Elk Creek Watershed Council, Umpqua Basin, Oregon

Elk Creek Instream Habitat Improvement

The Elk Creek Habitat Improvement Project was developed to improve summer habitat for juvenile coho in the mainstem Elk Creek. It also addressed two of the most significant limiting factors in the Elk Creek Watershed: low summer flows and high water temperatures. The project constructed a series of eight large boulder weirs in a half mile section of Elk Creek that was dominated by bedrock. Initially, the weirs would back up water and create a deep pool, but over time, sediment would seal up the weir and collect behind it, covering the bedrock channel. This layer of sediment would help reduce summer water temperatures, and it would slowly release the water it trapped, thereby extending summer flows.

1/8  This section of Elk Creek was nearly all bedrock.
2/8  The boulders used in these weirs had to be big to keep from being moved by the high winter flows in Elk Creek.
3/8  Eric Himmelreich, ODFW Habitat Biologist, during construction.
4/8  This weir has created a deeper pool behind it with more places for young coho to hide.
5/8  As the water is slowed by the weir, sediment drops out and begins to cover the bedrock. This layer of sediment will help keep summer water temperatures down, and it will also support the macro-invertebrates that provide food for juvenile fish.
6/8  Sand and gravel is beginning to seal up this weir.
7/8  Not just improved habitat for fish.
8/8  During high flows in winter, the weirs are totally under water.