Morphometric Studies of Subhumid and Semiarid Drainage Basins, Texas Panhandle and Northeastern New Mexico

Data from five drainage basins in the Texas Panhandle and northeastern New Mexico characterize the recent history of regional drainage basin formation and landscape development around the margins of the Southern High Plains. Because stream flow records for most streams in the area are only available for the last 15 yr, morphometric (shape) measurements are used to obtain a long-term, basinwide view of the geomorphic history of these watersheds. Several lines of evidence suggest that the Little Red River basin has developed more rapidly than other basins in the study and that it may continue to do so in the future. Hypsometric analysis of topographic maps and isopach maps of salt-bearing formations reveals that the Little Red River basin has had the fastest rate of denudation and that a thicker section of Permian salt has dissolved beneath that basin than beneath Duck Creek or Alamogordo Creek basins. Comparison of drainage density values for basin headwaters only along the Caprock Escarpment suggests that the Little Red River basin will have the fastest rate of scarp retreat in the future. Similarly, ruggedness numbers for entire basins suggest that the Little Red River basin has the highest potential for future erosion, whereas Duck Creek basin has the lowest. However, relief ratios of the basins imply that, other things being equal, Alamogordo Creek could export more sediment through its channel than the other streams examined. Examination of ruggedness number and magnitude shows that each basin has moderate flood potential. Flooding occurs as a function of rainfall intensity and duration and of land surface slope and dissection by stream channels. Long-term rates of denudation based on hypsometric analysis range from 4 to 21 inches/1,000 yr (10 to 53 cm/1,000 yr) for the last 290,000 to 600,000 yr. These rates are about 16 percent of the most rapid present-day rates. During the same period, lowering of the ground surface caused by subsidence and denudation has occurred at a rate of 10 to 36 inches/1,000 yr (25 to 91 cm/1,000 yr).