Multimodal quantification of ecosystem services on a reconnected floodplain: Insights from the Cosumnes River, California, USA

Abstract:

California's Sacramento-San Joaquin Delta drives an elaborate engineered water transfer system, but is inherently challenged by poorly constructed levees, sea level rise, degraded water quality, and compromised ecosystems. Increasingly, levee setbacks and breeches are used in floodplain restoration and reconnecting the region's rivers and streams. Such efforts are touted as a soft-path approach to lessening flood hazard risk, enhancing ecosystem functioning, improving water quality, and recharging local aquifers. Recent advances in spatial data fusion of high spatiotemporal resolution multispectral imagery and UAV-borne LiDAR, combined with hydrodynamic modeling and hydrologic time series, have resulted in novel data outcomes that can better inform future floodplain restoration efforts in planning and practice. Using the Cosumnes River floodplain in California as a case study, we use high-dimensional floodplain topography and vegetation response to quantify sediment retention, biomass accumulation, and carbon balance over space and time. The application of GEDI products to a single year also aids in data interpretation for the study site in past years and data. We augmented our multimodal field data with newly released GEDI satellite-borne data of riparian floodplain forest structure and waveform footprint to extend our observations to remnant and restored forests. These results indicate that floodplains with active flooding are characterized by more diverse species assemblages and densities, greater structural heterogeneity, and faster growth rates. Hyperlocal remote sensing can extend the informatic value of coarser spatial data and longer time frames to provide floodplain managers with better ecosystem monitoring insights and evaluation tools for assessing ecosystem restoration efforts.