Impervious SurfacesImpervious Surfaces

By: Carl Nielsen, Alex By: Carl Nielsen, Alex MacLean, Jessie Kerr, Danielle MacLean, Jessie Kerr, Danielle

Duffy, & Kayleigh HurshDuffy, & Kayleigh Hursh

What They Are?What They Are?

Impervious surfaces are mainly constructed Impervious surfaces are mainly constructed surfaces - rooftops, sidewalks, roads, and surfaces - rooftops, sidewalks, roads, and parking lots - covered by impenetrable materials parking lots - covered by impenetrable materials such as asphalt, concrete, brick, and stone. such as asphalt, concrete, brick, and stone. These materials seal surfaces, repel water and These materials seal surfaces, repel water and prevent precipitation and melt water from prevent precipitation and melt water from infiltrating soils. Soils compacted by urban infiltrating soils. Soils compacted by urban development are also highly impervious. development are also highly impervious.

Materials like cement, asphalt, roofing, and Materials like cement, asphalt, roofing, and compacted soil prevent percolation of runoff into compacted soil prevent percolation of runoff into the ground. The amount of impervious surface the ground. The amount of impervious surface grows with increasing urbanization.grows with increasing urbanization.

General InformationGeneral Information

Water, the universal solvent, picks up pollutants Water, the universal solvent, picks up pollutants as it moves across the land's surface, including as it moves across the land's surface, including fertilizers, pesticides, automobile emissions and fertilizers, pesticides, automobile emissions and other human byproducts. Soil particles, other human byproducts. Soil particles, dislodged by the impact from raindrops hitting dislodged by the impact from raindrops hitting the ground and from sites cleared of vegetation, the ground and from sites cleared of vegetation, are carried to waterways with the moving storm are carried to waterways with the moving storm water. This increases the transfer of pollutants to water. This increases the transfer of pollutants to waterways and moves fertile soils from the land waterways and moves fertile soils from the land to creeks, rivers and bays. to creeks, rivers and bays.

Land Use Impervious Cover %

Forest 1%    

Urban/Suburban Open Land 3%    

Low Density Residential (0.5 units/acre)  12%    

Low Density Residential (1 units/acre) 20%    

Medium Density Residential (2 units/acre) 25%    

Medium Density Residential (3 units/acre) 30%    

Medium Density Residential (4 units/acre) 38%    

High Density Residential (5-7 units/acre) 40%    

Multifamily Townhouse (>7 units per acre) 65%    

Commercial 85%    

Parking – Unpaved 90%    

Roads/Paved Parking 100%  

What to expect when just 10% of a What to expect when just 10% of a watershed is covered with watershed is covered with

impervious surfaces: impervious surfaces: Increased pollutantsIncreased pollutants Increased erosion, leading to loss of trees Increased erosion, leading to loss of trees

and vegetation along the banks (at 8% to and vegetation along the banks (at 8% to 10% impervious surface coverage, 10% impervious surface coverage, streams double in the size of the bed due streams double in the size of the bed due to the increased volume)to the increased volume)

The temperature of the stream can The temperature of the stream can increase which can badly effect many increase which can badly effect many biological processes.biological processes.

Continued:Continued:

Decreased woody debris, a crucial habitat Decreased woody debris, a crucial habitat element for aquatic insects.element for aquatic insects.

Decrease in substrate quality.Decrease in substrate quality. Decrease in insect and fish diversity. At Decrease in insect and fish diversity. At

12% imperviousness, trout and other 12% imperviousness, trout and other sensitive species can no longer survive in sensitive species can no longer survive in the stream. the stream.

Local DataLocal Data

While studying Mill Creek we observed While studying Mill Creek we observed that the water was murky. This could be a that the water was murky. This could be a direct affect of impervious surfaces located direct affect of impervious surfaces located around Mill Creek. The surfaces allow around Mill Creek. The surfaces allow particles to run into the stream causing the particles to run into the stream causing the water to become dark and turbid.water to become dark and turbid.

Data Continued:Data Continued:

Also while collecting data at Mill Creek we Also while collecting data at Mill Creek we noticed that the banks of the creek were very noticed that the banks of the creek were very eroded which could have been caused by eroded which could have been caused by impervious surfaces. When impervious surfaces impervious surfaces. When impervious surfaces are in abundance the run off water flow is very are in abundance the run off water flow is very fast and powerful which can erode the banks of fast and powerful which can erode the banks of the creek.the creek.

High alkalinity in Musselman water data means High alkalinity in Musselman water data means that impervious surfaces could be causing runoff that impervious surfaces could be causing runoff with lots of local minerals to flow into the water.with lots of local minerals to flow into the water.

Interesting FactsInteresting Facts

When it rains, about 5% of the rain water When it rains, about 5% of the rain water runs off wooded areas and about 95% of runs off wooded areas and about 95% of the rain water runs off a parking lot. This the rain water runs off a parking lot. This all happens during only a mere one inch all happens during only a mere one inch storm.storm.

