Applications of Landsat imagery in the Great Plains

James S. Aber¹, Everett E. Spellman², Michael P. Webster¹, and Laura L. Rand³

1. Earth Science Department, Emporia State University, Emporia, KS 66801 (aberjame@esumail.emporia.edu).
   
2. Kansas Dept. Health and Environment, Forbes Field, Topeka, KS 66620.
   
3. Dept. of Geosciences, Fort Hays State University, Hays, KS 67601.

INTRODUCTION

Archive MSS datasets are now available at low cost from the EROS Data Center of the U.S. Geological Survey. These datasets span more than 20 years of observation and represent a tremendous resource for all manner of earth science applications. Powerful computers and sophisticated GIS software are available also at modest cost for image processing and analysis of satellite data. Thus, it is now possible to conduct state-of-the-art research with Landsat digital data on a relatively small budget.

Landsat MSS digital data and imagery are utilized here to demonstrate applications in geology and hydrology for two regions of the Great Plains--Devils Lake vicinity in northeastern North Dakota and the Flint Hills of east-central Kansas. Standard techniques utilized for image processing included haze correction, stretching, false-color composites, band ratios, classification, and time-series analysis. IDRISI software was employed for image processing and analysis.

A major aquifer, known as the Spiritwood aquifer, crosses Devils Lake vicinity from east-southeast to west-northwest. This aquifer is developed partly in bedrock and partly in loose sediment filling the preglacial Cannonball valley. The major depressions of Devils Lake are located above this aquifer. High ground-water pressure in the Spiritwood aquifer likely facilitated major glaciotectonic thrusting (Bluemle and Clayton 1984; Hobbs and Bluemle 1987).

Devils Lake is the terminal point of a large enclosed drainage basin that has no surface outlet at present. As a result of its terminal position, the water body of Devils Lake has undergone substantial changes in its elevation, surface area, salinity, and biomass. During the past 4000 years, Devils Lake has fluctuated several times between completely drying up and overflowing into either the Sheyenne River and/or Stump Lake basin to the east (Bluemle 1996). These changes resulted entirely from long-term climatic events.

According to established records, the maximum historical lake level was attained in the early 1800s, when it exceeded 1440 feet (439 m) elevation (Bluemle 1995), toward the end of the Little Ice Age. Between 1826 and 1830, the lake probably overflowed into Stump Lake, and it possibly may have overflowed to the Sheyenne River during part of this time. After the 1860s, lake level declined until 1940, when it fell to its lowest historical elevation of 1400 feet (427 m), at which time the lake was only 1 m deep--see Devils Lake record. The lake subsequently rose and exceeded 1425 feet (434½ m) during most of the 1980s (Fig. 3). Following a slight decline in the late 1980s and early 1990s, the lake is again rising; the water surface surpassed 1437 feet (438 m) elevation during the summer of 1996. Rising water threatens to flood the city of Devils Lake, Camp Grafton, roads, fields, sewage treatment plants, and other human facilities--see Ziebach Pass. The city has received funding to construct a dike that would provide protection up to 1440 feet, but if the current trend continues the lake may exceed this elevation during 1997--see Devils Lake hydrograph.

Both the prehistorical and historical fluctuations of Devils Lake level correlate with general climatic variations (Callendar 1968; Wiche 1986). Another factor that influences Devils Lake is storage of surface water runoff in the upstream chain of lakes. This chain of lakes also acts as a trap for sediment, so that little sediment is washed into Devils Lake. In addition, Devils Lake may loose or gain water from the underlying Spiritwood aquifer. Changes in water level of Devils Lake are, thus, caused by climatic variations, as modified by the surface and subsurface characteristics of the drainage basin. Recent modifications of drainage, agricultural practices, and other human factors have caused only slight effects on water levels in Devils Lake (Bluemle 1995); however, runoff from land north of the lake has washed in substantial salts and agricultural wastes.

