Erosion and Sedimentation Control
Public Works | Engineering Division
Soil Erosion
Soil erosion is the removal and loss of soil from its original location by the action of water, gravity, ice, or wind.
During grading activities, soil erosion is mostly caused by the force of falling or flowing water. There are several common ways water erodes soil.
Raindrop Erosion
Raindrop erosion is caused by the direct impact of falling drops of rain dislodging soil particles which are then easily transported by runoff.
Sheet Erosion
Sheet erosion is the removal of surface soil by the action of raindrop splash and runoff as water moves in broad sheets over the land.
Rill Erosion
Rill and gully erosion occur when runoff concentrates in rivulets and creates grooves, called rills, in the soil surface. Rills may develop into gullies.
Sedimentation
Sedimentation is the settling of eroded soil into the various parts of our storm water drainage systems, channels, streams, wetlands and lakes. Sedimentation can be a large factor in urban flooding by impeding stormwater run-off through culverts, ditches, and streambeds. Additionally, sediment buildup is very destructive to valuable salmon spawning beds. Damage to Skagit County’s environment and drainage systems can be prevented by either controlling erosion before it happens, or by trapping the sediment before it leaves the disturbed area. Generally, it is less costly and easier to prevent the topsoil from eroding than it is to trap the sediment once the erosion process has begun.
Erosion Control Measures, such as, vegetation mulch, ground covers and phasing projects can help reduce erosion. By reducing soil exposure, less sediment will be released into the rainfall runoff. While erosion control usually involves planting or seeding after grading activities, in most cases, existing vegetation is the easiest and least costly form of erosion control. Leaving strips or buffer areas around drainage courses is a very cost effective way to prevent and control erosion.
Types of Sediment Trapping
In this view, rocks are used to help maintain credibility of the slight slope of the yard.
Rocks are used here to trap the water pooling in the area.
Erosion and Sedimentation in Skagit County
Soil erosion and sedimentation problems are created by the unwanted movement of the soil due to removal or disturbance of vegetative groundcover. Agriculture, forestry and commercial and residential development are major contributors to erosion in Skagit County.As development in Skagit County continues to increase, the problems and associated costs with soil erosion and sedimentation are also increasing. Unless basic and simple steps are taken to protect our soils, drainage systems and streams will be increasingly impacted. There will be increased chance of flooding, higher maintenance costs, and environmental damage including the destruction of vital salmon spawning beds.
How does this affect me?
- Extra expenses
- Permitting delays
- Work stoppages
- Fines
An erosion control plan does not need to be extravagant or expensive. In many cases, simple leaving some groundcover may be sufficient to prevent erosion. In any case, early planning can mean significant savings in time and money.
For further information on erosion and sedimentation control, please contact Development Review of Skagit County Public Works.
