U.S. Department of the Interior

U.S. Geological Survey

Scientific Investigations Report 2011–5165

In cooperation with the Chagrin River Watershed Partners

Hydraulic Characteristics of Low-Impact Development 

Practices in Northeastern Ohio, 2008–2010

Minimum of 9-in. of 

scarified native material

24 in. of planting mix

6-in. PVC overflow

to bioretention basin

(flows to flume 2)

6-in. PVC storm outlet from downspouts

Pavers

2-in. coarse 

compacted 

aggregate

Gravel

Native 

Material

2-in. of sand

Drainage pipe to 

bioretention basin

(flume 3)

All aggregate compacted to 70% relative density

Filter fabric
Cover drawing. Construction detail of paver parking lot and rain garden for 

Washington Street site, Geauga County, Ohio. (Modified from engineer drawings 

provided by Cawrse and Associates, Inc.)

Inset photo, top. One of the rain gardens along Sterncrest Drive site, Cuyahoga 

County, Ohio, showing monitoring equipment, drainage grate, and plant growth 

from October 2008.

Inset photo, center. Flume 2 at Washington Street site, Geauga County, Ohio. 

measuring any overflow from the rain garden.

Inset photo, bottom. Washington Street rain garden showing weather station 

and plant growth, August 2008. (Photograph by Cawrse and Associates, Inc., 

employees.)
Hydraulic Characteristics of Low-Impact 

Development Practices in 

Northeastern Ohio, 2008–2010

By Robert A. Darner and Denise H. Dumouchelle

In cooperation with the Chagrin River Watershed Partners

Scientific Investigations Report 2011–5165

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: 2011

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reproduce any copyrighted materials contained within this report.

Suggested citation:

Darner, R.A., and Dumouchelle, D.H., 2011, Hydraulic characteristics of low-impact development practices in 

northeastern Ohio, 2008–2010:U.S. Geological Survey Scientific Investigations Report 2011–5165, 19 p.
Contents

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

Introduction.....................................................................................................................................................1

Purpose and Scope ..............................................................................................................................1

Description of the Study Area ............................................................................................................3

Hydrologic Characteristics at the Sterncrest Drive Site.........................................................................3

Site Description.....................................................................................................................................3

Methods..................................................................................................................................................6

Data Analysis and Description ...........................................................................................................6

Hydrologic Characteristics at the Washington Street Site.....................................................................8

Site Description.....................................................................................................................................8

Methods................................................................................................................................................10

Data Analysis and Description .........................................................................................................13

Summary and Conclusions.........................................................................................................................19

Acknowledgments.......................................................................................................................................19

References Cited..........................................................................................................................................19

Figures

1. Map of the location of the study area.......................................................................................2

2. Site plan for stormwater best-management practice along Sterncrest Drive 

site, Cuyahoga County, Ohio .......................................................................................................3

3. Photographs of one of the rain gardens along Sterncrest Drive site, 

Cuyahoga County, Ohio, showing monitoring equipment, drainage grate, 

and plant growth from May 2008 to July 2010..........................................................................4

4. Construction detail for bioswale and rain gardens along Sterncrest Drive 

site, Cuyahoga County, Ohio .......................................................................................................5

5. Graph of the annual average duration and depths for precipitation events 

that exceeded the 0.75-inch design storm at Sterncrest Drive site, 

Cuyahoga County, Ohio................................................................................................................8

6. Site plan for stormwater best-management practices at Washington 

Street site, Geauga County, Ohio ...............................................................................................9

7. Construction detail for Washington Street site, Geauga County, Ohio 

showing, A, Paver parking lot and, B, rain garden................................................................10

8. Photographs of the flumes at Washington Street site, Geauga County, Ohio. 

Flume 1, A, measures surface flow over the parking lot; flume 2, B, 

measures any overflow from the rain garden, and flume 3, C, measures 

the flow from the drain line. ......................................................................................................11

9. Hydrograph of typical precipitation event at the Washington Street 

site showing the spreadsheet selections of begin, peak, and end of 

flow, as well as the centroids of flow and precipitation ......................................................13

10. Runoff ratio for the pervious-paver/rain-garden BMP at Washington 

Street site, Geauga County, Ohio, April through October 2009 and 2010 ..........................14

iii
11. Boxplots of climatological and flow characteristics, Washington Street 

site, Geauga County, Ohio, 2009 and 2010. A, Runoff ratio. B, Maximum 

daily air temperature (degrees Celsius). C, Centroid lag. D, Precipitation 

event size. E, Precipitation intensity. F, Precipitation duration...........................................15

12. Photographs of Washington Street rain garden showing weather station 

and plant growth from October 2008 to August 2010............................................................16

13. Time-domain reflectometer relative soil moisture for one month, 

cluster A, Washington Street site, Geauga County, Ohio. 

The graph shows that the BMP does not have time to return to a 

steady state before the next precipitation event. .................................................................17

14. Boxplots of specific-conductance lag times for six soil-moisture sensors 

and runoff, 2009 and 2010, Washington Street site, Geauga County, Ohio. ......................18

Tables

1. Precipitation events that exceed 0.75 inch and rain-garden overflow events, 

April–October, 2008–2010, Sterncrest Drive site, Cuyahoga County, Ohio..........................6

2. Rain garden overflow time, duration, and precipitation-event depths, 

Sterncrest Drive site, Cuyahoga County, Ohio. .......................................................................7 

3. Precipitation depths that exceed the 1-, 2-, 5-, and 10-year recurrence 

intervals for the area including Sterncrest Drive site, Cuyahoga County, Ohio.................7

4. Number of overflow events and precipitation events that exceeded the 

0.75-inch design storm at Sterncrest Drive site, Cuyahoga County, Ohio...........................7

5. Depth of time-domain reflectometers at Washington Street site, 

Geauga County, Ohio..................................................................................................................14

iv

Conversion Factors

Multiply By To obtain

Length

inch (in) 2.54 centimeter (cm)

inch (in) 25.4 millimeter (mm)

foot (ft) 0.3048 meter (m)

Area

square foot (ft2) 0.09290 square meter (m2)

square mile (mi2) 2.590 square kilometer (km2) 

Volume

cubic foot (ft3) 0.02832 cubic meter (m3) 

Flow rate

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

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

°F=(1.8×°C)+32
Hydraulic Characteristics of Low-Impact Development 

Practices in Northeastern Ohio, 2008–2010

By Robert A. Darner and Denise H. Dumouchelle

Abstract

Low-impact development (LID) is an approach to 

managing stormwater as near to its source as possible; this is 

accomplished by minimizing impervious surfaces and promoting more natural infiltration and evapotranspiration than is typically associated with developed areas. Two newly constructed 

LID sites in northeastern Ohio were studied to document their 

hydraulic characteristics.

