River Corridors in Our Backyards
Few people doubt that the extremes of weather we've experienced of late will abate any time soon. Rivers and streams last spring rose to heights not seen since the flood of September, 1938, and similar events will likely transpire ever more frequently. Damage caused by stream and river flooding is resulting in ever increasing costs and risks.
As we build and develop in upland areas, increases in impervious areas increase the likelihood of damage downstream. The standard "engineering response" to controlling rivers has been to channelize, dredge and berm the flood prone river, but that is actually counter productive. Attention needs to be paid to the entire watershed area.
A stable stream is neither growing nor shrinking: it can move sediment through the system without depositing it or without creating any additional erosion. Stable streams have a profile that changes very little over time. They generally meander and twist, creating wide eddies that slow the water, and have adjacent flood plain areas covered with natural vegetation, which the river or stream can inundate periodically, thus dissipating large quantities of water. Once they are confined to deeper channels, streams become less stable. The overbank floods that once left the channel to flow across the floodplain become confined, exerting powerful forces on the channel boundaries. Culverts and bridge footings can be undermined, creating costly repair bills. Consider that several of the Rowley bridges washed out last spring have still not been repaired.
Maintaining the quality of our local streams and the rivers they flow into is in everyone's interest. We need to be pro-active beyond their banks, and recognize that upland activity determines in large measure how those streams will function.
"Floods are 'Acts of God' but flood losses are largely acts of man."
Gilbert White, 1942