Project Summary

The Great Bay National Estuarine Research Reserve, the University of New Hampshire, and Antioch University New England worked to improve information regarding flood risk in the Lamprey River Watershed in New Hampshire. This project developed a methodology for assessing flood risks and, based on future land use and climate change scenarios, provides decision-makers, planners, and the public with products to support land-use decision-making.

Background

The Great Bay Estuary is one of the largest on the Atlantic Coast and is located nearly 10 miles inland. One of the many rivers that drain into the estuary is the Lamprey River, which originates in the Saddleback Mountains and flows 47 miles to its mouth at the estuary. The Lamprey River Watershed drains approximately 212 square miles. The primary towns in the watershed are Candia, Deerfield, Durham, Epping, Lee, Northwood, Nottingham, Newmarket, and Raymond. Major flood events in October 2005, May 2006, April 2007, and March 2010 caused infrastructure damage and habitat degradation. Other stressors to the system include development pressures and climate change impacts, such as sea-level rise, precipitation changes, flooding, erosion, increased storms, and landslides. Development and land-use change combined with climate change effects can affect flood events in both magnitude and frequency.

Researchers from the University of New Hampshire and Geosyntec Consultants developed and refined a methodology for assessing flood risks to the Lamprey River Watershed associated with land use and climate change scenarios.

Implementation

The initial project was funded by the Cooperative Institute for Coastal and Estuarine Environmental Technology (CICEET); subsequent funding was obtained from the National Sea Grant Law Center and New Hampshire Sea Grant. Scientists assessed flood risks under different urban growth/land use and climate change scenarios (greenhouse gas emissions, sea-level rise, temperature fluctuations, precipitation levels). The main products included municipal-scale maps of the 100-year flood risk boundaries and river discharge at specific locations in the watershed. The project also involved an education component, including fact sheets, videos, and a website where the public, local policymakers, and planners can learn more about 100-year flood events, how climate and land use affect flooding, and what actions can be taken.

Outcomes and Conclusions

In the Lamprey River Watershed, decision-makers, planners, and the public now have access to new information on the physical and economic impacts of flood risk based on future land use patterns and climate change scenarios.

Resources:

Assessing Flood Risk in the Lamprey River Watershed

New Hampshire Statewide GIS Clearinghouse: Project Details 

Lamprey River Watershed Generalized Land Use Maps

Citation

Gregg, R. M. (2020). Assessing the Risk of 100-year Freshwater Floods in the Lamprey River Watershed of New Hampshire Resulting from Climate Change and Land Use [Case study on a project of the Great Bay National Estuarine Research Reserve, University of New Hampshire, and Antioch University New England]. Product of EcoAdapt's State of Adaptation Program. Retrieved from CAKE: https://www.cakex.org/case-studies/assessing-risk-100-year-freshwater-floods-lamprey-river-watershed-new-hampshire-resulting-climate-change-and-land-use (Last updated July 2020)

Project Contacts