Interpretation of glacial geomorphology

These two trends of ice-shoved hills may be interpreted as features formed by thrusting at the margins of two converging ice lobes (Aber et al. 1993). One lobe advanced locally from the north or northwest in the West Bay/Crow Hill vicinity, while the other moved locally from the northeast in the East Bay/Devils Heart Butte region, with Main Bay/Sullys Hill at the junction of the two. The two ice lobes probably advanced together, or at least at about the same time, to the North Viking and Cooperstown ice margins. However, some parts of the Crow-Sullys Hill complex may have formed in association with the Heimdal or Pekin ice margins.

A well-defined melt-water drainage system can be seen south of the ice-shoved hills. Four drainage routes are: Big Coulee, Black Slough, the channel that begins at Twin Lakes, and the Long Lake channel. These drainage channels, particularly Big Coulee, are quite distinctive on Landsat images. All four channels carried melt water away from the glacier margin at the ice-pushed hills into the Sheyenne valley a short distance to the south. To the north, Sixmile Bay may have been eroded by a subglacial melt-water stream flowing toward the Devils Lake basin. Creel Bay may have a similar origin. These bays/valleys are here interpreted as tunnel valleys formed by melt-water erosion under the ice.

Good preservation of this assemblage of glacial landforms suggests that subsequent glaciation either did not advance over this vicinity or did little to modify the hill-hole pairs and associated landforms. The association of large ice-shoved hills, melt-water spillways, deposits of hydrodynamic blowouts--see Devils Heart Butte, and tunnel valleys indicates that a substantial volume of water was released during creation of these landforms. This water was derived from both the glacier and the Spiritwood aquifer (Bluemle 1993).

Interpretation of lake hydrology

Algal blooms have an appearance similar to land vegetation on Landsat MSS images. The algae is dark in visible bands and bright in short-infrared bands. The blooms often take place in summer or autumn, when lake water temperature is relatively warm--see algal mat. Large algal blooms are depicted on certain images in East/Black Tiger Bays and central Devils Lake/Creel Bay. Extensive algal mats are apparently more common in the deep, clear waters of central Devils Lake and East Bay, as opposed to the shallow muddy water of West Bay. This difference may reflect the ability of sunlight to penetrate deeper in clean water and support more photosynthesis. However, algal blooms can take place in any portion of Devils Lake.

It is clear that bedrock structural features have exerted a strong influence onstream erosion patterns in east-central Kansas--see river map. Major lineaments are oriented toward the northwest (Fall/Neosho) and north-northeast (Walnut). These lineaments are defined by straight, continuous stream valleys, discontinuous valley segments, or en echelon stream valleys. The major lineaments correspond to well-known surficial joint sets, which in turn give the appearance of being related to deep-seated faults (Berendsen and Blair 1991).

Valley patterns are especially conspicuous on Landsat images of the Flint Hills region, because of high topographic relief and strong contrast in landuse between valleys (row crops) and uplands (pasture). Landsat images reveal linear stream valleys that meet at angular junctions--see autumn image. Valleys in upper portions of the South Fork Cottonwood River, North Branch Verdigris River, and headwaters of the Fall River are parallel, trending about 350°. In fact, the Fall River headwater valleys are in direct alignment, across the drainage divide, with the North Branch Verdigris and South Fork Cottonwood River valleys. We propose to call this NNW-SSE trend (350°-170°) the Verdigris lineament, and we suggest that it represents an important fracture pattern in bedrock of east-central Kansas-see joint set 4.

The upper North Branch Verdigris River takes an abrupt turn toward the east, changing its direction by 100°. This feature is one of the most prominent drainage anomalies in Kansas. During the Neogene, the ancestral Verdigris River presumably flowed across this region from west to east (Aber et al. 1995). Subsequent stream capture by the Cottonwood drainage diverted the upper ancestral Verdigris, leaving the unusual barbed drainage pattern in the North Branch Verdigris River.

ACKNOWLEDGEMENTS