Snohomish Estuary Wetlands Study. Volume IV. Delineation of Wetland Boundaries

摘要

Wetlands boundaries in the Snohomish River Basin were delineated according to Army Corps of Engineers (Corps) definition presented in Corps permit regulations (33 CFR 323.2). These definitions are based primarily on occurrence of wetland vegetation and concepts relating the presence of such vegetation to conditions of soil saturation. The delineation of wetland boundaries defines to some degree a jurisdictional context for other portions of the Snohomish Estuary Wetlands Study, of which this is a part. Field investigations of the estuarine and riverine portions of the Basin were carried out during 1977 and 1978, coupled with analysis of color infrared and black and white aerial photographs of the area. These investigations and analyses led to the establishment of a recommended boundary line for 'adjacent wetlands'. Boundary lines have been delineated on the 1:6000 scale maps and 1:12,000 scale black and white aerial photographs which form the major product of this study. The primary geophysical and hydrologic processes and features which have influenced wetland development in the Snohomish Basin are: tidally influenced watertables; Long term variability of water level; Natural berm formation; Point bar and gravel bar formation; and Oxbow lake formation. The two main ecological features are: Transition zones and Succession.