Integrating tools to scope coordinated reservoir-floodplain management for climate resilience Jeff Opperman and Andy Warner, The Nature Conservancy

Annual flood damages in U.S. (1903 – 2011) Source: NOAA

Competition in multipurpose reservoirs Flood control

The value of connected floodplains

Status quo operation – flood pool empty

Status quo operation – flood pool in use during flood

Status quo operation – vulnerable to drought

“new” water Reallocation of flood pool to other uses

Reallocation – modeled increase in flood risk

$ Reallocation – investments in flood-risk reduction

$

Bulletin 17B flood frequency analysis using HEC-SSP; period of record hydrology Inflows Reservoir operations with HEC-ResSim (scenarios of reducing flood storage) Hydropower revenue Water supply Recreation Ability to provide environmental flows Flood hydrology Inundation patterns: HEC-GeoRas Flood damages: HAZUS Model components Flood pool % current: 100, 75, 50, 25, 0

Study Sites Mokelumne River Savannah River

Savannah River Reservoir Reallocation and Floodplain Management

Savannah River Reservoir Reallocation and Floodplain Management

Savannah River Reservoir Reallocation and Floodplain Management

Savannah River Reservoir Reallocation and Floodplain Management

Savannah River Reservoir Reallocation and Floodplain Management

Savannah River Reservoir Reallocation and Floodplain Management

Mokelumne River Reservoir Reallocation and Floodplain Management

Reoperation = reservoir can provide spring e-flows for salmon 4x more often Reared in river habitat Reared in floodplain habitat

Bulletin 17B flood frequency analysis using HEC-SSP; period of record hydrology Inflows Reservoir operations with HEC-ResSim (scenarios of reducing flood storage) Hydropower revenue Water supply Recreation Ability to provide environmental flows Flood hydrology Inundation patterns: HEC-GeoRas Flood damages: HAZUS Potential additional model components Flood pool % current: 100, 75, 50, 25, 0 Hydrology with climate change Floodplain values