitors were 

installed at the stream edge, approximately 0 to 2 ft above the 

streambed depending upon stream depth. Site locations were 

chosen to divide the study area into equally sized subbasins 

and to characterize sediment transport from construction 

sites, while accounting for site suitability and attempting to 

avoid backwater conditions. Data were collected every 5 or 

15 minutes (15-minute data were collected at basin outlets); 

real-time data are available on the USGS Kansas Water Science Center Web page (http://nrtqw.usgs.gov/ks/). Monitor 

maintenance and data reporting generally followed procedures 

described in Wagner and others (2006) with the exception 

of increased length between calibration checks (approximately 2 to 3 months). Length between calibration checks 

was extended beyond the recommended monthly frequency 

because of the absence of pH and dissolved oxygen sensors, 

which are most prone to calibration drift. Turbidity records 

generally were rated good (error of 5 to 10 percent) and 

occasionally fair (10 to 15 percent) on the basis of guidelines 

developed by Wagner and others (2006).

Solinst Levellogger (Ontario, Canada) sensors and (or) 

radar gage sensors were installed to monitor gage height. 

Streamflow was measured and calculated using methods 

described in Kennedy (1983, 1984). Rating curves comparing 

gage height and streamflow were developed using streamflow 

measurements and the slope-conveyance method (Kennedy, 

1984). Streamflow records were compiled without regular 

streamflow measurements during low-flow conditions, which 

have a negligible effect on sediment loads. Nonstandard development of streamflow record required a “poor” rating, implying that 95 percent of daily flows could be in error by more 

than 15 percent. Streamflow was not estimated at site SM1b 

because of consistent backwater conditions. Backwater conditions also were present during base-flow conditions at site 

SM1a, but because stormflow peaks were much larger than 

at site SM1b, backwater was not apparent during observed 

stormflow conditions, and streamflow estimates compared 

favorably to upstream site SM1, streamflow conditions were 

estimated at site SM1a. Streamflow values and interpretations 

are considered more uncertain at site SM1a because of periodic backwater conditions.

With the exception of site MI7, streamflow and waterquality data were not collected from November 30 to 

December 18, 2006; January 10 to February 20, 2007; and 

December 7, 2007 to February 16, 2008, because of freezing conditions. Sensors were removed during these periods 

because stream ice expansion can potentially crush monitoring equipment (site MI7 is located at a deep pool below ice). 

Precipitation during the winter of 2006–07 generally consisted 

of snow, and thus streamflow and sediment concentrations 

observed at site MI7 generally were at (or near) base-flow 

conditions. Four storms occurred during the winter of 2007–08 

that resulted in increased streamflow at site MI7 while sensors 

were removed at other sites. Storms occurred from December 11 to 13, 2007 [peak streamflow, 530 cubic feet per second 

(ft3/s)], January 8 to 9, 2008 (peak streamflow, 260 ft3/s), 

January 10 to 11, 2008 (peak streamflow, 560 ft3/s), and February 5 to 7, 2008 (peak streamflow, 1,790 ft3

/s). For purposes of 

comparing streamflow and sediment loading between sampling sites, computations of streamflow and sediment loading 

exclude these periods from analysis. Because aggregate measures of streamflow were similar between sites LM1 and LM2, 

total flow and the flow volume of two small storms missing at 

site LM1 from April 6 to 16, 2007, were estimated using data 

from site LM2.

Individual storms were delineated based on observed 

rainfall and streamflow conditions as described in Lee and 

others (2009). Base flow (defined as wastewater discharge and 
16 Effects on Suspended-Sediment Transport in Johnson County, Northeast Kansas, February 2006 through November 2008

groundwater flow) and stormflow (defined as overland flow 

and interflow) parts of the streamflow record were separated 

using the base-flow index program (BFI; Wahl and Wahl, 

2006). Storms in which more than 0.5 in. of rain occurred 

on the Mill Creek Basin were assigned a whole number 

(1–63) starting at the beginning of the study period. Storms 

in which streamflow increased relative to base-flow conditions in response to less than 0.5 in. of rainfall on the basin 

were assigned a decimal dependent upon the whole-numbered 

storms they fell between. The beginning and end of stormflow periods were assigned from the first few values before 

an observed rise in streamflow after a period of rainfall, until 

streamflow values were not consistently decreasing as a result 

of the previous storm (or beginning of the next storm).

Stormflow volumes were determined by subtracting the 

volume of base flow from the volume of streamflow transported during the storm. A consistent criteria was not used 

to determine the beginning and end times of storms because 

back-to-back rainfall periods occasionally increased streamflows before a complete return to base-flow conditions, 

multiple storms at headwater sampling sites often could not be 

isolated at downstream sites (and thus were combined into one 

storm), and data analysis indicated that a small percentage of 

stormflow volume and sediment loads occurs during the beginning and end of stormflow periods, and that minor changes in 

storm beginning and end times have a negligible effect on the 

computed cumulative stormflow volume and sediment load. 

The gage and water-quality monitor installation at site CL1a 

was destroyed by storm debris on September 13, 2008, and 

was replaced on September 24, 2008. Total stormflow for the 

storm during this period was estimated by multiplying the 

stormflow for the same storm at site CL1 by the percentage of 

total stormflows at CL1a compared to site CL1 (9.4 percent).

Rainfall data were collected and analyzed from 18 tipping-bucket rain gages located in and around the Mill Creek 

Basin from February 2006 through November 2008 (Overland 

Park Stormwatch, 2009; Lee and others, 2009). Data from the 

rain gages were combined and weighted using Thiessen polygons (Thiessen and Alter, 1911) to estimate rainfall characteristics for basins upstream from sampling sites.

Suspended-sediment-concentration samples generally 

were collected at a minimum of five locations equally distributed across the stream cross section according to methods 

described in Nolan and others (2005). At riffles less than 3 ft 

wide and 0.5 ft deep, samples were collected by dipping a 

bottle in the center of the cross section. All other samples were 

collected through equal-width increment sampling methodologies, using USGS-approved samplers (Nolan and others, 

2005).

Quality Assurance

Median values of cross-section turbidity measurements 

were used to compute SSC using regression analysis. Crosssection turbidity measurements were used in regression 

analysis (as opposed to values from in-stream monitors) 

because in-stream values were not collected in real-time, and 

thus occasionally were malfunctioning or were subject to 

environmental fouling during sample collection. To ensure 

that the values of the cross-section turbidity readings represent those recorded by in-stream continuous water-quality 

sensors, comparisons of turbidity values were made between 

in-stream sensors and the median of cross-section measurements. Samples from all sampling sites were aggregated to 

determine if consistent bias existed between cross-section and 

point-turbidity data among sampling sites. Relations between 

turbidity readings were accurate (R2 = 0.98) and had a near 1:1 

relation (slope = 1.01; fig. 8). These data verify that continuous water-quality-sensor readings generally were representative of stream-water quality across the width of the stream 

cross section under a variety of streamflow conditions (0.98 to 

1,190 ft3/s) and that in-stream sensor values were reproducible by an independently calibrated sensor. Replicate samples 

were not collected for SSC samples because random errors in 

laboratory analysis contribute to error observed within regression analyses with turbidity (see “Regression Models” section 

in this report).

Regression Models

Regression analysis was used to develop statistical 

models relating SSC from in-stream samples to the median 

of turbidity values collected across the stream cross section. Suspended-sediment-concentration and turbidity values 

were log-transformed to better approximate normality and 

homoscedasticity in the data distribution. After development 

of the regression relation, variables were retransformed back 

to a linear scale. Because this retransformation can cause bias 

when adding load estimates with time, a bias-correction factor 

(Duan’s smearing estimator; Duan, 1983) was used to correct 

for potential bias (Helsel and Hirsch, 2002). Uncertainty of 

regression estimates were determined by the 95-percent prediction intervals (Helsel and Hirsch, 2002). Regression methods used in this study generally follow guidelines described 

in Rasmussen and others (2009a). Continuous SSC and load 

computations, uncertainty, and duration curves are available 

on the World Wide Web at URL http://nrtqw.usgs.gov/ks/. 

With the exception of sampling site SM2, 5 to 14 samples 

were collected at newly installed sampling sites in an attempt 

to represent the range of turbidity values observed at each site 

(table 4). Selected samples were collected in 2009 to verify 

patterns in regression relations observed at sites SM1a and 

SM1b. Site SM2 had fewer samples because of difficulty of 

manually sampling stormflow conditions in the small basin. 

Maximum SSCs ranged from 160 milligrams per liter (mg/L) 

at sampling site SM2 to 3,300 mg/L at site SM1 (table 4). 

Site CO1 had smaller maximum and mean SSC values likely 

because of sediment trapping by Lake Lenexa and several 

additional small impoundments within the basin (fig. 2; 

table 4). Mean SSC values were smaller at site MI5 because 
Methods 17

y = 1.01x

R2 = 0.98

0

200

400

600

800

1,000

1,200

1,400

1,600

0 200 400 600 800 1,000 1,200 1,400 1,600

TURBIDITY FROM IN-STREAM WATER-QUALITY SENSORS, 

FORMAZIN NEPHELOMETRIC UNITS (YSI MODEL 6136)

CROSS SECTION MEDIAN OF TURBIDITY VALUES, FORMAZIN NEPHELOMETRIC UNITS (YSI MODEL 6136)

Figure 8. Linear fit between cross section median and in-stream turbidity readings at sites in the Mill Creek Basin, Johnson

County, northeast Kansas, February 2006 through November 2008.

Table 4.  Suspended-sediment concentration and percent silt/clay (less than 63-micrometer diameter) for samples

collected at Mill Creek sampling sites, Johnson County, northeast Kansas, February 2006 through March 200

[mg/L, milligrams per liter; μm, micrometer]

Sampling 

site

(fig. 1)

Number 

of 

samples

Maximum

suspendedsediment

concentration 

(mg/L)

Minimum 

suspendedsediment 

concentration 

(mg/L)

Mean 

suspendedsediment 

concentration 

(mg/L)

Standard

deviation 

(mg/L)

Maximum 

percentage 

of sediment 

less than 

63 μm

Minimum 

percentage 

of sediment 

less than 

63 μm

Mean 

percentage 

of sediment 

less than 

63 μm

CL1a 5 1,960 100 600 770 100 84 96

CL1b 6 2,280 63 780 780 100 95 98

CL1 14 1,920 49 650 550 100 91 98

CL2 13 1,530 110 660 470 100 69 96

CO1 8 510 59 240 150 99 93 97

LM1 7 760 55 370 290 100 96 98

LM2 10 1,530 50 490 520 100 91 98

MI3 8 910 130 360 270 97 89 93

MI4 10 1,150 94 510 340 100 73 94

MI5 6 410 130 220 110 99 97 98

SM1 8 3,300 110 1,210 1,190 100 93 99

SM1a 5 950 15 480 400 100 95 98

SM1b 6 710 26 340 260 100 93 98

SM2 2 160 105 130 36 93 79 86
18 Effects on Suspended-Sediment Transport in Johnson County, Northeast Kansas, February 2006 through November 2008

the site was not located at a bridge, and samples could not be 

collected during increased flow conditions. Sediment concentrations at sites CL1a, CL1b, CL1, CL2, and SM1 often were 

increased for prolonged periods during stormflow conditions, 

providing more opportunity to collect larger maximum and 

mean SSC values than other sampling sites.

In addition to the distribution of SSC values, the grain size 

and color of suspended sediment are the primary factors that 

affect the turbidity/SSC regression (Downing, 2006). Turbidity has been shown to accurately estimate SSC in northeast 

Kansas streams with a preponderance of silt- and clay-sized 

sediment (Christensen and others, 2000; Rasmussen and others, 

2005, 2008; Lee and others, 2008, 2009). Silt- and clay-sized 

sediment composed the vast majority of suspended-sediment 

samples at all Mill Creek sampling sites, as only 3 of 108 samples (sites CL2, MI4, and SM2) had less than 89 percent silt/

clay particles. Sand did not comprise a larger part of the sediment-grain-size distribution during increased flow conditions, 

indicating that sand-sized material generally was not suspended 

within stream channels. All three of the samples with less than 

89 percent silt/clay particles were collected during mediumto low-flow conditions when sediment concentrations were 

relatively small. Laboratory analysis indicated that sediment 

concentrations for two of these samples were biased by insect 

parts (site MI4) and sand-sized precipitate (site CL2).

Two linear regression relations (as opposed to multiple, 

site-specific relations) were developed between turbidity 

and SSC data for 14 sampling sites (fig. 9). Two samples 

were collected during conditions in which in-stream turbidity values were greater than the sensor limit [approximately 

1,200 formazin nephelometric units (FNU)]. These samples 

were not included because the use of the maximum turbidity 

value would bias the regression relation (methods to estimate 

SSC during periods of turbidity maxima are described later in 

this report). Regression relations were aggregated among sites 

because soils in the Mill Creek Basin are similar in terms of 

particle size, mineralogy, and organic content (Lee and others, 

2009). One regression relation was developed for sites SM1a 

and SM1b, and one for the remaining 12 sampling sites. An 

analysis of covariance (ANCOVA) test was performed to test 

whether or not regression relations were significantly different 

(Helsel and Hirsch 2002). ANCOVA results indicated a statistically significant [p-value less than 0.01] difference in y-intercept values between the aggregate regression relation from 

sites SM1a and SM1b and from the remaining 12 sites. Differences are likely because larger-grained sediments settled out in 

the sediment forebay (upstream from sites SM1a and SM1b). 

Turbidity sensors are known to exhibit increased response to 

fine particles (approximately 1 μm; Sadar, 1998), thus finer 

grain-size distributions of suspended sediment at sites SM1a 

and SM1b resulted in a turbidity/SSC regression relation with 

a smaller slope (0.916) than the relation at the other 12 sites 

(0.982). Although two samples from site SM1b (turbidity 

values of 22 and 117) plotted beneath the established relation, 

larger turbidity samples at site SM1b had a similar relation with 

SSC values compared to those at SM1a, indicating that there is 

not a large difference in the turbidity/SSC relation during the 

periods when sediment concentrations are the largest (fig. 9). 

Relations at sites directly downstream from reservoirs (sites 

CO1 and MI3) were not significantly different from the overall 

relation because reservoirs only affected 40 percent of the 

basin, and outflows from Lake Lenexa lagged storms, and thus 

did not affect sediment grain-size distributions during storms.

Despite the addition of 30 samples at existing and new 

sites, the regression relation (slope of 0.982, y-intercept 0.28) 

was similar to the relation established for the eight sampling 

sites in 2007–08 (slope of 0.969, y-intercept 0.32) (fig. 9; 

Lee and others, 2009). Turbidity explained 93 percent of the 

variability in SSC values at the 12 Mill Creek sites. Residuals from each regression relation generally were distributed 

evenly around the best-fit line; individual sampling sites did 

not exhibit consistent bias in relation to the regression line 

(fig. 9). Relations were aggregated because turbidity/SSC relations were similar among sampling sites because soils in the 

Mill Creek Basin are similar in terms of particle size, mineralogy, and organic content (Evans, 2003), and data analyzed 

among multiple sites (Lee and others, 2009) indicated consistent relations and estimates of sediment loading.

Estimating Periods of Turbidity Truncation

YSI model 6136 turbidity sensors can record values 

from 0 to 2,000 FNU—the maximum recordable value varies 

among individual sensors (YSI Inc., 2010). When in-stream 

turbidity values are larger than maximum sensor values, sensors record the maximum value, resulting in underestimation 

of actual in-stream turbidity. Turbidity truncation measurements for only minutes can bias results because typically it 

occurs when sediment concentrations and loads are largest. 

Varying turbidity maxima and amounts of truncated data 

among sampling sites also bias comparisons of sediment loads 

and yields between sites. Estimates of turbidity during periods 

of truncation are performed as described and evaluated in Lee 

and others (2009). If turbidity and streamflow covary before 

and after the truncation period, the turbidity/streamflow ratio 

before and after sensor truncation is multiplied by continuous streamflow data during the period of sensor truncation 

to obtain a time-series estimate of turbidity. If turbidity and 

streamflow do not covary, the slope of turbidity measurements 

are interpolated for the period of sensor truncation (similar to 

methods described in Bragg and others, 2007).

Estimating data during periods of truncation increased 

sediment loads at sampling sites from 0 to about 24 percent 

(table 5). Truncated data at sites CL1, CL2, CO1, LM1, LM2, 

MI3, MI4, MI5, and MI7 were estimated from June 2007 to 

November 2008 (February 2006 to June 2007 are described in 

Lee and others, 2009); data considered from newly installed 

sites were from the entire period of sensor operation. Other 

than sites SM1 (24.3 percent), SM2 (11.3 percent), and SM1a 

(10.0 percent), estimates of sensor truncation increased sediment transport by less than 10 percent. Sites SM1 and SM1a 
Methods 19

10

100

1,000

10,000

10 100 1,000 10,000

SUSPENDED-SEDIMENT CONCENTRATION, IN MILLIGRAMS PER LITER

CL1a

CL1b

CL1

CL2

CO1

LM1

LM2

MI3

MI4

MI5

SM1

SM2

95-percent prediction

 interval 

Regression fit

log (SSC) = 0.982 log(Turb) + 0.28

R2 = 0.93

n = 95

RMSE = 0.11

Bias correction factor (Duan, 1983) = 1.03

1

10

100

1,000

10,000

1 10 100 1,000 10,000

TURBIDITY, IN FORMAZIN NEPHELOMETRIC UNITS (YSI Model 6136)

SM1a

SM1b

log (SSC) = 0.916 log(Turb) + 0.30

R2 = 0.97

n = 11

RMSE = 0.10

Bias correction factor (Duan, 1983) = 1.02

EXPLANATION

[SSC, suspended-sediment concentration; turb, turbidity; R2, coefficient of determination

n, number of samples; RMSE, root mean-squared error]

A

B

Figure 9. Regression relations between turbidity and suspended-sediment concentration at A, 12 Mill

Creek sites and B, 2 sites downstream from detention basins near Shawnee Mission Lake, Johnson County,

northeast Kansas, February 2006 through March 2009.
20 Effects on Suspended-Sediment Transport in Johnson County, Northeast Kansas, February 2006 through November 2008

had extensive truncation because of upstream construction; 

sediment loading estimates from this site are considered more 

uncertain than estimates from other sites. Larger percentage 

increases at site SM2 were caused by relatively little flow 

and smaller sediment load. Turbidity truncation at other sites 

occurred either rarely or during smaller flows, and thus did not 

substantially affect sediment loading estimates.

