1. Scope

Keywords

Rationale

The number of floods in the US (excluding tropical cyclones) exceeding 1 billion dollars in damages has increased from 4-8 per decade (1980-2009) to 18 in a single decade (2010-2019).2 Almost 23% of the world’s population (1.81 billion people) are now exposed to flood depths greater than 0.15 meters in a 100-year flood event (floods from all causes), driven by complex interactions between climate change, urbanization, and socioeconomic factors. The Upper Mississippi River basin, like many river watersheds, is experiencing an increase in both the amount and the intensity of precipitation events, leading to the river being above flood stage at several locations for 5-10 times as long in the past decade compared to the previous 80 years. 4 The recent increase in flood frequency, magnitude, duration and economic impact has resulted in a need for additional cost-effective, large-scale approaches that use natural systems to help mitigate inland flood impacts. This guide covers options for using Nature-based solutions to help mitigate impacts from rainfall driven inland flooding along streams, rivers, reservoirs, lakes and wetlands. It does not cover flooding caused by infrastructure failure, coastal flooding impacted by sea-level rise, flooding caused by cyclones, or flooding from snowmelt or glacial melting. This guide presents options for Nature-based Solutions focused on watershed level management options, to complement current flood mitigation strategies used at the national, state, municipal and local level. 2 NOAA National Centers for Environmental Information (NCEI) U.S. Billion-Dollar Weather and Climate Disasters (2023). https://www.ncei.noaa.gov/access/billions/, DOI: 10.25921/stkw-7w73 3 https://www.nature.com/articles/s41467-022-30727-4 4https://www.noaa.gov/sites/default/files/2022-03/Technical_Version_Upper_MS_River_Communicating_CC.pdf