H033-0005
Compound Inundation Modeling of a 1-D Idealized Coastal Watershed

Tuesday, 8 December 2020
Poster
Felix Luis Santiago-Collazo1, Matthew V Bilskie2 and Scott C Hagen1,3, (1)Louisiana State University, Civil and Environmental Engineering, Baton Rouge, LA, United States, (2)University of Georgia, Athens, GA, United States, (3)Louisiana State University, Center for Coastal Resiliency, Baton Rouge, LA, United States
Abstract:
Low-gradient coastal watersheds can be susceptible to flooding from numerous mechanisms such as rainfall, tides, and storm surge. Compound flooding occurs when at least two of these mechanisms happen simultaneously or in close succession (Santiago-Collazo et al., 2019, DOI:10.1016/j.envsoft. 2019.06.002). To assess compound flooding, different inundation models, observed data, and/or a combination of these are joined through varying techniques involving one-way, loosely, tightly or fully coupled approaches.

Here we present a one-dimensional (1-D), tightly coupled compound inundation model, based on the shallow water equations, that is capable of simulating the variations of the free water surface in the ocean domain (i.e. tide and storm surge modeling), rainfall-runoff in the upland region of the watershed (i.e. hydrology modeling), and compound flooding within a defined coastal transition zone (Bilskie & Hagen, 2018, DOI:10.1002/2018GL077524). The compound inundation modeling occurs within a single modeling framework, transferring flux information through internal memory using a moving boundary at the shoreline. To test this compound inundation model, various 1-D transects, representing an idealized low-gradient coastal watershed, were developed and applied with numerous rainfall-runoff/tides/storm surge combinations that vary in magnitude, time and space. These flooding scenarios include antecedent rainfall conditions in the watershed region and rainfall events associated with tropical cyclones before and after landfall.

One of the main goals is to evaluate each flooding mechanism, separately and their combination, to aid in the identification of generalized coastal transition zones and enhance the production of flood maps for varying regions in the coastal watershed. The main research hypothesis is that the relationship between rainfall-runoff, tides, and storm surge is non-linear; therefore, adding the individual effects of these flooding mechanisms may over- or under-estimate the compound flood level within the transition zone. The desire is a more holistic compound inundation model that can be a critical tool for decision-makers, stakeholders, and authorities by providing aid in disaster and evacuation planning to potentially save human lives and enhance resilience.

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