Digital elevation models (DEMs) of the Elwha River delta, Washington, August 2011

This part of the data release presents a digital elevation model (DEM) derived from bathymetry and topography data of the Elwha River delta collected in August 2011. Two dams on the Elwha River, Washington State, USA trapped over 20 million m3 of sediment, reducing downstream sediment fluxes and contributing to erosion of the river's coastal delta. The removal of the Elwha and Glines Canyon dams between 2011 and 2014 induced massive increases in river sediment supply and provided an unprecedented opportunity to examine the response of a delta system to changes in sediment supply. The U.S. Geological Survey developed an integrated research program aimed at understanding the ecosystem responses following dam removal that included regular monitoring of coastal and nearshore bathymetry and topography. As part of this monitoring program, the USGS conducted a bathymetric and topographic survey in the Strait of Juan de Fuca on the Elwha River delta, Washington (USGS Field Activity Number W-06-11-PS). Bathymetry data were collected using two personal watercraft (PWCs), each equipped with single-beam echosounders and survey-grade global navigation satellite system (GNSS) receivers. Topography data were collected on foot with GNSS receivers mounted on backpacks. DEM surfaces were produced from all available elevation data using linear interpolation.

本次公开数据集的此部分，呈现了基于2011年8月采集的美国华盛顿州埃尔瓦河三角洲水深与地形数据生成的数字高程模型（Digital Elevation Model, DEM）。美国华盛顿州境内的埃尔瓦河上曾建有两座水坝，累计拦截了超过2000万立方米的泥沙，降低了下游泥沙输运通量，进而加剧了该河滨海三角洲的侵蚀。2011年至2014年间，埃尔瓦水坝与格莱恩斯峡谷水坝的拆除工作大幅提升了河流的泥沙供给量，为探究三角洲系统对泥沙供给变化的响应提供了前所未有的研究契机。美国地质调查局（U.S. Geological Survey, USGS）曾发起一项综合研究计划，旨在探究水坝拆除后的生态系统响应，该计划包含对海岸及近岸水深与地形的常态化监测工作。作为该监测计划的一部分，美国地质调查局于华盛顿州埃尔瓦河三角洲所在的胡安·德富卡海峡开展了水深与地形测量工作（美国地质调查局野外活动编号：W-06-11-PS）。水深数据通过两艘个人水上载具（Personal Watercraft, PWC）采集，每艘载具均搭载单波束测深仪与测量级全球导航卫星系统（Global Navigation Satellite System, GNSS）接收机。地形数据则通过背负式GNSS接收机徒步采集获取。研究团队通过线性插值法，基于所有可用高程数据生成了该数字高程模型曲面。