Gullies Program


Gullies are common erosional landforms in San Mateo County, and have the potential to deliver significant amounts of sediment to local coastal creeks and streams. Gullies vary in size and are typically formed in poorly consolidated sediment. Many of these local coastal creeks are Total Maximum Daily Load listed for sediment. Addressing the issue of gully erosion may help restore creeks and improve conditions for protected species.

Coho salmon and steelhead are fish native to our local creeks and streams. Over the past 50 years they have experienced a significant decline, and are now in danger of extinction. Erosion is a natural occurrence in most of our local watersheds in coastal San Mateo County. However, human-induced erosion can cause an unhealthy abundance of sediment in our local streams. Excess sediment degrades fish spawning and rearing habitat and impacts aquatic insects that serve as their food. When sediment enters streams excessively, both bank stability and the stream’s ability to carry floodwaters are impaired. Excessive sediment can also adversely affect drinking water quality, supply and cost.

This project will focus on gullies in the Butano watershed that have the potential to deliver sediment to Butano Creek. This project looks at the relative significance of gullies in supplying sediment to coastal creeks, identify human-induced factors that either initiate or enhance gully erosion, and identify potential gully erosion remediation options.


  • NRCS
  • Landowners
  • Regional Water Quality Control Board

RCD Contact: Sara Polgar