A roadside best-management practice (BMP) was constructed by replacing about 1,400 linear feet of existing ditches 

with a bioswale/rain garden BMP consisting of a grassed 

swale interspersed with rain-garden/overflow structures. 

The site was monitored in 2008, 2009, and 2010. Although 

some overflows occurred, numerous precipitation events exceeding the 0.75-inch design storm did not result in overflows. 

A second study site consists of an 8,200-square-foot 

parking lot made of a pervious pavers and a rain garden that 

receives runoff from the roof of a nearby commercial building. A comparison of data from 2009 and 2010 indicates that 

the median runoff volume in 2010 decreased relative to 2009. 

The centroid lag times (time difference between centroid of 

precipitation and centroid of flow) decreased in 2010, most 

likely due to more intense, shorter duration precipitation 

events and maturation of the rain garden. Additional data 

could help quantify the relation between meteorological variables and BMP efficiency. 

Introduction

The Chagrin River watershed, which covers parts of 

Cuyahoga, Geauga, Lake, and Portage Counties in northeastern Ohio (fig. 1), is increasingly affected by impervious 

surfaces and stormwater runoff related to urban and suburban development. Geauga County, for example, comprises 

54 percent of the watershed area and is northeast Ohio’s 

second-fastest growing county in terms of population increase 

(Geauga County Planning Commission, 2005). Increasing 

amounts of impervious area can result in increased stormwater 

runoff and erosion, which deliver sediment and other pollutants to the Chagrin River and its tributaries. Some of these 

stormwater runoff impacts may be mitigated through planning 

and low-impact construction designs.

Low-impact development (LID) is a best-management 

practice (BMP) approach to managing stormwater as near to 

its source as possible; this is accomplished by minimizing impervious surfaces and promoting more natural infiltration and 

evapotranspiration than is typically associated with developed 

areas. A variety of BMPs can be incorporated into LID sites, 

such as rain gardens, bioretention features, and pervious pavements. Documenting the performance of the various practices, 

both in terms of water quantity and quality, is a significant 

facet in evaluating the impact of LID on stormwater runoff. 

LID performance metrics can include reductions in runoff 

volumes and (or) increases in infiltration or evaporation rates. 

The Chagrin River Watershed Partners, Inc. (CRWP), received 

a grant from the U.S. Environmental Protection Agency to 

help implement and monitor BMPs used at two LID study 

sites as a means to promote distributed stormwater management. The U.S. Geological Survey (USGS), in cooperation 

with the CRWP, installed monitoring equipment and collected 

hydrologic data at these two sites in the Chagrin River watershed where LID techniques were implemented. The results of 

the USGS study will be used in conjunction with water-quality 

data collected by the CRWP to better define the performance 

of bioswale, pervious-paver, and rain-garden stormwater 

BMPs. Installation of BMPs within each LID study site was 

completed by partnering landowners or community governments, in cooperation with the CRWP.

Purpose and Scope

The purpose of this report is to describe the BMPs 

installed at two LID sites in the Chagrin River watershed in 

northeastern Ohio and present hydrologic data gathered to help 

characterize their performance. Precipitation and runoff data 

for the Sterncrest Drive site were collected from April through 

October in 2008, 2009 and 2010; data for the Washington 

Street site were collected from April through October in 2009 

and 2010.
2 Hydraulic Characteristics of Low-Impact Development Practices in Northeastern Ohio, 2008–2010

Figure 1. Location of the study area

Project Area

OHIO

2 KILOMETERS

0 2 MILES

0 1

1

LANDER RD

lley Creek

McFarlandCr

Chagrin River

Chagrin

River

Sterncrest Drive

CUYAHOGA

GEAUGA

Washington 

Street

81°28'W 81°24 W

41°26 N

41°24 N

Cuyahoga River

Chagrin River

Cuyahoga River

Euclid Creek

Grand River

Lake Erie

GEAUGA

CUYAHOGA

LAKE

SUMMIT PORTAGE

TRUMBULL ASHTABULA

41°40'N

41°20'N

81°40'W 81°20 W 81°0 W

Base from U.S. Geological Survey

Digital Data, UTM Zone 17 N

North American Datum of 1983.

10 20 MILES

10 20 KILOMETERS

0

0

Chagrin River

 drainage area

EXPLANATION

Chagrin River

 drainage area

Road

Site locations
Hydrologic Characteristics at the Sterncrest Drive Site 3

Description of the Study Area

Located east of the Cleveland metroplex, the Chagrin 

River watershed drains 265 mi2 of gently rolling hills in northeastern Ohio. The two study sites are near the Chagrin River 

crossing from Geauga into Cuyahoga County. The Sterncrest 

Drive site is in Cuyahoga County, near the western boundary of the watershed. The Washington Street site is in Geauga 

County, in the upper reaches of the watershed (fig. 1). The 

area has a humid, temperate climate with a 29-year average 

annual precipitation of between 38 and 47 in., 62 percent of 

which falls from April through October (Midwest Regional 

Climate Center, 2010). Land use is highly variable and 

includes urban, suburban, rural-residential, forested, and 

agricultural uses. Glacial sediments ranging from a few feet 

to around 100 ft in thickness overlie sandstone and shale bedrock. Most soils in the watershed are formed in the clay-rich 

glacial till; their permeability generally is low to very low, and 

they may need to be drained for development (Musgrave and 

Holloran, 1980; Williams and McCleary, 1982).

Hydrologic Characteristics at the 

Sterncrest Drive Site

The soil at the Sterncrest Drive site is a Wadsworth silt 

loam, described as “somewhat poorly drained” with moderately low to very low permeability. The water table is near 

land surface, particularly in the winter and spring or during 

unusually wet periods, so the soil has little capacity to store 

infiltrated water. In the area near the intersection of Sterncrest 

Drive and Lander Road, there has been a history of yard and 

road flooding during periods of moderate precipitation. In an 

effort to alleviate flooding, bioswales were installed along 

Sterncrest Drive, with construction ending in November 2007.

Site Description

About 1,400 linear feet of existing ditches along 

Sterncrest Drive were replaced with a bioswale/rain garden 

BMP consisting of a grassed swale interspersed with raingarden/overflow structures. The bioswale receives stormwater 

runoff predominantly from the adjacent roadway and overland 

runoff from the single-family residential area. The road is not 

curb-and-gutter construction, so water flows from the paved 

surface into the swale.

