Determining soil erosion rates on semi-arid watersheds using radioisotope-derived sedimentation chronology

Authors

V. O. Polyakov, USDA-ARSFollow
M. N. Nichols, USDA-ARS
M. A. Nearing, USDA-ARSFollow

Document Type

Article

Date of this Version

2017

Citation

Earth Surf. Process. Landforms 42, 987–993 (2017), DOI: 10.1002/esp.4057.

Comments

U.S. government work.

Abstract

This study investigates erosion dynamics of the past 90 years in three small semi-arid watersheds with histories of grazing and vegetation change. Activity of ¹³⁷Cs and excess ²¹⁰Pb from 18 cores collected from sedimentation ponds were measured using a gamma spectrometer. The sediment was dated using a constant rate of supply (CRS) model. This study represents the first time that reservoir sediment accumulation rates determined from fallout isotopes have been verified by direct volumetric measurements of aggradation based on topographic surveys. Measured sedimentation in the ponds ranged between 1.9 and 2.3cm y^-1, representing average sediment delivery rates from the watersheds of between 0.6 and 2.0 t ha^-1 y^-1. These sediment delivery rates were in agreement with those established by other methods for similar catchments in the region. Past variations in sedimentation rates were identified and correlated with recorded history of anthropogenic disturbance. ¹³⁷Cs and ²¹⁰Pb methods are suitable for use in arid environments and can complement each other to increase reliability of erosion rate estimates. The abundance of stock ponds in southwestern USA presents an opportunity to quantify historic erosion and sediment transfer dynamics in areas that have not been well studied or instrumented.