Ordinance 3129-09 - Laserfiche WebLink

Restoration and Land Use Concepts erosion (lowering of grades) and deposition of natural woody debris all occurring. In general, more sedimentation than erosion is anticipated in restored tidal areas because these areas are composed off-channel habitat with relatively low water velocities as compared to the mainstem of the Snohomish River. However, design level hydraulic modeling of specific restoration options would be needed to specifically predict where erosion and sedimentation would occur. The following is a description of specific habitat types that are anticipated once the tidal and non-tidal areas are restored: 1. Mudflat: This is a largely unvegetated habitat type that would be exposed at low tides and covered with water most of the time. Mudflat habitat is anticipated in areas that are approximately 2 feet or more below the daily high tides. Water depths at daily high tides (mean higher high water [MHHW]) would range from 2 to 9 feet in most areas. Mudflats would include areas with stranded large woody debris, particularly in shallower areas, as well as deeper channels from tributary creeks, and dendritic channels (described below). Initially, mudflats are anticipated to develop over the majority of the restored tidal areas if these areas are not regraded. The extent of these areas is anticipated to decrease over time as sedimentation from tidal inundation and periodic flooding, and establishment of adjacent marsh areas occurs. 2. Tidally Influenced Emergent Marsh: This habitat is anticipated to be dominated by freshwater emergent marsh species such as sedges (Carex Sp.), rushes (juncus Sp.), bulrushes (Scirpus Sp.), cattails (Typha Sp.), and other herbaceous perennials such as Wapato (Sagitaria Sp) and Skunk Cabbage. These species grow from 1 to 4 feet high and would form a fringe between the riparian floodplain forest and the mudflat. They may also develop in "islands" that have the appropriate water depth and are surrounded by mudflats. Most of these emergent marsh species are capable of tolerating inundation of up to 2 feet; however, initial colonization would occur at shallower depths and move outward over time. These species also will occur up to 2 feet above high tide (MHHW) but would tend to be increasingly mixed with shrub and tree Riparian Floodplain forest species moving upgradient. Large woody debris, tributary and dendritic channels would also occur in this habitat type. Over time, this habitat type would expand into areas that are initially mudflat, as sedimentation from tidal inundation, periodic floods, and sequestration of sediment from the colonization by emergent plants themselves occurs. 3. Riparian Floodplain Forest: The riparian floodplain forest includes forested wetlands and non-wetland forests. Both types of forest would include a mix of deciduous and Draft Subarea Plan June 2009 Everett Marshland 37 070346-01