Hat Creek Enhancement
Proposed actions would restore the natural form and enhance hydrologic and biological function of the channelized Hat Creek stream and surrounding riparian ecosystem along a 4000’ reach immediately upstream of the confluence with Rising River.
Restore a more natural and aesthetic stream pattern and dimension through the reach.
Enhance the stream habitat and function as refugia for juvenile native rainbow trout.
Reduce the sediment transport capacity of the channelized Hat Creek reach.
Restore the tendency for peak flows to spread across a broad floodplain surface, especially in the lower 27-acre wetland complex.
Enhance the capacity of the lower acreage to filter sediment during peak runoff.
Maintain agricultural productivity in adjacent irrigated pastures.
Regrade the eroded return pond outlet and redirect overflow across a broad wetland area to reduce agricultural runoff into Rising River.
Restore the wetland habitat and vegetative vigor across the lower 21.7 acres.
Restore the riparian habitat along the upper 8.3 acre stream corridor.
Provide 2.7 acres of new open-water waterfowl habitat.
Monitoring & Reporting
Aquatic Biological Resources Monitoring: Comprehensive monitoring of aquatic habitat will be performed twice for this project—once prior to project implementation (in the existing linear channel of this reach of Hat Creek), and once again postproject, approximately a year later, after conditions in the newly-restored channel have stabilized.
Each of these monitoring activities will involve the following subtasks:
Assessment of Fish Habitat: The first task would involve mapping and determination of areal extent of key trout habitat types in the existing channelized section of Hat Creek. This would be done in late fall or winter so that surveyors could concurrently assess whether or not trout were using, or had used, the stream reach for spawning. This information will provide a pre-project baseline of how much potential spawning and rearing habitat exists in the reach.
Fish Survey (during trout rearing period to assess spawning/rearing use): The second task will provide a direct measure of the number of fish that utilize the reach during the survey period. All fish life stages will be collected and counted. Trout lengths will be measured as well. The numbers of fish of different life stages, particularly trout, present in the reach will provide information on the current use and importance of the reach for holding and rearing.
Aquatic Macro-Invertebrate Sampling: The third task will be done separately from fish sampling. This can be done any time; we will likely target spring or early summer. This will provide information on the numbers and diversity of aquatic insects and other invertebrates in the reach. These numbers are indicators of the health and vigor of the aquatic food web in the reach. This analysis involves laboratory processing of all samples collected to identify and quantify invertebrate samples.
Data from all three of these surveys can be used to determine the success and degree of improvement resulting from the channel restoration project in terms of habitat improvement, fish usage, and foodweb health and vigor. This will involve repeating the surveys after the project is complete and conditions have re-stabilized.
Long-Term Management Strategy
The first component of ensuring the long-term durability of this project is the post-project effectiveness monitoring, which describes the key attributes that will be assessed to affirm whether or not the restored channel and floodplain are now operating as predicted, particularly during and following highflow events in the first two-three years post-project.
The key goal for long-term assessment and maintenance of this project is to ensure that there is a frequent floodplain connection with the active channel. Probably most every year at some point in the season, the floodplain should take some flow volume. Given normal rainfall and streamflow regimes, this should be expected on average every 1.5 years. An indicator of problematic response would be channel incision, where the design channel began to form a gully. However, in comparison to many sites where projects like this have been successfully implemented, that risk of channel gullying is a low concern here because of the proximity of bedrock, and the lack of any incision, even in the straight ditch line, where one would expect to see such response over time. The reason for this is that Rising River (with which Hat Creek joins just beyond the end of the project area) provides a consistent base elevation at the lower end, helping keep these forces low, due to low slope of channel.
In the longer term, once the new channel stabilizes with the expected range of dynamic morphology in a low-gradient setting such as this, project assessment will involve comparative analysis of current channel configuration with original channel design on an approximately five-year basis. The new and old cross-sections of the channel will be plotted on the same chart in order to look for trends of dimension change that might indicate the channel is out of equilibrium with the watershed conditions. No one point defines this, so it has to be coupled with other transects, field observations, experience, etc. to reach a