CHAPTER 3 



CHARACTERISTICS OF THE STUDY AREA 



Location and Physiography 



The Missouri River Breaks comprise a 10 to 50-km-wide by 

 300 km-long belt of rugged badlands along the Missouri River 

 and its tributaries in northcentral Montana. Distinguished 

 from adjacent rolling plains by physiographic and vegetative 

 characteristics, the "breaks" have long been recognized to 

 provide superior habitat for mule deer within the Missouri 

 Plateau Region of the northern Great Plains. 



Our study was conducted primarily within a 

 representative, 275 km 2 area located at 47°30' north latitude, 

 108°30' west longitude, approximately 40 km northeast of Roy, 

 in central Montana (Figs. 3.1 and 3.2). The area extends 

 about 30 km east from U.S. Highway 191 and 7-11 km south from 

 the Missouri River. It encompasses two major drainages, Sand 

 Creek and Carroll Coulee, that dissect the area in a dendritic 

 pattern and become progressively wider, deeper, and steeply 

 sloped as they approach the river (Fig. 3.3). Close 

 interspersion of sharply-cut drainageways or "coulees" and 

 open ridges that extend onto the area from adjacent plains 

 provides the characteristic badlands or breaks topography 

 (Fig. 3.4). 



The entire area slopes gently to the north and east. 

 Elevations range from about 945 m along the southern edge of 

 the area to about 685 m on the Missouri River floodplain. The 

 greatest relief over the shortest distance occurs near the 

 river on the northern portion of the area. Rolling plains 

 extend, with slightly increasing elevation, to the south and 

 southwest. 



Soils of the area are derived primarily from the Bearpaw 

 Shale Formation and are predominantly heavy clay loams of the 

 Lismas-Thebo series, with moderate amounts of salts. Shallow 

 layers of glacial till occur on the highest level ridgetops . 

 These soils are relatively impermeable to water and runoff is 

 high. Extensive natural erosion is characteristic, especially 

 on steep sparsely vegetated slopes, where underlying shales 

 are exposed, and along ephemeral streamcourses . The soils are 

 considered too shallow, too heavy and plastic, and generally 

 too steep for cultivation (Gieseker et al. 1953). 



The Missouri River provides permanent water along the 

 northern boundary of the study area. Sand Creek and Carroll 

 Coulee are intermittent streams which flow only during spring 

 runoff or following heavy rains. There are 62 man-made 

 stockwater impoundments and 4 wells, developed to provide 



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