Raindrop Impact as the Force Initiating Soil Erosion

The 20-100 mm portion of a yellow podzolic soil (Albaqualf) from the Ginninderra Experiment Station (A.C.T.) was used in a rainfall simulator and flume facility to elucidate the interactions between raindrop impact, overland water flow and straw cover as they affect soil erosion. A replicated factorial design compared soil loss in splash and runoff from 50 and 100 mm h-1 rainfall, the equivalent of 100 mm h-1 overland flow, and 50 and 100 mm h-1 rainfall plus the equivalent of 100 mm h-' overland flow, all at 0, 40 and 80% straw cover on a 9% slope. As rainfall intensity increased, soil loss in splash and runoff increased. Within cover levels, the effect of added overland flow was to decrease splash but to increase total soil loss. This is due to an interaction between raindrops and runoff which produces a powerful detaching and transporting mechanism within the flow known as rain-flow transportation. Airsplash is reduced, in part, because of the changes in splash characteristics which accompany changes in depths of runoff water. Rain-flow transportation accounted for at least 64% of soil transport in the experiment and airsplash accounted for no more than 25% of soil transport The effects of rainfall, overland flow and cover treatments, rather than being additive, were found to correlate with a natural log transform of the soil loss data.

Download Full-text

Estimating Raindrop Kinetic Energy: Evaluation of a Low-Cost Method

Applied Engineering in Agriculture ◽

10.13031/aea.11518 ◽

2017 ◽

Vol 33 (4) ◽

pp. 551-558 ◽

Cited By ~ 2

Author(s):

Jian Wang ◽

Dexter B. Watts ◽

Qinqian Meng ◽

Thomas R. Way ◽

Qingfeng Zhang

Keyword(s):

Soil Erosion ◽

Kinetic Energy ◽

Loess Plateau ◽

Filter Paper ◽

Rainfall Intensity ◽

Low Cost ◽

Rotating Disks ◽

The Loess Plateau ◽

Rainfall Events ◽

Raindrop Impact

Abstract. The Loess Plateau of China is regarded as the most intensively eroded region in the world and soil erosion caused by raindrop impact is a common occurrence on agricultural land within this region. Therefore, understanding the influence of rainfall energy on the soil surface is needed to improve prescriptions for best management practices aimed at mitigating erosion. Disdrometers for measuring rainfall energy are presently available; however, these are relatively expensive and their use may not be justified for determining raindrop energy for predictive soil erosion models in regions where there are limited economic resources. To overcome this constraint, a device was tested for evaluating size and velocity of water drops during rainfall events. This device utilized two rotating disks combined with filter paper to obtain raindrop diameter and velocity which can then be used for determining the kinetic energy of falling raindrops. With this device, raindrop diameter was determined from the resultant raindrop stain left on the filter paper during rainfall events and velocity was calculated from the time it took a falling raindrop to travel between the pair of rotating disks. Measurements were taken for approximately 10 minutes during each of six rainfall events of different intensities over a three month period (from June to August of 2013). The smallest raindrop measured was 0.39 mm diameter and the largest was 5.92 mm diameter. The event average raindrop diameter increased with increasing event rainfall intensity. The minimum raindrop impact velocity was 1.47 m s-1, the maximum was 9.45 m s-1, and the event average terminal velocity increased as event rainfall intensity increased. Estimated raindrop kinetic energy ranged from 0.04 × 10-6 J to 4728.21 × 10-6 J, with event mean raindrop kinetic energy ranging from 40.33 x 10-6 J to 276.94 × 10-6 J. The relationship between estimated event rainfall kinetic energy and event rainfall intensity was represented by an exponential function. The disk device was also compared to an optical disdrometer. The data collected for rainfall intensity, raindrop diameter, and velocity were statistically similar between the two devices. Results from this study show that this low-cost method can be used to estimate rainfall kinetic energy in the Loess Plateau region of Northwest China. Keywords: Loess Plateau, Raindrop diameter, Raindrop velocity, Rainfall intensity.

Download Full-text

Investigating the Role of Raindrop Impact on Hydrodynamic Mechanism of Soil Erosion Under Simulated Rainfall Conditions

Soil Science ◽

10.1097/ss.0b013e3182639de1 ◽

2012 ◽

Vol 177 (8) ◽

pp. 517-526 ◽

Cited By ~ 56

Author(s):

Juan An ◽

Fenli Zheng ◽

Jia Lu ◽

Guifang Li

Keyword(s):

Soil Erosion ◽

Simulated Rainfall ◽

Hydrodynamic Mechanism ◽

Raindrop Impact

Download Full-text

The use of a raindrop aggregate destruction device to evaluate sediment and soil organic carbon transport

Geographica Helvetica ◽

10.5194/gh-70-167-2015 ◽

2015 ◽

Vol 70 (2) ◽

pp. 167-174 ◽

Cited By ~ 4

Author(s):

