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Abstract: Microtopography, Runoff Processes, Sediment Transport, and Their Implications for Land-Use Planning in the Central Texas Hill Country

William M. Marsh, Nina L. Marsh

The hill country near Austin is characterized by a stepped microtopography formed by alternating beds of hard limestone and soft marl in the Edwards Formation. These micro-landforms control the distribution of soil, with thick residual soils (up to 3 m deep) lying over the risers and thin transported soils (less than 0.25 m deep) on the treads. Detailed field studies in the Barton Creek watershed reveal that hillslope processes are governed by these features. Infiltration rates on risers typically exceed 10 cm/hr, and overland flow rarely extends beyond one tread-riser-tread sequence. Sediment transport is limited by this system, and sinks are abundant on hillslopes. Small drainage basins function as partial-area storm-water systems, with much more water and sediment held in storage t an generally thought by city planners and engineers. These discoveries provide new opportunities for improved site planning and local storm-water management in areas undergoing development.

AAPG Search and Discovery Article #90983©1994 GCAGS and Gulf Coast SEPM 44th Annual Meeting, Austin, Texas, October 6-7, 1994