Abstract:
ABSTRACT
The modern day City of Winnipeg is situated on the poorly drained floor of pro-glacial Lake Agassiz, one of the flattest regions on earth. Within the area now bounded by the Perimeter Highway sixteen major streams and at least twenty small coulees once emptied into the Àssiniboine and Red Rivers. Behind the levees of these rivers large areas of marsh existed providing detention storage of surface waters. The overflow from these wetlands fed many of the streams. The first settlers in the region mimicked the natural drainage regime by damming the waters of the streams to drive grist mills. Later agricultural settlers, occupying the uninhabited but marginally drained lands behind the levees began to drain the wetlands. During the explosive growth period of the City (1880-1910) the drainage regime was radically altered and an expensive and inadequate conduit system was substituted in it's place. Serious flooding episodes have occurred from the first alterations up to the present day. In an attempt to solve the flooding problems, overcome the expense of conduit systems and add amenity, a series of stormwater retention ponds was introduced by private developers in 1965. Functually these impoundments imitate the original hydraulic relationship between the ponds, wetlands and streams of the native landscape. Approximately on hundred years after the elimination of the natural drainage regime, Plan Winnipeg 1981 calls for the preservation of all natural watercourses in recognition of their high value for storm drainage and recreational amenity. Of the original thirty-six streams and coulees only nine exist today. All wetland storage areas have been eliminated. This practicum traces the historical progression of land drainage in the City of Winnipeg, summarizes the design criteria for future urban stormwater management, and outlines the present condition and rehabilitation of the historic water features.