Estimating Sediment Loading during Periods of 

Missing Turbidity Data

Data occasionally are missing from the continuous 

turbidity record because of environmental fouling or turbiditysensor malfunction. When sensors malfunction during storms, 

sediment transport is unaccounted for, biasing computations 

of sediment load. Sediment loading estimates during periods 

of turbidity-sensor malfunction are performed as described 

in Lee and others (2009). If turbidity sensors failed during 

low-flow periods, turbidity values were interpolated using data 

before and after the missing period. If the turbidity sensor at 

a site failed during a storm, sediment loads were estimated by 

establishing relations in stormflow-weighted suspended-sediment concentrations (SWSCs) between that site and a nearby 

sampling site. Stormflow-weighted suspended-sediment 

concentrations are the average sediment concentration for a 

given volume of stormflow. Stormflow-weighted suspendedsediment concentrations from sites within the same basin are 

useful in estimating storm-sediment 

loads because they incorporate factors 

(such as soils, rainfall intensity, and 

antecedent conditions) that are similar 

between sites and storms. Stormflowweighted suspended-sediment concentrations are calculated by dividing the 

turbidity-predicted sediment load (in 

tons) by the total stormflow volume 

(in acre-feet) of an individual storm 

and multiplying by a unit conversion 

[x 907.2 kilograms per ton (kg/ton) x 

1,000,000 milligrams per kilograms 

(mg/kg) x 1,233,482 liters per acrefeet (L/acre-ft)] to obtain the storm 

SWSC in milligrams per liter. Regression relations are then established 

between the logarithm of SWSCs for 

sites immediately upstream or downstream to estimate SWSCs for storms 

with missing turbidity data. Estimated 

SWSCs (in milligrams per liter) were 

multiplied by the total stormflow (in 

acre-feet) observed during the missing 

storm (and a unit conversion, 0.00136) 

to derive an estimate of suspendedsediment load (in tons) for the missing 

storm. If storms were not observed at 

nearby sampling sites because of too 

little streamflow or malfunctioning sensors, regression relations developed between stormflow volume and sediment load 

among individual storms at each sampling site were used to 

estimate sediment load (denoted by superscript “a”; table 6).

Data considered at sites CL1, CL2, CO1, LM1, LM2, 

MI3, MI4, MI5, and MI7 were from June 2007 to November 2008 (February 2006 to June 2007 were described in Lee 

and others, 2009); data considered from other sites are for 

the entire period of sensor operation. Debris destroyed the 

streamgage and turbidity sensor at site CL1a in September 

2008, and thus no streamflow or turbidity-sensor data were 

measured during storm events 58 and 59 (table 6). Total stormflow at site CL1a was estimated by computing the percentage 

of total stormflow transported by these events at downstream 

site CL1, and multiplying the percentage by the total stormflow observed at site CL1a for the same study period. Stormflow/sediment load regression relations were then used to 

estimate sediment loading for each storm. Sediment loading 

was not computed at site SM1b because persistent backwater 

conditions precluded estimation of continuous streamflow.

Five of the 15 sites did not have missing turbidity data 

during any storm, and only 3 of the sites had missing turbidity 

data that resulted in estimation of 10 percent or more of total 

sediment loading (MI5, 10 percent; MI3, 18 percent; CL1b, 

40 percent). Aggregate measures of sediment loading at these 

sites (especially site CL1b) are more uncertain than other 

sites.

Table 5.  Sediment-load estimates during periods of turbidity truncation for sampling

sites in the Mill Creek Basin, Johnson County, northeast Kansas, February 2007 through

November 2008.

[mm, month; yr, year; --, no data]

Sampling 

site

(fig. 1)

Period of streamflow/

sediment record 

(excluding periods 

of freezing;

(mm/yr–mm/yr)

Hours of 

truncated 

turbidity 

data

Sediment load 

without estimation 

during turbidity 

truncation

(tons)

Sediment load 

with truncated 

periods 

estimated 

(tons)

Percentage 

increase

CL1a 02/07–11/08 7.8 900 910 1.1

CL1b 02/07–11/07 10.8 3,000 3,200 6.7

CL1 06/07–11/08 4.0 10,400 10,700 2.9

CL2 06/07–11/08 5.5 16,300 16,500 1.2

CO1 06/07–11/08 0 2,200 2,200 0

LM1 06/07–11/08 .7 6,600 6,700 1.5

LM2 06/07–11/08 .7 11,400 11,400 0

MI3 06/07–11/08 .6 1,400 1,400 0

MI4 06/07–11/08 3.4 17,800 18,100 1.7

MI5 06/07–11/08 2.7 25,200 26,900 6.7

MI7 06/07–11/08 8.2 48,900 49,100 .4

SM1 02/07–11/08 112 1,770 2,200 24.3

SM1a 02/08–11/08 21.7 1,000 1,100 10

SM1b 02/08–11/08 9.7 -- -- --

SM2 02/07–11/07 1.5 18 20 11.3
Table 6.  Periods of missing turbidity record, regressions used to estimate stormflow-weighted suspended-sediment concentrations and sedimenestimated suspended-sediment load for sampling sites in the Mill Creek Basin, Johnson County, northeast Kansas, February 2007 through Novemb[mi2, square mile; mm, month; yr, year; SWSC stormflow-weighted suspended-sediment concentration, in milligrams per liter; R2, coefficient of determination; RMSE, root SSL, suspended-sediment load; Q, total stormflow; --, no data]

Sampling

site

(fig. 1)

Basin

drainage

area 

(mi2)

Period of streamflow/sediment 

record (excluding 

periods of freezing) 

(mm/yr–mm/yr)

Missing 

storms SWSC regression relation/R2

Duan's 

bias 

correction

(Duan, 1983)

RMSE

Estimated 

storm suspendedsediment load 

(tons)

Suspendedsediment load at 

upstream/downstream site during 

same period (tons)

Suspendedsediment load 

without estimated 

storm loads 

(tons)

CL1a 0.7 02/07–11/08

a41

41.1

b58b59

Log(SWSC@CL1a) = 0.52logSWSC@CL1 + 1.39 

(.75) Log(SSL) = 1.21logQ - .32 (.83)

1.101.29

0.19

.34

8.6

.96

1.96.2

--

3.4 (CL1)

25.8 (CL1)

931 (CL1)

910 

CL1b 2.8 2/07–11/07

121313.114.1

a14.2

Log(SWSC@CL1a) = 0.62logSWSC@CL1 + 1.22 

(.85) Log(SSL) = 1.57logQ - 1.02 (.90)

1.101.33

.20.36

711

1,060

216131

15.7

2,060 (CL1) 

1,770 (CL1) 475 

(CL1)

131 (CL1)

-- 

3,200 

CL1 5.5 06/07–11/08 40.1 41 Log(SWSC@CL1) = 1.11logSWSC@CL2 - .31 (.86) 1.2 .29 50.9 3.4 71.4 (CL2) 6.8 (CL2) 10,700 CL2 10.9 06/07–11/08 -- -- -- -- -- -- 16,500 CO1 5.1 06/07–11/08 -- -- -- -- -- -- 2,200 LM1 8.8 06/07–11/08 -- -- -- -- -- -- 6,700 LM2 12.1 06/07–11/08 45.1 45.2 Log(SWSC@LM2) = 1.18logSWSC@LM1 - .35 (.85) 1.19 .29 5.0 2.3 4.6 (LM1) 2.2 (LM1) 11,400 MI3 2.8 06/07–11/08

254141.145.145.25859

Log(SWSC@MI3) = 0.48logSWSC@MI4 +1.23 (.72) 1.51 .26

1.7

37.4

7.53.31.91.4

245

2.0 (MI4)

189 (MI4)

24.0 (MI4)15.5 (MI4)

4.5 (MI4)6.6 (MI4)

1,810 (MI4)

1,400 

MI4 19.7 06/07–11/08 -- -- -- -- -- -- 18,100 MI5 31.7 06/07–11/08

20.220.3212223384141.159

Log(SWSC@MI5) = .95logSWSC@MI4 + .10 (.89) 1.09 .19

4.29.1

49.879.9

261313192

27.5

2,170

3.8 (MI4)

10.3(MI4)

44.8 (MI4)77.8 (MI4)

231 (MI4)251 (MI4)189 (MI4)

24.0 (MI4)

1,810 (MI4)

26,900 

MI7 57.4 06/07–11/08

27283030.1

Log(SWSC@MI7) = 1.01logSWSC@MI5 - .06 (.92) 1.09 .17

3,760

561287

40.0

1,640 (MI5)

257 (MI5)178 (MI5)

28.4 (MI5) 

49,100 

SM1 .6 02/07–11/08 a20 Log(SSL) = 1.57logQ - .64 (.87) 1.49 .42 .34 -- 2,300 SM1a 1.3 02/08–11/08 -- -- -- -- -- -- 1,100 SM1b 1.4 02/08–11/08

45.145.25258.1

-- -- -- -- -- -- 

SM2 .2 02/07–11/07 a14.2 Log(SSL) = 0.78logQ - .23 (.60) 1.35 .72 1.6 -- 20 

a Estimated from total stormflow/sediment load equation.b Stormflow estimated by comparison with same storm at site CL1, sediment load then estimated from total stormflow/sediment load equation.
22 Effects on Suspended-Sediment Transport in Johnson County, Northeast Kansas, February 2006 through November 2008

Sediment Transport in Johnson County, 

Kansas

Study results for sediment transport in Johnson County, 

Kansas consider data collected from 2006 through 2008 and 

are organized into four sections. Sections are organized by 

discussion of (1) total and annual rainfall, streamflow, and 

sediment transport in the Mill Creek Basin from 2006 to 2008, 

(2) sediment transport from subbasins with increased construction activity, (3) frequency and storm-by-storm analysis 

of streamflow and sediment transport in the Mill Creek Basin 

from 2006 to 2008, and (4) a comparison of streamflow and 

sediment among the five largest basins in Johnson County 

from 2006 to 2008.

Total and Annual Rainfall, Streamflow, and 

Sediment Transport in Mill Creek from 2006 

to 2008

Annual average rainfall from 1931 to 2008 in Olathe, 

Kansas (excluding 1950 because of data error), was 39.0 in. 

Rainfall during 2006 (36.4 in.) and 2007 (44.5 in.) was 

between the 25th and 75th percentile of annual rainfall, whereas 

2008 (49.5 in.) was greater than the 75th percentile of annual 

rainfall (National Oceanic and Atmospheric Administration, 

2009). The maximum observed rainfall during the study period 

for a single day in Olathe, Kansas (central to the study area), 

was 5.8 in. on July 30, 2008 (National Oceanic and Atmospheric Administration, 2009); larger than the 10-year daily 

recurrence interval (5.29 in.), but smaller than the 25-year 

recurrence interval (6.27 in.) estimated for Johnson County 

(Overland Park Stormwatch, 2009).

Rainfall volume was quantified for each subbasin in Mill 

Creek, and streamflow and stormflow volume were computed at each sampling site in the basin during the periods 

of streamgage/water-quality monitor operation from 2006 to 

2008 (Overland Park Stormwatch, 2009; table 7). Stormflow 

comprised most of the flow at each sampling site from 2006 

to 2008, from 56 percent of the total streamflow at site MI3 to 

96 percent of observed flow at site CL1b. Base- and low-flow 

periods were not computed at sampling sites CL1a and SM2 

because too few measurements were made to characterize 

the low-flow portion of the streamflow record. Base-flow 

volumes were not estimated at sampling sites SM1a or SM1b 

because of backwater conditions. Sites SM1 (50 percent), 

SM1a (48 percent), CL1b (41 percent), MI3 (39 percent), CO1 

(36 percent) and LM1 (33 percent) had the most stormflow 

as a percentage of rainfall in the basin. All of these sites are 

headwater sites, and are thus less influenced by groundwater 

contributions than lower elevation downstream sampling sites. 

Additionally, increased impervious surface area upstream from 

sites SM1, SM1a, LM1, and MI3 route more rainfall directly 

to streams. Site CO1 has substantially less upstream impervious surface (10.8 percent); however, relatively steep slopes 

(table 2) in this subbasin may have led to increased stormflows 

relative to the amount of rainfall.

A storm on June 4, 2008, resulted in the largest peak flow 

during the period of record for all sites except site CL1a (and 

for sites out of operation in 2008). Peak-flow values from this 

storm at sites CL2 (2,400 ft3/s) and MI7 (8,800 ft3/s) were 

larger than 2-year recurrence intervals (2,030 and 7,770 ft3/s, 

respectively) but less than 5-year recurrence intervals (4,200 

and 13,630 ft3/s, respectively) estimated by Perry and others 

(2004). Peak-streamflow values at sites LM2 (5,180 ft3/s) and 

MI5 (7,320 ft3/s) were larger than 5-year recurrence intervals 

(4,180 and 5,860 ft3/s, respectively) but less than 10-year 

recurrence intervals (5,990 and 8,430 ft3/s, respectively).

The turbidity/SSC model was applied to continuous 

turbidity data (fig. 9) to obtain continuous, 5-minute estimates of SSC at each sampling site. Time-series (5 minute) 

streamflow values (in cubic feet per second) were multiplied 

by 5-minute computations of SSC and by a unit-conversion 

factor [x 1/1,000 milligram per gram (mg/g), x 1/453.6 gram 

per pound (g/lb), and x 28.32 liter per cubic foot (L/ft3)] to 

compute time-series suspended-sediment discharge in pounds 

per second. Five-minute sediment discharge computations are 

summed and multiplied by a unit conversion factor [x 300 seconds x 1 ton/2,000 pounds (lbs)] to compute sediment loads 

(in tons) for periods of interest. Sediment loads, yields, and 

SWSCs were calculated for each sampling site by calendar 

year (2006–08, table 8). Periods when monitors were removed 

during freezing conditions (January 1 to February 20, 2006; 

December 1 to December 18, 2006; January 10 to February 20, 2007; and December 6, 2007 to February 20, 2008) 

were excluded from this analysis. Stormflow-weighted 

suspended-sediment concentrations were computed to characterize average sediment concentrations for a given volume 

of stormflow. Stormflow-weighted suspended-sediment 

concentrations are computed by dividing the sediment load 

(in tons) by the total stormflow (in acre-feet) for a period of 

interest and multiplied by a conversion factor [x 907.2 kg/ton 

x 1,000,000 mg/kg x 1,233,482 L/acre-ft], to report data in 

milligrams per liter.

Among the sites monitored continuously from 2006 

to 2008 (CL1, CL2, CO1, LM1, LM2, MI3, MI4, MI5, and 

MI7) sediment yields were substantially larger in the Clear 

Creek Basin [CL1; 3,400 tons per square mile (tons/mi2); 

CL2, 2,600 tons/mi2; table 8]. Subbasins partially regulated by impoundments (site CO1, 640 tons/mi2

; site MI3, 

950 tons/mi2) and those with stable urban land use (site LM1, 

1,200 tons/mi2; site LM2, 1,300 tons/mi2; site MI3, 

950 tons/mi2) had the smallest sediment yields in the Mill 

Creek Basin. Sediment yields from the Clear Creek Basin 

were approximately 2 to 3 times those from the more rural 

(and impounded) Coon Creek Basin and the older, stable 

urban Little Mill Creek and upper Mill Creek Basins (table 8).

