THE RECREATION OF MEANDERS ALONG ARTIFICIALLY STRAIGHTENED STREAM CHANNELS IN NEW ENGLAND

Artificial straightening of stream channels in New England has occurred for over 200 years. Although no longer a common practice, channelization was undertaken for several reasons including log drives, railroad and highway construction, and flood control. Despite incision and widening along the straightened reaches, excess sediment and flow energy are still conveyed downstream, even in areas altered over 100 years ago. While the straightened planform geometry is ubiquitous on many alluvial streams throughout New England, meanders are locally reforming by two primary processes referred to as breakouts and build-outs. Breakouts occur where woody debris, ice, or sediment temporary clogs the channel and forces floodwaters to breakout onto the floodplain with enough stream power to scour a new meander on the floodplain surface. Build-outs result as the stream is diverted around sediment building out into the channel at the confluence of tributaries. Erosion of the opposite bank eventually leads to the formation of a meander. Combinations of the two mechanisms can also occur where a resistant bank is present opposite sediment building out from a tributary, thereby causing a backwater effect upstream that results in a breakout condition. In certain instances, the channel might reoccupy previously abandoned meanders, making the history of straightening and subsequent remeandering difficult to decipher. Confirmation of meander recreation along a given reach is also complicated where subsequent agricultural or urbanization practices obliterate evidence of the abandoned straightened channel segment. Identification of the mechanisms for meander recreation and the likely areas of their future occurrence is critical for managing flood and erosion hazards. Additionally, mimicking the natural processes of meander formation can lead to the successful restoration of degraded aquatic habitat and reduction in flood and erosion hazards downstream.