Hydrological Modelling Using a Rainfall Simulator over an Experimental Hillslope Plot

Abstract

Hydrological processes are complex to compute in hilly areas when compared to plain areas. The governing processes behind runoff generation on hillslopes are subsurface storm flow, saturation excess flow, overland flow, return flow and pipe storage. The simulations of the above processes in the soil matrix require detailed hillslope hydrological modelling. In the present study, a hillslope experimental plot has been designed to study the runoff generation processes on the plot scale. The setup is designed keeping in view the natural hillslope conditions prevailing in the Northwestern Himalayas, India where high intensity rainfall events occur frequently. A rainfall simulator was installed over the experimental hillslope plot to generate rainfall with an intensity of 100 mm/h, which represents the dominating rainfall intensity range in the region. Soil moisture sensors were also installed at variable depths from 100 to 1000 mm at different locations of the plot to observe the soil moisture regime. From the experimental observations it was found that once the soil is saturated, it remains at field capacity for the next 24-36 h. Such antecedent moisture conditions are most favorable for the generation of rapid stormflow from hillslopes. A dye infiltration test was performed on the undisturbed soil column to observe the macropore fraction variability over the vegetated hillslopes. The estimated macropore fractions are used as essential input for the hillslope hydrological model. The main objective of the present study was to develop and test a method for estimating runoff responses from natural rainfall over hillslopes of the Northwestern Himalayas using a portable rainfall simulator. Using the experimental data and the developed conceptual model, the overland flow and the subsurface flow through a macropore-dominated area have been estimated/analyzed. The surface and subsurface runoff estimated using the developed hillslope hydrological model compared well with the observed surface runoff for a rainfall intensity of 100 mm/h. The surface runoff hydrograph was very well predicted by the model, with correlation coefficient (R 2 ) and Nash-Sutcliffe efficiency coefficient (E) as 0.95 and 0.91, respectively. The observed soil/macropore storage component was estimated with the help of water balance equation and compared with the model predicted macropore storage. The error in computing the soil/macropore storage was estimated as 0.38 mm i.e., 13%.

Analysis of Urban Flood Inundation Patterns According to Rainfall Intensity Using a Rainfall Simulator in the Sadang Area of South Korea

“…Sci. 2020, 10, x FOR PEER REVIEW 2 of 13 were designed to move the device in the study area [3][4][5]. Thus, the devices were limited to generating a rainfall intensity of around 100 mm/h.…”

“…Roberts and Klingeman [2] developed a rainfall simulator generated by using seven nozzles arranged in a row, and flood runoff experiments were conducted in a model of a river basin. The rainfall simulator was used for field studies to investigate soil crusting and erosion, and portable rainfall simulators were designed to move the device in the study area [3][4][5]. Thus, the devices were limited to generating a rainfall intensity of around 100 mm/h.…”

The increase of rainfall erosivity and initial soil erosion processes due to rainfall acidification

“…The rainfall simulator can be used on rugged terrain as the telescopic legs allow levelling at any slope angle from 0 to 45°. Simulated rainfall is produced with two movable Veejet 80100 nozzles (Blanquies, Scharff, & Hallock, 2003;Chouksey, Lambey, Nikam, Aggarwal, & Dutta, 2017;Pall, Dickinson, Beals, & McGirr, 1983) with a diameter of 4.5 mm. Each nozzle is installed in a metal deposit to collect and reuse the excess of rainfall (that is not sprayed on the plot) and then returned to the pumping system.…”

Numerical evaluation of laboratory apparatuses for the study of infiltration and runoff

“…A direct measurement of runoff may be obtained by means of a runoff apparatus (RA), also referred to in the literature as physical model or rainfall simulator (Montebeller et al, 2001;Alves Sobrinho et al, 2008;Sousa Júnior et al, 2017;Chouksey et al, 2017). An RA must reproduce, under a controlled laboratory environment, rainfall and geotechnical conditions with characteristics that are similar to those found in the field.…”