Development of a digital land cover data base for the Selawik National Wildlife Refuge

Abstract

Digital land cover and terrain data of the Selawik National Wildlife Refuge were produced by the U.S. Geological Survey's (USGS) Earth Resources Observation Systems Alaska Field Office for the U.S. Fish and Wildlife Service. These and other environmental data were incorporated into a Fish and Wildlife Service geographic information system to prepare a comprehensive conservation plan and an environmental impact statement for the refuge and to assist in research and management of the refuge. The digital data base, stored on tapes, includes land cover classifications from Landsat multispectral scanner data, elevation, slope, and aspect data for the area covered by the USGS Selawik and Shungnak l:250,000-scale topographic maps. The maps incorporate more than 90 percent of the refuge. Additional digital data in the data base include (a) land cover of the entire refuge at 50-, 200-, and 400-m pixel sizes derived from Landsat multispectral scanner data; (b) Landsat multispectral scanner data registered to a 50-m Universal Transverse Mercator grid; (c) elevation, slope, aspect, and solar illumination data registered to each Landsat scene; (d) stream hydrography and surficial geology digitized from USGS l:250,000-scale quadrangle maps; and (e) Refuge and wilderness boundaries. In addition to the digital products, color hard copy maps were produced from the l:250,000-scale quadrangle base land cover, elevation, slope, and aspect digital data. Any use of trade, product, or firm names in this publication is for descriptive purposes only and does not constitute endorsement by the U.S. Geological Survey. I7 Hughes STX Corporation, Work performed under U.S. Geological Survey contract 1434-92-C-4004. ? U.S. Fish and Wildlife Service. INTRODUCTION The Alaska National Interest Lands Conservation Act (ANILCA, Public Law 96-487) was enacted in 1980 to provide and conserve certain public lands in Alaska. The Act instructs the U.S. Fish and Wildlife Service (USFWS) to identify and describe the habitats of the fish and wildlife resources on the Selawik National Wildlife Refuge (SNWR). Because vegetation forms the basis of habitat (Egler, 1977) and topography affects the vegetative composition and use of habitat, a digital data base containing land cover and terrain data such as elevation, slope, and aspect was needed. The USFWS and the U.S. Geological Survey (USGS) Earth Resources Observation Systems (EROS) Data Center entered into a cooperative project to develop this data base which was used to prepare a comprehensive conservation plan and an environmental impact statement for the Refuge. These data are also being used in research and management on the Refuge. Published vegetation maps of the refuge are limited. Broad or regional land cover classifications were produced by Kuchler (1966) at a scale of 1:7,500,000, and Selkregg (1975) at a scale of 1:1,500,000. Becia (1987) produced l:60,000-scale maps that covered a few western portions of the refuge. A computerassisted analysis of Landsat multispectral scanner (MSS) data was used because (1) high-altitude aerial photography for the refuge was limited; (2) complete satellite coverage of the refuge could be obtained; (3) the level of detail would be adequate to meet most of USFWS planning, research, and management needs; and (4) the data base could be registered to other data bases and quickly retrieved. This paper describes the methodology used to produce the land cover classification and accompanying data base, as well as the different types of products developed. STUDY ARE A The SNWR encompasses approximately 3.2 million acres of land and water in northwestern Alaska (fig. 1). The study area covers roughly 1 degree of latitude and 6 degrees of longitude. Figure 1. Near here. The refuge is contained in the western Alaska Province, Intermontane Plateau, physiographic division as described by Wahrhaftig (1965). The refuge is bordered on the north by the Kobuk River and Waring Mountains, and by Hotham Inlet and Selawik Lake on the west. To the south are the Selawik Hills extending eastward to the Purcell Mountains. The Selawik River, which flows westward into Selawik Lake, bisects the refuge. The refuge consists mainly of broad river floodplains such as the Kobuk River delta in the northwest, and lake-dotted lowlands. Most of the refuge is underlain by glacial moraine deposits and by stream and lake deposits. To the north, the Waring Hills are underlain by Cretaceous sedimentary rocks (Wahrhaftig, 1965). Large, inactive and small, active sand dunes are prominent in the north central portion of the refuge. Permafrost throughout the refuge causes patterned ground and occasional pingos. S E L A W I K N A T I O N A L W I L D L I F E R E F U G E