Floods as Agents of River Restoration Project Summary

This project looks at the effects of large floods on rivers and the processes at work when such stresses hit. The investigation plans to show how to help land, ecosystems and communities recover from disturbances such as floods and humans re-arranging streams.

Using the Chickley River in the northwest Massachusetts town of Hawley and stretches of the Connecticut River in Vermont as natural laboratories, we investigate how floods reverse human efforts to straighten --or channelize-- rivers, and what controls a river’s process of returning to a naturally more sinuous and complex state.

The Northeast in general and Vermont in particular have a long history of river channelization from logging to engineering for flood control, and Hurricane Irene provided testing grounds to study flooding effects on rivers. The Chickley River in the Deerfield River watershed offers a case study in human-engineered changes, including a major restoration project.

Dating back to the 1930s and 1940s, the notion was that too much water was the problem in a flood, which seemed logical, so engineers thought they’d get rid of all that water as fast as possible by channelizing. That is, digging deeper and straighter channels to get the water away quickly.

But rivers don’t always work best when they are deep and straight and fast. Channelization greatly increases the water’s energy, so in the next flood event, channelized rivers have a huge amount of power to carve away roads, move houses, reposition gravel bars and generally destroy everything in their path. It’s a fire hose effect.

We are using historic and recent topographic maps, field surveys, measurements and photographs of rivers before and after floods and human intervention to contribute to basic scientific understanding of the physical controls that move channelized rivers back to complexity. We will also develop a mathematical model to predict how quickly rivers will re-establish complexity.