Cumulative sediment yields from 2006 to 2008 increased 

coincidental with increases in impervious surface from 2005 

to 2006 (fig. 10A), but were unrelated to increases in impervious surface from 2006 to 2008 (fig. 10B). This is potentially 
Table 7.  Total rainfall, streamflow and stormflow volumes, and peak streamflow upstream from and at Mill Creek sampling sites, Johnson northeast Kansas, February 2006 through November 2008.[mi2, square mile; ft3/s, cubic feet per second; --, no data; rainfall data from Overland Park Stormwatch Program, 2009]

Sampling 

site

(fig. 1)

Basin 

area

(mi2)

Percent 

impervious 

surface,

2008

Total rainfall

(acre-feet)

Total streamflow

(acre-feet)

Total stormflow

(acre-feet) 

2006 2007 2008 2006 2007 2008 2006 2007 2008

CL1a 0.7 10.9 -- 1,500 1,600 -- 340 470 -- 340 470 CL1b 2.8 18.8 -- 6,300 -- -- 2,700 -- -- 2,600 -- CL1 5.5 11.3 8,400 12,500 12,500 1,200 4,100 4,900 1,100 4,000 4,500 CL2 10.9 13.1 16,800 24,800 24,900 4,400 9,000 10,700 3,000 7,800 9,900 CO1 5.1 10.8 8,100 11,100 11,800 1,700 4,800 6,800 1,400 3,900 6,000 LM1 8.8 30.7 14,400 20,600 21,400 4,000 9,000 10,500 3,500 7,100 8,200 LM2 12.1 27.1 19,800 28,300 29,400 3,900 9,000 9,200 3,300 8,000 8,200 MI3 2.8 35.1 4,800 6,800 6,900 3,200 4,700 5,000 1,600 2,600 3,000 MI4 19.7 24.8 32,200 44,500 47,700 10,900 21,200 25,700 7,300 15,700 17,400 MI5 31.7 17.8 51,600 72,100 76,500 12,700 25,100 16,900 8,900 18,100 21,200 MI7 57.4 18.8 92,600 132,000 136,700 17,800 43,600 53,800 14,200 34,100 40,400 SM1 .6 27.7 -- 1,300 1,500 -- 600 910 -- 540 860 SM1a 1.3 26.5 -- -- 3,100 -- -- -- -- -- 1,500 SM2 .2 1.5 -- 500 -- -- 40 -- -- 40 -- 
Table 8.  Total suspended-sediment load, yield, and stormflow-weighted suspended-sediment concentrations at Mill Creek sampling sites, Johnson February 2006 through November 2008. [mi2, square mile; tons/mi2, tons per square mile; mg/L, milligrams per liter; --, no data] Sampling site (fig. 1) Basin area (mi2) Increase in percentage of impervious surface from 2005 to 2006 Increase in percentage of impervious surface from 2006 to 2008 Suspended-sediment load (tons) Suspended-sediment yield (tons/mi2) Stormflow-weighted suspended-esdiment concentration (mg/L) 

2006 2007 2008 2006 2007 2008 2006 2007 2008 CL1a 0.7 5.0 3.1 -- 570 440 -- 810 630 -- 1,220 690 

CL1b 2.8 6.1 1.9 -- 5,300 -- -- 1,900 -- -- 1,500 -- CL1 5.5 3.5 1.0 1,100 10,100 7,500 200 1,800 1,400 740 1,800 1,200 CL2 10.9 2.9 .9 2,000 14,800 11,900 180 1,400 1,100 490 1,400 890 CO1 5.1 1.3 .5 280 1,200 1,800 60 230 350 150 220 220 LM1 8.8 1.1 .8 1,400 4,900 4,200 160 550 470 290 500 370 LM2 12.1 .9 .7 1,600 7,000 7,600 130 570 620 350 640 680 MI3 2.8 .9 2.2 620 1,100 930 220 380 330 290 290 230 MI4 19.7 2.6 1.6 5,800 14,300 12,800 300 730 650 590 670 540 MI5 31.7 2.0 1.0 6,100 16,900 23,100 190 530 730 500 690 800 MI7 57.4 1.9 1.0 10,400 36,200 39,500 180 630 690 540 750 700 SM1 .6 3.9 2.5 -- 990 1,300 -- 1,700 2,200 -- 1,200 1,100 SM1a 1.3 3.6 1.5 -- -- 1,100 -- -- 850 -- -- 580 SM2 .2 1.4 0 -- 20 -- -- 100 -- -- 370 -- 
Sediment Transport in Johnson County, Kansas 25

0

500

1,000

1,500

2,000

2,500

3,000

3,500

4,000

0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0

SUSPENDED-SEDIMENT YIELD, IN TONS PER SQUARE MILE (2006–08)

INCREASE IN PERCENTAGE OF IMPERVIOUS SURFACE (2005–06)

0

500

1,000

1,500

2,000

2,500

3,000

3,500

4,000

0.4 0.6 0.8 1.0 1.2 1.4 1.6 1.8 2.0 2.2 2.4

SUSPENDED-SEDIMENT YIELD, IN TONS PER SQUARE MILE (2006–08)

INCREASE IN PERCENTAGE OF IMPERVIOUS SURFACE (2006–08)

Data from Johnson County Automated 

Mapping Information System, written 

commun., 2009

A

B

DA

mi2

%

Imp

Drainage area

Square miles

Percent

Impervious surface area, 2008

DA

mi2

%

Imp

Drainage area

Square miles

Percent

Impervious surface area, 2008

CL1

DA = 5.5 mi2

0% impounded

Imp: 11.3%

CL2

DA = 10.9 mi2

Imp: 13.1%

CO1

DA = 5.1 mi2

40% impounded

Imp: 10.8%

LM1

DA = 8.8 mi2

0% impounded

Imp: 30.7% 

LM2

DA = 12.1 mi2

0% impounded

Imp: 27.1% 

MI3

DA = 2.8 mi2

36% impounded

Imp: 35.1%

MI4

DA = 19.7 mi2

5% impounded

Imp: 24.8%

MI5

DA = 31.7 mi2

19% impounded

Imp: 17.8% 

MI7

DA = 57.4 mi2

10% impounded

Imp: 18.8%

CL1

DA = 5.5 mi2

0% impounded

Imp: 11.3%

CO1

DA = 5.1 mi2

40% impounded

Imp: 10.8%

LM1

DA = 8.8 mi2

0% impounded

Imp: 30.7% 

LM2

DA = 12.1 mi2

0% impounded

Imp: 27.1% 

MI3

DA = 2.8 mi2

36% impounded

Imp: 35.1%

MI4

DA = 19.7 mi2

5% impounded

Imp: 24.8%

MI5

DA = 31.7 mi2

19% impounded

Imp: 17.8% 

MI7

DA = 57.4 mi2

10% impounded

Imp: 18.8%

9% impounded

CL2

DA = 10.9 mi2

Imp: 13.1%

9% impounded

Figure 10. Relation between suspended-sediment yield from 2006 to 2008 and increases in impervious

surface A, from 2005 to 2006 and B, from 2006 to 2008, Mill Creek sites, Johnson County, Kansas.
26 Effects on Suspended-Sediment Transport in Johnson County, Northeast Kansas, February 2006 through November 2008

because there was more construction (and thus soil disturbance) from 2005 to 2006, and relatively little stormflow 

during 2006 to transport sediment through the stream network. 

Although general patterns appear to exist between construction activity and sediment transport on a basin scale, several 

site-specific factors, such as management practice, impoundments, construction-site slope, site proximity to streams, 

sediment deposition and resuspension, and stream-channel 

erosion complicate relations between landscape activities and 

sediment yield.

Because of smaller amounts and less intense rainfall, 

2006 typically had less than one-half of the stormflow, and 

one-third of the sediment load compared to 2007 and 2008. 

Larger stormflows in 2007 and 2008 resulted in substantially 

larger sediment loading at sites affected by urban construction. 

Site CL1 had nearly 4 times the flow in 2007 than in 2006, but 

more than 9 times the sediment transport, whereas site CL2 

had 2.6 times more flow in 2007 than in 2006, but 7.8 times 

the sediment transport. Predominantly urban and rural sites 

had 1.7 to 2.7 times the flow in 2007 than in 2006, but only 

1.7 to 4.1 times the sediment transport. These comparisons 

indicate that at sites with substantial soil disturbance, the 

amount of flow is the predominant factor limiting sediment 

transport. Smaller supplies of sediment available for transport 

in urbanized basins limit increases in sediment transport as a 

result of a wetter year. Site SM2, downstream from a predominantly undeveloped, parkland basin had less than one-half the 

sediment yield (100 tons/mi2) and generally smaller SWSC 

values (370 mg/L) than other basins in Mill Creek; however, 

data at site SM2 may be biased because of difficulty measuring flashy flow conditions (and thus inability to verify theoretical streamflow ratings). Relatively small sediment yields 

and SWSC values in 2007 at site SM2 (table 8) indicate that 

sediment yields from small, unimpacted subbasins likely are 

similar (or less than) those from predominantly established 

urban basins.

Although stormflows were slightly larger at all sampling 

sites (1.0 to 1.6 times) in 2008 than in 2007, sediment loads 

decreased at sites CL1a, CL1, CL2, LM1, MI3, and MI4. 

Decreases in sediment transport may be related to transport 

of readily erodible sediment supplies in 2007 and (or) less 

active construction area upstream from these sites from 2006 

to 2008. With the exception of site MI3, impervious surfaces 

upstream from these sites increased more in 1 year from 2005 

to 2006 (0.9 to 5.0 percent) than during the subsequent 2 years 

from 2006 to 2008 (0.8 to 2.2 percent). Sampling sites in the 

Clear Creek Basin had nearly triple the increase in impervious surface area from 2005 to 2006 (site CL1, 3.5 percent; 

site CL2, 2.9 percent), than during the subsequent 2 years 

(site CL1, 1.0 percent; site CL2, 0.9 percent; table 8; fig. 10).

Increases in stormflow from 2007 to 2008 resulted in 

increases in sediment transport at sites CO1, LM2, MI5, MI7, 

and SM1. Construction in the Coon Creek Basin from 2006 to 

2008 was concentrated along an unregulated tributary in the 

northern part of the subbasin, possibly enabling eroded soils 

to be readily transported downstream. Construction upstream 

from SM1 (described in “Land Use” and subsequent parts of 

this report) was ongoing throughout 2007 to 2008, but was not 

paved at the time aerial photography was taken (March 2008; 

fig. 3) and, therefore was not accounted for in impervious 

surface estimates. Visual observations were made of commercial construction contributing excess sediment to a tributary 

1,300 ft from Little Mill Creek between sites LM1 and LM2, 

but the magnitude of the sediment contribution is unknown. 

Continued increases in sediment loading from 2007 to 2008 

at downstream sites MI5 and MI7 may be related to either 

sediment contributions from sediments deposited in (or near 

channels) or from streambank erosion.

Sediment Transport from Subbasins with 

Increased Construction Activity

Streamflow and (or) sediment concentrations were 

computed in the headwaters of the Clear Creek Basin (CL1a 

and CL1b) and upstream from Shawnee Mission Lake (SM1, 

SM1a, SM1b) in 2007 and (or) 2008 to better understand the 

effects of construction sites on sediment transport in Johnson 

County, Kansas.

Turbidity Levels Relative to U.S. Environmental

Protection Agency Construction Effluent

Guidelines

Beginning on February 1, 2010, the U.S. Environmental Protection Agency (USEPA) required all construction 

sites greater than 1 acre to obtain permit coverage to meet 

guidelines designed to limit discharge of pollutants (primarily sediment) as a result of construction activity (U.S. Environmental Protection Agency, 2009). Initial implementation 

of the guidelines required all construction sites to implement 

pollution prevention measures, erosion and sediment controls, 

and soil stabilization measures (U.S. Environmental Protection 

Agency, 2009). Beginning August 1, 2011, all sites that disturb 

greater than 20 acres of land at once will be required to monitor discharges and comply with a mean-daily turbidity criteria 

of 280 nephelometric turbidity units (NTU; U.S. Environmental Protection Agency, 2009). Monitoring and numeric criteria 

will be extended to all sites greater than 10 acres at once on 

February 1, 2014 (U.S. Environmental Protection Agency, 

2009). Although storms with rainfall greater than the 2-year, 

24-hour storm (3.6 inches in Johnson County) will be exempt 

from USEPA criteria, the cumulative 24-hour rainfall did 

not exceed 3.6 inches in either of the monitored basins with 

increased construction activity.

To evaluate the applicability and potential effect of new 

USEPA construction guidelines, mean-daily turbidity values at 

sites in the construction-impacted Clear Creek and Shawnee 

Mission Lake Basins were compiled in 2007 and 2008 and 

compared to numeric criteria. However, these comparisons 

are not applicable to construction guidelines because sampling 
Sediment Transport in Johnson County, Kansas 27

sites were not directly downstream from construction sites, 

and because turbidity measurements made by YSI model 6136 

sensors may or may not be applicable to future criteria, as 

individual states will determine how to measure turbidity 

(U.S Environmental Protection Agency, 2009). Monitoring 

downstream from areas under construction likely underestimate actual turbidity from construction sites, but because of 

additional stormflow, downstream sites could also overestimate the duration in which turbidity values are elevated. The 

results of comparing different turbidity units are less certain. 

Because turbidity is the measurement of an apparent physical 

property, different turbidity units only distinguish various measurement methods, and thus do not assure consistent reporting. 

Additionally, comparisons among instruments generally are 

not consistent across variation in the particle size, color, and 

concentration of suspended sediments (Pavelich, 2002).

Mean-daily values downstream from the City Center 

North construction site exceeded the 280 NTU criteria during 

17 days in 2007, and during 15 days in 2008. Actual values 

from the City Center North construction site may exceed 

criteria more frequently, as runoff from this site was diluted by 

runoff from park and residential land between the construction 

and sampling site. Sites SM1a and SM1b exceeded criteria 

less frequently than site SM1 (9 and 8 days, respectively) 

because of further dilution of stormflows by runoff from 

parkland, and because of sediment deposition in the upstream 

sediment forebay. Mean-daily turbidity values at site SM2 did 

not exceed turbidity criteria during 2007, an indication that 

background daily turbidity values are less than the numeric 

criteria. Because dry conditions were present for much of 2007 

at site SM2, turbidity values observed during low-flow conditions were interpolated during dry periods to allow comparison of turbidity conditions with other sampling sites. Regular 

exceedance of criteria 1,400 ft downstream from a construction site with extensive erosion and sediment controls (such as 

those implemented on the City Center North site) may indicate 

the need for additional erosion and sediment controls and 

(or) treatment to bring discharges from construction sites into 

compliance with future numeric turbidity criteria.

Mean-daily turbidity values at site CL1a exceeded 

USEPA criteria during 6 days, and site CL1b exceeded 

USEPA criteria during 7 days in 2007, and turbidity levels did 

not reach criteria at site CL1a in 2008. However, similar to 

site SM1, turbidity values at sampling sites are likely smaller 

than in discharges directly downstream from construction 

sites. Turbidity values were smaller at sampling sites CL1a 

and CL1b compared to those observed at site SM1 because 

less of the upstream basin was occupied by construction 

activities.

Sediment Transport in the Clear Creek Basin

In addition to sampling sites CL1 and CL2 (operated 

from 2006 to 2008) site CL1a was installed and operated from 

February 2007 to November 2008, and site CL1b was installed 

and operated from February through November 2007. Sites 

were installed to characterize predominant sediment sources 

and transport from the subbasin upstream from site CL1 

(which had the largest documented sediment yields in Johnson 

County from February 2006 to June 2007; Lee and others, 

2009). Several construction sites were active in the headwaters 

of Clear Creek from 2005 to 2008 including several housing 

developments, two areas of road construction, and two schools 

(fig. 5; table 3). Sites downstream from increased recent and 

active construction sites in the headwaters of the Clear Creek 

Basin had among the largest annual sediment yields in the 

Mill Creek Basin during 2007 and (or) 2008 (630 to 

1,900 tons/mi2).

Although the subbasin upstream from CL1a had the 

most construction activity from 2005 to 2008 and multiple 

failures of sediment controls were observed (fig. 6), sediment yields and SWSCs were smaller than those observed at 

downstream Clear Creek sites with less construction (table 8). 

This may have been because most construction sites upstream 

from site CL1a were distant from streams (S4, R1, and S2; 

fig. 5), and thus sediments eroded from these sites are more 

likely to deposit on land surfaces and within stream channels. Substantial sediment deposition observed in Clear Creek 

upstream from site CL1a (fig. 6C) after spring storms in 2007 

indicate that relatively smaller sediment transport capacities 

in the headwaters of the basin may not effectively transport 

sediments through the stream network. Sediments observed 

to have been deposited in the stream network upstream from 

site CL1a in May 2007 (fig. 6C) were still present on October 25, 2007, despite several large storm events (fig. 11), indicating the potential for more extended or permanent storage of 

eroded sediments in headwater drainages.

Sediment yields from the subbasins between sites CL1a 

and CL1b (obtained by subtracting the sediment load observed 

at site CL1a from sediment loads observed at site CL1b and 

dividing by the intermediate drainage area; 2,250 tons/mi2; 

table 8) and between CL1b and CL1 (1,780 tons/mi2; table 8) 

were more than double the sediment yields of other subbasins 

(excluding site SM1 upstream from Shawnee Mission Lake) 

within Mill Creek in 2007. Large yields at these sites likely are 

related to increased active construction directly adjacent to the 

stream channel between these sites (fig. 5). Sediment eroded 

from construction sites adjacent to stream channels have less 

distance to travel before being transported by stormflows in 

Clear Creek. Additionally, sediments eroded from construction sites before the study period may have been deposited 

within the stream network (figs. 6C and 11) and resuspended 

by storms in 2007 and 2008. Visual observation of the stream 

channel in October 2008 (fig.11B) indicated substantial sediment deposition throughout the stream reach as a result of 

construction activities on Clare Road (fig. 5). Large increases 

in sediment yield between sites CL1a and CL1 (table 8) likely 

result from a combination of previously eroded, deposited, 

and resuspended sediments from upstream construction sites, 

and recently eroded sediments from construction activities 

adjacent to the stream channel.
28 Effects on Suspended-Sediment Transport in Johnson County, Northeast Kansas, February 2006 through November 2008

A

B

Figure 11. A, Sediment deposition in the Clear Creek channel upstream from site CL1a, October 2007,

and B, deposition in the Clear Creek channel adjacent to Clare Road construction, Lenexa, Kansas,

October 2008. Photograph A by Dale Clark, City of Lenexa and photograph B by Patrick P. Rasmussen,

U.S. Geological Survey.
Sediment Transport in Johnson County, Kansas 29

Stormflow volume, sediment load, and sediment yield 

were computed for the five largest storms at all Clear Creek 

sampling sites in 2007 (in which sites CL1a and CL1b were 

operational), as well as the largest storm in 2008 (in which 

site CL1b was no longer operational; fig. 12). During the first 

two large storms of 2007, sediment yields were much larger at 

site CL1 (150 and 280 tons/mi2) than at upstream sites CL1a 

(49 and 73 tons/mi2) and CL1b (69 and 170 tons/mi2); however, during the next three storms in the fall of 2007, sediment 

yields were larger at site CL1b with respect to the amount 

of stormflow (indicated by larger SWSC values), and with 

respect to drainage area (indicated by larger sediment yields) 

compared to other sites in the basin. Larger sediment yields 

observed at site CL1b during storms in the late summer and 

fall of 2007 may be related to increased sediment contributions from recent and ongoing upstream construction activity 

adjacent to Clear Creek (table 3). Stormflow and sediment 

yields and SWSC values for storms at site CL1a generally 

were smaller than other sites in the basin, likely because 

construction sites were relatively distant from streams most 

able to convey eroded sediments. Site CL2 had smaller sediment yields and SWSCs compared to sites CL1b and CL1 for 

individual storms and annually (fig. 12; table 8). Smaller sediment yields at site CL2 are likely related to less construction 

activity in the basin between sites CL1 and CL2, and potentially related to sediment deposition in the less sloping stream 

channel between sites CL1 and CL2. Comparison of sediment 

yields among headwater and downstream sites in the Clear 

Creek Basin indicated that factors such as site and stream 

slope, the current phase of construction, management practices, and site location relative to streams affect the amount 

and length of time it takes eroded sediment to be transported 

downstream.

