Soil Splash Erosion Research Articles

Utilizing palm-leaf geotextile mats to conserve loamy sand soil in the United Kingdom

Despite palm-leaf geotextile mats having the potential to advance soil conservation technologies, field studies using geotextiles as complete cover and buffer strips in reducing rates of soil erosion by water are limited. Hence, the utilization of these mats as a potential soil conservation technique is investigated at Hilton, east Shropshire, UK (52°33′5.7″N, 2°19′18.3″W). Geotextile mats constructed from Borassus aethiopum (Borassus palm of West Africa) and Mauritia flexuosa (Buriti palm of South America) leaves are termed Borassus mats and Buriti mats, respectively. Field experiments have been conducted at Hilton since January 2007, to study the effects of emplacing Borassus and Buriti mats on the erosion of a loamy sand soil. Two sets (12 plots each) of experiments were established to study the effects of Borassus and Buriti mats on splash height and splash erosion. In both sets, 6 randomly-selected plots were completely covered with mats, and the rest were bare. Ten runoff plots (10 × 1 m on a 15° slope) were also established, with duplicate treatments to study the effectiveness of these mats for soil and water conservation. The treatments were: (i) bare soil; (ii) permanent grassed; (iii) bare soil with 1 m Borassus mat buffer zones at the lower end of the plots; (iv) bare soil with 1 m Buriti mat buffer zones at the lower end of the plots and (v) completely covered with Borassus mats. Results (during 22/01/07–21/01/08; total precipitation = 919.0 mm; n = 22 sets of measurements) indicate that Borassus mat-cover on bare soil significantly ( P < 0.05) reduced total soil splash erosion by ∼90% compared with bare plots (24.81 kg m −2). Plots with Borassus mats had 51% less mean splash height than bare plots ( n = 21 sets of measurements). However, Buriti mat-cover on bare soils had no significant ( P < 0.05) effect on soil splash height or splash erosion. Results of runoff plots (08/01/07–14/01/08; total precipitation = 923.4 mm; n = 29 sets of measurements) showed permanent grass plots had the smallest runoff coefficient and the largest sediment yield reduction effectiveness (SYRE). Total runoff from the Borassus buffer zone plots (4.1 L m −2) was ∼83% less than the bare plots and total sediment yield was ∼93% less than the bare plots (2.32 kg m −2). Although, Borassus buffer zone plots had similar effects in reducing soil loss to Borassus completely-covered plots, the later treatment yielded ∼50% more runoff. Borassus buffer strip plots had less SYRE than the Buriti buffer zone plots. Mass per unit area and thickness of both geotextiles decreased after 3 months of surface application. However, moisture sorption depth and cover percentage of both geotextiles increased. Hence, it is recommended to cover palm-mat geotextiles as buffer strips for soil and water conservation on erodible moderate slopes.

Drip-tips do not impair the development of epiphyllous rain-forest lichen communities

Drip-tips are a common phenomenon in tropical rain forests, often believed to facilitate drainage of water from the leaf surface and, in that way, reduce epiphyll growth. Some authors suggest a function in reducing splash soil erosion, leaching of substances from the leaf, and light reflectance, while other studies did not find any such correlations. We used an experimental approach to test for the effect of drip-tips on the development of epiphyllous lichen communities. Artificial leaves with and without pronounced drip-tips were exposed in a tropical lowland rain forest at La Selva Biological Station (Costa Rica) for a period of 38 mo, and the physical behaviour of rainwater was tested. On leaves with drip-tips, the water ran off in small, frequent drops 8–30 mm3 in size. On leaves without drip-tips, the water accumulated in the apex region and dripped off periodically in large drops 50–150 mm3 in size. Nevertheless, there was no significant difference in the development of epiphyllous lichen communities on leaves with and without drip-tips, in terms of area covered, species richness and composition. However, leaves without drip-tips had more debris accumulated in the apex region and, at the same time, fewer lichen species present in this region. Thus, while drip-tips do have an influence on how water is channelled off the leaf surface, they do not impair the development of epiphyllous lichen communities, except for the apex region where the presence of drip-tips does in fact enhance, not reduce, the establishment of lichens, by preventing the accumulation of debris. We conclude that, while drip-tips may have an ecological function, this function is unrelated to the development of epiphyllous lichen communities.

Evaluation of rainfall erosivity in Bheta Gad catchment, Kumaun Hills of Uttar Pradesh, central Himalayas.

The importance of the size of raindrop in causing soil detachment and splash has long been recognized, although the total energy expended on erosion by splash may be small. The aggressiveness of rainfall or its capacity to cause detachment can be expressed in terms of drop size, rainfall intensity and kinetic energy or momentum. An attempt has been made to determine the rainfall erosivity (EI) of two gauged stations where continuous rainfall recorders were installed, on the basis of rainfall characteristics. Thus, the relationship between average storm EI30 (rainfall erosivity for 30 minutes interval) values and average depths of rainfall could be developed for the Bheta Gad basin of the Gomati River in the Hindu-Kush Himalayas. The analysis has revealed that if factors other than rainfall remain constant, soil splash erosion from cultivated fields is directly proportional to the rainstorm parameter identified as EI.

Influence of wind speed on rainsplash erosion

Measurement of soil splash erosion on an event-based scale under natural rainfall was carried out on a field plot. Kinetic energy of precipitation was calculated according to a model that incorporates horizontal terminal velocities of raindrops induced by wind speed. A digital raingauge with a high output resolution was used to measure precipitation. Erosivity indexes were worked out based on the assumption that those minutes with the highest energy input in an event are decisive for soil detachment.