The existing ditches were excavated to a depth of approximately 5 ft, after which an 8-in. perforated drain pipe 

was installed in the north bioswale and a 15-in. perforated 

drain was installed in the south bioswale. The ditches were 

backfilled with permeable sediments—engineered soil media 

that consisted of 70 percent sand and 30 percent peat/leaf compost—to create the bioswales. The 15-in. perforated drain pipe 

runs the length of the bioswale on the south side of the road, 

and nonperforated storm drain pipe crosses from the north 

drain pipe to the south drain pipe at the each of the paired rain 

gardens. There are nine rain gardens in all, five to the north 

and four to the south of Sterncrest Drive (fig. 2). Flow in 

the perforated drain north of Sterncrest Rd enters one of five 

rain gardens before passing to the drain to the south, where 

four additional rain gardens have been constructed. Each rain 

garden covers an oval area of about 95 ft2 (20 ft by 6 ft), and 

the surface is planted with perennials and is mulched. In the 

center of each rain garden is a 2-ft-square elevated grate to 

allow water that ponds sufficiently, but that does not infiltrate 

through the rain garden, to overflow into to the storm-sewer. 

The top of the grate is approximately 6 in. higher than the surrounding land surface of the rain garden (fig. 3). One drawback to this design is that the drains discharge to the village’s 

stormwater drains at Lander Road (fig. 2) and, therefore, are 

subject to backwater if the storm drains reach capacity or 

become plugged.

Figure 2. Site plan for stormwater 

best-management practice along 

Sterncrest Drive site, Cuyahoga 

County, Ohio.

The construction details of 

the bioswale are shown in figure 4. 

One important difference between 

the bioswale and the rain gardens 

is the type of vegetation used 

for cover. The bioswale is only 

1.5 ft wide and covered with turf 

grass, whereas the rain gardens are 

6 ft wide, planted with perennials, 

and mulched with double-shredded 

wood mulch (figs. 2 and 3).

 ̄

Rain garden (SR1 and SR2

 are instrumented)

House

Pipe flow

Driveway

EXPLANATION

SR1

SR2

Sterncrest Road

Lander Road

POND
4 Hydraulic Characteristics of Low-Impact Development Practices in Northeastern Ohio, 2008–2010

Figure 3. Photographs of one of the rain gardens along Sterncrest Drive site, Cuyahoga County, Ohio, showing 

monitoring equipment, drainage grate, and plant growth from May 2008 to July 2010.

Data logger

Lysimeter sampling Crest-stage pipe

ports

Data logger

Crest-stage pipe

Crest-stage pipe

Data logger

Lysimeter sampling

ports

B October 9, 2008

A May 7, 2008

C July 14, 2010

 Lysameter sampling port 

 obscured by plant growth 
Hydrologic Characteristics at the Sterncrest Drive Site 5

Figure 4. Construction detail for bioswale and rain gardens along Sterncrest Drive site, Cuyahoga County, Ohio (modified from engineer 

drawings provided by Orange Village, Ohio).

18 in.

9 in. of tilled soil

Limestone gravel

8-15 in. perforated drain

Backfill, 70% sand / 

 30% compost

4 in. of sand

3 in.

3 in.

2 ft 6 in. minimum

Sod

4-in. plastic edging

Native material

Asphalt pavement

Typical rain garden detail section A-A'

Filter fabric

Typical swale detail section B-B'

4 in. of sand

18 in.

3 in.

3 in

2 ft 6 in. minimum depth

8 or 15 in. perforated drain

Limestone gravel

9 in. of tilled soil

Backfill, 70% sand / 

 30% compost Native material

Asphalt pavement Sod 12 in.

Filter fabric

2-ft square 

 overflow grate

A A'

B B'

Plan view of 

bioswale-rain garden system

Asphalt pavement

Sod over backfill 

 material
6 Hydraulic Characteristics of Low-Impact Development Practices in Northeastern Ohio, 2008–2010

Methods

An unheated tipping-bucket rain gage and an air-temperature sensor were installed behind Orange Village Hall, 

approximately 1,400 ft west-northwest of the site. The rain 

gage registers precipitation in 0.01-in. increments that are 

summed by a data logger over intervals of 10 minutes. Precipitation depths and peak intensities for 10-, 30-, 60-, 120-, and 

1,440-minute intervals were determined. Recurrence intervals 

of precipitation at the site were estimated by using precipitation-frequency tables compiled by the National Oceanic and 

Atmospheric Administration (Bonnin and others, 2004). 

The overflow grates on two rain gardens, one north 

(SR1) and one south (SR2) of Sterncrest Drive (fig. 2), were 

instrumented with sensors that measured specific conductance 

and temperature. These sensors were used to determine the 

occurrence and duration of overflows; however, without additional instrumentation, the volume of the overflows could 

not be computed. The sensors were connected to a data logger 

adjacent to the rain garden. The data logger queried the sensor 

every minute and recorded the measurement if there was a 

change since the last measurement. Data also were recorded 

every 6 hours to ensure that the data logger was operational 

during periods when sensor readings were unchanging. 

The maximum water levels in the SR1 and SR2 rain 

gardens were recorded with a crest-stage gage—a simple 

instrument that records only the highest water elevation, or 

stage, reached between routine maintenance visits when the 

gage is reset. The datum of the crest-stage gages and the 

elevations of the low points on the overflow grates (points of 

no overflow) were determined by means of differential leveling relative to common local reference points. The crest-stage 

reading was compared to the elevation of the overflow grate 

to verify that overflow did, or did not, occur as indicated by 

the sensor measurements. In no case was an overflow event 

indicated by a crest-stage gage without an overflow event also 

being indicated by a sensor reading. It cannot be said with 

certainty whether the reverse was true because more than one 

overflow event may have occurred between inspections of the 

crest-stage gage.

Data Analysis and Description

The following analysis pertains to the time periods 

April 3, 2008, to October 31, 2008; and March 1 to October 

31 in 2009 and 2010. The design storm for the site is 0.75 in. 

of precipitation, but the associated duration was not specified; therefore, an analysis was done to determine the amount 

of time over which 0.75 in. of precipitation would not cause 

an overflow event. The weather-station data were used to 

determine how many times the total amount of precipitation in 

24-, 48-, 72-, and 96-hour time periods exceeded the 0.75-in. 

design storm (table 1).

There were 15 overflows at the SR1 rain garden, 14 of 

which occurred when the total precipitation exceeded 0.75 in. 

sometime in the previous 96 hours (table 2). The only exception was event 6, when the total precipitation was 0.74 in. 