Sediment Transport in the Shawnee Mission

Lake Basin

Sampling site SM1 was installed 1,400 ft downstream 

from the 68-acre City Center North residential and commercial 

construction site in February of 2007 to characterize sediment transport from the construction site to Shawnee Mission Lake (fig. 3). Because this was the only construction site 

upstream from site SM1 during the study period, and the rest 

of the subbasin consists of park and residential land (and thus 

would only marginally increase downstream sediment loads), 

sediment loads at this site were completely attributed to the 

City Center North site. Sampling sites SM1a and SM1b were 

37

37

72 34 44 52 49 73 82 107 84 74 37 160

110 118 97 99

69

49

170

340

230

170

53

150

71 71

90

120

150

280

240

160

140

440

36

92

65 61

71

100

92

200

180

120

89

330

0

500

1,000

1,500

2,000

2,500

3,000

3,500

4,000

5/6/2007 5/7/2007 8/9/2007 10/13/2007 10/17/2007 6/3/2008

STORMFLOW VOLUME, IN ACRE-FEET AND SEDIMENT LOAD, IN TONS 

Stormflow volume—Number indicates

 stormflow yield, in acre-feet per 

 square mile

Sediment load—Number indicates

 sediment yield, in tons per square

 mile

Number indicates stormflow-weighted 

 sediment concentration, in milligrams

 per liter 

980

980

1,370

2,070

1,890

1,610

1,390

1,100

740

2,020

2,550

2,140

2,340 1,420

1,770

1,610

1,400

1,040

1,240

1,150

920

1,460

2,720

2,370

CL1a CL1b CL1 CL2 CL1a CL1b CL1 CL2 CL1a CL1b CL1 CL2 CL1a CL1b CL1 CL2 CL1a CL1b CL1 CL2 CL1a CL1b CL1 CL2 No data

Figure 12. Stormflow volume and sediment load for selected large storms in the Clear Creek Basin, Johnson County,

Kansas, 2007 through 2008.
30 Effects on Suspended-Sediment Transport in Johnson County, Northeast Kansas, February 2006 through November 2008

installed in February 2008 to monitor sediment concentrations 

and loading through a sediment forebay (directly upstream 

from site SM1a) and a wetland (directly upstream from site 

SM1b) constructed in winter 2007–08 and planted in the 

spring of 2008. Because of backwater conditions, only streamflow conditions deemed unaffected by backwater were estimated at site SM1a, and continuous streamflow was not computed at site SM1b. Changes in sediment concentration during 

storm events were used to characterize wetland effects on sediment transport to the lake. At normal pool levels, total storage 

in the forebay is 1.8 acre-ft, and storage in the wetland is 

approximately 7 acre-ft (T. Stanton, Olsson Associates, written 

commun., 2009). Sediments were not dredged from either the 

settling basin or the wetland during the study period (T. Stanton, Olsson Associates, written commun., 2009). The sediment 

forebay was constructed to protect wetland vegetation from 

heavy sediment loads (T. Stanton, Olsson Associates, written 

commun., 2009), whereas the wetland was constructed to provide aquatic habitat and educational and recreational activities 

to the public, and to treat post-construction runoff through filtration and nutrient uptake by wetland vegetation (T. Stanton, 

Olsson Associates, written commun., 2009). The constructed 

wetland was designed to enable connectivity between the 

lake and wetland for fish and canoes, and thus provides only 

minimal detention of flows during storms (T. Stanton, Olsson 

Associates, written commun., 2009).

Mass grading was undertaken at the City Center North 

construction during the spring and summer of 2007; steep 

slopes resulted in extensive cut and fill (R. Beilfuss, City of 

Lenexa, written commun., 2008). The entire site was disturbed 

throughout this period and large fill piles were located on the 

northeast and southwest corners of the site. Initial sediment 

controls included 5-ft high mulch berms along the northern 

border of the site, and silt fences around the fill piles, the 

entire site perimeter, and downgradient toward the central 

tributary on site. Three rock check dams were installed along 

the central tributary, and a small sediment-control pond 

was installed in an east-central location on the construction 

site (three planned sediment ponds were not installed until 

June 2007 because sanitary sewer lines intersected a pond 

location; R. Beilfuss, City of Lenexa, written commun., 2008). 

City of Lenexa erosion-control inspectors noticed extensive 

failures of mulch berms and rock checks after an approximate 

1.6-in. storm March 29–30, 2007. City staff mandated mulch 

berm replacement and improved maintenance and repair of 

existing mulch berms and sediment-control fences, gravel 

facement and installation of an additional rock-check dam, 

dredging the existing sediment pond, and installation of three 

additional ponds with skimmers, and added flocculants to outflow pipes. Other than an additional sediment discharge noted 

in mid-August 2007 (because of a contractor dumping sediment pond deposits along a tributary on the northeast corner 

of the site), inspections indicated the site had good erosion and 

sediment-control practices through the remainder of the study.

Sediment yields at sampling site SM1 in 2007 

(1,700 tons/mi2) and 2008 (2,200 tons/mi2) were among 

the largest in the county (only sites CL1 and CL1b in 2007 

were larger; 1,800 tons/mi2 and 1,900 tons/mi2, respectively). 

Assuming all of the sediment transported past sampling 

site SM1 originated from the construction site, yields from 

the City Center North site were 9,300 tons/mi2 in 2007 and 

12,200 tons/mi2 in 2008. Annual sediment yields attributed to 

the construction site were 5 to 55 times those from other sampling sites in the Mill Creek Basin (table 8). Although these 

yields are much larger than other subbasins in the county 

with mixed land uses, sediment yields were small relative 

to yields observed from historical construction sites without 

erosion and sediment controls in the United States (2,300 to 

140,000 tons/mi2/yr; Wolman and Schick, 1967; Yorke and 

Herb, 1978). Given erodible soils, steep slopes, and the relatively large size of this construction site, as well as relatively 

wet years in 2007 and 2008, annual sediment yields were 

relatively small compared to the range of historically observed 

values. Thus, extensive on-site erosion and sediment-control 

practices likely are responsible for the relatively small sediment yields compared to historical unregulated sites.

Stormflow volume, sediment load, SWSC, and rainfall 

amount and intensity were defined for the 20 largest storms in 

2007 to characterize factors affecting sediment transport from 

the City Center North construction site (fig. 13). Sediment 

loading at site SM1 primarily was related to the amount and 

intensity of rainfall and antecedent rainfall conditions. The 

largest storm, in terms of rainfall amount (October 13, 2007), 

had the fourth-most intense rainfall, and transported the most 

sediment. Although the storm on August 9, 2007, had the 

second-most rainfall and second-highest rainfall intensity, 

dry conditions preceding the storm resulted in less runoff and 

consequently, resulted in less sediment transport (but still 

relatively large SWSCs). Storms that occurred immediately 

after another large storm (May 7, October 15, and October 17, 2007) had smaller SWSCs than preceding storms. 

Thus, the most sediment transport with respect to drainage 

area (sediment yields) or with respect to flow (SWSCs) would 

be expected from large, intense rainstorms that were preceded 

by relatively small storms that saturate surface soils. Despite 

observed improvements in sediment-control practices and 

installation of additional sediment-control ponds (fig. 13), 

decreases in the amount of sediment transported during storms 

were not apparent relative to the larger effects of storm magnitude, rainfall intensity, and antecedent rainfall. Despite having 

caused failure of multiple sediment controls on-site, the storm 

on March 29, 2007, had smaller SWSC values than many 

subsequent storms. A lack of substantial change in sediment 

loading from storms through 2007 indicated that improved 

erosion and sediment-control measures could not be credited 

with immediate changes in downstream sediment loading.

Stormflow volume and sediment load were computed at 

sampling sites SM1 and SM1a, and average sediment concentrations were computed at sites SM1, SM1a, and SM1b for the 

10 largest storms in 2008 (fig. 14). Sediment yields and SWSC 

values observed at sampling site SM1 were relatively smaller 

during storms in 2008 than in 2007. A comparison of similar 
Sediment Transport in Johnson County, Kansas 31

storms on June 12, 2008 [stormflow volume, 58 acre-ft; rainfall intensity, 5.6 inches per hour (in/h); fig. 14] and October 17, 2007 (52 acre-ft and 4.6 in/h, respectively; fig. 13), 

indicated that the storm in 2008 transported a much smaller 

sediment load (75 tons compared to 112 tons) and had a much 

smaller SWSC (950 mg/L compared to 1,580 mg/L) relative 

to 2007. A storm on October 15, 2008, had substantially more 

flow (25 acre-ft) than a storm observed on the same date in 

2007 (7.4 acre-ft) but transported only 21 tons of sediment 

(compared to 13 tons in 2007) thus having a SWSC about 

one-half (620 mg/L) of the 2007 storm (1,250 mg/L). Smaller 

sediment loading (relative to streamflow) at this site may 

because of changes in construction phasing (from mass grading to building construction) and (or) a lag between decreases 

in sediment loading and improved management practices at 

the construction site.

Annual sediment loads were slightly larger at sampling 

site SM1 (1,300 tons) than those estimated downstream at 

site SM1a (1,100 tons) during 2008, despite nearly double 

the drainage area at site SM1a (table 8). However, sediment 

transport from the basin between sites SM1 and SM1a is 

expected to be small because the basin is occupied by established residential (built primarily from 1988 to 1999) and 

park land uses (table 2). The sediment yield from the adjacent, 

predominantly residential basin LM1 in 2008 (470 tons/mi2; 

table 8), was used (after being multiplied by the basin areas 

between sites SM1 and SM1a; 0.7 mi2) to estimate a contribution of 330 tons of sediment from the basin between sites SM1 

and SM1a. Under this assumption, approximately 530 tons 

of sediment are estimated to have been deposited (33 percent 

of the incoming load) within the sediment forebay (and the 

upstream channel) during 2008. Assuming a bulk density 

of 18 pounds per cubic foot (lb/ft3); (as observed in the top 

1 to 2 in. of the Shawnee Mission Lake sediment core collected in 2007; Lee and others, 2007), 1.4 acre-ft of sediment 

is estimated to have been deposited in or upstream from the 

sediment forebay. Observations at the site indicated sediment 

deposition in the sediment forebay at normal pool levels, as 

well as on the streambed upstream from the forebay. Thus 

the 1.4 acre-ft of sediment estimated to have been deposited 

in the 1.8-acre-ft forebay likely is distributed upstream, in, 

and around the normal pool volume of the forebay; however, 

given the compounding error from streamflow and sediment 

concentration estimates, estimates of sediment loads from the 

basin between sites SM1 and SM1a, and uncertainty regarding the bulk density of deposited material, these estimates are 

considered uncertain.

Average sediment concentrations (as opposed to SWSCs) 

were computed for individual storms to enable comparison of sediment transport from sampling sites SM1 and 

SM1a through the constructed wetland to site SM1b (downstream from the wetland in backwater conditions; fig. 14). 

1,390

2,370

240

2,020

770

690

560

3,340 1,240

2,860

2,300 1,520

2,180

2,580

2,170

420

3,150

1,250

1,580

520

0

20

40

60

80

100

120

140

160

180

02/24/0703/01/0703/23/0703/29/0704/03/0704/10/0704/13/0705/06/0705/07/0705/30/0706/01/0706/30/0708/09/0709/07/0709/25/0710/08/0710/13/0710/15/0710/17/0710/22/07

STORMFLOW VOLUME, IN ACRE-FEET AND SEDIMENT LOAD, IN TONS

0.91 (0.98)

0.91 (0.98)

1.0 (0.27)

0.35 (2.5)

1.6 (2.0)

0.5 (0.71)

2.3 (4.8)

1.2 (0.38)

1.1 (0.95)

1.2 (1.7)1.7 (1.7)

1.5 (2.4)

1.0 (0.47)

0.59 (0.80)

0.66 (1.2)

1.9 (7.8)3.0 (7.5)

2.2 (4.6)

0.45 (1.1)

3.4 (4.1)

0.62 (0.33)

All sediment

ponds installed

Stormflow volume

Sediment load

Number indicates stormflow-weighted 

 sediment concentration, in milligrams

 per liter

Storm rainfall, in inches. Number 

 in parenthesis is maximum 

 5-minute rainfall intensity,

 in inches per hour

1,390

Sediment

controls

strengthened

Figure 13. Stormflow volume and sediment load for the 20 largest storms at site SM1, Lenexa, Kansas, 2007.
32 Effects on Suspended-Sediment Transport in Johnson County, Northeast Kansas, February 2006 through November 2008

Comparison of average sediment concentrations between 

individual storms can effectively evaluate sediment deposition 

in the wetland because contributing basin areas upstream from 

sites SM1a and SM1b were approximately the same (table 

1), storage in the sediment forebay and wetland were small 

relative to large storms, and the timing of rising, peak, and 

recessions in gage height during storms were nearly (less than 

5 minutes difference) identical between sampling sites.

Site SM1 had approximately double (2.2 to 1.7 times) the 

average sediment concentrations of site SM1a during the largest storms, because of the influx of less turbid water from the 

intervening residential and parkland part of basin, and because 

of sediment deposition in and upstream from the sediment 

forebay between the sites. Average storm-sediment concentrations were larger at sampling site SM1b (downstream from 

the wetland) than sampling site SM1a (upstream from the 

wetland) for 9 of the 10 largest storms (ranging from 1.5 to 

0.9 times; fig. 14). Examination of time-series turbidity data 

indicate nearly identical patterns of turbidity among the two 

sites during most storms, whereas turbidity values occasionally remained larger during the falling limb of the storm at 

sampling site SM1b. Suspended organic matter in the lake 

may result in increased turbidity values at site SM1b toward 

the end of storms. Similar turbidity values among sites during the largest storms indicated little reduction in sediment 

loading to the lake through the wetland. Increased sediment 

deposition in the sediment forebay relative to the wetland 

likely is caused by deposition of larger silt-sized particles in 

and upstream from the settling basin, and continued transport 

of clays through the wetland and into Shawnee Mission Lake. 

980

1,280

1,950

1,000 1,000

950

1,490

1,500

620

860

360

370

740

360

540

520 900

530

330

590

0

50

100

150

200

250

300

350

400

450

500

2/16/2008 3/17/2008 6/3/2008 6/5/2008 6/8/2008 6/12/2008 7/29/2008 9/12/2008 10/15/2008 10/22/2008

STORMFLOW VOLUME, IN ACRE-FEET

SEDIMENT LOAD, IN TONS

SEDIMENT CONCENTRATION, IN MILLIGRAMS PER LITER

Stormflow volume (SM1) 

Sediment load (SM1) 

Stormflow volume (SM1a) 

Sediment load (SM1a) 

Average sediment concentration (SM1) 

Average sediment concentration (SM1a) 

Average sediment concentration (SM1b) 

SM1 

(7.0) 3.6

1.4 (0.34)1.5 (0.47)

1.3 (3.7)1.4 (6.2)2.0 (5.6)3.1 (3.9)5.0 (4.8)1.7 (1.2)

(1.2) 0.82

SM1a SM1 SM1a SM1 SM1a SM1 SM1a SM1 SM1a SM1 SM1a SM1 SM1a SM1 SM1a SM1 SM1a SM1 SM1a

1.4 (0.34)

980 Number indicates stormflow-weighted 

 suspended-sediment concentration, 

 in milligrams per liter

Storm rainfall, in inches. Number in 

 parenthesis is maximum 5-minute 

 rainfall intensity, in inches per hour

EXPLANATION

Figure 14. Stormflow volume, sediment load, and average sediment concentration for the 10 largest storms upstream from

Shawnee Mission Lake, Lenexa, Kansas, 2008.
Sediment Transport in Johnson County, Kansas 33

Sediment trapping by the wetland could increase as vegetation 

planted in spring 2008 becomes more fully established. Thus, 

the pertinent conclusion of comparisons between sites up and 

downstream from the constructed wetland is that before the 

establishment of wetland vegetation, hydraulic retention by 

the wetland did not substantially reduce sediment loading to 

Shawnee Mission Lake.

Frequency and Storm-by-Storm Analysis of 

Streamflow and Sediment Transport in the 

Mill Creek Basin

Frequency analysis of continuous streamflow and sediment concentration values was conducted to better understand the magnitude and timing of streamflow and sediment 

transport in the Mill Creek Basin. Duration plots display how 

frequently a given continuous streamflow value (reported in 

cubic feet per second) is exceeded during the study period 

(fig. 15), the total amount of streamflow transported past site 

MI7 was also computed for each year (and reported below). 

Duration plots are displayed annually since the first full year 

of record (2003) at sampling site MI7 to compare the study 

period to all previously observed conditions (fig. 15). Calendar 

year 2008 recorded the most total flow (61,100 acre-ft) during 

the period of record, and the most flow exceeded less than 

10 percent of the time (38,400 acre-ft), but had slightly smaller 

peak-flow values (8,800 ft3/s) than during calendar year 

2004 (9,700 ft3/s; fig. 15). Calendar year 2006 had the least 

amount of streamflow on record (19,500 acre-ft) and calendar 

year 2007 had the third-most flow on record (47,500 acre-ft).

To facilitate site-to-site comparisons in the Mill Creek 

Basin during similar hydrologic conditions, only data from 

calendar years 2007 and 2008 (February 2007 through 

November 2008) were considered for frequency analysis. Data 

from site CL1a was not included because low-flow parts of the 

streamflow record were not computed. Streamflow-duration 

curves were calculated at Mill Creek sampling sites to compare the timing and magnitude of continuous streamflow data 

among sites. Because the number of sampling sites inhibit the 

display of duration curves at all nine sites, statistics derived 

from the flow-duration curves (streamflow values at 1-, 5-, 

10-, 25-, 50-, 75-, 90-, 95-, and 99-percent exceedance) are 

compared among sites (fig. 16). Sites with larger drainage area 

had larger streamflows for more prolonged periods relative 

to headwater sites. Wastewater discharge increased base-flow 

values at sites MI3, MI4, MI5, and MI7, decreasing the range 

of low-flow conditions relative to sites without wastewater 

discharge (fig. 16A). To better distinguish potential effects of 

land use on streamflow distribution, streamflow statistics were 

normalized by upstream basin area (fig. 16B). After normalization, 1-percent streamflow exceedance values were largest at 

sites MI3 [37 cubic feet per second per square mile 

(ft3/s/mi2)], SM1 (31 ft3/s/mi2) and MI4 (29 ft3/s/mi2). Sites 

MI3, SM1, and MI4 had relatively large areas of impervious surface (35.1, 27.7, and 24.8 percent impervious, 

respectively), which routed more rainfall directly to streams. 

