Low Impact Development
Though originally formed for flood management in 1959, Coon Creek Watershed District incorporated water quality protection issues into its Mission Statement in 1990:
"Managing groundwater and the surface water drainage system to:
- Prevent property damage
- Maintain hydrologic balance
- Protect water quality for the safety and enjoyment of citizens and the preservation and enhancement of wildlife."
Coon Creek Watershed District Tools
If you think about what's in your toolbox, you are probably confident that you have the right tool for the job at hand. And, if you need a tool for a different job or a better tool is available, you can add another tool to your toolbox. It pays in economy of time, safety, and effort to have the right tool for the job.
Similarly, when it comes to water resources, Coon Creek Watershed District (CCWD) uses planning as one tool for anticipating changes in water quality. One example is the Water Quality Plan discussed in another article Planning on Clean Water. The Water Quality Plan showed that many water quality tools CCWD is currently using are adequate for predicted trends.
Low Impact Development Purpose
In the future, changes are coming in how we look at the design of development in order to minimize impact on the landscape, including water quality. Low Impact Development (LID) is a design process that is being added to the management ‘toolbox' at watershed districts.
The goal of LID is to mimic the predevelopment landscape processes of a site after its development. This includes water resource issues such as nutrient flow, groundwater recharge, and site hydrology.
For example, if the hydrology of a site is unchanged, the site would probably not produce stormwater runoff, now regarded as a major pollutant of our waters. (Stormwater is the water runoff from land, usually after rainfall or snowmelt.) Runoff comes primarily from impervious surfaces that are features of development such as:
Developing Without Impervious Surfaces
One method of developing without impervious surfaces is to use Best Management Practices (BMPs) that infiltrate, filter, store, evaporate, or detain runoff at its source. That is, 'keeping the rain where it drops.'
Stormwater is handled through smaller, cost-effective landscape features at the lot site. Many factors must be considered such as soil permeability, depth of water table, and slope. Examples are grass swales, rain gardens, green roofs, and pervious pavements.
Low Impact Development may not completely replace the need for conventional stormwater practices like piping, ponding, channelization, or other traditional engineering methods used to divert stormwater from the lot to a distant location.
Maintenance issues can also be more complicated than for conventional stormwater methods because they are located on private property where changeover of homeownership may affect upkeep (replacement of dead or diseased vegetation, re-mulching as needed, periodic mowing and removal of sediments, or annual high-powered vacuuming of pervious pavements to remove sediments from porous areas.)
Another Low Impact Development tool is conservation design. This is where development is located and designed according to the topography of the land while preserving sensitive and prized community resources. It may result in neighborhoods of partial-acreage lots in order to reduce the amount of road and driveway surface, and thereby result in more open space.
In fact, LID practices can result in more and better planned development that has minimal impact on water, and land, resources while often providing better quality of life features. There's nothing like having the right tool for the job. For more information, contact CCWD at 763-755-0975 or by email.
Sources for this material are:
- Anoka Conservation District
- Coon Creek Watershed District
- Environmental Protection Agency
- Minnesota Pollution Control Agency