Proof-of-Concept for Nonintrusive and Undisturbed Measurement of Sediment Infiltration Masses Using Gamma-Ray Attenuation

Abstract

Fine sediment infiltration into gravel riverbeds adversely affects the riverine ecology and influences hyporheic exchange processes. So far, different sampling methods have been utilized to measure the amount of infiltrated sediment masses in the field and laboratory. Most of these methods disturb the sediment bed, and only a few provide a vertical gradation of infiltrated sediment masses. Therefore, this study presents the proof-of-concept for a nonintrusive and nondestructive technique for measuring the masses of infiltrated fine sediments in high-resolution vertical profiles using the gamma-ray attenuation (GRA) method in laboratory flume experiments. First, the principal functionality of the GRA method was successfully tested on preliminary experiments, which consisted of a box filled with spheres, known masses of infiltrated sediments, and water. Afterward, the GRA method was applied in a laboratory flume with a simplified gravel bed to test the repeatability of the measuring concept under varying boundary conditions. The accuracy of the measured infiltration masses for the preliminary box tests show a deviation of less than 5% compared to gravimetrically determined masses, which proves the applicability of the GRA method. Furthermore, the repeatability tests of the flume experiments yielded deviations from 1.4% to 7.7%, which is still in an acceptable range, considering the complexity of the infiltration process. Based on the obtained results, the nonintrusive and nondestructive GRA method provides a profound basis for further in-depth investigations of fine sediment infiltration and accumulation in gravel riverbeds.