What is Urban Stormwater?
When it rains, or the snow melts in Utah, where do you think all the water goes? Does it soak into the ground? Does it sit in puddles until it evaporates? The water actually does both of these things. Some of the water will also flow over the land surface, heading downhill to the nearest stream or ditch. We call this stormwater runoff.
In cities and towns, the water can't soak through the pavement, rooftops, and concrete, like it can into the soil. This means that there's more stormwater runoff in cities and than in forests and fields. The water flows off impervious surfaces such as driveways, rooftops, sidewalks, and parking lots, and usually flows straight into a storm drain. These grates in the road connect to pipes which carry the water directly to your local stream or lake.
The percent of impervious surface in a small watershed is a good indicator of potential water quality impacts in streams draining that area. The streams in watersheds with more than 10% impervious cover will probably have impacted water quality. The more impervious cover, the greater the risk.
Identifying Risks to Water Quality in Urban Areas
using Impervious Surface Analysis
(click here for entire pdf version of publication)
Impervious surface areas cover much of urban landscapes. These surfaces restrict the ability of storm water to soak into the soil. Instead, water runs off directly into our streams or into our storm drains which then discharge into streams. This runoff contains a heavy pollutant load which can lead to water quality impacts.
Percent impervious area - a new planning tool:
The percent of impervious surface in a small watershed is a good indicator of potential water quality impacts in streams draining that area. The streams in watersheds with more than 10% impervious cover will probably have impacted water quality. The more the impervious cover the greater the risk.
Maps can really tell the story:
GIS mapping technology is available to most towns today. Maps can be made which show the risk to water quality from different parts of a city. This helps direct attention to areas at risk and gives us new insights into planning decisions.
What we can do:
The maps indicate the risk to water quality, but there are many actions that the city can take to reduce this risk.
- Reduce the impervious area associated with roads and parking (60% of the impervious surface in an urban area is transportation associated).
- Identify and protect critical habitat areas, including wetlands, sensitive waters and areas with highly erosive soils.
- Manage development and redevelopment to reduce runoff and protect water quality through better design and best management practices.
- Encourage landscaping using plants with low water needs.
- Educate the public on how they can reduce water pollution from yards, automobiles and pets.
- Encourage open space development and the use of buffer strips.
Community Actions to Reduce Water Quality
Impacts of Stormwater
(click here for pdf version of entire publication)
Ensure effectiveness of your town commissions:
- Know the roles and responsibilities of local officials and commissions.
- Establish a water resources advisory committee to coordinate communication across commissions.
- Establish a conservation commission separate from inland wetlands (if now combined) to facilitate conservation planning.
- Stay informed about key issues by attending workshops and reading educational materials.
Protect priority natural resources commissions:
- Initiate comprehensive planning.
- Conduct a natural resource inventory.
- Prioritize areas for protection.
- Avoid development in sensitive watershed and aquifer areas.
- Develop plans of action, such as a watershed management plan & an open space plan.
- Revise zoning and subdivision regulations (land use controls) to support town plans
- Review town maintenance procedures.
Incorporate design objectives into your regulations that will protect water quality, and look for them in site plan review commissions:
- Retain the natural landscape (vegetation, contours and natural drainage).
- Reduce impervious surfaces: parking roads, sidewalks, driveways, compacted earth
- Emphasize on-site drainage for treated stormwater
- Encourage riparian buffers to protect wetlands and waterways.
- Require proper septic system placement, design and maintenance.
- Require that plans include stormwater management plans
- Keep watershed maps on hand for determining where proposed developments are within your watersheds.
Encourage or require, and enforce use of a variety of best management practices (BMPs):
- Require stormwater best management practices and ensure their maintenance.
- Encourage/require management plans for parks, golf courses & agricultural operations.
- Enforce erosion control for logging, construction and agricultural activities
- Conduct regular street and storm drain cleaning
- Support and enforce maintenance, such as vacuuming pavement and cleaning out stormwater control structures.
- Consider pet waste disposal ordinances.
- Educate and support your citizens on pollution prevention.
Support restoration efforts and encourage redevelopment:
- Support restoration efforts where feasible.
- Strive to “infill” in developed areas rather than increase sprawl.
- Improve existing site design when opportunities arise.
- Require BMP retrofits during redevelopment.
And more. . .
- Help organize special events, such as lake days and stream outings.
- Sponsor workshops for target audiences such as developers, contractors and public works departments.
- Support school programs that focus on natural resources.
- Support studies of natural resources to learn more about your town’s unique resources.