This report examines geomorphic processes across the Santa Paula Creek watershed at both the hillslope and mainstem channel scale. At the hillslope scale, field observations combined with literature values were used to construct estimates of average annual hillslope sediment production and delivery to the channel network, based on land cover, geology, and topographic relief. This sediment production is ultimately driven by tectonic uplift across the watershed, with uplift rates determined by prior studies that are reviewed here for context. The calculated rate of sediment production, in turn, can be constrained by empirical data on historic sediment removal in the lower reaches of Santa Paula Creek, which provides a check on the likely accuracy of the methodology we have used.

Within the mainstem channel, channel morphologic evolution over the past century was assessed using historic and current aerial photography and topography. Mainstem sediment transport dynamics were then assessed based on current hydrology, bed sediment size, and channel morphologic characteristics. The results from both hillslope and inchannel analyses have then been combined to determine the primary historic and current impacts on sediment transport and delivery within the watershed (both natural and anthropogenic) and develop a conceptual model of geomorphic processes. The conceptual model is then used to summarize important geomorphic characteristics that should inform appropriate future
management decisions.