L. Xiao ◽

Y. Hu ◽

P. Greenwood ◽

N. J. Kuhn

Keyword(s):

Soil Erosion ◽

Organic Carbon ◽

Soil Organic Carbon ◽

Size Distribution ◽

Agricultural Soils ◽

Natural Sediment ◽

Soil Fractions ◽

Aggregate Breakdown ◽

Erosion Models ◽

Raindrop Impact

Abstract. Raindrop impact and subsequent aggregate breakdown can potentially change the movement behaviour of soil fractions and thus alter their transport distances when compared against non-impacted aggregates. In a given water layer, the transport distances of eroded soil fractions, and thus that of the associated substances across landscapes, such as soil organic carbon (SOC) and phosphorous, are determined by the settling velocities of the eroded soil fractions. However, using mineral size distribution to represent the settling velocities of soil fractions, as often applied in current erosion models, would ignore the potential influence of aggregation on the settling behaviour of soil fractions. The destructive effects of raindrops impacting onto aggregates are also often neglected in current soil erosion models. Therefore, the objective of this study is to develop a proxy method to effectively simulate aggregate breakdown under raindrop impact, and further identify the settling velocity of eroded sediment and the associated SOC. Two agricultural soils with different sandy and silty loam textures were subjected to rainfall using a raindrop aggregate destruction device (RADD). The aggregates sustained after raindrop impact were fractionated by a settling tube into six different classes according to their respective settling velocities. The same mass amount of bulk soil of each soil type was also dispersed and sieved into the same six classes, to form a comparison in size distribution. The SOC content was measured for each settled and dispersed class. Our results show the following: (1) for an aggregated soil, applying dispersed mineral grain size distribution, rather than its actual aggregate distribution, to soil erosion models would lead to a biased estimation on the redistribution of eroded sediment and SOC; (2) the RADD designed in this study effectively captures the effects of raindrop impact on aggregate destruction and is thus able to simulate the quasi-natural sediment spatial redistribution; (3) further RADD tests with more soils under standard rainfall combined with local rainfalls are required to optimize the method.

Download Full-text

Soil crusting in relation to global soil degradation

American Journal of Alternative Agriculture ◽

10.1017/s088918930000446x ◽

1992 ◽

Vol 7 (1-2) ◽

pp. 56-62 ◽

Cited By ~ 10

Author(s):

Malcolm E. Sumner ◽

William P. Miller

Keyword(s):

Soil Erosion ◽

Soil Degradation ◽

Seedling Emergence ◽

Soil Surface ◽

Clay Dispersion ◽

Soil Crusting ◽

The World ◽

Global Soil ◽

Raindrop Impact

The formation of crusts or seals at the soil surface is exceedingly important in determining how much rainfall infiltrates into the soil and how much runs off, causing soil erosion. This paper explores the processes involved in the formation of crusts, such as raindrop impact and clay dispersion, to formulate a picture of the mechanisms involved. We discuss the major consequences of crusting, namely, runoff, erosion, and impaired seedling emergence, and present strategies to reduce soil degradation. Examples are offered from many parts of the world.

Download Full-text

The role of the geometry and frequency of rectangular rills in the relationship between sediment concentration and stream power

Soil Research ◽

10.1071/s97019 ◽

1997 ◽

Vol 35 (6) ◽

pp. 1359 ◽

Cited By ~ 2

Author(s):

B. Fentie ◽

C. W. Rose ◽

K. J. Coughlan ◽

C. A. A. Ciesiolka

Keyword(s):

Soil Erosion ◽

Overland Flow ◽

Sediment Concentration ◽

Stream Power ◽

Flume Experiments ◽

Erosion Processes ◽

Physically Based ◽

The Relationship ◽

Raindrop Impact

We examined, both experimentally and theoretically, whether rilling results in higher soil erosion than would have occurred without rilling. The possibility of rilling occurs when overland flow-driven erosion processes are dominant over erosion due to raindrop impact, and that is the situation assumed in this paper. Stream power (or a quantity related to stream power such as shear stress) is commonly used to describe the driving variable in flow-driven erosion. Five flume experiments were designed to investigate the relationship between stream power and sediment concentration and how this relationship is affected by the ratio of width to depth of flow (r), and the frequency or number of rills per metre width (N) of rectangular rills. This paper presents the results of these experiments and uses a physically based soil erosion theory to show that the results of the 5 flume experiments are in accord with this theory. This theory is used to investigate the effect of all possible rectangular rill geometries and frequencies on the maximum possible sediment concentration, i.e. the sediment concentration at the transport limit, by developing general relationships for the influence of r and N on sediment concentration. It is shown that increased stream power, which can be due to rilling, does not necessarily result in higher sediment concentration.

Download Full-text