SURFICIAL GEOLOGIC MAP OF THE WOOD RIVER VALLEY PROJECT AREA, IDAHO GEOLOGICAL SURVEY STATEMAP PROGRAM

The Idaho Geological Survey has been a partner in the USGS STATEMAP program since its inception in 1993. The projects vary in scale, scope, and geologic province, but four themes underpin the Survey’s geologic mapping program: (1) advancement of geologic understanding, (2) cutting-edge digital cartography and databases, (3) new mapping of 1:24,000-scale bedrock and surficial geologic maps, and (4) new mapping of 1:100,000-scale geologic maps to meet the long-term goal of digital geologic coverage of the entire state. The Surficial Geologic Map of the Wood River Valley is an example of the first three themes.

The Wood River Valley is a world-class, four-season recreation destination that is experiencing one of the highest growth rates in Idaho. The area includes the municipalities of Sun Valley, Ketchum, Hailey, and Bellevue as well as numerous adjacent subdivisions. The map of this area is the product of a three-year surficial mapping project to address geotechnical needs in the municipal and private lands of the growth corridor. The mapping was conducted at 1:24,000 scale beginning in the main valley and extending into the tributary canyons where new growth is concentrating. Parts of eleven quadrangles were mapped. Prior to the project there was no complete surfical map coverage of the area. Characteristics of the surficial units and the glacial and alluvial stratigraphy have been standardized. Geologic hazards mapping includes delineation of active river wash, alluvial terraces, avalanche tracks, debris chutes, and landslide scarps and deposits.

This map features colored geologic units on a 1:50,000-scale shaded relief base. The shaded relief was created in the visualization software World Construction Set 5 where eleven 30-meter digital elevation models were imported and seamlessly joined. The digital landscape is exaggerated 1.5 times to emphasize the surficial terrain and geomorphic landforms. Texture and color were added and the final image was geo-rectified in Arc-GIS. Adobe Illustrator 10 was used for map layout and to drape the geology onto the shaded relief base.