A few days ago I received a copy of Ducks Unlimited Canada’s submission to the province of Manitoba’s Surface Water Management Strategy consultation. As I expected, it was well-written with lots of interesting and specific examples of wetland drainage contributing to the worsening of floods over the past couple of decades. As they put it so succinctly “Channelization and wetland drainage do a great job at what they are intended do – and that is facilitating and accelerating the movement of water onto downstream neighbours.”
As many of us working on water issues in Manitoba know, Lake Winnipeg is the ultimate downstream recipient of floodwaters and all that they bring with them. It is well recognized that floodwaters carry excess nutrients, phosphorus and nitrogen, that fuel the growth of blue-green algae. So decreasing flooding will be a huge benefit to water quality in the lake, not to mention all the other important reasons why we want to decrease flood threats.
One of the items in the DUC report that really caught my attention was a description of several studies done in the Mississippi River Valley that demonstrated the contribution of wetland drainage there to greater river flow rates. One of the studies concluded that a restoration of seven percent of the watershed could provide enough water storage to deal with an extreme flood event on a large scale. Another study done by the U.S. Army Corps of Engineers recommended the acquisition and protection of wetlands as the least expensive method of flood control. The Charles River Basin Authority subsequently paid $10 million to acquire 3,400 hectares of wetlands which act as a natural storage area for flood control. The same amount of flood control provided by the conventional dams and levees would have cost $100 million. So saving wetlands can be a big cost saving as well.