There were seven overflows at the SR2 rain garden; five of 

the seven events occurred when the precipitation exceeded 

0.75 in. sometime in the previous 96 hours (table 2). The only 

exceptions are two unexplained events (17 and 18, table 2) 

that occurred about 6 hours apart on April 25, 2010. 

Most of the overflow events were the result of precipitation less than a 1-year recurrence interval (tables 2 and 3). 

Exceptions are events 2, 5, 16 and 20. Event 2 at SR1 received 

0.81 in. of precipitation in a 10-minute period, exceeding the 

recurrence interval for a 10-year precipitation event. The same 

storm produced 1.15 in. of precipitation in 1 hour, exceeding the recurrence interval for a 1-year precipitation event. 

Event 5 at SR1 received 0.64 in. of precipitation in 10-minute 

period and 1.06 in. in 1 hour, equivalent to 2-year and 1-year 

precipitation events, respectively. Event 16 at SR2, the site 

received 1.11 in. in 1 hour, equivalent to a 1-year precipitation 

event. Event 20 at SR2 received 0.68 in. of rain in a 10-minute 

period, exceeding the recurrence interval for a 2-year precipitation event (Bonnin and others, 2004).

There is concern that, over time, fine-grained sediments 

will clog the surface of the bioswale and rain garden, resulting in more overflows (Ontario Ministry of the Environment, 

2003). Counting the number of overflow events each year 

could help indicate whether the bioswale/rain garden BMP 

performance is changing; however, such an analysis requires 

that consideration be given to the characteristics of the precipitation events in each year. The average total precipitation 

depth in 2008 and 2009 was similar; however, average total 

precipitation depth decreased in 2010, and the events were 

more intense (fig. 5). Over the 3 years of available data, there 

appears to be a trend of increasing overflow events (table 4); 

however, 3 years of data are insufficient for a trend analysis. 

In 2008 and 2009, a difference in the number of overflows 

between SR1 and SR2 was documented (table 4). A possible 

explanation for this is the difference between the 8-in. drain 

pipe at SR1 and the 15-in. drain pipe at SR2 and (or) the 

variable precipitation characteristics.

Table 1. Precipitation events that exceed 0.75 inch and raingarden overflow events, April–October, 2008–2010, Sterncrest 

Drive site, Cuyahoga County, Ohio.

Total time 

prior to overflow (hours)

Number of 

storms 

>0.75 inch

Overflow 

events

SR1

Overflow 

events

SR2

24 35 9 4

48 38 12 5

72 39 14 5

96 47 14 5
Hydrologic Characteristics at the Sterncrest Drive Site 7

Table 2. Rain garden overflow time, duration, and precipitation-event depths, Sterncrest Drive site, Cuyahoga County, Ohio. 

[Red highlight, 10-year precipitation event; green highlight, 2-year precipitation event; yellow highlight, 1-year precipitation event (based on precipitation 

magnitude and frequency computations by Bonnin and others, 2004)]

Event

Overflow characteristics

Precipitation depth (inches)

Maximum in prior 24 hours Total for time prior to start of overflow 

(hours)

Raingarden 

location

Begin 

date

Duration 

(minutes)

10-

minute 1-hour 3-hour 12-hour 24 48 72 96 

1 SR1 5/3/08 149 0.21 0.44 0.49 0.98 1.00 2.00 2.00 2.04

2 SR1 7/8/08 25 0.81 1.15 1.15 1.15 1.15 1.15 1.15 1.15

3 SR1 10/3/08 116 0.04 0.12 0.25 0.26 0.26 0.72 2.49 3.21

4 SR1 7/1/09 219 0.13 0.25 0.30 0.32 0.37 1.18 1.18 1.22

5 SR1 7/17/09 5 0.64 1.06 1.06 1.07 1.07 1.07 1.07 1.07

6 SR1 8/1/09 157 0.12 0.22 0.35 0.59 0.59 0.59 0.74 0.74

7 SR1 8/10/09 66 0.42 0.74 0.74 0.74 0.74 1.03 1.15 1.15

8 SR1 8/29/09 48 0.30 0.88 0.94 1.46 1.89 1.96 1.99 1.99

9 SR1 4/25/10 69 0.23 0.51 0.51 0.53 1.02 1.02 1.02 1.02

10 SR1 5/17/10 49 0.01 0.05 0.09 0.11 0.11 0.11 0.11 1.13

11 SR1 5/31/10 209 0.39 0.78 0.78 0.89 0.89 0.89 0.89 0.89

12 SR1 6/6/10 161 0.48 0.48 0.74 0.77 0.77 0.92 0.92 0.94

13 SR1 6/28/10 124 0.24 0.44 0.44 0.64 1.08 1.08 1.08 1.08

14 SR1 7/14/10 66 0.01 0.01 0.01 0.02 0.02 0.80 0.80 0.80

15 SR1 9/16/10 7 0.46 0.57 0.57 0.86 0.86 0.86 0.86 0.87

16 SR2 8/10/09 15 0.42 1.11 1.11 1.11 1.11 1.39 1.52 1.52

17 SR2 4/25/10 3 0.05 0.17 0.20 0.29 0.29 0.29 0.29 0.29

18 SR2 4/25/10 52 0.05 0.17 0.37 0.51 0.51 0.51 0.51 0.51

19 SR2 4/26/10 8 0.23 0.52 0.55 0.72 0.88 1.23 1.23 1.23

20 SR2 5/14/10 15 0.68 0.70 0.88 0.88 0.94 0.94 1.58 1.58

21 SR2 6/6/10 12 0.48 0.48 0.74 0.77 0.77 0.92 0.92 0.94

22 SR2 7/14/10 4 0.00 0.00 0.00 0.00 0.00 0.79 0.80 0.80

Table 4. Number of overflow events and precipitation events 

that exceeded the 0.75-inch design storm at Sterncrest Drive 

site, Cuyahoga County, Ohio.

Year

 (Apr.–Oct.)

Overflows,

SR1

Overflows,

SR2

24-hour 

precipitation 

>0.75 inch

2008 3 0 12

2009 5 1 11

2010 7 6 12

Table 3. Precipitation depths that exceed the 1-, 2-, 5-, and 

10-year recurrence intervals for the area including Sterncrest 

Drive site, Cuyahoga County, Ohio. 

