The substrate enhancement pilot project (SEPP) extent GIS layer represents an area where an artificial substrate will be placed. The artificial substrate, consisting of a mixed size class of gravel, is aimed at providing a more suitable substrate for sturgeon eggs and early-life rearing habitat. The location of the SEPP extent was created by analyzing the egg-mat network, bathymetric features, surficial sediment facies, and streamflow characteristics. The egg-mat data represent points where sturgeon eggs were captured in previous years, indicating a preference of spawning location. The bathymetry and surficial sediment facies data were used to delineate areas that were relatively flat and completely within the areas of lucustrine clay outcroppings. The streamflow data, consisting of acoustic doppler current profiles throughout the reach, was used to determine areas where the streamflow velocities were high enough to maintain sediment transport of sand and fine grained sediment so that deposition of that sediment would be minimal. The SEPP extent represents an area where sturgeon have spawned previously, located on a low sloped and predominanly lucstrine clay surface, and in an area of relatively high streamflow velocities.