Additionally, construction and steep slopes upstream from 

site SM1 likely led to compacted soils and increased overland 

flow. Sites LM1 and LM2 had similarly large areas of impervious surface (30.7 and 27.1 percent impervious, respectively) 

but had smaller 1-percent exceedance levels, potentially 

because of the estimated 120 stormwater detention basins in 

the headwaters of the basin (L. Kellenberger, Johnson County 

Stormwater Management Program, written commun., 2007).

Duration statistics for SSC values computed from continuous turbidity measurements (for sampling sites operated from 

February 2007 through November 2008) are displayed on a 

log-10 scale to compare the frequency of SSC values observed 

among sampling sites (fig. 17). One-percent (2,130 mg/L, 

site SM1; 990 mg/L, site CL1; 1,040 mg/L, site CL2), 5-percent (390 mg/L, site SM1; 250 mg/L, site CL1; 250 mg/L, 

site CL2) and 10-percent (200 mg/L, site SM1; 97 mg/L, 

site CL1; 120 mg/L, site CL2) SSC exceedance values 

indicated that sites SM1, CL1, and CL2 had the largest SSC 

values for the longest period of time. Basins upstream from 

these sites had the most land surface under construction from 

2005 to 2008 (figs. 1, 3, and 5; tables 2 and 3) without the 

presence of large (greater than 30 acre) upstream impoundments. One-, 5-, and 10-percent exceedance intervals were 

smallest at sites CO1, LM1, and MI3. Impervious surfaces and 

relatively stable vegetation in suburban basins LM1 and MI3 

decrease the potential for surface-soil erosion, thus limiting 

the duration of large sediment concentrations at these stations. 

Lake Lenexa (upstream from site CO1; fig. 2) and Waterworks 

Lakes (upstream from site MI3; fig. 2) and storm-detention 

basins (upstream from site LM1) also slow water velocities 

and trap suspended sediment upstream from their respective 

dams. Suspended-sediment-concentration values were larger at 

more frequently exceeded intervals (50 to 99 percent exceedance) at site MI3 likely because of consistent sediment discharge (likely organic material) from the upstream Mill Creek 

Regional wastewater-treatment facility. These sediments are 

deposited in the streambed between sampling sites, as shown 

by smaller SSC values at 50 to 99 percent exceedance intervals at downstream sites MI4, MI5, and MI7.

Understanding when and how sediments are transported 

can help resource managers implement practices targeted 

to storms that transport the most sediment. Additionally, 

fine sediment deposition in streambeds has been linked to 

decreases in the diversity of fish and macroinvertebrate communities (Walters and others, 2003; Freeman and Schorr, 

2004; U.S. Environmental Protection Agency, 2006). Fine 

sediments are most prone to deposit on streambeds when 

upstream soil disturbance results in prolonged, large sediment 

concentrations during relatively low-flow conditions. To compare the magnitude and duration of sediment concentrations 

relative to streamflow conditions and among sampling sites, 

5- or 15-minute estimates of sediment loading were sorted 

by the streamflows in which they occurred, and then summed 

(along with streamflow) for streamflow values exceeded less 

than 0.1 percent of the time, between 0.1 and 0.5 percent of 
34 Effects on Suspended-Sediment Transport in Johnson County, Northeast Kansas, February 2006 through November 2008

1

10

100

1,000

10,000

0 10 20 30 40 50 60 70 80 90 100

2003

2004

2005

2006

2007

2008

10

100

1,000

10,000

0 1 2 3 4 5 6 7 8 9 10

STREAMFLOW, IN CUBIC FEET PER SECOND

FREQUENCY OF EXCEEDANCE, IN PERCENT

2003

2004

2005

2006

2007

2008

A

B

Figure 15. Streamflow exceedance for A, hourly streamflow values and B, the top 10 percent of hourly streamflow

values at Mill Creek at Johnson Drive (sampling site MI7; fig. 1), Johnson County, northeast Kansas, 2003 through

2008.
Sediment Transport in Johnson County, Kansas 35

0.001

0.01

0.1

1

10

100

1,000

10,000

STREAMFLOW, IN CUBIC FEET PER SECOND 

A STREAMFLOW DURATION STATISICS 

1 

5 

10 

25 

50 

75 

90 

95 

99 

Frequency of

 exceedance,

 in percent 

STREAMFLOW, NORMALIZED BY SUBBASIN AREA, 

IN CUBIC FEET PER SECOND PER SQUARE MILE

0.0001

0.001

0.01

0.1

1

10

100

B STREAMFLOW DURATION STATISICS (NORMALIZED BY SUBBASIN AREA)

CL1 CL2 CO1 LM1 LM2 MI3 MI4 MI5 MI7 SM1

CL1 CL2 CO1 LM1 LM2 MI3 MI4 MI5 MI7 SM1

EXPLANATION

Figure 16. Duration statistics for A, streamflow and B, streamflow normalized by subbasin area for Mill Creek sampling sites

operated from February 2007 through November 2008, Johnson County, northeast Kansas.
36 Effects on Suspended-Sediment Transport in Johnson County, Northeast Kansas, February 2006 through November 2008

the time, between 0.5 and 1 percent of the time, and then for 

every half percentage of time up to 100 percent. Sediment 

loading data summed for each streamflow exceedance interval 

were then divided by the total streamflow (for the same 

streamflow exceedance interval) to produce a flow-weighted 

suspended-sediment concentration (FWSC) for each interval of streamflow exceedence. Flow-weighted suspendedsediment concentrations (x-axis) are then compared to the 

percentage of the time streamflow values are exceeded 

(log-scale; y-axis) to best display the frequency of sediment 

concentrations among sites (fig. 18).

Streamflows exceeded less than 1 percent of the time 

generally consist of much of the large storms (greater than 

2 in. of rainfall; fig. 19), approximately the peak of average 

sized storms (generally between 1 to 2 in. of rainfall), and 

transported between 73 and 91 percent of sediment among 

sampling sites (table 9). Streamflows exceeded between 

1- and 10-percent of the time generally contained the initial 

rising limb, and end of the falling limb of stormflow hydrographs during large (greater than 2 in. of rainfall) storms, and 

nearly all of the average (and smaller) sized storms (approximatey1 in. of rainfall; fig. 19). Streamflow exceeded less than 

10 percent of the time transported nearly all (93 to 100 percent; table 9) of the sediment load at sampling sites in the Mill 

Creek Basin. The largest streamflow conditions generally had 

the largest FWSCs (table 9; fig. 18), indicating that sediment 

loads generally increased exponentially with increasing flow 

at Mill Creek sampling sites. The largest storms come into 

contact with more surface and channel soils, and once these 

soils are suspended, larger flows have an increased capacity 

to transport sediments downstream. However available sediment supplies can become limited at the largest streamflows, 

and thus FWSC values decreased at the largest streamflow 

values (exceeded less than 0.1 percent of the time) relative to 

more frequently exceeded streamflow values at site CL2, and 

relatively smaller increases in FWSC values were observed at 

many sampling sites.

Other than in the construction-affected Clear Creek and 

Shawnee Mission Lake Basins, FWSCs were generally larger 

during streamflows exceeded 1 and 10 percent of the time 

at downstream (sites LM2, MI5, MI7) relative to upstream 

(LM1, MI3, MI4) sites (table 9). Larger average FWSCs during stormflow conditions at downstream sites generally did not 

correspond to larger sediment yields, but were more indicative 

of less episodic streamflow conditions downstream from larger 

basins. Increased duration of sediment transporting flows at 

sites with larger drainage areas is, therefore, an important 

0.1

1.0

10

100

1,000

10,000

SUSPENDED-SEDIMENT CONCENTRATION, IN MILLIGRAMS PER LITER

1 

5 

10 

25 

50 

75 

90 

95 

99 

Frequency of

 exceedance,

 in percent 

EXPLANATION

CL1a CL1 CL2 CO1 LM1 LM2 MI3 MI4 MI5 MI7 SM1

Figure 17. Duration statistics for suspended-sediment concentrations at Mill Creek sampling sites, February 2007 through

November 2008, Johnson County, northeast Kansas.
Sediment Transport in Johnson County, Kansas 37

consideration when comparing SSC among sites with varying 

basin size.

Average FWSC values at 0.1 to 1 percent streamflow 

exceedance intervals were smallest at sites CO1 and MI3 

because of sediment deposition in upstream reservoirs. 

Flow-weighted suspended-sediment concentrations during 

peak flow (0.1 to 1 percent exceedance) conditions from the 

unimpounded, established urban basin in the headwaters of 

the Little Mill Creek Basin (site LM1) were approximately 

double that observed from the partially impounded, established, urban basin in the headwaters of Mill Creek (station 

MI3). However, FWSCs were similar among these sites during 

smaller streamflow conditions, indicating that the uncontrolled 

impoundments in the headwaters of the Mill Creek Basin 

primarily decreased sediment concentrations during peak-flow 

conditions.

Soil disturbance from construction sites upstream from 

sites SM1, CL1, and CL2 resulted in the largest FWSCs during nearly all stormflow conditions (0.1 to 10 percent streamflow exceedance; fig. 18). As shown previously, streamflow 

value exceeded less than 1 percent of the time contribute most 

of the annual sediment loads; however, increased FWSCs during smaller flows at these sites may have detrimental effects 

on stream biota because of decreased light penetration and 

increased fine sediment deposition in streambeds. Larger SSC 

values at site SM1 during both stormflow and base-flow conditions were coincident with several inches of fine sediment 

deposition observed on the streambed, and indicate decreased 

light penetration at this site throughout the study.

Sediment Transport from Varying Storms

Sixty-three storms with rainfall more than 0.5 in. were 

observed in the basin upstream from sampling site MI7 

(fig. 20); 34 storms with less than 0.5-in. rainfall resulted in 

stormflow at one or more of the other sampling sites in the 

Mill Creek Basin. These storms were summarized and designated decimal numbers depending on the whole numbered 

storms they fell between. Occasionally multiple, separate 

rainfall periods occurred during a single day, and therefore 

cumulative daily rainfall values sometimes were greater than 

0.5 in., whereas values for individual storms were less than 

0.5 in. (fig. 20).

Stormflow periods defined in this study from February 

2006 through November 2008 occurred approximately 29 percent of the time, and transported nearly all (97 to 100 percent) 

of the sediment load at sampling sites. The 10 largest storms 

transported 63 percent of the total sediment load at site MI7 

(fig. 21). The two storms, which transported the most sediment 

0

500

1,000

1,500

2,000

2,500

3,000

3,500

0.1 1.0 10.0 100.0

FLOW-WEIGHTED SUSPENDED-SEDIMENT CONCENTRATION, IN MILLIGRAMS PER LITER

PERCENTAGE OF TIME STREAMFLOW WAS EXCEEDED

SM1

CL1

CL2

MI3

CO1

LM1

LM2

MI4

MI5

MI7

Sampling site

Figure 18. Flow-weighted suspended-sediment concentrations compared to streamflow exceedance at Mill Creek

sampling sites, Johnson County, northeast Kansas, February 2007.
38 Effects on Suspended-Sediment Transport in Johnson County, Northeast Kansas, February 2006 through November 2008 Between 1- and 10-percent streamflow exceedance interval Less than 1-percent streamflow exceedance interval Streamflow Suspended-sediment loading 40353025201510

50 0

800700600500400300200100

4/17/08

12:00

4/18/08

0:00

4/18/08

12:00

4/19/08

0:00

4/19/08

12:00

4/20/08

0:00

4/20/08

12:00

4/21/08

0:00

4/21/08

12:00

STREAMFLOW, IN CUBIC FEET PER SECOND

Storm No. 42, 0.95-inch rain on April 17, 2008Storm No. 47, 3.1-inch rain on June 3, 2008

EXPLANATION

DATE AND TIME

DATE AND TIME

STREAMFLOW, IN CUBIC FEET PER SECOND

400350300250200150100500 0

500

4,5004,0003,5003,0002,5002,0001,5001,000

10/17/07

0:00

10/18/07

0:00

10/19/07

0:00

10/20/07

0:00

10/21/07

0:00

10/22/07

0:00

SUSPENDED-SEDIMENT LOADING, IN POUNDS PER SECOND

SUSPENDED-SEDIMENT LOADING, IN POUNDS PER SECOND

Storm No. 33, 2.3-inch rain on October 22, 2007

1,4001,2001,0008006004002000 0

9,0008,0007,0006,0005,0004,0003,0002,0001,000

10,000

6/3/08

12:00

6/4/08

0:00

6/4/08

12:00

6/5/08

0:00

6/5/08

12:00

6/6/08

0:00

Figure 19. Streamflow and suspended-sediment loading at less than 1-percent streamflow exceedance intervals and between 1- and 10-percent exceedanceintervals for three storms at site MI7, Johnson County, northeast Kansas, 2007 through 2008.
Table 9.  Streamflow and sediment transport during streamflow values exceeded less than 1and 10 percent of the time, Mill Creek, Johnson CoKansas, February 2007 through November 2008.[mi2, square mile; ft3/s, cubic feet per second; mg/L, milligrams per liter]

Sampling 

site 

(fig. 1)

Basin 

area 

(mi2)

Peak 

flow

(ft3/s)

Streamflow value exceeded less than 1 percent of the time Streamflow value exceeded less than 10 perc

Streamflow

(ft3/s)

Total flow less 

than 1 percent 

exceedance 

level

(acre-feet)

Percentage 

of total 

flow

Total suspendedsediment

transported at 

flows exceeded 

less than 1 percent 

of the timea

(tons)

Percentage 

of total

sediment 

loada

Flowweighted 

suspendedsediment 

concentration 

(mg/L)

Streamflow

(ft3/s)

Total flow 

less than 

10 percent 

exceedance 

level

(acre-feet)

Percentage 

of total

flow

Total suspendedsediment 

transported at flow

exceeded less tha

10 percent of the 

timea

(tons)

CL1 5.5 2,630 120 5,400 60 14,700 91 2,010 6 7,800 87 16,000 CL2 10.9 2,400 270 7,900 41 23,000 87 2,140 28 14,500 75 26,100 

CO1 5.1 430 110 2,800 24 1,800 73 480 23 7,000 61 2,300 

LM1 8.8 3,350 160 5,400 29 7,400 87 1,000 32 11,500 61 8,400 LM2 12.1 5,180 230 7,700 43 12,400 88 1,180 21 14,100 78 14,100 

MI3 2.8 680 100 2,200 23 1,600 73 520 13 5,100 53 2,100 MI4 19.7 4,840 580 14,600 31 20,800 81 1,050 52 29,300 63 25,500 MI5 31.7 7,320 570 16,600 31 31,900 86 1,410 59 34,400 63 36,700 MI7 57.4 8,800 1,180 30,000 31 62,100 79 1,520 124 64,900 67 77,400 

SM1 .6 250 19 460 30 1,700 75 2,670 2.5 1,000 66 2,200 

aSediment load does not include estimates of missing values.
40 Effects on Suspended-Sediment Transport in Johnson County, Northeast Kansas, February 2006 through November 2008

(June 4, 2008, and March 1, 2007; fig. 21), were the first 

storms in each calendar year with more than 1.5 in of rainfall and maximum rainfall intensities of more than 1.1 in/h. 

Despite having only the fifth-most rainfall (3.07 in.) and the 

second-most intense maximum hourly rainfall (2.05 in/h), the 

storm on June 4, 2008, had the highest peak flow (8,800 ft3/s) 

and transported the largest sediment load among storms at 

11 of the 14 sampling sites (fig. 21). Despite having only the 

seventh-most rainfall (2.04 in.) and the ninth-most intense 

maximum hourly rainfall (1.40 in/h), the first, large storm in 

2007 (March 1) transported the largest sediment load at 3 of 

the 14 sampling sites, sediment loads among the other 11 sites 

were only marginally less than those observed during the 

storm on June 4, 2008 (fig. 21).

Storms on August 9, 2007, October 13, 2007, and September 13, 2008, had similar or larger rainfall amounts (3.30, 

3.32, and 5.04 in., respectively) and maximum rainfall intensities (5.4, 1.85, and 2.03 in/h, respectively) than storms on 

June 3, 2008, and March 1, 2007, but transported substantially 

less sediment among sampling sites. The storm on September 

13, 2008, transported the most streamflow at nearly all sampling sites, but moved a substantially smaller sediment load 

than storms on June 4, 2008, and March 1, 2007. Increased 

sediment transport from the first, large storm of each calendar 

year indicate increased runoff and erosion during storms that 

occur before vegetation is fully established, and may indicate 

that excess sediment supplies are eroded or disaggregated by 

the freeze/thaw processes during fall/winter months.

Antecedent rainfall conditions also affected flow and 

sediment loading conditions observed during storms. Peak 

flows for stormflows observed at sampling site MI7 were 

largest on June 4, 2008 (8,800 ft3/s), and September 13, 2008 

(7,300 ft3/s), partially because of smaller storms that saturated 

soil conditions before larger rainfall events. Although storms 

on August 9, 2007, and October 13, 2007, had similar rainfall 

volumes and intensities to the storm on June 3, 2008, they 

were not preceded by recent rainfall, and thus initial rainfall 

was likely absorbed by soils, resulting in smaller peak flows 

and smaller sediment-transport capacities.

Examination of patterns of streamflow and sediment 

transport among headwater and downstream sampling sites 

help illustrate how sediment is transported through basins. 

