You may be looking to move water safely from one place to another on your property to alleviate ponding. If you have compacted areas that don’t drain well or your groundwater is high, you may be able to safely convey water across your landscape with these techniques to a place where stormwater can infiltrate.
In the strategies outlined below, conveyance of water occurs via a channel with a gentle downhill grade allowing water to move by gravity and in some cases remove contaminants and improve water quality.
Before you consider routing or rerouting water, you will want to consider the following to ensure you are not creating further problems:
- The volume of water you want to move
- Peak flow rate
- Types of contaminants that might be present in the stormwater
- Adjacent land uses
- Soil types
- Where the water is discharging
Here you will learn the basics about two kinds of conveyance systems. Click an item below to jump to a topic, or scroll down to view them all.
Refer to the WSU Fact Sheet: Options for Managing Surface Water Drainage to learn more.
A bioinfiltration swale is a heavily vegetated open channel that moves water slowly. It is specially engineered to primarily convey stormwater and secondarily to achieve some infiltration and pollutant removal. The grass-like plants used in a bioswale help filter out oils, sediment, and other roadway contaminants, by transporting them from impervious surfaces such as roads, driveways, and parking lots. Water is moved along the swale more slowly than a conventional drainage ditch, allowing water to filter through the plants and infiltrate into compost-amended soils below.
See the Fact Sheet Bioinfiltration Swales for more information.
A drainage ditch is an open channel that moves water quickly from one place to another. It provides little to no water quality treatment; however, it can be helpful in moving water to or from an area where treatment occurs.
Comparison of conveyance options
|Features||Bioinfiltration Swale||Drainage Ditch|
|Purpose||Moving water slowly from one area to another, treating it along the way, improving water quality, and reducing flooding.||Removing water quickly from one area to another to reduce flooding.|
|Design||* Flat bottom sloping at a slight gradient to allow slow water conveyance.|
* Dense plantings slow water to allow for infiltration, removing contaminants.
* May require engineering.
* May have check dams.
|* Typically, U or V-shaped bottom with varying downhill slopes that conveys large volumes of water from the area|
* Homeowner can design.
* May have check dams.
|Soils||Typically amended with compost.||Native soils. No amendment.|
|Water Quality and Treatment||Effective for trapping sediment and associated pollutants.||Little to no water quality treatment.|
|Vegetation||70% coverage minimum; hardy native grasses, sedges, and rushes in treatment area.||Not planted, however, turfgrass and other vegetation commonly grow in them. Could be lined with gravel to reduce the potential for erosion.|
|Maintenance||Mowing (only when just grasses are planted), leaf and sediment removal.||Cleaning ditches of plants (grasses can be left and mowed), leaves, and sediment as needed.|