Murky Creeks? Help Keep them Clear

Ask any child what is in a creek and they will reply, “water.” Ask them to take a look at the creek water after a rainstorm and they will change their answer to “dirt.” In California’s North Coast, there is so much “dirt” in local rivers, streams, and creeks that 61 percent of our waterways are considered impaired for sediment by regional regulators.
Some of this sediment is natural – from soil, rock, sand, silt and clay. Our planet is always changing, and rocks erode, stream banks collapse, and soil washes off the land and goes into rivers. The waterways carry the sediment to new locations where, over eons, it creates new land formations and other geologic features.
But human activity can lead to the rapid creation of sediment, often in amounts that nature can’t handle. Excess sediment can be the result of runoff from unpaved or poorly built roads, poor landscaping practices, logging, construction, farming and other activities. By replacing nature’s natural filters (vegetated lands and porous soils) with buildings, roads, and parking lots, people contribute to making the creeks dirtier. Unfortunately, sediment isn’t just an aesthetic issue. It can harm fish and other aquatic wildlife — including endangered coho salmon and threatened Chinook salmon and steelhead. Excess sediment blocks sunlight, limits visibility, clogs fish gills, and harms fish eggs.  Sediment also causes water quality problems for people, farmers, and businesses. When excess sediment settles in a creek bed, it can create blockages that lead to flooding.
Every year it’s estimated that enough sediment to cover 152 acres one-foot deep settles in the Laguna de Santa Rosa. The sediment reduces the amount of space available in the Laguna to hold flood waters and creates shallower channels that allow the invasive plants like Ludwigia to grow.
In the past, we managed land by draining rainwater from the property, sending it to storm drains and creeks as quickly as possible. This practice has led to increased peak flows in creeks causing rapid erosion of creek banks and ultimately releasing sediment into the water.  State regulations in the past two decades have sought to improve water quality by slowing the runoff of rainwater from developed land.  Many “tools” have been developed to slow runoff, remove sediments and contaminants, and divert water to permeable areas to soak into the ground instead of allowing all stormwater to flow to storm drains. These tools can be found in the City of Santa Rosa and County of Sonoma’s “Storm Water Low Impact Development Technical Design Manual” or “LID Manual” for short. Another useful stormwater management guide is “Slow it. Spread it. Sink it!” written and distributed by the Southern Sonoma Resource Conservation District.
This article was authored by Craig Scott, Public Works Director/City Engineer for the City of Cloverdale and Ann DuBay, Principal Program Specialist of the Sonoma County Water Agency.