The Challenge
Increased flooding, sea level rise and changes in groundwater are predicted to impact coastal and inland wetland extent and function in the future and mapping updates will help us predict future vulnerable resource areas.
Project Alignment with ResilientMass Plan Priority Actions
The wetland mapping update addresses the recommendations made in the final report of the 2023 ResilientMass funded project, “To develop a GIS mapping tool for climate coastal and inland wetlands to identify resource area vulnerability corridors.” Specifically, the recommendation to update the statewide wetland maps with modern methods and current imagery.
Climate Resilience Project Scope
Although it is predicted that wetland extent will change in many areas due to changes in temperature, higher water levels, shifting vegetation assemblages and other factors impacting habitat quality of wetlands, predicting specific changes and vulnerabilities is not feasible currently with our existing tools and data. To better assess wetland vulnerability, we need to start with updated baseline data. An update to the MassDEP statewide wetland layer is necessary as the imagery it was based on, and the manual mapping technology used, is nearly 20 years old. An accurate wetland assessment is an integral piece in the steps toward identifying areas of climate vulnerability, quantification of carbon in wetlands, and assessment of wetland change.
This project worked toward the recommended further action goals that were developed in the previous year of ResilientMass funding for the “Feasibility Analysis to Develop a Wetland Resource Area Vulnerability Corridor mapping Tool.” We advanced our statewide wetland update by field verifying and calibrating a wetland mapping model that was previously developed by Regenerative Design Group (RDG) as a pilot for the “No Net Loss of Carbon in Wetlands” project, furthering goals of the Massachusetts Clean Energy and Climate Plan (CECP). The probabilistic wetland model uses machine learning tools and incorporates topographic, hydrological, spectral and vegetation data to identify probable wetland areas. The initial work on the probabilistic wetland model found that our MassDEP wetland layer likely underrepresents the wetland extent by missing some forested and smaller wetlands that were not readily identified with manual photo interpretation methods. The field work and model calibration done through this 2025 ResilientMass funding has resulted in updated wetland data that will need to be further field verified before it can be used as a statewide wetland map.
Metrics and Results
Although wetland mapping and vulnerability is not specifically identified in one of the ResilientMass Priority Metrics, the metrics related to wetlands and natural environment benefit from our wetland mapping effort.
Through this wetland mapping project we successfully:
- Digitized 324 regulatory wetland delineations representing 1,084 acres of wetland and 1,119 acres of upland to train the model.
- Conducted desktop verification using the 2019 USGS leaf off ortho imagery of 1000 random points in areas modeled as wetlands, inconclusive or coastal wetlands.
- Visited a total of 1,059 field locations and verified in the field the presence of wetland or upland and the wetland classification type.
- Developed a draft probabilistic wetland map layer based on the the above field work and training data.
Best Practices and Lessons Learned
The probabilistic wetland mapping data is a preliminary step towards development of an updated statewide wetland layer with improved accuracy. The mapping exercise resulted in useful data about wetlands extent, identification of areas that may be more vulnerable to flooding, and a gradient of other hydrologic dynamics in an area.
Best practices and lessons learned include the need to further develop a strategy for the release and use of the data products when they are fully verified.
Further Action
The next step is to continue to verify the results of the probabilistic wetland map through aerial imagery analysis, wetland delineations and field ground truthing. The recommendation is to scale the above field and imagery data acquisition by a factor of 3 to 4 to sufficiently improve the mapping data and create an update to the MassDEP statewide wetland map for publication and public use. We expect that a future iteration of the model based on increased field verification will greatly improve upon the existing 2005 MassDEP wetland map. However, in any case the wetlands mapped will be for planning purposes only and will not be to the site level needed for regulatory wetland boundary determinations. Site specific delineations will still be required for permitting.