[Based on precipitation magnitude and frequency computations by Bonnin 

and others, 2004]

Recurrence 

interval 

(years)

Precipitation depth (inches)

10-minute 1-hour 3-hour 12-hour 24-hour

1 0.50 0.99 1.24 1.75 2.04

2 0.60 1.21 1.51 2.10 2.45

5 0.72 1.53 1.92 2.62 3.05

10 0.81 1.77 2.24 3.06 3.54
8 Hydraulic Characteristics of Low-Impact Development Practices in Northeastern Ohio, 2008–2010

The current dataset shows the variability in the performance of a newly established rain garden BMP. Sometimes 

a slow steady rain over a number of days will eventually 

overwhelm the BMP (overflow event 3). In other situations a 

short, intense storm will cause an overflow (overflow event 2). 

Of the 22 total recorded overflow events, 13 occurred when 

precipitation in the previous 24 hours exceeded the design 

storm (0.75 in.); 7 other events can be linked to precipitation within the previous 96 hours, and, as mentioned previously, 2 unexplained events at the SR2 site occurred 6 hours 

apart. The BMP performed better than expected in that there 

were more precipitation events exceeding the design storm 

of 0.75 in. without causing overflows than events that caused 

an overflow. However, the long-term sustainability in performance of the bioswale/rain garden BMP is unclear.

Hydrologic Characteristics at the 

Washington Street Site

The Washington Street site is a commercial site in 

west-central Geauga County (fig. 1) near the headwaters 

to an unnamed tributary to McFarland Creek (tributary to 

Aurora Branch of the Chagrin River). This was a new commercial construction project in 2008 that followed Leadership 

in Energy and Environmental Design (LEED) principles to 

maximize land use in a sustainable manner. The site has pervious pavers, a rain garden, and a bioretention basin to minimize 

runoff and maintain an aesthetically pleasing look to the site.

Site Description

Stormwater BMPs on the site include a rain garden, an 

8,200-ft2 parking lot made of pervious pavers (with surface 

and subsurface drains), and a detention basin and vegetated 

swale (figs. 6 and 7). The rain garden is 400 ft2 in area 

(20 ft by 20 ft) (fig. 7) and receives runoff from approximately 

one-half (3,400 ft2) of a nearby commercial roof. The rain 

garden is not isolated from the parking-lot subsurface gravel; 

therefore, drainage from the gravel may contain a portion 

of the roof runoff not used or infiltrated in the rain garden. 

Runoff from the other half of the commercial roof drains to a 

detention basin via a vegetated swale. The detention basin also 

receives discharge from the pervious paver subsurface drain, 

an overflow drain from the rain garden, and any overland runoff from the driveway, parking area, and adjacent properties. 

Because the detention basin receives water from sources other 

than the new construction (a preexisting building and some 

flow from neighboring properties), not all inputs required to 

determine a water budget could be measured; therefore, data 

collection and analysis were focused on a water budget for the 

pervious paver-parking lot and the rain garden. 

Figure 5. Annual average duration and depths for precipitation events that exceeded the 0.75-inch design storm at 

Sterncrest Drive site, Cuyahoga County, Ohio.

0

0.2

0.4

0.6

0.8

1.0

1.2

1.4

1.6

1.8

Event total 10-minute 30-minute 1-hour 2-hour 3-hour 6-hour 12-hour 24-hour

Precipitation, in inches

2008

2009

2010

EXPLANATION
Hydrologic Characteristics at the Washington Street Site 

9

Figure 6. Site plan for stormwater best-management practices at Washington Street site, Geauga County, Ohio (modified from engineer drawings provided by Cawrse and Associates, Inc.).

WEATHER STATION

SWALE

BIORETENTIONBASIN

BUILDING

RAIN

GARDEN

EXISTING PARKING

STORM

WATER OUTLET

STRUCTURE

existing stream

Flume

Time domain reflectometry cluster

Downspout

Drain lines and flow direction

Land surface contour, interval 1-ft

Porous pavers

EXPLANATION

Features are proportional butprecise dimensions are unknown

FLUME 3

FLUME 1

FLUME 2

STORM OUTLET PIPE

FROM DOWNSPOUTS

6" PVC INLET

FOR OVERFLOW OUTFLOW TO BIO-RETENTION BASIN

TDR

CLUSTER

B

TDR

CLUSTER

A

4" PERF PVC SUBDRAIN

 PERF PVC SUBDRAIN 4" PERF PVC SUBDRAIN 4"

4" PVC STM

6" PVC STM

6" BLDG STM CONN.

STM.C 0.

STM. C.0.

 STM 6"
10 Hydraulic Characteristics of Low-Impact Development Practices in Northeastern Ohio, 2008–2010

Figure 7. Construction detail for Washington Street site, Geauga County, Ohio. A, Paver parking lot. B, rain garden. 

(Modified from engineer drawings provided by Cawrse and Associates, Inc.)

Methods

Discharge from the pervious-paver subsurface drains 

(flume 3, fig. 6), overland flow from the parking lot (flume 

1, fig. 6), and overflow from the rain garden (flume 2, fig 6 

and 7) were determined by means of prefabricated H-flumes 

(fig. 8). Water levels in the flumes were measured in attached 

external stilling wells by means of pressure transducers connected to data loggers that initiated and stored the water-level 

readings. Water levels, specific conductance, and temperatures 

were measured every minute and, at a minimum, recorded 

every 10 minutes. When the stage exceeded 0.05 ft above no 

flow, any change in water level of more than 0.01 ft also was 

recorded. The corresponding specific conductance and water 

temperature were stored with each coincident water-level 

reading. 

A weather station that included a heated tipping-bucket 

rain gage and an air-temperature sensor was maintained at 

the site. The rain gage registered precipitation in 0.01-in. 

increments, summed by the data logger over intervals of 

10 minutes. Precipitation peak depths and the intensities for 

10-, 30-, 60-, 120-, and 1,440-minute intervals were determined for each precipitation event and compared to recurrence 

intervals determined from the tables in Bonnin and others 

(2004).

During construction of the parking lot, two clusters of 

three time-domain reflectometer (TDR) sensors were permanently installed in the permeable base under the pavers. The 

TDRs determines soil moisture content by measuring the 

permittivity, or dielectric constant, of the soil resulting from 

changes in soil moisture. Sensors in each cluster were installed 

at different depths below the ground surface to facilitate 

Typical Rain Garden Detail

Minimum of 9-in. of 

scarified native material

24 in. of planting mix

6-in. PVC overflow

to bioretention basin

(flows to flume 2)

6-in. PVC storm outlet from downspouts

A

B

Typical Paver Detail

Pavers

2-in. coarse compacted aggregate

Gravel

(vary depth to accommodate grading)

Native Material

2-in. of sand

Drainage pipe to 

bioretention basin

(flume 3)

All aggregate compacted to 70% relative density

Filter fabric
Hydrologic Characteristics at the Washington Street Site 11

Figure 8. Photographs of the flumes at Washington Street site, Geauga County, Ohio. 

