Integrative Method for Quantifying Floodplain Habitat

Abstract

Restoring functional, self-sustaining floodplain habitats requires explicit consideration of the flow dynamics that once created healthy floodplain ecosystems. This paper describes a new method for quantifying the benefits of river projects by linking the spatial and temporal characteristics of floodplains to define the functional habitat they create. Combining standard hydrologic and hydraulic analysis, habitat can be quantified using area-duration-frequency (ADF) curves for several durations and across multiple frequencies of flood occurrence. From this, a value can be created for expected annual habitat (EAH) analogous to expected annual damages (EAD) used in flood risk analysis. To illustrate this method, a modeling case study was conducted on the Lower San Joaquin River in California. The case study shows that a levee setback to restore floodplain connectivity could benefit splittail fish populations but not rearing salmonids. The development of ADF curves and EAH values is a transparent and replicable means to examine the effects, impacts, and benefits of policy and projects on riverine species and ecosystems.