Ordinance 3129-09 - Laserfiche WebLink

Background Information Mile 7 to 15.5. The district has a total of 8.5 miles of levees that protect it from flooding. Prior to the construction of the Marshland levees and drainage system, the floodplain in the Marshland area was generally inundated during late spring and early winter. The Marshland subarea has experienced eight major flood events since 1964. In general, any flood that exceeds a 5-year magnitude will result in flooding in the Marshland subarea. The presence of a groundwater aquifer within the subarea is unknown (City of Everett 2002). However, a seasonal water table can be found at 18 to 36 inches in depth during wetter months of the year within the floodplain area (Toth and Houck 2001). 2.1.3 Plants and Animals The general landcover types within the Marshland sub-basin include scrub-shrub communities, croplands, medium and high impervious surface, mixed forest, marsh, and open water (Purser and Simmonds from Toth and Houck 2001). Western hemlock, Douglas fir, red alder, and big leaf maple make up the majority of the forest cover. The sub-basin's riparian buffer is limited to one band of trees on the bank, and of this band, only 7 percent is found in areas that are not isolated by dikes (Toth and Houck 2001). The Salmon Overlay (SO) to the Snohomish Estuary Wetlands Integration Plan (SEWIP) notes that seven species of anadromous salmonids are supported by the Snohomish River; these include Chinook (Oncorhynchus tshawytscha), coho (0. kisutch), chum (0. keta), and pink salmon (0.gorbuscha), steelhead (0. mykiss), and cutthroat (0. clarkil) and bull trout (Salvelinus confluentus). Large portions of the subarea were once potential salmon- and trout-rearing habitat during seasonal flooding. Today, these species are unable to access off- channel sites due to the dikes surrounding the area. Salmon do enter the Marshland area during flooding events with 5-year magnitude or greater. Then they are either stranded or damaged/killed as they go through the pump station back to the River. Historically, the larger Marshland area has been described as containing thousands of acres of oxbows, beaver ponds, and emergent and forested wetlands (Tulalip Tribes 2001; Snohomish County and SCSRB 2005). By 1885, diking and draining within the greater Marshland area had "altered more than half of the original wetlands" (Toth and Houck 2001). The National Wetland Inventory (NWI) identifies 239 acres of wetlands within the Marshland (of which Draft Subarea Plan June 2009 Everett Marshland 13 070346-01