Hydraulic Modeling of Vegetation Restoration and Disturbance in Alvarado Creek

The goal of this research is to understand the effects of vegetation and canopy disturbance on urban stream hydraulics, within Alvarado Creek, a tributary to the San Diego River in San Diego, California. This poster will include hydrologic and hydraulic modeling of stream restoration practices that are intended to reduce fire potential and alleviate flooding potential. Participants will learn about the relation between canopy cover and water temperature, depth, velocity, stream power and flood inundation. This work focuses on Del Cerro (DC), which was burned in June 2018. After the first post-fire year, the study site underwent vegetation restoration in November 2020 to reduce the density of non-native plants and burned canopy along the stream. Field observations included significant regrowth of invasive plants in Spring and Summer of 2021, increased stream water temperatures, and decreased in-stream grain size distributions. The model was calibrated for five storms and evaluated visually and statistically with the root mean squared error (RMSE) and percent bias (%bias). The final calibrated model performed well, where RMSE for 2019 calibrations reached 0.05 m and %bias was 9.02%. The RMSE for 2021 was 0.05 m and %bias was 8.58%. Our results provide insight into the responses of small urban stream reaches to invasive vegetation and canopy removal. The final calibrated parameters can serve as a baseline for future studies, without field data available, to predict the hydrologic and hydraulic response to disturbance or vegetation restoration efforts. Understanding the relationships of parameters that are connected to the presence or lack of riparian canopy can be useful information for future urbanized stream restoration projects. This research aims to provide a greater understanding of potential impacts restoration efforts may have on the hydraulics of a disturbed urbanized channel following a recent fire, providing a baseline for future simulations.