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Rainy Days Part II: From sprinkles to storms, and beyond | Guest Column
In the first article of our stormwater series, we discussed flooding issues around the county and the technical and financial assistance that is available to county residents. This week, in our second article in the series, we will address unwanted puddles and ponds on your property.
By Ed Hale, manager
SJ County Public Works Stormwater Utility
Most of us don’t think about managing stormwater until we need to. Have you experienced flooding or ponding on your property? If so, help is available if you need it.
Stormwater is a resource that supports many aspects of our lives and environment. Good stormwater management directs stormwater to uses that are beneficial, like aquifer recharge and maintaining stream flow while controlling the negative impacts such as flooding and contamination.
Many of the calls received at Public Works are related to water-ponding in an area where it is neither desired nor intended. To manage this water and redirect it to beneficial uses we need to think about where it came from and how to get it back where it belongs.
When we develop our property we typically remove some vegetation, trees and brush, and add structures like homes and driveways.
Some of the things that happen when developing our property include: removal of vegetation increases the amount of water runoff that needs to be managed; soil becomes less permeable without the actively growing root systems, so less water soaks into the ground; the house, driveway, and other structures keep more water from seeping into the ground so that water now has to be managed as runoff; some of our landscaping, like lawns, result in less permeable surfaces than the vegetation that was removed.
Our property likely absorbed rainwater well before development. After development, however, there is usually more water to manage because there are fewer permeable areas to put the extra water and some of those areas are not as permeable as they used to be. The result is ponded water; a misplaced resource.
So how can we deal with this?
We need to get the water where it needs to go. In most cases, providing a method for the water to seep into the ground is a good option. All soils are permeable to some degree, sand more so than clay. Getting the water to seep into sandy soils is fairly easy.
What if you have clay soils? Infiltration is still a good option but you will need to add the water to a larger area to get the same amount of water to seep into the ground. Infiltration can also be enhanced by cultivating specific types of plants that have active roots systems in the seepage area. The soils themselves can also be modified to improve infiltration.
Another approach is to reduce the concentrated flow of runoff on the property. If all the runoff from a property flows into a single pipe it can create a lot of force. With all that force it has more of a tendency to runoff rather than sink in.
This can be addressed by either keeping the water from concentrating in the first place, or by building a small structure to spread the water out after in is concentrated. You may have noticed that some roofs have gutters that collect all the water that falls on the roof and concentrate it in the downspout. The force of the water coming off the roof can then erode the ground and has reduced opportunity to seep into the ground.
Concentrated sources like this can be slowed down and spread over a larger area, thus allowing more infiltration. In some cases the water is simply allowed to drip off the edge of the roof, rather than being collected in gutters. This eliminates the concentrated discharge of the downspout and allows for infiltration into the ground over a larger area.
Our properties have a lot of similarities and differences. For that reason it is best to consult an expert to determine which approach is best for your property.
Not all of the approaches described above are appropriate for all properties. Technical assistance is available from the Surface and Stormwater Assistance Program (SSWAP), at no cost, to help you consider ways to improve the stormwater management on your property.
Contact a member of the SSWAP team at: San Juan County Public Works, Ed Hale, 370-0500, http://sanjuanco.com/publicworks/stormwater.aspx
—Town of Friday Harbor Public Works, Wayne Haefele, 378-2154, http://www.fridayharbor.org/whom%20to%20call/Maint.htm
—San Juan Islands Conservation District, Linda Lyshall, 378-6621, or visit http://sanjuanislandscd.org/water-2/lid-bmp/
(Next up: “Got Muddy Pastures? We Can Help. Managing Stormwater on Agricultural Land”)