History tells the story of prosperous Franklin County towns settled along rivers. Residents used the rivers as a source of food, water, transportation and power. The benefits of the rivers far exceeded the risk of damage to homes and businesses from floods. People erected dams to power mills, and straightened and channelized rivers to accommodate homes, agriculture and businesses. Fast forward to the present time and flood damages are the legacy of historic manipulations of the river and current efforts to repair flood damage.
Flooding is the most common natural hazard in Massachusetts. Flood damages occur due to rising rivers that cover land with water and fluvial (river-related) erosion. The common response to flood damage has been to try and manage the river by dredging, armoring the banks with riprap, constructing berms, and straightening the river channel. This approach, while well intentioned, is not sustainable and has led instead to an escalating cycle of increasing flood damages and costly repairs. Each of our towns can easily point to numerous roads, culverts, bridges and/or retaining walls along a river that have failed numerous times.
Floods are inevitable so what is a sustainable, cost-effective river management option to reduce flood losses for our towns? Avoidance: limiting new development in the river corridor. This approach allows room for the river to change its flow, width and depth over time, which reduces flood damages to structures, fluvial erosion losses and habitat degradation. Strategies for protecting existing homes, roads and other infrastructure will continue to include bank armoring and river restoration projects. Preserving the river’s floodplain functions and limiting new development in the river corridor will help to protect existing at risk structures, too.
What does the river corridor look like?
A river corridor is more than a fixed setback from the river, like the 200 foot setback regulated under the Rivers Protection Act. A river corridor can be wider or narrower than the 100-year floodplain boundary. A river corridor includes the river, its banks and the land close to the river that carries flood waters and accommodates the meander pattern or movement of the river.
With grant funding from FEMA/MEMA, FRCOG hired Field Geology Services to apply the Vermont Agency of Natural Resources’ Fluvial Erosion Hazard (FEH) risk assessment and mapping methodology to delineate a river corridor for the South River, which flows through Ashfield and Conway. The advantages of the FEH methodology versus a traditional fixed setback are that this approach is:
- Science-based; considers the entire watershed and river processes, including fluvial erosion.
- Focuses on sensitive areas – those that are most vulnerable to human and natural stressors.
- Encourages identification of future problem areas.
- Enables protection of infrastructure and habitat.
Now that the river corridor is mapped, what are some tools towns can use to implement an Avoidance Strategy?
One tool developed by FRCOG is a draft model River Corridor Protection Overlay District Zoning Bylaw. The degree of protection provided by a River Corridor Protection Overlay District depends upon the needs of the individual town, but could include limits on new structures, prohibition of certain land use activities, or limits on the amount of vegetation that can be removed for new development or limits on the amount of new impervious surfaces (think asphalt). Over time, this option will do the best job of minimizing human/river conflicts.
This project for the South River Watershed was the first application of the VT ANR river corridor mapping protocols in Massachusetts. With future funding, FRCOG hopes to map more river corridors in Franklin County and develop other innovative tools for protecting these important resource areas and adjacent infrastructure. For further information about the project, please contact: Kimberly Noake MacPhee, P.G., Land Use & Natural Resources Program Manager at [email protected] or 413.774.3167 x130.