Digital elevation models (DEMs) of the Elwha River delta, Washington, August 2012

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 2012. 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-05-12-PS). Bathymetry data were collected using two survey vessels, 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.

本次发布的数据部分呈现了基于2012年8月采集的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)。美国华盛顿州埃尔瓦河上的两座大坝曾拦截了逾2000万立方米的沉积物，导致下游输沙量锐减，并加剧了该河沿海三角洲的侵蚀。2011年至2014年间，埃尔瓦大坝与格莱恩斯峡谷大坝的拆除工作大幅提升了河流的沉积物供给量，为研究三角洲系统对沉积物供给变化的响应提供了前所未有的契机。美国地质调查局 (U.S. Geological Survey, USGS) 发起了一项综合研究计划，旨在探究大坝拆除后的生态系统响应，其中包含沿海及近岸水深与地形的常态化监测工作。作为该监测计划的组成部分，美国地质调查局于华盛顿州胡安·德·富卡海峡的埃尔瓦河三角洲开展了水深与地形测量（美国地质调查局野外活动编号：W-05-12-PS）。水深数据由两艘测量船采集，每艘船均配备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。研究团队基于所有可用高程数据，采用线性插值法生成了该区域的DEM曲面。