Climate Change Adaptation of Urban Stormwater Infrastructure

Abstract

The final analysis of historical (TP-40), current (Atlas 14), and future predicted storm events for three watersheds in Minnesota (Duluth, Minneapolis, Rochester) has shown that current design philosophy is not sufficient to prevent flooding from 10-year and larger design storm events and that flood depth and duration will increase given current climate projections. Several stormwater infrastructure adaptation strategies were assessed for reducing flood depth and duration: Baseline (existing conditions), adding rain gardens (aka, Infiltration Basins), adding new wet ponds, retrofitting existing stormwater ponds to be ?Smart Ponds, adding new Smart Ponds while also converting existing ponds into Smart Ponds, or upsizing of stormwater pipes to convey more water. In watersheds that are mixed urban, suburban, and rural like Rochester?s Kings Run or Duluth?s Miller Creek sub-watersheds, the most cost-effective climate change adaptation strategy was to build new stormwater wet ponds (Extra Ponds strategy) to treat the impervious surfaces not currently treated by existing wet ponds and other stormwater BMPs. In the fully developed urban 1NE watershed in Minneapolis, the most cost-effective (excluding land costs) climate change adaptation strategy was building wet ponds (Extra Ponds). Securing property for building new stormwater infrastructure in fully developed urban watersheds like 1NE may be a substantial cost compared to other watersheds. Smart Ponds do not require additional land for implementation and thus represent a relatively low-cost alternative that will be more beneficial in watersheds with numerous existing wet ponds.