Storms were grouped by the amount of stormflow transported 

(less than 1 acre-ft, between 1 and 10 acre-ft, between 10 and 

100 acre-ft, between 100 and 1,000 acre-ft, and more than 

1,000 acre-ft) and the total sediment load and SWSCs were 

computed for storms within each group (fig. 22). Headwater sites generally transported much more sediment (per 

0

0.5

1

1.5

2

2.5

3

3.5

4

2/1/063/1/064/1/065/1/066/1/067/1/068/1/069/1/06

10/1/0611/1/0612/1/06

1/1/072/1/073/1/074/1/075/1/076/1/077/1/078/1/079/1/07

10/1/0711/1/0712/1/07

1/1/082/1/083/1/084/1/085/1/086/1/087/1/088/1/089/1/08

10/1/0811/1/0812/1/08

RAINFALL, IN INCHES

9 10

12

13

14 15

16

17

18

19

1

2

3

4

5

6

7

8

11

20

28

29

23

27

26

22

25

21

24

40

35

36

31

33

34 30

41

42 43

37

60

38

39 44

47

50

48

49

45

46

51

52

59

57

56

62

61

55

53

58

54

63

32

Data from Overland Park Stormwatch Program, 2009

Figure 20. Daily rainfall in the basin upstream from site MI7 (fig. 1) and numbered storms with more than 0.5 inch of rainfall,

Johnson County, northeast Kansas, February 2006 through November 2008.
Sediment Transport in Johnson County, Kansas 41

0

50

100

150

200

250

300

350

400

450

500

SUSPENDED-SEDIMENT YIELD, IN TONS PER SQUARE MILE

TEN LARGEST STORMS IN ORDER OF DECREASING LOAD AT MOST DOWNSTREAM SITE (MI7)

CL1a

CL1

CL2

CO1

SM1

LM1

LM2

MI3

MI4

MI5

MI7

* Sites CL1a and SM1 

 were not installed

14

CL1a

CL1

CL2

CO1

SM1

LM1

LM2

MI3

MI4

MI5

MI7

* Sites CL1a and SM1 

 were not installed

Number indicates cumulative

 percentage of suspended-

 sediment load transported by 

 storms at site M17

14

27

33

38

42 47 51 55 59 63

0

2,000

4,000

6,000

8,000

10,000

12,000

14,000

SUSPENDED-SEDIMENT LOAD, IN TONS

6/4/08 3/1/07 9/13/08 10/13/08 4/1/07 8/9/07 5/7/07 5/6/07 8/27/06* 3/3/08

6/4/08 3/1/07 9/13/08 10/13/08 4/1/07 8/9/07 5/7/07 5/6/07 8/27/06* 3/3/08

Figure 21. Suspended-sediment load and yield for the 10 largest storms in the Mill Creek Basin, Johnson County, northeast

Kansas, February 2006 through November 2008.
42 Effects on Suspended-Sediment Transport in Johnson County, Northeast Kansas, February 2006 through November 2008

10

21

20

1 0 0

26

40

21

0

16

42

32

2

0 0 17

57

22

0

200

400

600

800

1,000

1,200

1,400

1,600

1,800

2,000

Less than 1

Less than 1

1 to 10

1 to 10

1 to 10

10 to 100

10 to 100

10 to 100

100 to 1,000

100 to 1,000

100 to 1,000

Greater than 1,000

Greater than 1,000

Greater than 1,000

STORMFLOW-WEIGHTED SUSPENDED-SEDIMENT CONCENTRATION, IN MILLIGRAMS PER LITER

10

CL1a

CL1

CL2

MI7

Indicates number of storms

 within flow interval

RANGE OF STORMFLOW IN (ACRE-FEET) TRANSPORTED BY STORMS DURING STUDY PERIOD

1

51

45

1

7

43

44

2

0 17

57

22

0

200

400

600

800

1,000

1,200

1,400

1 Indicates number of storms

 within flow interval

LM1

LM2

MI7

1

21

46 20

0

2

16 48

25

0

9

34

34

1

0 0 2

34

54

10

0 0

24

42

11

0 0 17

57

22

0

200

400

600

800

1,000

1,200

1,400

1,600

1 Indicates number of storms

 within flow interval

MI3

CO1

SM1

MI4

MI5

MI7

A

B

C

Figure 22. Stormflow-weighted suspended-sediment concentrations for groups of storms in the A, Clear Creek, B, Little Mill

Creek, and C, mainstem Mill Creek subbasins, Johnson County, northeast Kansas, February 2006 through November 2008.
Sediment Transport in Johnson County, Kansas 43

stormflow volume) than downstream sites during smaller 

storms (generally less than 100 acre-ft). Stormflow-weighted 

suspended-sediment concentrations for storms at sampling site 

CL1a in the Clear Creek Basin were more than double that of 

downstream sites within the same stormflow interval, likely 

a result of comparing larger intense storms at headwater sites 

(thus with more erosive power and more overland flow) to 

smaller, less intense storms at downstream sites. This also is 

because headwater streams with steeper slopes (table 2) have 

more ability to transport and suspend sediments (for the same 

flow volume) than larger, less-sloping downstream channels.

The most downstream sampling site in Little Mill Creek 

(LM2) had larger SWSCs than the upstream sampling site 

(LM1) throughout the range of flow values (fig. 22B), indicating additional sources of sediment contributing to the stream 

between sampling sites. Sediment yields were smaller at site 

LM2 than at site LM1 from February 2006 through June 2007 

(Lee and others, 2009), potentially indicating either that new 

sediment sources began contributing to the stream between 

sampling sites, or decreased sediment transport upstream from 

site LM1 during the study period. To further analyze when the 

additional source(s) of sediment became available in the basin, 

SWSCs were computed for storms of varying magnitudes 

(less than 50 acre-ft, between 50 and 100 acre-ft, between 

100 and 500 acre-ft, and greater than 500 acre-ft) in each of 

calendar years 2006, 2007, and 2008 (fig. 23). During 2006, 

SWSCs were slightly larger at site LM2 than at site LM1 during small (50 to 100 acre-ft) and medium (100 to 500 acre-ft) 

size storms, but no storms occurred greater than 500 acre-ft. 

During 2007, SWSCs were slightly larger at site LM1 than site 

LM2 during small (less than 50 acre-ft), storms, but generally were similar during larger storms. However, during 2008, 

SWSCs were larger at site LM2 than at site LM1 during all 

storms. Compared to large storms in 2007, approximately 

20 percent more sediment was transported (per stormflow) 

for the largest storms at site LM2 during calendar year 2008, 

whereas approximately 22 percent less sediment was transported (per stormflow) at site LM1 during 2008 than in 2007. 

This analysis indicates an increase in sediment supplies available between sites LM1 and LM2, and a decrease in sediment 

supply upstream from site LM1.

Stormflow-weighted suspended-sediment concentrations are compared among storm categories at sites SM1, 

CO1, and sites on the mainstem of Mill Creek to illustrate 

the effect of drainage area and construction on sediment 

transport (fig. 22C). During small storms (less than 1 acre-ft), 

SWSCs were similar among sites SM1, CO1, and MI3 (50 to 

120 mg/L). However, during small (1 to 10 acre-ft), moderate 

STORMFLOW-WEIGHTED SUSPENDED-SEDIMENT CONCENTRATION, IN MILLIGRAMS PER LITER

1

2

5

3 8

9

0 0

7

8

7 8

15

12

4 5

9

17 11

5

17

14

3

4

RANGE OF STORMFLOW (IN ACRE-FEET) TRANSPORTED BY STORMS IN EACH CALENDAR YEAR

Greater

than 50

50 to 100 100 to 500 Greater

than 500

Greater

than 50

50 to 100 100 to 500 Greater

than 500

Greater

than 50

50 to 100 100 to 500 Greater

than 500

2006 2007 2008

LM1

LM2

1 Indicates number of storms 

 within flow interval

0

200

400

600

800

1,000

1,200

Figure 23. Stormflow-weighted suspended-sediment concentrations by year for storm ranges at sites in the Little Mill

Creek Basin, Johnson County, northeast Kansas, February 2006 through November 2008.
44 Effects on Suspended-Sediment Transport in Johnson County, Northeast Kansas, February 2006 through November 2008

(10 to 100 acre-ft), and larger (more than 100 acre-ft) storms, 

SWSCs from site SM1 were more than 5 times that of site 

CO1, and more than 2.5 times the SWSCs of sites on the 

mainstem of Mill Creek (MI3, MI4, MI5, and MI7). Although 

SWSCs increase with larger storms, the rate of increase is less 

in the smallest basins, while the rate of change continues to 

increase in larger basins, indicating that during progressively 

larger storms, sediment transport may continue to increase, but 

at smaller rates relative to stormflow.

Sediment loading for individual storms was evaluated 

against storm-specific factors, such as the amount of stormflow, rainfall amount and intensity, and antecedent streamflow 

and sediment transport. Characteristics of storm intensity 

include maximum rainfall intensity at 5, 15, 30, and 60 minutes, and the total kinetic energy of the storm (Brown and Foster, 1987). Measures of antecedent conditions include the total 

stormflow volume and sediment load transported in the past 

15, 30, 60, and 90 days. Antecedent conditions data were tabulated for the first storm at sampling sites using data acquired 

since site installation. Although peak streamflow typically 

was better related with sediment loading than total stormflow, 

it was not considered because it encapsulated (and obscured) 

variability associated with total flow and rainfall intensity.

Stepwise multiple regression analysis was performed on 

log-transformed variables representing these factors, as was 

done in Lee and others (2009). All regression variables were 

log-transformed to approximate homoscedasticity and normality in regression residuals. Independent variables were added 

to regression equations if data distributions generally were 

normal and homoscedastic with respect to regression residuals. Independent variables also had to significantly improve 

(defined as a p-value less than 0.05) the regression relation and 

result in a decreased prediction error sum of square (PRESS) 

statistic, an indication that the independent variables added to 

the regression equation had the smallest amount of error when 

making new predictions (Helsel and Hirsch, 2002). Because 

of multicollinearity among measures of rainfall intensity 

and antecedent conditions, one variable from each category 

that most improved the fit of the regression equation was 

included in the analysis; thus, a maximum of three independent variables (total flow, a measure of rainfall intensity, and 

a measure of antecedent rainfall, streamflow, or sediment-load 

conditions) were included in the regression equations (table 

10). Variance inflation factors among independent variables 

in regression relations were all less than 2.0, indicating that 

independent variables generally were uncorrelated (Helsel and 

Hirsch, 2002).

At all sites, storm-sediment loads were best explained 

by stormflow volume and secondarily by some measure of 

rainfall intensity. Intense rainfall increases erosion from land 

surfaces, the volume of overland flow (relative to subsurface 

flow), and the flow velocity (and thus sediment transport 

capacity) in rills, gullies, and stream channels. Recent, large 

storms immediately prior to observed storms or sediment 

transport resulted in significantly less sediment transport at all 

but one sampling site.

The y-intercept and slope of streamflow/sediment loading of the log-log regressions (first regression for each site in 

table 10) exhibited patterns corresponding to basin size and 

upstream land use. Smaller sites (fig. 24) generally had larger 

y-intercept values than larger sites, indicating that they transported larger sediment loads (per streamflow volume) during 

smaller storms. Streamflows from small storms take longer to 

move through the basin, providing more time for suspended 

sediments to deposit on the streambed, especially as channels 

become larger and less steep downstream. With the exception 

of construction-affected sites CL1 and SM1, smaller basins 

generally had smaller slopes between sediment load/storm 

flow volume relations than larger sites. Smaller sites likely 

have less sediment available for transport than larger sites 

during the largest storms. Sites CL1 and SM1 have much more 

sediment available for transport because of soil disturbance 

resulting in easily moveable sediment on soil surfaces and in 

streams.

Comparison of Sediment Loads Across Johnson 

County

Total stormflow and suspended-sediment loads and yields 

were compared among sampling sites operated downstream 

from the five largest basins (Blue River at Kenneth Road, 

site BL5; Cedar Creek near DeSoto, site CE6; Indian Creek 

at State Line Road, site IN6; Mill Creek at Johnson Drive, 

site MI7; and Kill Creek at 95th Street, site KI6b), in Johnson 

County (excluding identical periods in which sensors were 

removed because of freezing conditions) in 2006, 2007, and 

2008 (table 11). Mill Creek sites were included for the same 

period of record for comparative purposes. Turbidity sensors 

were removed at the end of 2007 at Cedar and Kill Creek sites, 

and thus sediment loading estimates were not available for 

calendar year 2008 (Rasmussen and others, 2008). Regression relations between turbidity and SSC were used from a 

previous study of these sites (Rasmussen and others, 2008), 

and any periods of missing record or turbidity truncation were 

estimated using methods described in “Estimating Periods 

of Turbidity Truncation” and “Estimating Sediment Loading 

during Periods of Missing Turbidity Data” sections in this 

report. Sediment loads increased by less than 0.3 percent for 

the Cedar Creek sampling site, and by 15.2 percent for the Kill 

Creek sampling site after estimating truncated and missing 

turbidity values from February 2006 to December 2007. Sediment loads increased by 1.2 percent for the Blue River sampling site and by 37 percent in the Indian Creek sampling site 

after estimating truncated and missing turbidity values from 

February 2006 through November 2008. The water-quality 

sensor at Indian Creek malfunctioned during an approximately 

25-year stormflow event (17,900 ft3/s; Perry and others, 2004) 

on July 30, 2008. Sediment loading estimated for this storm 

was 62 percent of the load for 2008 (94,300 tons) using stormflow/SSL relations for storms at Indian Creek. Because of the 

importance of this storm and lack of sediment data at this site 
Sediment Transport in Johnson County, Kansas 45

Table 10.  Multiple regression relations between suspended-sediment load and stormflow magnitude, rainfall intensity, and

antecedent rainfall and sediment-load conditions for Mill Creek sampling sites, Johnson County, northeast Kansas, February 2006

through November 2008.

[R2, coefficient of determination; RMSE, root mean-squared error; PRESS, prediction error sum of squares statistic; SSL, suspended-sediment load; Qtotal, 

total stormflow, in acre-feet; <, less than; P5, maximum rainfall intensity over 5 minutes, in inches per hour; P15, maximum rainfall intensity over 15 minutes, 

in inches per hour; Sed60, sediment load transported 60 days prior to event, in tons; P60 maximum rainfall intensity over 60 minutes, in inches per hour; Q15, 

stormflow during the past 15 days; Q60, stormflow during the past 60 days; Q90, stormflow during the past 90 days]

Sampling 

site

(fig. 1)

Regression relation

Number of 

independent 

variables

Number of 

storms

Adjusted 

R2 RMSE PRESS statistic 

p-value of new 

independent 

variable

CL1a Log(SSL) = 1.22log(Qtotal) - 0.31 1 51 0.84 0.34 5.99 <0.01

CL1a Log(SSL) = 1.13log(Qtotal) + 0.48log(P5) - 0.33 2 .90 .27 4.01 <.01

CL1 Log(SSL) = 1.80log(Qtotal) - 1.65 1 88 .93 .39 13.3 <.01

CL1 Log(SSL) =1.67log(Qtotal) + .47log(P15) - 1.41 2 .95 .34 10.4 <.01

CL1 Log(SSL) =1.68log(Qtotal) + .46log(P15) - .15(Sed60) - 1.01 3 .95 .32 9.44 <.01

CL2 Log(SSL) = 1.64log(Qtotal) - 1.69 1 92 .90 .39 14.03 <.01

CL2 Log(SSL) =1.50log(Qtotal) + 0.49log(P15) - 1.39 2 .92 .34 11.04 <.01

CL2 Log(SSL) =1.60log(Qtotal) + 0.47log(P15) - .015log(Q15) - 1.31 3 .93 .33 10.28 <.01

CO1 Log(SSL) = 1.25log(Qtotal) - 1.29 1 91 .79 .47 20.58 <.01

CO1 Log(SSL) =1.09log(Qtotal) + 0.56log(P60) - 0.78 2 .86 .39 14.36 <.01

CO1 Log(SSL) =1.18log(Qtotal) + 0.49log(P60) - 0.20log(Q15)- 0.56 3 .56 .38 14.01 .04

LM1 Log(SSL) = 1.59log(Qtotal) - 1.76 1 98 .75 .42 17.55 <.01

LM1 Log(SSL) =1.15log(Qtotal) + 0.80log(P15) - 0.81 2 .86 .31 9.52 <.01

LM1 Log(SSL) = 1.14log(Qtotal) + 0.81log(P15) -0.81log(Q60) + 0.84 3 .88 .28 8.12 <.01

LM2 Log(SSL) = 1.73log(Qtotal) - 1.98 1 91 .86 .43 16.92 <.01

LM2 Log(SSL) = 1.52(Qtotal) + 0.69log(P5) - 1.61 2 .92 .33 9.89 <.01

LM2 Log(SSL) = 1.56(Qtotal) + 0.64log(P5) - 0.20log(Q15) - 1.24 3 .92 .31 9.29 <.01

MI3 Log(SSL) = 1.19log(Qtotal) - 0.71 1 87 .85 .3 7.75 <.01

MI3 Log(SSL) = 1.07(Qtotal) + 0.34log(P5) - 0.56 2 .88 .26 6.07 <.01

MI3 Log(SSL) = 1.13(Qtotal) + 0.30log(P5) - 0.42log(Q15) + 0.40 3 .90 .24 5.25 <.01

MI4 Log(SSL) = 1.57log(Qtotal) - 1.74 1 99 .83 .41 16.89 <.01

MI4 Log(SSL) = 1.40(Qtotal) + 0.54log(P15) - 1.28 2 .87 .36 13.03 <.01

MI4 Log(SSL) = 1.36(Qtotal) + 0.61log(P15) - 0.67(Q90) + 1.32 3 .89 .33 10.87 <.01

MI5 Log(SSL) = 1.78log(Qtotal) - 2.27 1 77 .91 .31 7.57 <.01

MI5 Log(SSL) = 1.65(Qtotal) + 0.41log(P15) - 1.93 2 .93 .27 5.96 <.01

MI5 Log(SSL) = 1.61(Qtotal) + 0.48log(P15) - 0.47log(Q60) - .14 3 .94 .25 5.19 <.01

MI7 Log(SSL) = 1.76log(Qtotal) - 2.52 1 89 .89 .36 11.7 <.01

MI7 Log(SSL) = 1.61(Qtotal) + 0.41log(P15) - 2.07 2 .92 .32 9.76 <.01

MI7 Log(SSL) = 1.61(Qtotal) + 0.41log(P15) - 0.34(Q60) - 0.73 3 .92 .31 9.21 <.01

SM1 Log(SSL) = 1.57log(Qtotal) - 0.64 1 74 .86 .43 14.46 <.01

SM1 Log(SSL) = 1.48(Qtotal) + 0.49log(P5) - 0.57 2 .91 .35 9.93 <.01

SM1 Log(SSL) = 1.46(Qtotal) + 0.51log(P5) - 0.52log(Q90) + 0.69 3 .92 .33 8.81 <.01
46 Effects on Suspended-Sediment Transport in Johnson County, Northeast Kansas, February 2006 through November 2008

for a comparable storm, sediment loading at site IN6 during 

2008 is subject to substantial uncertainty.

