Impacts of Sand and Gravel Mining on Physical Habitat of the Colorado River and Tributaries, Central Texas

By

SAUNDERS, GEOFFREY P.

Lower Colorado River Authority, Austin, TX

The Colorado River of Texas is an important water resource in the Coastal Plains and Gulf Coast regions. The river is a source of water for municipal and agricultural use, and provides habitat for game fish and protected species. Increasing water demand is requiring optimal management of the resource.

Almost all anthropological impacts on the Colorado River are regulated and monitored. One exception is sand and gravel mining in the floodplain. Frequently, unregulated gravel pits are developed on the bank of the river, making mining operations susceptible to flooding but also making the river vulnerable to environmental impact.

Possible impacts of riparian sand and gravel mining include channel instability, erosion and deposition, effects on aquatic habitat and riparian ecology, and even property boundary changes. Aquatic habitat needed to support game fish and protected species may be degraded by changes in flow velocity, channel depth and substrate material. Excessive turbidity caused by suspended sediment can reduce light penetration in the water column, thus affecting aquatic plant growth. Riparian ecology, including the habitat of terrestrial plants and animals, is directly impacted. These effects and others can be characterized by performing physical habitat assessments in affected reaches.

This paper documents impacts of sand and gravel mining on physical habitat at specific locations on the Colorado River and the Pedernales River in Central Texas.