Apr 30, 2015

Promoting Atmospheric-River and Snowmelt-Fueled Biogeomorphic Processes by Restoring River-Floodplain Connectivity in California’s Central Valley

by
Joan L. Florsheim, Michael D. Dettinger
,
Geomorphic Approaches to Integrated Floodplain Management of Lowland Fluvial Systems in North America and Europe
  • Discusses potential biogeomorphic benefits from intentional levee breaks and weir overflow on the managed floodplain-river system of California’s Sacramento and San Joaquin River watershed (Central Valley)
  • States that climate and flood variability still dictate the frequency of unintentional levee breaks despite many decades of engineering
  • States that, of particular consequence are the so-called atmospheric-river (AR) storms
  • Finds that since 1951, 81 % of breaks have occurred as a result of AR storms and flooding, while most of the rest occurred during snowmelt floods
  • States that intentional levee breaks or planned weir overflows that are designed for floodplain restoration can facilitate a return towards more natural and dynamic biogeomorphic processes
  • Summarizes current understanding of climate processes and flood variability that govern unintentional levee breaks or weir overflow
  • Reviews examples of alternative flood management approaches in the Central Valley that promote processes necessary to restore or sustain lowland floodplain biogeomorphology
  • Finds that future climate-driven changes in flood regime, such as enhanced flooding during winter months or more frequent atmospheric rivers, could be accommodated by additional intentional levee breaks or planned weir overflow for restoration
  • Holds that implementation of these alternatives could be used to improve restoration policy and management of floods in embanked river floodplains