Throughout the study period, Indian Creek transported 

more stormflow and sediment relative to the other large urbanizing and rural basins, only slightly less than yields observed 

from subbasins in the Mill Creek Basin which were immediately downstream from concentrated urban construction 

(table 11). Stormflow yields from 2006 to 2008 (calculated by 

summing stormflows for each year and dividing by drainage 

area) from the Indian Creek Basin were more than 1.5 times 

those from the urbanizing Mill Creek and primarily rural 

Blue River Basins, and sediment yields from 2006 through 

2008 were more than 2.3 times those from the Mill Creek or 

Blue River Basin. Comparison of all five basins from 2006 to 

2007 (monitors were removed from the Cedar and Kill Creek 

Basins during 2008), indicated that the smallest stormflow and 

sediment yields were observed in the rural Kill Creek Basin, 

and predominantly rural Cedar Creek Basin (table 11). Blue 

River, despite having predominantly rural land use and little 

urban development (1.3 percent impervious surface increase 

since 2003; fig. 7), had similar sediment yields to Mill Creek 

in 2006 and 2007, and substantially larger sediment yields in 

2008. One potential explanation is that the Blue River Basin 

has no large (greater than 30-acre) impoundments, and thus 

has a larger area contributing sediments relative to the Cedar, 

Kill, and Mill Creek Basins.

Comparison of annual stormflow and sediment transport 

can help illustrate differences within and among basins during 

wet and dry periods. In 2006, the five largest basins had annual 

rainfall totals ranging from 29.2 in. (site KI6b) to 31.8 in. 

(site MI7) compared to 39.7 in. of rainfall (site KI6b) to 

45.5 in. of rainfall (site MI7) in 2007 (Overland Park Stormwatch, 2009). Although rainfall was only about 1.25 times 

greater in 2007 than in 2006, stormflows at rural sites (BL5, 

CE6, and KI6b) in 2007 were 3.6 to 5.0 times those of 2006, 

whereas stormflows at urban and urbanizing sites in 2007 were 

only 1.5 times (IN6) and 2.5 times (MI7) those in 2006. This 

is because impervious surfaces in more urban basins route 

rainfall to streams during both wet and dry periods, whereas 

soils and vegetation in rural basins absorb a larger percentage 

of rainfall during dry periods. Thus stormflow and sediment 

yields from more urban basins are substantially larger than 

those from primarily rural basins during dry years (such as 

2006; table 11). However, during wet years (such as 2007 and 

2008), saturated soils or rainfall in excess of soil infiltration 

capacity result in more pronounced increases in stormflow 

and sediment loading in rural basins compared to more urban 

basins (table 11). Increased flows in the rural Cedar and 

Kill Creek Basins in 2007 relative to 2006 resulted in larger 

SM1 (0.6) CL1a (0.7) MI3 (2.8) CO1 (5.1) CL1 (5.5) LM1 (8.8) CL2 (10.9) LM2 (12.1) MI4 (19.7) MI5 (31.70) MI7 (57.4)

Y-INTERCEPT FOR RELATIONS BETWEEN STORMFLOW AND SEDIMENT LOAD

-3

-2.5

-2

-1.5

-1

-0.5

0

0

0.2

0.4

0.6

0.8

1

1.2

1.4

1.6

1.8

2.0

SLOPE OF RELATIONS BETWEEN STORMFLOW AND SEDIMENT LOAD

SAMPLING SITES IN ORDER OF INCREASING BASIN AREA 

(BASIN AREA, IN SQUARE MILES)

Y-intercept

Slope

Figure 24. Slope and y-intercept of log-log relations between streamflow and sediment loading for storms at Mill Creek

sampling sites, Johnson County, northeast Kansas, February 2006 through November 2008.
Table 11.  Annual stormflow, stormflow yield, suspended-sediment load and yield, and stormflow-weighted suspended-sediment concentrations at Johnson County, northeast Kansas, February 2006 through November 2008.[mi2, square mile; mg/L, milligrams per liter; --, no data]

Sampling 

site

(fig. 1)

Basin 

area

(mi2)

Total stormflow

(acre-feet)

Stormflow yield

(acre-feet/mi2)

Suspended-sediment load 

(tons)

Suspended-sediment yield 

(tons/mi2)

2006 2007 2008 2006 2007 2008 2006 2007 2008 2006 2007 2008 

Sampling sites in the Mill Creek Basin

CL1a 0.7 -- 340 470 -- 490 670 -- 570 440 -- 810 630 CL1b 2.8 -- 2,600 -- -- 900 -- -- 5,300 -- -- 1,900 -- CL1 5.5 1,100 4,000 4,500 200 700 800 1,100 10,100 7,500 200 1,800 1,400 CL2 10.9 3,000 7,800 9,900 270 700 910 2,000 14,800 11,900 180 1,400 1,100 CO1 5.1 1,400 3,900 6,000 280 760 1,170 280 1,200 1,800 60 230 350 LM1 8.8 3,500 7,100 8,200 400 810 930 1,400 4,900 4,200 160 550 470 LM2 12.1 3,300 8,000 8,200 270 660 680 1,600 7,000 7,600 130 570 620 MI3 2.8 1,600 2,600 3,000 560 940 1,060 620 1,100 930 220 380 330 MI4 19.7 7,300 15,700 17,400 370 800 880 5,800 14,300 12,800 300 730 650 MI5 31.7 8,900 18,100 21,200 280 570 670 6,100 16,900 23,100 190 530 730 MI7 57.4 14,200 34,100 40,400 250 610 730 10,400 36,200 39,500 180 630 690 SM1 .6 -- 540 860 -- 1,000 1,500 -- 990 1,300 -- 1,700 2,200 SM1a 1.3 -- -- 1,400 -- -- 1,090 -- -- 1,300 -- -- 1,000 SM2 .2 -- 40 -- -- 200 -- -- 20 -- -- 100 -- 

Sites at outlets of other large basins

BL5 65.7 11,700 42,300 50,400 180 640 770 15,400 38,200 64,100 230 580 980 CE6 58.5 8,800 32,900 -- 150 560 -- 5,000 30,500 -- 90 520 -- IN6 63.1 35,900 54,700 64,000 570 900 1,000 34,300 84,100 150,900 540 1,300 2,400 KI6b 48.6 4,700 23,500 -- 100 480 -- 2,100 17,600 -- 44 360 -- 
48 Effects on Suspended-Sediment Transport in Johnson County, Northeast Kansas, February 2006 through November 2008

increases in stormflow (3.7 and 5.0 times, respectively) and 

sediment loading (6.1 to 8.4 times, respectively) than increases 

in stormflow and sediment load observed at site IN6 from 

2006 to 2007 (1.5 times the stormflow, 2.4 times the sediment 

load). For unknown reasons, site BL5 was the only site that 

had a larger relative increase in stormflow (3.6 times) than in 

sediment loading (2.5 times) from 2006 to 2007.

Streamflow and sediment transport were defined for individual storms to further characterize when and how sediments 

are transported through the larger basins. From 2006 to 2007, 

95 individual storms were observed to increase streamflow 

relative to base-flow conditions at Indian Creek, compared 

to 55 at Mill Creek, 51 at Cedar Creek, 38 at Kill Creek, and 

24 at Blue River. Fifty-one storms were observed in 2008 at 

Indian Creek, 39 at Mill Creek, and 27 at Blue River (number of storms shown in figure 25 for 2006 through 2008 are 

slightly less because of occasional turbidity sensor malfunction during storms). Impervious surfaces in urbanized basins 

increased runoff relative to rainfall, resulting in the observation of more storms.

Among four of the five largest sampling sites, SWSCs 

during storms with more than 5,000 acre-ft of flow were 

smaller than during storms consisting of 1,000 to 5,000 acreft of flow, indicating that sediment supplies are becoming 

limited during the largest storms. During smaller-sized storms, 

SWSCs are among the smallest at the Indian Creek sampling 

site, likely because runoff from small storms (0 to 500 acre-ft) 

was transported from impervious surfaces, and thus did not 

erode surface soils and had little capacity to erode stream 

channels. However, nearly twice the number of large storms 

(greater than 1,000 acre-ft) were observed at the Indian Creek 

sampling site relative to other sites, and SWSCs for these 

storms were larger than those observed at other sites. Thus 

despite having larger and more frequent stormflows, sediment 

supplies are abundant enough within the Indian Creek Basin 

and stream channel to result in larger SWSCs than observed 

at other basins in the county. The number of large storms 

was relatively similar among Blue River and Mill Creek, but 

SWSCs were larger at Blue River for all storms greater than 

500 acre-ft. As previously described, this is likely partially 

related to differences in the occurrence of large impoundments 

between the two basins. Fewer storms were observed at the 

Cedar and Kill Creek sites because data were not collected in 

2008, and because rainfall resulted in less runoff at these sites. 

Increased construction activity (1.8 percent increase in impervious surface from 2003 to 2008; fig. 7) in the Cedar Creek 

Basin is potentially the cause of increased sediment loads relative to the Kill Creek Basin (table 11; fig. 25).

3

13

11

20

4

15

8

8

8

1

15

64

21

6

6

22 3

6

1

16

37

17

20 2

0

200

400

600

800

1,000

1,200

STORMFLOW-WEIGHTED SUSPENDED-SEDIMENT CONCENTRATION OF FLOW RANGE, IN MILLIGRAMS PER LITER

Less than 100 100 to 500 500 to 1,000 1,000 to 5,000 Greater than 5,000

RANGE OF STORMFLOW FOR STORMS OBSERVED FROM 2006 to 2008, IN ACRE-FEET

3

Blue River

Cedar Creek

Indian Creek

Kill Creek

Mill Creek

Indicates number of storms 

 within flow interval 

Largest basins in

 Johnson County

36

Figure 25. Stormflow-weighted suspended-sediment concentrations during different storm sizes at the five largest

sites in Johnson County, northeast Kansas, February 2006 through November 2008.
Summary and Conclusions 49

Since 2003, the amount of urban construction has been 

similar between Indian and Mill Creek (3.7 percent increases 

in impervious surface area), but sediment yields at site IN6 

are more than double that of site MI7. Increased stormflow 

and sediment yields in the Indian Creek Basin relative to other 

large basins in Johnson County can primarily be attributed to 

(1) fewer small, and no large surface-water impoundments 

within Indian Creek, and (2) differences in how the timing or 

urban development affects sediment transport in larger basins. 

Although only 10 percent of the Mill Creek Basin is controlled 

by larger (more than 30-acre) impoundments, there also are 

substantially more small impoundments which act to trap sediment and reduce downstream sediment transport relative to the 

Indian Creek Basin.

Consistently larger sediment loading in Indian Creek 

from 2004 to 2008 relative to other basins in Johnson County 

(Rasmussen and others, 2008) indicates that the basin and 

stream channel are still adjusting in response to historical 

urbanization in the basin. Increased sediment transport in the 

Indian Creek Basin relative to smaller sediment loads from 

similar urban subbasins within the Mill Creek Basin is likely 

a result of the scale at which sediment transport is being 

assessed. Along with natural variability in soils, topography, 

and geology, contributing basin area is an important factor 

controlling how human disturbances affect downstream sediment transport. Sediment deposition on the floodplains and 

streambeds of larger, less-sloping stream channels has been 

shown to delay (or mask) relations between surface erosion 

and downstream sediment transport (Trimble, 1977, 1997, 

1999; Simon and Rinaldi, 2000; Gellis and others, 2008). 

Historically deposited sediments can decrease streambank 

stability and be resuspended by subsequent stormflows, thus 

delaying increases in sediment transport relative to the initial 

change in surface erosion. Also, more frequent, larger stormflows in urban basins increase erosive forces on streambanks, 

which may have decreased stability as a result of previous 

sediment deposition or changes to riparian land use (Trimble, 

1997). Additionally, as eroded sediments reach streams in 

urbanized basins, they are more efficiently transported by 

larger total and peak streamflows and shorter stormflow recessions. The resulting pattern more efficiently transports sediments during extreme flows, while leaving less opportunity 

for sediment deposition during stormflow recession periods. 

Reconnaissance of the Indian Creek Basin after the 25-year 

storm on July 30, 2008, indicated little to no deposition of 

sediment of floodplains (fig. 26A) and several mass failures of 

sections of channel bank (fig. 26B). Soils from channel-bank 

failures typically were still aggregated, likely to be transported 

by subsequent storms. Therefore, increased sediment transport from the Indian Creek Basin is likely caused by frequent 

stormflows that erode streambed and streambank sediments.

Summary and Conclusions

The U.S. Geological Survey, in cooperation with the 

Johnson County Stormwater Management Program, investigated the effects of urbanization, construction activity, management practices, and impoundments on sediment transport 

in Johnson County, Kansas, from February 2006 through 

November 2008. Streamgages and continuous turbidity sensors were operated at 15 sampling sites in the urbanizing Mill 

Creek Basin, and at 4 sampling sites downstream from the 

other largest basins in Johnson County. Six of the sites within 

the Mill Creek Basin were used to assess sediment transport 

from two subbasins (Clear Creek headwaters and upstream 

from Shawnee Mission Lake) with substantial area under construction both before and during the study period.

Among the sites monitored continuously in the Mill 

Creek Basin from 2006 to 2008, sediment yields were largest from the urbanizing Clear Creek Basin; approximately 

2 to 3 times those from older, more stable urban or rural 

basins. Subbasins partially regulated by impoundments and 

those with stable urban land use had the smallest sediment 

concentrations and loads in the Mill Creek Basin. Cumulative 

sediment yields from 2006 to 2008 increased coincidental with 

increases in impervious surface from 2005 to 2006, but were 

unrelated to increases in impervious surface from 2006 to 

2008. This is potentially because there was more construction 

(and thus soil disturbance) from 2005 to 2006, and relatively 

little stormflow during 2006 to transport sediment through the 

stream network. Although increased sediment transport was 

generally related to increased construction activity in small 

basins within Mill Creek, several site-specific factors, such as 

management practice, impoundments, construction-site slope, 

site proximity to streams, sediment deposition and resuspension, and stream-channel erosion complicate relations between 

landscape activities and sediment yield.

Mean-daily turbidity values at sampling sites downstream 

from small basins with increased construction activity were 

compared to U.S. Environmental Protection Agency turbidity criteria designed to reduce discharge of pollutants from 

construction sites. The U.S. Environmental Protection Agency 

numeric turbidity criteria specifies that effluent from construction sites greater than 20 acres not exceed a mean-daily 

turbidity value of 280 nephelometric turbidity units beginning 

in 2011; this criteria will apply to sites greater than 10 acres 

beginning in 2014. Although the numeric criteria would not 

have been applicable to data from sampling sites in Johnson 

County because they were not directly downstream from construction sites and because individual states still have to determine details regarding enforcement of this criteria, a comparison was made to characterize the potential of construction 

site effluent in Johnson County to exceed U.S. Environmental 

Protection Agency Criteria, even under extensive erosion and 

sediment controls. Numeric criteria were exceeded at sampling 

sites downstream from basins with increased construction 

activity for multiple days during the study period, potentially 
50 Effects on Suspended-Sediment Transport in Johnson County, Northeast Kansas, February 2006 through November 2008

A

B

High-water mark

Figure 26. A, High-water mark on golf course and B, area of channel-bank failure after the 25-year

storm on July 30, 2008, at Indian Creek, Johnson County, northeast Kansas.
References Cited 51

indicating the need for additional erosion and sediment controls and (or) treatment to bring discharges from construction 

sites into compliance with future numeric turbidity criteria.

Sites downstream from increased recent and active construction sites in the headwaters of the Clear Creek Basin had 

among the largest annual sediment yields in the Mill Creek 

Basin (630 to 1,900 tons per square mile). Although the most 

upstream site in the Clear Creek Basin (0.7 square mile) had 

the largest percentage of area undergoing construction, and 

multiple failures of sediment controls were observed, sediment yields at this site were consistently smaller than those 

observed at downstream sampling sites. This may have been 

because construction sites in the headwaters of the basin were 

distant from streams, and thus sediments eroded form these 

sites were more likely to deposit on land surfaces and within 

smaller stream channels. Comparison of sediment yields 

among headwater and downstream sites in the Clear Creek 

Basin indicated that factors such as site and stream slope, the 

current phase of construction, management practices, and site 

location relative to streams affect the amount and length of 

time it takes eroded sediment to be transported downstream.

