Description

1) Do recent advancements in 2D capabilities make 1D models obsolete?
Bo Juza, PhD, CFM, TUFLOW, bo.juza@bmtglobal.com
Co-presenters: Rusty Jones, russell.jones@bmtglobal.com; Chris Huxley, chris.huxley@bmtglobal.com

Abstract: Over past decades, advancements in Graphics Procession Unit (GPU) capabilities and relatively low costs have made them uniquely suited for parallel processing, significantly reducing runtime and increasing capabilities to process large datasets. Since the early 70’s, numerical models have been used for flood and coastal studies, facing struggles between data availability, processing speed, project scale, numerical schema capabilities, model stability and other factors that influenced overall 1D, 2D or 3D schematization. While 1D models are still the backbone of large-scale flood modeling and real time forecasting, 2D models have become tools of choice for most flood inundation mapping and complex hydrodynamic modeling projects. The grid or element sizes used for a 2D hydraulic model can have a major bearing on the accuracy and defensibility of the model. Wrong schematization of the system could have a significant impact on project outcomes. If the 2D cell sizes are too coarse, the physical terrain and hydraulic complexity may be poorly represented leading to unacceptable inaccuracies and a high degree of uncertainty in the results. Conversely, 2D cell sizes that are unnecessarily fine result in excessively long simulation times and workflow inefficiencies, impacting project schedule and cost. Models that can experience the most acute inaccuracies due to mesh resolution are whole of catchment direct rainfall or rain-on-grid models, and riverine and urban surface water flood models where the primary flow paths are modeled using an overly coarse 2D resolution. This can cause substantial retention of water and poor conveyance as the flows down the waterways. Examples of various mesh size convergence tests for first order, second order and sub-grid sampled 2D schemes are discussed and presented. Comparison to 1D and 1D+ complex model schematization is being considered.

2) Inland to Coastal Flooding and Everything in Between: A Perspective from Caribbean Islands
Felix Santiago Collazo, University of Georgia, fsantiago@uga.edu
Co-presenters: Luis Cordova-Lopez; Walter F. Silva-Araya

Abstract: Coastal watersheds are prone to the impacts of multiple flood hazards during compound flood events. These events can produce inundation from intense and prolonged rainfall and inland penetration of storm surges, thus exacerbating the flood hazard. The Caribbean Region is particularly sensitive to this combination of events due to frequent cyclonic events affecting small and steep coastal watersheds. Current practices have started to implement multi-hazard modeling techniques for inundation assessments. However, there are discrepancies on the “best” strategy to characterize compound floods, and the use of multi-hazard models in government agencies and consulting engineering firms has not been widely implemented. This presentation will highlight the best modeling practices for compound flood models that couple hydrologic and coastal processes. New modeling techniques and applications will be discussed that improve our ability to capture the complex interactions that characterize multiple flood hazards. Results from various case studies along the Caribbean will be discussed, including their application to other geographical areas such as the Gulf of Mexico and the US East coast. This research aim is to identify generalized flood transition zones and enhance the production of flood maps for varying regions in a coastal watershed, which are crucial in flood risk assessments. 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 decrease property damage.

3) A Fast and Flexible Framework for Flood Damage Assessments
Frederique de Groen, Deltares, frederique.degroen@deltares.nl
Co-presenters: Kathryn Roscoe, Kathryn.Roscoe@deltares.nl

Abstract: Societies are struggling worldwide to cope with the impacts of many types of floods (pluvial, fluvial, flash, coastal, and groundwater). Recent improvements to process-based hydrodynamic models, including the ability to account for compound flooding events, has led to more accurate inundation predictions. Combining these improved inundation results with a rapid, reliable, and easy-to-use tool for assessing economic flood damages will lead to more accurate mapping of spatial flood risk, helping to identify priority areas for adaptation and mitigation investments. This presentation will describe the Delft Flood Impact Assessment Tool (Delft-FIAT), a state-of-the-art tool that calculates flood damages, risk, and risk-reduction benefits of adaptation or mitigation options. Delft-FIAT is flexible and transparent, allowing users to input their own flood maps and to define, view, and modify exposure data and depth-damage curves. It calculates damages at the asset level, including individual buildings, road segments, and utilities, and it outputs damages both at asset level and to user-specified aggregation scales (e.g., neighborhoods). The speed, flexibility, and tested reliability of Delft-FIAT makes it well suited for a variety of uses, such as evaluating adaptation and mitigation investment options, testing impacts of uncertainty in depth-damage curves or exposure data, and connecting with other software in decision-support systems. Delft-FIAT provides a consistent and reliable flood damage calculation framework that can be freely used in the flood mitigation and adaptation community. Collaboration with local, regional, state, national, and international agencies has inspired a research and development plan for Delft-FIAT that includes the processing of social vulnerability in damage assessments, automated uncertainty analysis, supporting wind and wave damage assessment, automated exposure model-building support, and automatically generated damage-output scorecards or dashboards. This presentation is intended to be interactive in exploring ideas for future development with the participants.