Resource capability units: their utility in land-and water-use management with examples from the Texas coastal zone

A resource capability unit is an environmental entity--land, water, area of active process, or biota--defined in terms of the nature, degree of activity, or use it can sustain without losing an acceptable level of environmental quality. Units are established by recognizing elements of first-order environmental significance, whether dominantly physical, biologic, or chemical. These include (1) physical units (geologic substrate and soil units), where physical properties are of primary importance; (2) process units, such as beaches, washover channels, floodplains, escarpments, and dunes where active physical processes are dominant factors; (3) biologic units,such as reefs, marshes, swamps, and grassflats where biologic activity and habitation assume first-order significance; and (4) man-made units such as spoil heaps, dredged channels, canals, and made land where man's activity has resulted in important environmental modification. Capability of water systems is defined by the nature and distribution of sediment substrate, overall salinity patterns, circulation, tidal influence, depth variations, turbidity, fresh-water influx, distribution of biologic communities, and water chemistry. This report outlines (1) the nature of resource capability units, (2) the basic factors and properties exhibited by the units that define the limits of their use, and (3)the application of resource capability units to environmental management. Specific examples are shown for the 20,000 square miles of the Texas Coastal Zone, where a wide variety of resource units occur in an area of diverse human activities.