Annual sediment yields attributed to a large, 68-acre 

construction site upstream from Shawnee Mission Lake 

(9,300 tons per square mile in 2007; 12,200 tons per square 

mile in 2008) were 5 to 55 times those from other sampling 

sites in the Mill Creek Basin. However given increased precipitation, steep slopes, and erodible soils, annual sediment yields 

were relatively small compared to the range in values historically observed from construction sites without erosion and 

sediment controls in the United States (2,300 tons per square 

mile to 140,000 tons per square mile). Sediment loads were 

monitored from the sampling site 1,400 feet downstream from 

the construction site through a 1.8-acre-foot sediment forebay 

and a 7-acre-foot constructed wetland into Shawnee Mission 

Lake. The sediment forebay is estimated to have reduced 

downstream sediment loading by approximately 33 percent; 

the wetland did not have a measureable effect on downstream 

sediment transport. Comparison of relations between turbidity and sediment concentration upstream and downstream 

from the sediment forebay indicate that the sediment forebay likely caused deposition of larger, silt-sized particles, 

whereas smaller-sized sediments were transported through 

the wetland and into the lake. Comparison of mean sediment 

concentrations during storms at sites up and downstream from 

the constructed wetland indicated that hydraulic retention by 

the wetland did not substantially reduce sediment loading to 

Shawnee Mission Lake.

More detailed analysis of continuous streamflow and 

continuous turbidity-computed sediment concentrations was 

conducted to better understand how various factors affect the 

magnitude and timing of sediment transport in the Mill Creek 

Basin. Sediment concentrations at sites downstream from 

increased construction activity were larger than during both 

stormflow and base-flow conditions, likely decreasing light 

penetration through streamwater and increasing fine sediment deposition to streambeds. Urban and rural basins with 

reservoirs had decreased sediment loading relative to similar 

basins without reservoirs. Analysis of sediment loading across 

streamflow conditions indicated that the largest 1 percent of 

streamflows transported 73 to 91 percent of total sediment 

loads among sampling sites, and that the largest 10 percent of 

streamflows transported 93 to 100 percent of stream-sediment 

loads. Reservoirs in the Mill Creek Basin trapped sediments, 

decreasing downstream sediment loads, and reducing sediment 

concentrations primarily during peak-flow conditions. Multiple regression analysis of the factors affecting sediment transport indicated that increasing stormflow volume and rainfall 

intensity resulted in significant increases in sediment loading 

at all sites, whereas recent, large storms decreased sediment 

supplies available for transport by subsequent storms.

 Among the five largest sampling sites in Johnson County 

(Blue River and Cedar, Indian, Kill, and Mill Creeks) the 

mature, highly urbanized basin (Indian Creek) had sediment 

yields more than double those observed from other large 

basins in the county, only slightly less than yields observed 

from small subbasins in the Mill Creek Basin which were 

immediately downstream from increased construction activity. 

The smallest stormflow and sediment yields were observed 

in the predominantly rural Cedar and Kill Creek Basins. 

Larger sediment yields observed in the predominantly rural 

Blue River Basin were similar to those in the urbanizing Mill 

Creek Basin, in part because of a lack of large surface-water 

impoundments. Consistently large sediment yields observed 

at Indian Creek since sampling began in 2004 indicate that 

increased sediment transport is likely caused by a large-scale 

basin and stream-channel response to urbanization (rather than 

specific construction activities). Although a lack of large and 

small impoundments partially explains larger sediment yields 

from the Indian Creek Basin, increased sediment transport is 

likely caused by frequent stormflows that erode streambed and 

streambank sediments.

References Cited

Bragg, H.M., Sobieszczyk, S., Uhrich, M.A., and Piatt, D.R., 

2007, Suspended-sediment loads and yields in the North 

Santiam River basin, Oregon, water years 1999–2004: U.S. 

Geological Survey Scientific Investigations Report 2007–

5187, 26 p.

Brown, L.C., and Foster, G.R., 1987, Storm erosivity using 

idealized intensity distributions: Transactions of the American Society of Agricultural Engineers, v. 30, p. 379–386.

Christensen, V.G., Jian, X., and Ziegler, A.C., 2000, Regression analysis and real-time water-quality monitoring to 

estimate constituent concentrations, loads, and yields in the 

Little Arkansas River, south-central Kansas, 1995–1999: 

U.S. Geological Survey Water-Resources Investigations 

Report 00–4126, 36 p.
52 Effects on Suspended-Sediment Transport in Johnson County, Northeast Kansas, February 2006 through November 2008

Downing, J., 2006, Twenty-five years with OBS sensors—The 

good, the bad, and the ugly: Continental Shelf Research, 

v. 26, p. 2,299–2,318.

Duan, N., 1983, Smearing estimate—a nonparametric retransformation method: Journal of the American Statistical Asssociation, v. 78, p. 605–610.

Evans, B.C., 2003, Soil survey of Johnson County, Kansas: 

U.S. Department of Agriculture, Natural Resources Conservation Service, p. 367.

Freeman, P.L., and Schorr, M.S., 2004, Influence of basin 

urbanization on fine sediment and macroinvertebrate assemblage characteristics in Tennessee Ridge and valley streams: 

Journal of Freshwater Ecology, v. 19, no. 3, p. 353–362.

Gellis, A.C., and others, 2008, Sources, transport, and storage 

of sediment in the Chesapeake Bay Watershed: U.S. Geological Survey Scientific Investigations Report 2008–5186, 

95 p.

Guy, H.P., 1969, Laboratory theory and methods for sediment 

analysis: U.S. Geological Survey Techniques of WaterResources Investigations, book 5, chap. C1, 58 p.

Guy, H.P., 1970, Sediment problems in urban areas: U.S. Geological Survey Circular 601–E, 13 p.

Helsel, D.R., 1984, Contributions of suspended sediment from 

highway construction and other land uses to the Olentangy 

River, Columbus, Ohio: U.S. Geological Survey WaterResources Investigations Report 84–4336, 35 p.

Helsel, D.R., and Hirsch, R.M., 2002, Statistical methods in 

water resources—Hydrologic analysis and interpretation: 

U.S. Geological Survey Techniques of Water-Resources 

Investigations, book 4, chap. A3, 510 p., accessed March 

2008, at http://pubs.usgs.gov/twri/twri4a3/.

Hirsch, R.M., and Gilroy, E.J., 1984, Methods of fitting a 

straight line to data—Examples in water resources: Water 

Resources Bulletin, v. 20, no. 5, p. 705–711.

Kennedy, E.J., 1983, Computation of continuous records of 

streamflow: U.S. Geological Survey Techniques of WaterResources Investigations, book 3, chap. A13, 53 p.

Kennedy, E.J., 1984, Discharge ratings at gaging sites: U.S. 

Geological Survey Techniques of Water-Resources Investigations, book 3, chap A10, 59 p.

Lee, C.J., Mau, D.P., and Rasmussen, T.J., 2005, Effects of 

nonpoint and selected point contaminant sources on streamwater quality and relation to land use in Johnson County, 

northeastern Kansas, October 2002 through June 2004: 

U.S. Geological Survey Scientific Investigations Report 

2005–5144, 104 p.

Lee, C.J., Juracek, K.E., and Fuller, C.C., 2007, Bottom-sediment accumulation and quality in Shawnee Mission Lake, 

Johnson County, Kansas, 2006: U.S. Geological Survey 

Scientific Investigations Report 2007–5274, 10 p.

Lee, C.J., Rasmussen, P.P., and Ziegler, A.C., 2008, Characterization of suspended sediment loading to and from John 

Redmond Reservoir, East-Central Kansas, 2007–08: U.S. 

Geological Survey Scientific Investigations Report 2008–

5123, 25 p.

Lee, C.J., Rasmussen, P.P., Ziegler, A.C., and Fuller, C.C., 

2009, Transport and sources of suspended sediment in 

the Mill Creek Basin, Johnson County, northeast Kansas, 

2006–07: U.S. Geological Survey Scientific Investigations 

Report 2009–5001, 52 p.

Leopold, L.B., Huppman, R., and Miller, A., 2005, Geomorphic effects of urbanization in forty-one years of observation: Proceedings of the American Philosophical Society, 

v. 149, no. 3, p. 349–371.

Morris, G.L., and Fan, Jiahua, 1997, Reservoir sedimentation 

handbook: New York, McGraw-Hill, [variously paged].

National Oceanic and Atmospheric Administration, 2009, 

Climatological data summary for Olathe, Kansas: National 

Climatic Data Center database, accessed March 3, 2009, at 

http://www.ncdc.noaa.gov/oa/climate/sitelocator.html.

Nolan, M.K., Gray, J.R., and Glysson, D.G., 2005, Introduction to suspended-sediment sampling: U.S. Geological Survey Scientific Investigations Report 2005–5077, CD–ROM.

O’Connor, H.G., 1971, Johnson County geohydrology: Kansas 

Geological Survey, accessed July 2008, at http://www.kgs.

ku.edu/General/Geology/Johnson/index.html.

Osterkamp, W.R., Heilman, P., and Lane, L.J., 1998, Economic considerations of Continental Sediment-Monitoring 

Program: International Journal of Sediment Research, v. 13, 

no. 4, p. 12–24.

Overland Park Stormwatch, 2009, Overland Park, Kansas, 

flood warning system: City of Overland Park, accessed 

January 6, 2009, at 

http://www.stormwatch.com/index.asp.

Owens, D.W., Jopke, P., Hall, D.W., Balousek, J., and Roa, A., 

2000, Soil erosion from two small construction sites, Dane 

County, Wisconsin: U.S. Geological Survey Fact Sheet 

109–00, 4 p.

Pavelich, M.P., 2002, Turbidity studies at the national water 

quality laboratory, in Proceedings of the Turbidity and 

Other Surrogates Workshop, April 30–May 2, 2002, Reno, 

Nev., 3 p.
References Cited 53

Perry, C.A., Wolock, D.M., and Artman, J.A., 2004, Estimates 

of flow duration, mean flow, and peak-discharge frequency 

values for Kansas stream locations: U.S. Geological Survey 

Scientific Investigations Report 2004–5033, 219 p.

Poff, L.N., Bledsoe, B.P., and Cuhaciyan, C.O., 2006, Hydrologic variation with land use across the contiguous United 

States—Geomorphic and ecological consequences for 

stream systems: Geomorphology, v. 79, p. 264–285.

Poulton, B.C., Rasmussen, T.J., and Lee, C.J., 2007, Assessment of biological conditions at selected stream sites in 

Johnson County, Kansas, and Cass and Jackson Counties, 

Missouri, 2003 and 2004: U.S. Geological Survey Scientific 

Investigations Report 2007–5108, 68 p.

Rasmussen, T.J., Ziegler, A.C., and Rasmussen, P.P., 2005, 

Estimation of constituent concentrations, densities, loads, 

and yields in lower Kansas River, northeast Kansas, using 

regression models and continuous water-quality monitoring, January 2000 through December 2003: U.S. Geological 

Survey Scientific Investigations Report 2005–5165, 117 p.

Rasmussen, T.J., Lee, C.J., and Ziegler, A.C., 2008, Estimation 

of constituent concentrations, loads, and yields in streams of 

Johnson County, northeast Kansas, using continuous waterquality monitoring and regression models, October 2002 

through December 2006: U.S. Geological Survey Scientific 

Investigations Report 2008–5014, 103 p.

Rasmussen, P.P., Gray, J.R., Glysson, G.D., and Ziegler, A.C., 

2009a, Guidelines and procedures for computing time-series 

suspended-sediment concentrations and loads from instream turbidity-sensor and streamflow data: U.S. Geological Survey Techniques and Methods, book 3, chap. C4, 

18 p.

Rasmussen, T.J., Poulton, B.C., and Graham, J.L., 2009b, 

Quality of streams in Johnson County, Kansas, and relations to environmental variables, 2003–07: U.S. Geological 

Survey Scientific Investigations Report 2009–5235, 84 p.

Renwick, W.H., Smith, S.V., Bartley, J.D., and Buddemeier, 

R.W., 2005, The role of impoundments in the sediment 

budget of the conterminous United States: Geomorphology, 

v. 71, p. 99–111.

Sadar, M.J., 1998, Turbidity Science: Hach Company Technical Information Series Booklet No. 11, accessed May 18, 

2010, at 

http://www.hach.com/fmmimghach?/CODE:L7061549|1.

Schoewe, W.H., 1949, The geography of Kansas: Transactions 

of the Kansas Academy of Science, v. 52, no. 3, p. 261–333.

Simon, A., and Rinaldi, M., 2000, Channel instability in the 

loess area of the Midwestern United States: Journal of 

the American Water Resources Association, v. 36, no. 1, 

p. 133–150.

Thiessen, A.H., and Alter, J.C., 1911, Climatological data for 

July 1911—District No. 10, Great Basin: Monthly Weather 

Review, July 1911, p. 1,082–1,089.

Trimble, S.W., 1977, The fallacy of stream equilibrium in contemporary denudation studies: American Journal of Science, 

v. 277, p. 876–887.

Trimble, S.W., 1997, Contribution of stream channel erosion 

to sediment yield from an urbanizing watershed: Science, 

v. 278, p. 1,442–1,444.

Trimble, S.W., 1999, Decreased rates of alluvial sediment storage in the Coon Creek basin, Wisconsin: Science, v. 285, 

p. 1,244–1,246.

U.S. Census Bureau, 2008, State and county quickfacts: U.S. 

Census Bureau database, accessed November 2009, at 

http://quickfacts.census.gov/qfd/states/20/20091.html.

U.S. Department of Commerce, 1961, Rainfall frequency 

atlas of the United States for durations from 30 minutes to 

24 hours and return periods from 1 to 100 years: Weather 

Bureau Technical Paper No. 40, 65 p.

U.S. Environmental Protection Agency, 2005, Stormwater 

phase II final rule, Construction site runoff minimum control measure: Fact Sheet 2.6, EPA 833–F–00–008, 4 p.

U.S. Environmental Protection Agency, 2006, Wadeable 

streams assessment: EPA 841–B–06–002, p. 1–98.

U.S. Environmental Protection Agency, 2009, Effluent limitations guidelines and standards for the construction and 

development point source category—Final rule, Federal 

Register, 40 CFR Part 450, 64 p.

Vice, R.B., Guy, H.P., and Ferguson, G.P., 1969, Sediment 

movement in an area of suburban highway construction, 

Scott Run basin, Fairfax County, Virginia, 1961–1964: U.S. 

Geological Survey Water-Supply Paper 1591–E, 46 p.

Wagner, R.J., Boulger, R.W., Jr., Oblinger, C.J., and Smith, 

B.A., 2006, Guidelines and standard procedures for continuous water-quality monitors—Site operation, record 

computation, and data reporting: U.S. Geological Survey 

Techniques and Methods 1–D3, 51 p. plus 8 attachments, 

accessed November 2006, at 

http://pubs.water.usgs.gov/tm1d3.

Wahl, T.L., and Wahl, K.L., 2006, BFI—A computer program 

for determining an index to base flow: Bureau of Reclamation, accessed August 26, 2008, at 

http://www.usbr.gov/pmts/hydraulics_lab/twahl/bfi/.

Walling, D.E., and Gregory, K.J., 1970, The measurement 

of the effects of building construction on drainage basin 

dymanics: Journal of Hydrology, v. 11, no. 2, p. 129–144. 
54 Effects on Suspended-Sediment Transport in Johnson County, Northeast Kansas, February 2006 through November 2008

Walters, D.M., Leigh, D.S., and Bearden, A.B., 2003, Urbanization, sedimentation, and the homogenization of fish 

assemblages in the Etowah River Basin, USA: Hydrobiologia, v. 494, p. 5–10.

Wolman, M.G., 1967, A cycle of sedimentation and erosion in 

urban river channels: Geografiska Annaler, v. 49a, no. 2–4, 

p. 385–395.

Wolman, M.G., and Schick, A.P., 1967, Effects of construction 

on fluvial sediment, urban and suburban areas of Maryland: 

Water Resources Research, v. 3, no. 2, p. 451–464.

Wood, P.J., and Armitage, P.D., 1997, Biological effects of fine 

sediment in the lotic environment: Environmental Management, v. 21, no. 2, p. 203–217.

YSI Incorporated, 2010, YSI 6136 turbidity sensor documentation: YSI Incorporated, accessed February 26, 2010, at 

www.ysi.com/media/pdfs/spec-sheets/E56-6136-TurbiditySensor.pdf.

Yorke, T.H., and Herb, W.J., 1978, Effects of urbanization on 

streamflow and sediment transport in the Rock Creek and 

Anacostia River basins, Montgomery County, Maryland, 

1962–74: U.S. Geological Survey Water-Supply Paper 1003, 

76 p.
Publishing support provided by:

Rolla Publishing Service Center

For more information concerning this publication, contact:

Director, USGS Kansas Water Science Center

4821 Quail Crest Place

Lawrence, KS 66049

(785) 842–9909

Or visit the Kansas Water Science Center Web site at:

http://ks.water.usgs.gov

Back cover.  Map showing location of basin boundaries in Johnson County, northeast Kansas, 2008.

Blue River

Captain Creek

Kill Creek

Cedar

Creek

Big Bull Creek

Litt e Bull Creek

Mi ll

Clear Cr

Coon Cr

Turkey Creek

Brush Cree

Ro

k

ck Creek

Indian Creek

Tomahawk Creek

Coffee Creek

Wolf Creek

Camp Branch

Branch

Little Mill Creek

t

s

e

e

f

l

Dykes

Kansas

River

Creek Indian Creek Basin

Mill Creek Basin

Kill Creek

Basin

Cedar Creek Basin

Olathe

Gardner

Blue River Basin
Blue

River

Captain Creek

Kill Creek

Cedar

Creek

Big Bull Creek

Litt e Bull Creek

Mi ll

Clear Cr

Coon Cr

Turkey Creek

Brush Cree

Ro

k

ck

Creek

Indian

Creek

Tomahawk Creek

Coffee

Cr

e

ek

Wolf Creek

Camp Branch

Branch

Little

Mill

Creek

t

s

e

e

f

l

Dykes

Kansas

River

Creek

Indian Creek

Basin

Mill Creek

Basin

Kill Creek

Basin

Cedar Creek

Basin

Olathe

Gardner

Blue River

Basin

Lee and Ziegler—Effects on Suspended-Sediment Transport in Johnson County, Northeast Kansas, February 2006 through November 2008—SIR 2010–5128