Flume 1, A, measures surface flow over the parking lot; flume 2, B, measures any overflow 

from the rain garden, and flume 3, C, measures the flow from the drain line.

B Flume 2

A Flume 1

C Flume 3
12 Hydraulic Characteristics of Low-Impact Development Practices in Northeastern Ohio, 2008–2010

analysis of the depth-dependent wetting characteristics of the 

permeable base material above the subsurface drains. The 

TDRs were controlled by a data logger that computed and 

recorded moisture content every 10 minutes.

The precipitation and flume-flow time-series data were 

analyzed by means of a spreadsheet. Each rainfall-runoff event 

(hereafter referred to simply as an “event”) was evaluated 

independently. For an event to be included in this study, it had 

to meet the following conditions: (1) for onset, a total at least 

0.05 in. of rainfall; and (2) for termination, discharge in the 

flume less than or equal to its pre-precipitation levels.

The beginning and end of the precipitation and runoff 

(discharge from flumes 2 and 3) were determined by first 

visually examining the rainfall hyetograph. For this study, the 

beginning of a precipitation event was defined as the time of 

the first recorded precipitation pulse (indicating the accumulation of 0.01 in. of rainfall). Values such as centroid lag time, 

runoff ratio, and other precipitation- and flume-flow characteristics were then calculated within the spreadsheet to further 

characterize the event.

In order to facilitate the event selection process, certain 

constraints were placed on the data to ensure more consistent 

detection of event start and end times. The flume-flow time 

series was smoothed by use of a moving-average process in 

which the value assigned to a given point in time was the average of the value observed at that time plus N values occurring 

immediately before and after the target value (where N is a 

smoothing factor, chosen by the analyst, based on the amount 

of “noise” in the time series). To help detect runoff start and 

end times, averaging windows (short time periods) were used 

to help prevent noise in the data from triggering false selection of these characteristics. The following definitions describe 

analyst-selectable parameters used for time-series smoothing; 

these parameters ensure consistent detection of event-related 

characteristics:

1. The smoothing factor is the number of data values before 

and after the given data value that are used to calculate 

an average value which is then assigned to the position 

(time) of the given data value. For example, a smoothing factor of 2 would result in the average of five values, 

two preceding the current value, the current value, and 

two following the current value. Smoothing the discharge 

values deemphasizes “noisy” data and allows for more 

consistent selection of event end points. The smoothed 

curve is used only for end point selection; all volume and 

centroid calculations are based on the raw, unsmoothed 

data.

2. The leading-edge window is the number of values that are 

evaluated to determine whether there is an upward trend 

in the data.

3. The percentage of the leading-edge window that needs 

to be rising indicates the beginning of a runoff event. 

For example, if the leading-edge window is 10 and the 

upward trend is set to 80 percent, then the first instance 

where 8 of 10 data values after the beginning of precipitation are increasing relative to their preceding value would 

be set as the beginning end point of the event. 

4. The analysis window is the total number of values after 

the start point that will be used to determine the end point. 

This is used to end the analysis before the beginning of 

the next precipitation event. 

5. The trailing-edge window is the number of preceding 

values that are averaged to check for the end of the runoff 

event. If, for example, the trailing edge window is set to 4, 

then four values preceding the current value are averaged. 

The first such average occurring after the end of precipitation that is less than or equal to the average discharge 

from before the event start time triggers the end of the 

runoff event.

 The following example is presented to illustrate the event 

selection process. In the example precipitation event, 0.86 

in. rain fell over 20.5 hours starting on April 3, 2008 (fig. 9). 

The following values were used to analyze this event:

1. smoothing factor = 8

2. leading-edge window = 5

3. percentage of the leading-edge window = 80 percent

4. analysis window = 1,200

5. trailing-edge window = 4

So, a total of 17 values (8 + 1 + 8 ) were averaged to 

smooth the discharge curve. The beginning of the runoff event 

occurs when 80 percent of five smoothed values are determined to be increasing relative to their immediately preceding 

values. The average of four raw discharge values prior to the 

beginning is determined. After the precipitation stops, the end 

of the runoff event is determined to be the time at which the 

first average of four consecutive raw discharge values is less 

than or equal to the beginning average. Once the start and end 

points are determined, the spreadsheet calculates the centroid 

(center of mass) of the precipitation and runoff, centroid lag 

times, volumes, precipitation characteristics, timing characteristics, and the runoff ratio.

The runoff ratio is defined as the total volume of runoff 

divided by the total volume of rain that fell on the roof and 

parking lot. The runoff ratio characterizes each runoff event 

with a number between 0 and 1. Runoff events with ratios 

closer to 0 indicate that more water was abstracted (not available for runoff) through evapotranspiration (ET), infiltration, 

or other losses than runoff events with ratios closer to 1. For 

the event described in figure 9, the total volume of precipitation on the parking lot and half the roof was computed to be 

834 ft3, and the volume discharge through the flumes was 

478 ft3. The ratio is 0.57, meaning 57 percent of the precipitation that fell on the site entered the detention basin as runoff. 
Hydrologic Characteristics at the Washington Street Site 13

Figure 9. Hydrograph of typical precipitation event at the Washington Street site showing the spreadsheet selections of begin, 

peak, and end of flow, as well as the centroids of flow and precipitation.

Centroid lag time is the time, in minutes, between the 

centroid of precipitation and the centroid of the flume flow 

(runoff). Centroid lag time is a measure of how quickly water 

moves off or through the impervious surfaces and other drainage routes to the discharge points. For the event described in 

figure 9, the centroid of the precipitation event was on April 3, 

2009, at 09:22, and the centroid of the flume flow was on April 

3, 2009, at 13:45, so the centroid lag time was 263 minutes. 

Data Analysis and Description

No runoff was recorded in flume 1, which measures 

surface runoff from the pervious paver parking lot, indicating 

all precipitation that fell on the parking lot either infiltrated 

through the void spaces between the pavers or evaporated. 

Runoff was recorded from flume 2, the rain-garden overflow, 

on three occasions with the largest volume being on August 

10, 2009, when 19.9 ft3 of water moved through the overflow 

in 24 minutes. Flume 2 also recorded overflows on May 14 

and May 18, 2010; these flows were both smaller than that 

measured during the August 2009 overflow. 

