Compound Inundation Modeling of a 1‐D Idealized Coastal Watershed Using a Reduced‐Physics Approach

Abstract

Low‐gradient coastal watersheds are susceptible to flooding caused by various flows such as rainfall‐runoff, astronomical tides, storm surges, and riverine flows. Compound flooding occurs when at least one coastal flood driver occurs simultaneously or in close succession with a pluvial and/or fluvial flood driver, such as during a tropical cyclone event. This study presents a one‐dimensional (1‐D), reduced‐order physics compound inundation model tested over an idealized coastal watershed transect under various forcing conditions (e.g., coastal and pluvial) that varied in magnitude, time, and space. This study aims to evaluate each flooding mechanism and the associated hydrodynamic responses by performing a sensitivity analysis and developing a non‐linear equation that could correlate the flood drivers with the severity of its flood. Compound inundation levels are affected by the magnitude and timing of each flooding mechanism. Results highlight the need to consider momentum exchange during a compound event and the importance of reduced‐physics approaches that can improve the interaction between flood drivers when paired with a moving coupling node approach. The desire is a more holistic compound inundation model that can be a critical tool for decision‐makers, stakeholders, and authorities who provide evacuation planning to save human lives and enhance resilience.