As winter moves along, the Waterville Plateau has started to see a fair amount of snow accumulation. Long-time residents of the Plateau know that the more snow that piles up, the wetter things are in the early spring, which can cause problems. The spring melt can be so intense that the resulting flow, or runoff, can cause disastrous floods that destroy homes, infrastructure, and croplands. However, even normal amounts of runoff from snow and rain can cause land erosion and polluted waterways. Water running over bare or poorly covered soil picks up sediment particles and transports it to streams. It can generate enough force to produce rills, gullies, or even cause landslides. As soil enters streams it causes an increase in salinity (salt), temperature, turbidity (cloudiness), and other metrics of water quality that negatively impacts fish, wildlife, and humans. Luckily, there are some things you can do to minimize these problems for you and your neighbors.
Soil transport occurs when water runs over bare or poorly-structured soil. To minimize the bare soil on your property, grow a community of different types of plants. Different plants have different root systems and stabilize the soil at different depths. This can build up soil structure and create a more stable soil environment. A good mix will be heavy on perennial plants because annual plants have shallow roots.
For the parts of your property that cannot be covered in growing plants, there are other options to absorb the erosive energy of water. You can use Bark mulch or gravel and rock for high-traffic areas. However rock tends to shed fine particles that can negatively impact water quality over time.
As you develop your property, think about whether you really need to pave any given area. When water runs over pavement, it picks up speed along with anything that happens to be on the pavement (i.e: motor oil, solvents, trash). This speedy flow then causes more erosion once the water reaches the end of the pavement. For areas that are already paved, consider surrounding the pavement with a buffer of vegetation or other ground cover to slow water and filter contaminants and sediments from leaving your land.
Fast-moving runoff entering a stream can create a downward cut in the channel. This cut will stir up even more sediment and over time the gentle slope of the bank will become a cliff prone to falling into the stream. Wetlands are considered critical areas in Washington for good reason. Wetlands have a diverse mix of plants that slow and filter water before it reaches waterways. Maintaining healthy wetlands is a cost-effective way to minimize damage from fast-moving runoff.
Slow It, Spread It, Sink It
Even if you do everything to manage runoff, there will still be areas where water flows in heavy rain and spring snowmelt. The knee-jerk reaction is to get this water into a pipe or concrete ditch and move it away from where it is unwanted. However, this approach just makes that water a bigger problem somewhere else. Instead of moving the water out, you should, “Slow it, spread it, sink it”. Planting grass in a floodable area or creating an artificial pond that can hold water until it soaks in can be good ways to slow and capture water.
Runoff is a natural process, but if not managed properly it can cause problems that start with erosion and end with pollution in the gills of fish such as Columbia River salmon. With a little planning, you can turn runoff water from a nuisance on your property to a source of lush beauty and ground water.
We thank the Washington State Department of Ecology for supporting this article.