Simulation of Rainfall Intensity and Slope Gradient to Determination the Soil Runoff Coefficient at Microplot Scale

Simulating rainfall is one of the valuable methods of measuring hydrological data and soil erosion processes. Rapid evaluation, high repeatability, and low cost are the reasons of using rain simulators. In this study, a rain simulator was constructed in dimensions of 3.0 × 3.0 × 3.0 m and it was protected on three sides by a plastic cover. An inclined table was used to create slopping surfaces of 5, 10, and 15%. Microplots were used in the dimensions of 0.2 × 0.4 × 1.0 m to collect and measure direct runoff in a bucket outside the device. Nozzles were calibrated to produce two different rainfall intensities 10 and 20 mmh−1 using sprinkler Model 5B at 8 and 12 psi, respectively. Furthermore, three different soil types, namely, clay loam (CL), silty clay (SC) loam, and SC were examined. In general, it was observed that with increasing the rainfall intensity and slope, the rate of runoff and sedimentation increase. SC soil at 15% slop offered the highest performance under the intensity of 20 mmh−1. SC and the CL soils produced the highest and lowest runoff coefficients, respectively. The CL soil produced the highest soil loss (1 kgm2 at 15% and I = 20 mmh−1). Further, it was concluded that a significant change (an average increase of 53%) in soil loss can be achieved as the rainfall intensity increased from 10 to 20 mmh−1.

Uji Laboratorium Pengaruh Kemiringan Lereng Terhadap Kejadian Longsoran Aliran Debris Pasir Merapi

The debris flow that happen on the of Mount Merapi is really hard to be seen, therefore, it is necessary to conduct laboratory-scale simulations to know when debris flows will happen as regard to rainfall intensity and the slope of Mount of Merapi. This research examines the correlation between the slope and the potential for debris flow at 25 mm/h rainfall intensity. This will be a reference for early warning of landslides on Mount of Merapi. This research uses a tool such as flume that sized 3 x 5 x 0,15 m as a model of slope of Mount of Merapi, and artificial rainfall apparatus as the rain simulator. The simulation is conducted using five years rainfall intensity of 25 mm/h in combination of slope i.e. 15, 20, 25, 30 and 35 degrees whereas the material used to represent the sediment is in form of sand taken from Gendol River upstream with 4,75 mm passing mesh sieves. The result of this simulation is the steeper the slope is, the faster the duration for the rain to cause debris flow. This research can be continued with change variation of rainfall intensity to understand the debris flows behavior. Keywords: Debris flow, Mount of Merapi, laboratory test, rainfall intensity, flume model

Ponding time, hydraulic conductivity and sorptivity – experimental determination by a single ring infiltrometer with rain simulator

<p>The continuous rain simulator used with very precise dosing enables both simulation of characteristic rainfall as well as accurate determination of infiltration rate and automatic calculation of hydraulic conductivity of soils under natural conditions. As a part of the research of infiltration processes induced by characteristic rainfalls, the effects of stormy rainfalls were verified in the described project stage. Stormy rain with constant intensity was applied by rain simulator in a single ring infiltrometer. Samples were tested in the laboratory (soils and kaolinite) and directly in the field. During rain infiltration was measured ponding time. Theoretical base of the research comes from non-steady state unsuturated vertical infiltration, which process (in one-dimensional flow conditions) can be described by Richard´s equation. Final simplified solution is provided by Philip´s simplified infiltration equtions. Hydraulic conductivity K was approximated from the analysis of time series of the process of vertical non-steady cumulative infiltration, going after ponding time. Sorptivity S was calculated by the numerical experiment with known values of stormy rain intensity, ponding time and hydraulic conductivity. Compared to traditional methods (single or double ring infiltrometer), soil hydro-physical characteristic (K, S) determined by this method is more reliable, informative and verified by ponding time.</p>

Effect of Extreme Rainfall Intensity on Matric Suction and Ground Movement

Increased intensity of rainfall events due to extreme climate change has led to the substantial increase in the occurrence of disasters, especially in a tropical-climate country such as Malaysia. Rainfall-induced landslide has become one of the most common types of disasters, and its triggering factors are still uncertain and impossible to predict. In this study, the effect of extreme rainfall intensity on groundwater behaviour is addressed through laboratory-scale testing. The adopted rainfall intensity is 60 mm/h, which was the heaviest hourly rainfall intensity recorded in Sarawak on 3rd January 2016 and 80 mm/h, which was the corresponding value recorded in Penang on 10th October 2016. The simulation is conducted on four cases. The simulated rainfall exhibits a duration of 6 h. In addition, the overall trend of the matric suction measurement and soil moisture in all cases is discussed on the basis of the results obtained from laboratory studies. After the rain simulator stopped, the matric suction decreases, and it remains stagnant, followed by a significant drop in the reading. For all cases, failure occurs, albeit at different times with different volumes of mass wasting.

Use of Software for Image Analysis and Calibration of Automated Rain Simulator

Aims: To calibrate and evaluate a rain simulator, with automatic operation, as well as determine the average size, the effect of the height of the equipment (2.12; 2.42 and 2.72 m) and of the oscillations of the spray nozzle of the rain simulator (21, 29 and 40 oscillations min-1). Finally, to test and to compare the results of the count of drops by the software of analysis and processing of images Able Image Analyser, ImageJ and Safira. Study Design: The experimental design was completely randomized, with 3 x 3 x 3 factorial scheme, with three repetitions (81 units). Place and Duration of Study: The research was conducted in a greenhouse, in the municipality of Rondonópolis, Mato Grosso, located geographically at latitude 16°27'49 "S, longitude 550°34'47" W. Methodology: For the calibration tests, the rainfall simulator was adjusted according to the heights (2.12; 2.42 and 2.72 m) and oscillations (21, 29 and 40 oscillations min-1), followed by trays with a uniform layer of wheat flour, 2 cm thick, where the simulated raindrops were sprayed for a period of 4 seconds. From this procedure, the drops were dried, sifted, weighed and counted. Droplet analysis was performed using three image analysis software Able Image Analyser, ImageJ and Safira. Results: The softwares Able Image Analyzer, ImageJ and Safira did not show any significant difference in counting of the number of drops. It was observed that in the oscillation factor in setting that if gets drops of larger size (21 oscillations min-1) the terminal velocity is also greater. In the height factor of the equipment, the drops presented larger sizes at the lower height (2.12 m). There are larger drops, higher terminal velocity as the height of the spray nozzle decreases, and higher kinetic energy value per unit area as the height of the spray nozzle increases. The range of drop sizes observed was 1.2 mm to 3.1 mm. Conclusion: Although the software does not present significant differences, the ImageJ software proved to be more suitable as a research tool, since it has the license of free use and greater ease of use. Satisfactory results were obtained compared to natural rains in more than one combination of height and swings.

Experimental Study of a Piezoelectric Rain Energy Harvester

Over the past few decades there has been significant advancement in the development of microelectronics. This has attracted attention of micro-scale energy harvester systems that could harvest energy from the operating environment of the microsystem. In this paper, rain energy harvesting using piezoelectric beam is tested. This paper seeks to create an experimentally validated proof of concept piezoelectric rain energy harvester using a piezoelectric beam. A rain simulator consists of six solenoid valves is designed to simulate different rain types. The effect of multiple water droplets impinging different positions on the piezoelectric beam is studied in this paper. Results show that a 4.5 ± 0.2 mm diameter water droplet falling at height of 0.82 m impinging the piezoelectric energy harvester is capable of generating a peak power of 0.16 mW.