Flume 3 recorded runoff from the pervious paver subsurface drains, which included any roof runoff not infiltrated or 

removed by ET in the rain garden. The runoff data from flume 

2 were included with the data from flume 3 to represent the 

total runoff from the site. 

 Only events with complete runoff hydrographs, precipitation, and TDR data were analyzed. A total of 34 out of 42 

precipitation events in 2009 and 36 out of 46 precipitation 

events in 2010 produced sufficient data for analysis. The runoff ratios for 2009 and 2010 (fig. 10) suggest an improvement 

in the performance of the BMP over time. One explanation 

may be the maturation of vegetation in the rain garden promoted more rapid infiltration through a denser root mass (Selbig 

and Balster, 2010). In addition, transpiration in 2010 may have 

been greater because the plants in the rain garden were more 

fully established (fig. 12).

0.10

0.00

0.01

0.02

0.03

0.04

0.05

0.06

0.07

0.08

0.09

0.040

0.000

0.005

0.010

0.015

0.020

0.025

0.030

0.035

4/2/09 12:00 4/3/09 0:00 4/3/09 12:00 4/4/09 0:00 4/4/09 12:00 4/5/09 0:00

Precipitation, in inches

Discharge, in cubic feet per sencond

Smoothed flow Start of flume flow Peak of flume flow

End of flume flow Raw measured flume flow Centroid of flume flow

Precipitation Centroid of precipitation

EXPLANATION
14 Hydraulic Characteristics of Low-Impact Development Practices in Northeastern Ohio, 2008–2010

 The Wilcoxon rank-sum statistic is a nonparametric test 

to compare two datasets, in this case different event characteristics from 2009 and 2010. Figure 11A shows that the 

runoff ratio decreased from 2009 to 2010 (p-value < 0.01), 

indicating that more water is being removed in 2010 than in 

2009 (presumably through ET or infiltration). Figure 11D and 

E show that although precipitation-event depths in 2009 and 

2010 were not statistically different, the intensity of the events 

increased (p-value = 0.02). During the same time, the centroid 

lag decreased (fig. 11C; p-value = 0.03), indicating that the 

water that moved through the BMP did so faster, possibly in 

response to the increased intensity (fig. 11E) and shorter duration (fig. 11F) of the precipitation events. Another possibility 

could be the development of preferential flow paths beneath 

the pavers. 

Some of the decrease in runoff in 2010 may be attributable to increased evaporation due to higher maximum daily air 

temperature (fig. 11B). The warmer weather could have heated 

the pavers and base material more in 2010 than in 2009, 

thereby increasing evaporation. Another possible explanation 

for the lower runoff ratios in 2010 could be the maturation 

and increased growth of the plants in the rain garden (fig. 12), 

with roots penetrating the clay rich substrate and increasing 

infiltration (Selbig and Balster, 2010). 

Figure 10. Runoff ratio for the pervious-paver/rain-garden BMP at Washington Street site, Geauga County, Ohio, 

April through October 2009 and 2010.

The TDRs were installed in gravel, which does not 

make sufficient contact with the sensors to permit an accurate 

measurement of moisture content. Therefore, soil moisture 

conditions for each TDR sensor were analyzed relative to 

each sensor’s annual mean value. The depth from top of the 

pavers to the TDRs are listed in table 5.

1.00

0.00

0.10

0.20

0.30

0.40

0.50

0.60

0.70

0.80

0.90

1/1/09 4/2/09 7/2/09 10/1/09 12/31/09 4/2/10 7/2/10 10/1/10 12/31/10

Runoff ratio, runoff volume/rain volume

Table 5. Depth of time-domain reflectometers at 

Washington Street site, Geauga County, Ohio.

Location 

on figure 6

Sensor 

number

Depth below top of 

pavers (feet)

Cluster A 1 2.8

Cluster A 2 1.5

Cluster A 3 1.2

Cluster B 4 2.7

Cluster B 5 1.7

Cluster B 6 1.5
Hydrologic Characteristics at the Washington Street Site 15

Figure 11. Boxplots of climatological and flow characteristics, Washington Street site, Geauga County, Ohio, 2009 and 2010. 

A, Runoff ratio. B, Maximum daily air temperature (degrees Celsius). C, Centroid lag. D, Precipitation event size. E, Precipitation 

intensity. F, Precipitation duration.

x

33 36

2009

2010

20 80 60 40 0

Precipitation duration, in hours

0.0 0.4 0.8 1.0 0.2 0.6

Runoff ratio, 

volume runoff / volume precipitation

0 10 20 30 40

Maximum air temperature, in degrees Centigrade

2009

2010

2009

2010

0.0 0.5 1.0 1.5 2.0

2009

2010

Precipitation event, in inches

2009

2010

0.0 0.4 0.8 1.4 0.2 0.6

Precipitation intensituy, in inches per hour

1.2 1.0

2009

2010

400 800 1,200

Centroid lag time, in minutes

33 36

x

x

o

o

33 36

33 36

x

o

o

o

x

x

x

33 36

x

33 36

200 600 1,000 0

30 Number of values

EXPLANATION 

x

x

o

o

Upper adjacent

75th percentile

Median

25th percentile

Lower adjacent

Lower outside

Lower detached

Upper detached

Upper outside

A

D E

B C

F Interquartile

range
16 Hydraulic Characteristics of Low-Impact Development Practices in Northeastern Ohio, 2008–2010

Figure 12. Photographs of Washington Street rain garden showing weather station and plant 

growth from October 2008 to August 2010. (Photographs by Cawrse and Associates, Inc., employees.)

Weather station

Weather station

B August, 2008

A October, 2008

C August, 2010
Hydrologic Characteristics at the Washington Street Site 17

Figure 13. Time-domain reflectometer relative soil moisture for one month, cluster A, Washington Street site, Geauga County, Ohio. 

The graph shows that the BMP does not have time to return to a steady state before the next precipitation event.

An analysis similar to that done for flume-flow was 

done for TDRs 1 through 6. Time between the centroid of the 

precipitation to the centroid of the soil-moisture curve was not 

used because the soil-moisture curve sometimes did not return 

to pre-event levels before the next precipitation event (fig. 13). 

Therefore, in the TDR analysis, the time from initial precipitation to the time the sensor indicates the presence of the wetting 

front is defined as the SC lag (or in the case of the flume the 

SC lag is the time from initial precipitation to start of flow). 

