The Natural Heritage Institute, in collaboration with Friends of Deer Creek, is preparing a stream restoration proposal for Deer Creek in Nevada County, California. The restoration plan focuses on the mainstem of Deer Creek between Scotts Flat Reservoir and Lake Wildwood. Establishing a clear picture of the hydrology of the creek and its tributaries is essential for drafting a restoration plan.

For the mainstem of Deer Creek, I developed a flood frequency curve from USGS gauge data on Deer Creek itself and on the nearby Oregon Creek. Oregon Creek’s topography, elevation, orientation, and size are similar to that of Deer Creek, so Oregon Creek is an appropriate instrument for Deer Creek. I use Oregon Creek gauge data to estimate ‘natural’ flows on Deer Creek, because Oregon Creek is a free flowing stream. I use the gauge data on Deer Creek itself to calculate current flows.

Deer Creek’s tributaries are ungauged, so there are no flow records that can be analyzed to estimate flows and to develop flood frequency curves. I collected and analyzed survey data to estimate bankfull flows on the tributaries to Deer Creek, and used two methods to calculate flows with return intervals of 2, 5, 10, 25, 50 and 100 years. The first method is Waananen and Crippen’s regional flood frequency relation, requiring inputs of drainage area, mean annual precipitation, and an altitude index. The second method of estimating flows, developed by Hedman and Osterkamp, relies on channel geometry and on classifying a stream according to its vegetation and climate. Comparing the total discharge from the tributaries with the discharge from the mainstem of Deer Creek for each return interval of interest shows that my estimates are reasonable: for both methods, the combined flows from the tributaries are less than the flow on Deer Creek.

NHI will use the results of this analysis, along with information on the geomorphology, riparian and stream habitats, benthic macroinvertebrates, and water quality, in formulating the Deer Creek restoration plan.

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