What is impervious surface mapping?

What is an impervious surface?

To better define what impervious surface mapping is, it is best to understand what an impervious surface is.

All land cover can be classified as either pervious or impervious. Pervious surfaces refer to permeable land surfaces that allow water to percolate into the ground. Impervious surfaces refer to land cover that is solid. Pervious surfaces can be thought of as natural ground cover: grass, trees, etc. Impervious surfaces can be thought of as a built environment: buildings, concrete, etc. Impervious surfaces can lead to water runoff, which can create hazards like flooding.

What are different types of impervious surfaces?

Impervious surfaces are usually found in the built environment; however, they can be found in the natural environment as well – such as nonporous rocks.

Types of impervious surfaces include:

• Buildings
• Bridges
• Driveways
• Highways
• Parking lots
• Paved surfaces
• Roads
• Roofs
• Sidewalks
• Swimming pools

Although the above is labeled as impervious surfaces, advancements in technology have allowed for the construction and use of permeable surfaces for things like roads, parking lots and sports complexes. Permeable pavement, for example, allows stormwater collection to reduce the amount of runoff.

Stormwater management involves proper mapping of surfaces. All types of land have a unique interaction with rainfall. This is where impervious surface mapping comes in.

What is impervious surface mapping?

Impervious surface mapping is a geospatial rendering of land cover on Earth’s surface that does not absorb water.

Different types of land cover can be broken down into pervious and impervious surfaces to assist with stormwater management. Stormwater mapping uses a Geographic Information System (GIS) to understand the impact of water from rain and snow. The maps are used to determine runoff or overflow risk.

Pervious and impervious surfaces can be mapped in conjunction with utility and sewer systems to provide insight into where runoff or overflow will occur. By utilizing these tools, stormwater systems can be better designed with more informed decisions.

Impervious surface mapping also allows utilities to better manage fees. Using data gathered, municipalities can calculate fees more accurately. Impervious surface mapping can also be used for flood control, emergency management and environmental monitoring.

What is impervious surface mapping used for?

Impervious surface mapping can be used for the following:

• Stormwater utility fees (SUFs)
• Flood control
• Emergency management
• Environmental monitoring
• Best Management Practices
• Pollution removal

How is impervious surface mapping done?

There are multiple ways to collect data for impervious surface mapping. When carrying out global mapping of impervious surfaces over large areas, remote sensing techniques are one of the most accurate.

Techniques used to capture data for impervious surfaces include:

• Optical imagery: Captures surface reflectance
• Synthetic-aperture radar (SAR): Structure and properties of materials
• Nighttime light imagery (NTL): Detect intensity of human activity

When these techniques are combined with geospatial analysis, the imagery can be analyzed, extracted and mapped into an impervious surface map.

How do you find impervious surface area?

According to the Vermont Department of Environmental Conservation, impervious surface areas include all hard top manmade surfaces in a given parcel. To find the total impervious surface area in a given parcel you must calculate the total area of impervious surfaces, add them together, then divide their total area by the area of the parcel.

Areas to measure include:

• Structures: Houses, decks, sheds, patios and large retaining walls
• Paved surfaces: Paved and unpaved driveways, parking areas and tennis courts
• Other compacted, non-vegetated areas