C. M. Woodruff

Stream Piracy near the Balcones Fault Zone, Central Texas

Geometrical, erosional, and depositional evidence indicates that three stream piracy events have occurred near the Balcones fault zone in Central Texas. The most ancient episodes of capture (perhaps as old as Miocene) diverted the major streams in the region from predominantly eastward courses to a trend roughly perpendicular to the newly developed Balcones escarpment. The other two types of piracy events are probably ongoing, but only one of these is strongly influenced by the geologic and physiographic setting near the Balcones fault zone. The other occurs only among low-order headwater drainage basins and is controlled by local bedrock and slope conditions and is not largely affected by the larger physiographic influences of the Balcones escarpment.

Test of Environmental Geologic Mapping, Southern Edwards Plateau, Southwest Texas

The southern Edwards Plateau, southwest Texas, is the recharge area for a thick limestone aquifer that supplies potable water to more than 850,000 people and irrigation water for more than 2,500 sq mi (6,500 sq km) of cropland. Because the increasing population effects a booming residential and recreational development in this region, information on the geological environment of the plateau must be made available to planners so that the aquifer can be safeguarded. A reconnaissance environmental mapping technique has been developed in a pilot study that is to precede a major regional mapping program. Constraints in developing the technique were plateau geology, land use, factors controlling recharge, and available materials, including aerial photography and maps. The basis for defining the environmental mapping units is dominantly geomorphic; lithologic differences are indicated where necessary. The units are: karstic tableland, karstic lowland, deeply dissected carbonate, moderately dissected carbonate, carbonate, shale, alluvial fan, terrace, flood plain, fan plain, and alluvial-colluvial material. Results of this mapping are directly applicable in land use planning.

Inland boundary determinations for coastal management purposes—an ecological systems approach to requirements of the federal coastal zone management Act of 1972

Abstract An analysis of ecological systems that both sustain and are sustained by coastal waters provides the key to a biophysical procedure for delineating inland coastal management boundaries. This analysis entails two basic tasks: (1) mapping the ecosystems that compose coastal waters and adjacent areas, and (2) charting sustaining flows among these systems. The resulting boundary encompasses all environments of coastal waters (subaqueous areas containing a measurable quantity of seawater) and all shore‐lands (either emergent or submergent environments that interchange sustaining materials, energy, or biota with coastal waters). As this biophysical procedure depends on the precise location of, and functional transfers among, coastal ecosystems, it provides a means both for assessing the consequences of human actions and for establishing a landward boundary for a management program. Alternative boundaries not based on locations and operations of coastal ecosystems would probably be either arbitrary or o...

Lineament Identification And The Edwards Aquifer Of Central Texas

This paper examines the analysis of a Landsat 4 TM scene for lineament detection in one area along the Balcones/Ouachita trend in Central Texas. Landsat imagery was enhanced to f a c i l i t at e lineament identification. Comparisons of lineament orientation are made among lineaments from a variety of image sources. A short discussion of edge enhancement techniques employed is included.