Delineation of Surficial Karst Manifestations using LiDAR and Pictometry in Ordovician Carbonates, Central Texas

Abstract

Recent advances in remote sensing technology have enabled widespread delineation and characterization of karst terrains based on surficial manifestations of subsurface occurrences. While sinkholes only partially represent void development within karsted terrains, they are windows into the karst system and can be significant geohazards. Sinkholes are characteristic of karst topography and represent subsurface groundwater flows which dissolve underlying rocks, mainly limestone, which causes voids or caves. In order to enhance Best Management Practices in karsted terrains, this study delineated karst features in Ordovician Ellenburger carbonates in San Saba and Lampasas counties, Texas, with an emphasis on identifying sinkholes at Colorado Bend State Park where the Texas Speleological Survey had previously identified more than 400 individual karst features. Traditional karst surveys rely on time-intensive, field-based, traverse mapping; however, LiDAR (Light Detection and Ranging) and aerial photography (Pictometry) were employed in this study to more efficiently characterize a large region.

LiDAR processing yielded a high-resolution digital elevation model (DEM) which was used to locate sinkholes based on DEM surface modeling of slope and overland flow accumulation; however, the resolution of features that were identifiable was limited to features greater than one meter in diameter and more than 20 centimeters deep due to data resolution. Subsequent pictometry analyses allowed for accuracy assessment, aerial vantage, and in situ measurements of individual features in order to prioritize specific features for further field-based characterization. Using this particular method of karst exploration helps manage time and effort in the field, consequently saving financial burden and providing efficient management of labor. In addition, the use of remote sensing will dramatically increase the area of investigation, enabling more effective delineation of spatial distribution of karst development.

AAPG Datapages/Search and Discovery Article #90219 © 2015 GCAGS, Houston, Texas, September 20-22, 2015