Flood regime typology for floodplain ecosystem management as applied to the unregulated Cosumnes River of California, United States

Abstract

Floods, with their inherent spatiotemporal variability, drive floodplain physical and ecological processes. This research identifies a flood regime typology and approach for flood regime characterization, using unsupervised cluster analysis of flood events defined by ecologically meaningful metrics, including magnitude, timing, duration, and rate of change as applied to the unregulated lowland alluvial Cosumnes River of California, United States. Flood events, isolated from the 107-year daily flow record, account for approximately two-thirds of the annual flow volume.Our analysis suggests six flood types best capture the range of flood event variability. Two types are distinguished primarily by high peak flows, another by later season timing and long duration, two by small magnitudes separated by timing, and the last by later peak flow within the flood event. The flood regime was also evaluated through inter-and intra-annual frequency of the identified flood types, their relationship to water year conditions, and their long-term trends. This revealed, for example, year-to-year variability in flood types, associations between wet years and high peak magnitude types and between dry years and the low magnitude, late season flood type, and increasing and decreasing contribution to total annual flow in the highest two peak magnitude classes, respectively. This research focuses needed attention on floodplains, flood hydrology, ecological implications, and the utility of extending flow regime classification typically used for environmental flow targets. The approach is broadly applicable and extensible to other systems, where findings can be used to understand physical processes, assess change, and improve management strategies.

Assessing impacts of dike construction on the flood dynamics of the Mekong Delta

“…The study presented in this paper aimed to fill these knowledge gaps by using 1-D and quasi2-D modeling to test the hypothesis that large-scale high dike construction reduces the 1 Defined as "the prevailing characteristics and distribution of flood pulses and variability within and across years, is controlled by geography, geology, climate, and human modifications and drives physical and ecological processes within floodplain ecosystems, affecting the diversity, abundance, and communities of species" (Whipple et al, 2017). flood retention capacity of the floodplains and increases water levels and the corresponding flood risk downstream. We first examined the impacts of dike construction on flood dynamics, focusing particularly on changes in river water levels and the spatial distribution of floods on the VMD floodplains.…”

Source Water Apportionment of a River Network: Comparing Field Isotopes to Hydrodynamically Modeled Tracers

“…Ultimately, as water moves through rehabilitated habitat its ecological value or potential cumulatively improves [44,45] It follows that the restoration-laden Cosumnes River carries with it the potential to boost restoration value within the MWT restoration: the last "pearl" in the string. Understanding the spatiotemporal patterns of SWF allows us to identify regions that retain source waters from the Cosumnes, and thus water that has a higher likelihood to contain nutrients or productivity from upstream restoration sites [31,46,47]. Being downstream of completed and ongoing restoration projects is not a unique trait of the MWT within the Delta.…”

“…Middle and Lost Sloughs are dead-end sloughs during non-flooding periods and convey Cosumnes overland flow during floods. The Cosumnes River is the only major river coming out of the Sierra Nevada Range without a major dam, allowing for a relatively natural hydrograph with natural overbank/floodplain flow [31]. Due to this hydrograph and a variety of restoration actions, the Cosumnes River provides floodplain rearing for a variety of native juvenile fishes and exports productivity downstream [32].…”

Not all breaks are equal: Variable hydrologic and geomorphic responses to intentional levee breaches along the lower Cosumnes River, California

“…The 109‐year‐long record of streamflows in the Cosumnes River at Michigan Bar (USGS Site 11335000; see Figure ) identifies highly variable peak annual discharges ranging from 6 m 3 /s (1977) to 2634 m 3 /s (1997). A flood regime typology for the Cosumnes River is explored thoroughly in Whipple, Viers, and Dahlke (). Only the loss of summer and fall baseflows in the lower reaches of the Cosumnes River due to regional surface and groundwater use deviates from a natural flow regime (Fleckenstein, Anderson, Fogg, & Mount, ).…”