Development of a Rainfall and Runoff Simulator for Performing Hydrological and Geotechnical Tests

Abstract

Laboratory apparatuses for the analysis of infiltration and runoff enable studies under controlled environments and at reduced costs. Unfortunately, the design and construction of such systems are complex and face difficulties associated with the scale factor. This paper presents the design, construction, and evaluation of a portable rainfall and runoff simulator. The apparatus allows the evaluation of unsaturated soils with and without vegetation cover, under a wide range of simulation scenarios. The apparatus also enables the control of the intensity, size, and uniformity of simulated raindrops for variable surface slope, specimen thickness, and length conditions. The monitoring of the volumetric water content and matric suction and a rigorous computation of water balance are ensured. The obtained results indicate that the automated rainfall generator produces raindrops with Christiansen uniformity coefficients higher than 70%, and with an adequate distribution of raindrop sizes under a range of rainfall intensities between 86.0 and 220.0 mm h−1. The ideal rainfall generator conditions were established for a relatively small area equal to or lower than 1.0 m2 and considering rainfall events with return periods of 10 to 100 years.

Evaluation of Rainfall Interception by Vegetation Using a Rainfall Simulator

“…However, difficulties related to scale factor may arise. Many devices have been developed and used to evaluate infiltration and runoff [7,[41][42][43][44][45], but only a few studies use physical models to evaluate the interception phenomena.…”

“…In this context, this study used the RS developed by [7,41], which was designed to evaluate the infiltration and runoff of unsaturated specimens with or without vegetation (Figure 3). This RS allows the control of the intensity, size, and uniformity of the simulated raindrops applied to specimen, with different dimensions and inclinations.…”

“…The specimen was extensively instrumented for the monitoring of matric suction and water content, using tensiometers and capacitive sensors, respectively (Figure 4f). Details regarding the preparation, installation, and operation of tensiometers and moisture sensors are described in [7,41]. Once the instrumentation was in place, the specimen was locked in alignment with the sprinkler system and rotated according to the desired slope (Figure 4e).…”

“…A simulated rainfall corresponding to 86 mm h −1 was applied in all tests, for a duration of 60 min and with a slope of 15 • . These rainfall characteristics are representative of the tropical region where this study was carried out [41]. The selected slope angle is commonly found in the field and in earthworks.…”

Implementation of the Green-Ampt Infiltration Model: Comparative between different numerical solutions

“…In situ tests are laborious, whether from the point of view of financial costs, equipment, test time and favorable climatic conditions. In contrast, physical and numerical models have gained strength in infiltration studies, either separately or together [14,18,20,21,33].…”