How is climate change affecting the river’s flows?
Cameron Wake is a research associate professor at the Institute for the Study of Earth, Oceans, and Space and the Department of Earth Sciences at the University of New Hampshire. He has been studying the effects of climate change and land-use on the Lamprey. Analysis of local weather history has shown that the number of extreme weather events has been increasing in the last 60 years. More rain falls more quickly, overwhelming the land’s ability to absorb water. The amount of rainfall in a severe storm has been up to four times the amount that once fell. Less snow is falling in winter, and, instead, more rain has been falling. What snow does accumulate melts earlier in the spring. The Lamprey, as a result, has experienced three severe floods in the past ten years, floods that historically have occurred only once in about a hundred years. These floods have damaged buildings and public infrastructure, such as roads and bridges.
In addition to changes in the weather, the area that surrounds the Lamprey has also changed significantly. What used to be forest or farm land has often been cleared to accommodate more people, resulting in more roads and buildings. Roads and buildings increase the amount of "impervious surface", meaning that precipitation goes across the land rather than down and through it. Also, some wetlands have been altered or filled. With the loss of these protective, absorptive areas, rain that falls onto the ground often goes straight to the river via storm drains or direct run-off.
Flood maps currently used by insurance companies and municipal planners are based on outdated weather and land use patterns. The lines on these maps that once defined the very rare, “100 year flood” need to be updated to include the potential of greater flood heights, and therefore, flood risks farther from the river. Dr. Wake is working to redefine the maps to fit the new realities. He is also including guidelines and tools for land use decisions regarding buffers, steep slopes, future development, road and drainage standards, development of open space, sewage treatment, hazard mitigation, and town master plans.
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