Nature-Based Features: developing a framework to shift them from risky investments to reliable and robust solutions

Nature-based features (NNBFs) have emerged over the past two decades as tools to leverage natural processes that provide a range of functions from flood reduction to pollutant removal. Despite their growing popularity, a notable gap remains between our understanding of internal NNBF processes and our ability to design NNBFs for specific objectives (e.g., x% reduction of peak storm flow, x% nitrogen reduction) by leveraging such processes. NNBF benefits are, as a result, difficult to quantify, making them a riskier investment compared to tried-and-true grey infrastructure alternatives. This knowledge gap must be filled if we want to design effective and sustainable NNBFs that are viewed on equal footing with grey infrastructure. This presentation will discuss the development of a non-tidal constructed wetland model for the purpose of evaluating design suitability across a range of performance metrics. This model, written in MATLAB, couples hydrologic, hydraulic, and water quality modules. It also allows the user to adjust the constructed wetland configuration (i.e., shape, area, grid cell water depths, vegetation placement, etc.) to maximize specific performance objectives including flood control, wildlife habitat, and water quality. Current efforts are also underway to build upon this design model concept to (1) expand to tidal wetland environments like salt marshes, (2) incorporate vegetation growth/death and morphologic processes, and (3) to incorporate future uncertainty into the design process to support the development of robust and sustainable NNBFs across a range of potential futures and landscape contexts. The overall aim of this work is to develop a framework that allows engineers and policy-makers to evaluate NNBF performance on level footing with grey infrastructure alternatives.