Louisiana Coastal Protection and Restoration Authority

Models and Coastal Project Prioritization: The ICM, CLARA, and Planning Tool

The The Louisiana Coastal Protection and Restoration Authority (CPRA), in conjunction with the Water Institute of the Gulf, has developed the Integrated Compartment Model (ICM) to screen and prioritize which flood risk mitigation projects get funded under the Coastal Master Plan. The ICM is a suite of reliable and validated models that characterize landscape change, storm surge flood risk, economic damage assessment, and project impacts over time. ICM outputs enable decisionmakers to select suites of projects that achieve master plan goals.

The Challenge

The Water Institute worked collaboratively to co-develop the ICM which predicts environmental changes within Louisiana’s delta and chenier plain wetlands. The ICM enables the state to look decades into the future using interconnected hydrodynamic, geomorphologic, and ecologic (both vegetation and species habitat suitability indices) sub models. The ICM includes Water Institute-updated datasets and boundary conditions, uncertainty analyses, and improvements to seven modeling components (sediment distribution, marsh edge erosion, vegetation, barrier shoreline, ecosystem outcomes, storm surge and wave, and risk assessment). These subroutines characterize the hydrodynamics, morpho-dynamics, and ecology and clarify what future conditions may be with or without a project or suite of projects. Impacts characterized include salinity, water level, water quality, land elevation and type, vegetation and species coverage and type, habitat suitability and community dynamics.

The Approach

A related model, the Coastal Louisiana Risk Assessment Model (CLARA), was developed collaboratively by RAND, The University of Purdue, and Water Institute staff. CLARA is used to evaluate project effectiveness against tropical weather events of different sizes and intensities and identifies flood depths associated with different frequencies of inundation across the coast (e.g. the 100-year flood depth). CLARA and the ICM are coupled, which enables ICM to process CLARA-evolved coastal landscapes at time intervals in the analysis. CLARA then predicts how future coastal changes would lead to increased risk of damage to buildings, vehicles, agricultural crops, ports, transportation infrastructure, and commercial assets. CLARA also assesses failure probabilities of structural protection systems (levees, floodwalls, etc.). Clara’s ultimate output is an estimate of direct economic damage, in current dollars, from coastal flooding and an assessment of which potential master plan projects could reduce this type of risk. The Planning Tool, optimization software developed by RAND, is a third analytical tool used in the Master Plan process. The Planning Tool evaluates individual restoration and risk reduction projects as well as alternatives (or groups of projects) under multiple environmental scenarios of changing sea level rise and other forcing conditions.

The suite of analysis allows Louisiana to characterize proposed project effects on land loss and land gain and how those landscape changes affect coastal flood risk, coastal habitats and biomass across the coast over the 50-year period of analysis.