Duffins Creek - Toronto and Region Conservation Authority

4CurrentConditionsThe Duffins Creek watershed, shown in Figure 2,is 283 km 2 in size and is located east of Torontowithin the Regional Municipalities of York andDurham. Local municipalities include the City ofPickering, Town of Ajax, Town of Whitchurch-Stouffville, Township of Uxbridge and Town ofMarkham.In 1991, The Toronto and Region ConservationAuthority (TRCA) retained Aquafor-BeechEngineering Limited to undertake a hydrologystudy. This study is currently being updated byAquafor-Beech Engineering.Physical CharacteristicsThe Duffins Creek watershed can be divided intofour physiographic regions with distinct topography,soil conditions and range of land surface elevations.These four physiographic regions include:• the Oak Ridges Moraine• the Halton Till Plain• the Lake Iroquois Shoreline• the Lake Iroquois PlainThe Oak Ridges Moraine is located in thenorthern third of the watershed. This region isthe headwaters of the Duffins Creek watershed,and is a distinctive area of high ridges andsand/gravel hills.The Halton Till Plain is centrally located in thewatershed. Topography is predominantly gentlyrolling, low-relief hills with the largest reliefproduced by the incised major stream valleys.Sometimes refered to as the south slope of themoraine, the Halton Till Plan contains a varietyof soils, some of which have proven to be excellentthrough more than a century of agricultural use.Several large areas with surficial clay deposits arelocated between Whitchurch-Stouffville andClaremont. The southern limit of the till plain ismarked by steep topographic gradients, whichdefine the former shoreline of Lake Iroquois.The Lake Iroquois Shoreline is located near the5th Concession Road which cuts across Pickeringand serves as the northern boundary where Ajaxmeets Pickering. Approximately 12,800 yearsago, glacial Lake Iroquois occupied the LakeOntario basin at a time when the Wisconsinanglacier blocked the St. Lawrence outlet andwater drained to the south-west. The glacialmeltwaters overflowed the banks of this basin, sothat the waters filled what is now the lower thirdof the Duffins watershed. The Lake IroquoisShoreline appears today as an irregular linebroken by strongly developed features such asembayments and river mouths, remnants of theonce coastal environment. The wave action fromthe waters of this glacial lake deposited boulderpavement or beach gravels along the shoreline(Chapman and Putnum, 1984).The Lake Iroquois Plain is located in the bottomthird of the watershed and consists primarily of agently rolling till plain. Soils in this region consistof a mixture of clay, silt and sand deposits, overlayingthe Halton Till. These stone-free lacustrine(lake-bottom) soils are fertile and suitable forhorticulture and have typically fared well fororchard crops. The largest relief is provided bythe deeply incised valleys of Duffins Creek.Duffins Creek has two major branches which joinapproximately one kilometre upstream ofHighway 2. The west branch originates northeastof Whitchurch-Stouffville and drains an area ofapproximately 135 km 2 . The east branch originatesnortheast of Claremont in the Oak Ridges Moraineand drains an area of approximately 143 km 2 .Both the east and west branches have a numberof tributaries including the following:West Duffins Creek• Stouffville Creek• Reesor Creek• Wixon Creek