1,361 gallons of water runs off a one-acre 1,361 gallons of water runs off a one-acre wooded area while 25,800 gallons of water wooded area while 25,800 gallons of water runs off a one-acre parking lot.runs off a one-acre parking lot.

Photo ExamplesPhoto Examples

County InfoCounty Info

County County Population Housing Units Area(sq. mi.)

Jefferson County WV 42190 17623 209.533943

Berkeley County WV 75905 32913 321.139069

Satellite Map of Mill Creek AreaSatellite Map of Mill Creek Area

Aggregate GradationAggregate Gradation

Aggregate is defined as a collective term Aggregate is defined as a collective term for sand, gravel, and crushed minerals.for sand, gravel, and crushed minerals.

When aggregate is mixed with asphalt as When aggregate is mixed with asphalt as a median, it can be used to create a a median, it can be used to create a slightly more porous road or surface.slightly more porous road or surface.

This mix allows water to infiltrate at a This mix allows water to infiltrate at a much great rate than existing dirt roads.much great rate than existing dirt roads.

It allows excess runoff move to its edges It allows excess runoff move to its edges and into existing drainage systems.and into existing drainage systems.

Continued:Continued:

The cleaner than dirt surface makes runoff The cleaner than dirt surface makes runoff water less turbid.water less turbid.

Though it is not recommended for high Though it is not recommended for high traffic areas this type off rode would be traffic areas this type off rode would be very beneficial to small back roads that are very beneficial to small back roads that are normally around rivers, and streams. normally around rivers, and streams.

Cost of Aggregate GradationCost of Aggregate Gradation

A regular road is about $5.04 per square meter. A regular road is about $5.04 per square meter. Aggregate Gradation costs about $15-$30.Aggregate Gradation costs about $15-$30. Though this type of road may be almost three to Though this type of road may be almost three to

six times more expensive then the cost of a six times more expensive then the cost of a regular road, in the end we believe the benefits regular road, in the end we believe the benefits will be far more valuable. Having a healthy will be far more valuable. Having a healthy watershed could bring the cost of having to filter watershed could bring the cost of having to filter or clean water down immensely. or clean water down immensely.

ConclusionsConclusions Our conclusions are very simple, but very important.Our conclusions are very simple, but very important. Impervious surfaces have a huge affect on Impervious surfaces have a huge affect on

watershed quality. They can be the cause of watershed quality. They can be the cause of increases pollutants and bed erosion. With such increases pollutants and bed erosion. With such things going on the population of the streams or things going on the population of the streams or rivers can decrease. With these pollutants in the rivers can decrease. With these pollutants in the stream we are also costing ourselves more money. stream we are also costing ourselves more money. We have to spend extra money to purify the water We have to spend extra money to purify the water we like to collect from our watershed for the running we like to collect from our watershed for the running water we use in our homes and the drinking water water we use in our homes and the drinking water we buy. By cleaning our watershed we can save we buy. By cleaning our watershed we can save money and creatures alike.money and creatures alike.

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"Impervious Surfaces in the Chesapeake Bay Watershed - The Woods Hole Research Center." The Woods Hole Research Center - Home Page. Web. 13 Apr. 2010. <http://www.whrc.org/midatlantic/mapping_land_cover/products/impervious_surfaces.htm>.

"Land Development - Maps - Chesapeake Bay Program." Chesapeake Bay Program - A Watershed Partnership. Web. 13 Apr. 2010. <http://www.chesapeakebay.net/maps.aspx?menuitem=15788>.

"Land Development - Photos - Chesapeake Bay Program." Chesapeake Bay Program - A Watershed Partnership. Web. 10 Apr. 2010. <http://www.chesapeakebay.net/photos.aspx?menuitem=15786>.

"Mill Creek West Virginia." Google Maps. Web. 12 Apr. 2010. <http://maps.google.com/maps?q=mill%20creek%20west%20virginia&rls=com.microsoft:en-us&oe=UTF-8&startIndex=&startPage=1&safe=active&um=1&ie=UTF-8&sa=N&hl=en&tab=wl>.

Bibliography Continued:Bibliography Continued:

"Statewide Indicators." Maryland Department of Natural Resources. Web. 13 Apr. 2010. <http://www.dnr.state.md.us/watersheds/surf/indic/md/md_pctimp_indmap.html>.

"Stormwater and Streams." Prince William Conservation Alliance. Web. 12 Apr. 2010. <http://www.pwconserve.org/issues/watersheds/stormwater/index.html>.

"What Is an Impervious Surface?" Chesapeake Bay and Mid-Atlantic from Space. Web. 13 Apr. 2010. <http://chesapeake.towson.edu/landscape/impervious/what_imp.asp>.