Tools for assessing hydrologic challenges and restoration potential of reservoir deltas: case studies from Southern California

California has lost nearly all its natural riparian ecosystems. Reservoir deltas represent an under-explored opportunity to restore these lost riparian forests across the west. However, flood magnitude, duration, frequency, timing, and rate of change are all modified along reservoir deltas, with varying impacts on key riparian species that support wildlife. I analyzed daily water elevation data from five reservoirs as case study sites and combined hydrologic and topographic data to delineate areas where riparian vegetation could become established. I compiled plant height data from a wide range of riparian restoration projects to evaluate the ability of riparian species to resist flood mortality. Finally, a case study illustrates challenges and lessons learned to guide future projects. Four of the five sites, while hydrologically highly modified, have portions of the drawdown zone where forest re-planting could be a feasible approach to expanding available habitat. Using these case studies, I developed a stepwise decision tree for integrating hydrologic data into site selection and restoration design. The framework illustrated in this report can be easily replicated to identify additional locations across the state where restoration has a higher likelihood of success and where additional data collection can further refine techniques.