Full Title: Living shoreline site suitability model transfer for selected water bodies within the Gulf of Mexico: A GIS and remote sensing-based approach

This project adapted an existing computer model for assessing the suitability of a site for construction of a living shoreline, applied the model to Perdido Bay/Wolf Bay/Ono Island complex in coastal Alabama; Lake Pontchartrain, Louisiana; and Galveston Bay, Texas, and developed an interactive decision support tool that allows for a rapid assessment of a site.

The Team: Chris Boyd (Lead Investigator, Troy University, boydc@troy.edu), Xutong Niu (Troy University), Stephen Jones (Geological Survey of Alabama), Lee Anne Wilde (Galveston Bay Foundation), and Marcia R. Berman (Virginia Institute of Marine Science)

Technical Monitor: Cynthia Meyer (cameyer@usbr.gov)

Federal Program Officer/Point of Contact: Frank Parker (frank.parker@noaa.gov)

This project began in June 2017 and ended in December 2020.

Award Amount: $519,853

Why it matters: Living shorelines are an infrastructure technique that uses native vegetation alone or in combination with offshore structures to stabilize the shoreline while maintaining natural coastal processes. Living shorelines provide a natural alternative to `hard’ shoreline stabilization methods like stone revetments or bulkheads, and provide numerous benefits including erosion control, the reduction of nutrient pollution, essential fish habitat, and buffering of the shoreline from waves and storms. This project will produce a decision support tool which property owners and environmental managers can use to determine what areas are best suitable for conversion from `hard’ shoreline to living shoreline infrastructure.

What the team did: In deciding whether a living shoreline is an appropriate solution for reducing erosion at a particular site, a living shoreline suitability computer model can be used to provide recommended upland and shoreline best management practices. This project customized an existing living shoreline suitability model developed by the Virginia Institute of Marine Science to work in Perdido Bay/Wolf Bay/Ono Island complex in coastal Alabama; Lake Pontchartrain, Louisiana; and Galveston Bay, Texas. In addition, the developers created an interactive decision support tool for these areas as well as Tampa Bay, Florida, where model adaptation was already underway, to illustrate the principles of the basic model and allow users to interact with it.

Summary of Outcome:

This project was funded to apply the Virginia Institute of Marine Sciences existing Living Shorelines Suitability Model (LSSM) (version 5.1) to 3 waterbodies in the Gulf of Mexico and to develop a new decision support tool to determine living shoreline suitability on the fly. This tool is now referred to as the Living Shorelines Decision Support Tool (DST). 

The LSSM was applied in 3 waterbodies in the Gulf of Mexico: Lake Pontchartrain, Louisiana, the Perdido Bay/Wolf Bay/Ono Island Complex, Alabama, and Galveston Bay, Texas. The LSSM delineates shoreline “Best Management Practices” with a preference for nature-based solutions for erosion control. It was originally developed to provide guidance for implementation of Virginias “living shoreline policy.” The LSSM is a Geospatial model that runs in ArcGIS and uses available GIS datasets. The data sets required to run the LSSM include; bank height, general beach width character, fetch, nearshore bathymetry, permanent upland infrastructure such as buildings or roads, public boat ramps, riparian land use, sand spits and man-made navigable canals, shoreline, shoreline structures, submerged aquatic vegetation, mangroves, tidal marsh, and tributary distinction. The model was generated using the ArcGIS model builder and follows a decision tree logic sequence for shoreline management decisions developed to improve on-site assessments for regulatory permit review of tidal shoreline. The data sets are imported into the model, and a recommended shoreline best management practice (BMP) is returned for a particular point/land parcel on the shoreline. The modeled recommendations can be exported as a shape file. An ArcGIS interactive web viewer was determined to be the best medium to deliver the model results to the desired end users that include: shoreline managers, restoration/conservation specialists, regulators, and the general public. The shoreline BMPs include: no action needed, non-structural living shoreline, existing marsh sill, plant marsh with sill, existing breakwater, maintain beach or offshore breakwater with beach nourishment, groin field with beach nourishment, revetment, revetment/bulkhead toe revetment, or area of special consideration. The special considerations include; ecological conflicts, highly modified area, land use management, or special geomorphic feature. 

A Living Shoreline Advisory Board was formed in each region to generate input on the model application to the individual regions in order to, ensure that all BMPs are applicable to that region and permittable by the local, state, and federal regulatory agencies. Four “Living Shoreline Advisory Boards” were created for this this project. These include the Tampa Bay, Coastal Alabama, Lake Pontchartrain, and Galveston Bay Living Shorelines Advisory Boards. 

The Tampa Bay advisory board was created to assist with the creation of the DST. The DST is a query-based tool, and does not operate in a GIS environment. Therefore, it does not need a geospatial database, and as a result it is not time sensitive. It follows the same decision tree logic that was developed for the LSSM with some modifications. The user is taken through a series of questions that ultimately leads to a recommended shoreline BMP. It is accessible via a computer or a mobile phone. The tool has built in “help” buttons to assist the user. The advantage of the Living Shoreline DST compared to the LSSM is that there are no GIS datasets that must be updated by a GIS professional overtime to ensure accurate BMP recommendations. 

Collectively the “two tools” can assist numerous stakeholders that include; shoreline management regulatory boards, local, state and federal agencies, NGOs, contractors, private citizens, local planners, engineers, and storm water managers to determine shoreline locations most suitable for living shorelines and other natural and nature-based features to control erosion and to improve community resiliency where feasible. The models were run, validated, and presented to the different Living Shorelines Advisory Boards at four workshops in the Gulf of Mexico to determine if any modifications were required for their specific water body region.

The LSSM models are available at the following websites:

• https://www.gsa.state.al.us/apps/CASIS/index.html
• http://troygeoamtics.maps.arcgis.com/apps/webappviewer/index.html?id=f10332f81b9547bb956272c088b282e4 
• https://cmap2.vims.edu/GBShoreProtectViewer/

The DST is available at:

• https://cmap2.vims.edu/LivingShoreline/DecisionSupportTool/index.html.