Mitigating flood hazards through natural infrastructure

Project Overview

Traditional approaches to reducing the risk of coastal and riverine floods include the construction of conventional infrastructure (CI) such as levees and floodwalls. Over the last decade, there has been a push towards Engineering With Nature (EWN) and the use of natural infrastructure (NI) (wetlands, barrier islands, coastal dunes, forest, riparian buffers) into resiliency and risk management planning to reduce flood impacts rather than relying on gray infrastructure alone. However, the relevant spatial scales and dimensions of NI need to be assessed to maximize flood protection benefits for a range of flood hazards and related risks. The spatial scale refers to how large or small a NI project must be to be most effective. High-performance, high fidelity, computer models of coastal and riverine floods provide a means to develop strategic and controlled digital environments to test how different NI features, combinations, and their size can provide flood risk reduction.

what we’re doing

methods

We plan to test how coastal and inland hazards respond to NI at various sizes and conditions through idealized numerical experiments. An idealized study allows controlled experiments to take place. For example, a single parameter can vary (tidal creek depth, for example) and we can assess how that change (different tidal creek depths) changes the system (change in water level or wave energy). In a similar way, we can vary channel sinuosity (curvature or bend), the height of the marsh surface, and marsh slope (how quickly does the marsh surface increase over a certain distance – think rise over run).

deliverables

We will identify recommendations for length-scaling needed to accomplish risk reduction goals using NI. Idealized coastal and fluvial model studies will be analyzed, as well as a “what if” scenario for the North Carolina OBX, and military bases.

How can riverine natural infrastructure benefit water quality?

Riverine natural infrastructure such as levee setbacks provide benefits beyond flood risk reduction, particularly for improving water quality. Reconnected floodplains can store and remove nutrients, sediment, and other pollutants, reducing pollution for downstream communities. When flows are slowed down and spread out, excess sediment can deposit in the floodplain. The slower flows also increase contact among the floodwater, soil, and vegetation. The floodplain vegetation can uptake and store the nutrients and pollutants, while microbial processes in the soil can permanently remove nutrients such as nitrogen via denitrification, thereby reducing algal blooms, improving drinking water treatment, and enhancing habitat for fish and other wildlife. We are planning to explore how natural infrastructure can be designed for water quality benefits, specifically studying how these benefits scale with different levee setback scenarios.

PUBLICATIONS

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