The SC lag times for the TDRs in 2010 are noticeably 

shorter than the those in 2009 (fig. 14). Part of this quicker 

response time could be attributed to the tendency toward more 

intense precipitation events in 2010 as compared to 2009 

(fig.11E) and/or the possible development of preferential flow 

paths. Preferential flow paths can develop over time as water 

movement through the BMP forms channels or as desiccation 

or settling cause fractures. With additional data, provided that 

the storm intensities and durations are similar to those in 2009 

or 2010, it may be possible to determine whether the quicker 

response is due to the precipitation intensity or the preferential 

flow paths.

Some additional evidence for the development of preferential flow paths can be seen by comparing the SC lag times 

in 2009 and 2010 with the runoff. The median SC lag time 

for runoff is much smaller than for the TDRs (fig. 14); this 

indicates that some water reaches the subsurface drains before 

the wetting front reaches the TDRs. This result is unexpected 

because the drains are deeper than the lowest TDR.

The BMPs at Washington Street were designed to reduce 

and delay runoff. The 2 years of data show that the median 

runoff ratio decreased from 2009 to 2010. The centroid lag 

times decreased in 2010, most likely in response to more 

intense, shorter duration precipitation events. Additional data 

could help quantify the relationship between meteorological 

variables and BMP efficiency.

0

0.1

0.2

0.3

0.4

0.5

0.6

8

-2

-1

0

1

2

3

4

5

6

7

9/1/10 9/6/10 9/11/10 9/16/10 9/21/10 9/26/10 10/1/10

Precipitation, in inches

Soil moisture content realtive to annual mean, in percent

TDR3 (1.3 ft)

TDR2 (1.5 ft)

TDR1 (2.8 ft)

Precipitation

EXPLANATION
18 Hydraulic Characteristics of Low-Impact Development Practices in Northeastern Ohio, 2008–2010

Figure 14. Boxplots of specific-conductance lag times for six soil-moisture sensors and runoff, 2009 and 2010, Washington Street site, Geauga County, Ohio.

o

xx

oo

xx o

x

xxxx o

o

xx

xx

xxx

x x

x

ooo

x

oo

x

sensor 1, 2009

sensor 1, 2010

sensor 2, 2009

sensor 2, 2010

sensor 3, 2009

sensor 3, 2010

sensor 4, 2009

sensor 4, 2010

sensor 5, 2009

sensor 5, 2010

sensor 6, 2009

sensor 6, 2010

runoff, 2009

runoff, 2010

2,000 1,500 1,000 500 0 35 24 35 25 35 26 35 25 35 24 35 23 33 36

Lag times, in minutes 30 Number of values

EXPLANATION 

o

x

x

o

Upper detachedUpper outsideUpper adjacent

75th percentileMedian25th percentileLower adjacentLower outsideLower detached

Interquartile

range
References Cited 19

Summary and Conclusions

Stormwater BMPs are intended to reduce the impact of 

additional runoff related to development. Low-impact development is a best-management-practice approach to manage 

stormwater as near to its source as possible by minimizing 

impervious surfaces and promoting the natural movement 

of water. To document the hydraulic characteristics of some 

of these designs, two newly constructed sites in northeastern 

Ohio were studied. One site consisted of a roadside raingarden/bioswale combination to reduce flooding; the other 

site consisted of a rain-garden/pervious-paver combination to 

reduce and delay runoff from a newly constructed commercial 

building and parking lot.

The roadside BMP along Sterncrest Drive involved 

the replacement of about 1,400 ft of existing ditches with a 

bioswale consisting of a grassed swale interspersed with rain 

garden/overflow structures. The site was monitored in 2008, 

2009, and 2010. Numerous precipitation events exceeding 

the 0.75-in. design storm were retained and infiltrated by the 

swales and rain gardens. The BMP performed better than 

expected, but the sustainability of the long-term performance 

is unclear. 

The Washington Street site consisted of a rain garden 

that received runoff from 3,400 ft2

 of commercial roof and an 

8,200 ft2 parking lot made of pervious pavers. Data from 2009 

and 2010 have shown a marked improvement in the reduction of runoff in just 1 year. Median runoff volume decreased 

in 2010 relative to 2009; however, the median runoff specific 

conductance lag time also decreased.

The results of this study indicate that low-impact development can be a useful approach to managing stormwater at 

these sites in northern Ohio. It should be noted, however, that 

this study did not assess winter months, so the analysis is not 

transferable to winter conditions.

Acknowledgments

The authors would like to thank Cawrse and Associates, Inc., and Orange Village for allowing the USGS access 

to monitor the BMPs, and Rachel Webb (formerly with the 

Chagrin River Watershed Partners) for many over-the-phone 

troubleshooting sessions that saved us countless hours on the 

road traveling to the site.

References Cited

Bonnin, G.M., Martin, D., Lin, B., Parzybok, T., Yekta, M., 

and Riley, D., 2004, Precipitation-frequency atlas of the 

United States: Silver Spring, Md., National Oceanic and 

Atmospheric Administration, National Weather Service, 

NOAA Atlas 14, v. 2, ver. 3, accessed August 5, 2009, at 

http://www.nws.noaa.gov/oh/hdsc/currentpf.htm.

Geauga County Planning Commission, 2005, Economic analysis plan for Geauga County, Ohio, accessed March 1, 2011 

at http://www.co.geauga.oh.us/Departments/Planning_

Commission/Main.aspx.

Midwestern Regional Climate Center, 2010, Station 331657 

Cleveland Hopkins, and station 331458 Chardon, accessed 

on December 30, 2010, at http://mrcc.isws.illinois.edu/

climate_midwest/mwclimate_data_summaries.htm.

Musgrave, D.K, and Holloran, D.M, 1980, Soil survey of 

Cuyahoga County, Ohio: U.S. Deptartment of Agriculture, 

Soil Conservation Service, 157 p., 64 sheets.

Ontario Ministry of the Environment, 2003, Stormwater 

management planning and design manual: Section 4.1.1, 

accessed June 1, 2011, at http://www.ene.gov.on.ca/

environment/en/resources/index.htm.

Selbig, W.R., and Balster, Nicholas, 2010, Evaluation of turfgrass and prairie-vegetated rain gardens in a clay and sand 

soil, Madison, Wisconsin, water years 2004–08: U.S. Geological Survey Scientific Investigations Report 2010–5077, 

72 p.

Williams, N.L., and McCleary, F.E., 1982, Soil survey of 

Geauga County, Ohio: U.S. Department of Agriculture, Soil 

Conservation Service, 169 p., 56 sheets.


Darner and Dumouchelle—Hydraulic Characteristics of Low-Impact Development Practices in Northeastern Ohio, 2008–2010—Scientific Investigations Report 2011–5165