Concentrated flow erosion rates reduced through biological geotextiles

Soil erosion by concentrated flow can cause serious environmental damage. Erosion‐control geotextiles have considerable potential for reducing concentrated flow erosion. However, limited data are available on the erosion‐reducing potential of geotextiles. In this study, the effectiveness of three biological geotextiles in reducing soil losses during concentrated flow is investigated. Hereto, runoff was simulated in a concentrated flow flume, filled with an erodible sandy loam on three slope gradients (13·5, 27·0 and 41·5%). Treatments included three biological geotextiles (borassus, buriti and bamboo) and one bare soil surface. Darcy–Weisbach friction coefficients ranged from 0·01 to 2·84. The highest values are observed for borassus covered soil surfaces, followed by buriti, bamboo and bare soil, respectively. The friction coefficients are linearly correlated with geotextile thickness. For the specific experimental conditions of this study, borassus geotextiles reduced soil detachment rate on average to 56%, buriti geotextiles to 59% and bamboo geotextiles to 66% of the soil detachment rate for bare soil surfaces. Total flow shear stress was the hydraulic parameter best predicting soil detachment rate for bare and geotextile covered surfaces (R² = 0·75–0·84, p <0·001, n = 12–15). The highest resistance against soil detachment was observed for the borassus covered soil surfaces, followed by buriti, bamboo and bare soil surfaces, respectively. Overall, biological geotextiles are less effective in controlling concentrated flow erosion compared with interrill erosion. Copyright © 2009 John Wiley & Sons, Ltd.     

Spatial variability in precipitation within the Hilton Experimental Site,Shropshire, UK (1982–2006)

Accurate precipitation measurements are essential for many hydrological and hydrogeological management strategies. Precipitation at the Hilton Experimental Site has been regularly measured since 1982. This paper summarises 157 rain gauge years of precipitation data, recorded between 1982 and 2006, using 11 rain gauges on the 0·5 hectare site. Precipitation varied markedly within the site. Precipitation totals were notably different between two adjacent rain gauges, the mean difference being 0·3% of the total. Variations in mean annual precipitation within the site were ?8%. Spatial variations in wind turbulence appeared to be the main factor influencing intra‐site variability. Precipitation totals varied with gauge exposure, with surface level gauges receiving ?5·9% more precipitation than standard rain gauges, the difference being less lower down the slope. On a steep (～15° ) slope, basal sections had 2·5–7·9% more precipitation. Upper gauges received less, probably due to turbulence as increased exposure on the top of the slope resulted in precipitation being carried over the gauge orifice. Results confirm that due attention must be given to the inherent variability of precipitation amounts when calculating precipitation inputs. Copyright © 2008 John Wiley & Sons, Ltd.     

Using palm‐mat geotextiles on an arable soil for water erosion control in the UK

To date, most studies of the effectiveness of geotextiles on soil erosion rates and processes have been conducted in laboratory experiments for less than 1 h. Hence, at Hilton (52°33′ N, 2°19′ W), UK, the effectiveness of employing palm‐mat geotextiles for soil erosion control under field conditions on arable loamy sands was investigated. 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. Duplicate runoff plots (10 m × 1 m on a 15° slope) had five treatments (bare, permanent grass, Borassus total plot cover, Borassus buffer strip and Buriti buffer strip). Borassus covered plots had about 72% ground cover and to differentiate between this treatment and Borassus buffer strips, the former treatment is termed Borassus completely‐covered. Runoff and eroded soil were collected from each bounded plot in a concrete gutter, leading to a receptacle. Results from 08/01/2007–23/01/2009 (total precipitation = 1776·5 mm; n = 53 time intervals) show that using Borassus buffer strips (area coverage ～10%) on bare soil decreased runoff volume by about 71% (P > 0·05) and soil erosion by 92% (P < 0·001). Bare plots had nearly 29·1 L m^?2 runoff and 2·36 kg m^?2 soil erosion during that period. Borassus buffer strip, Buriti buffer strip and Borassus completely‐covered plots had similar effects in decreasing runoff volume and soil erosion. Runoff volumes largely explain the variability in soil erosion rates. Although buffer strips of Borassus mats were as effective as whole plot cover of the same mats, the longevity of Borassus mats was nearly twice that of Buriti mats. Thus, use of Borassus mats as buffer strips on bare plots is highly effective for soil erosion control. The mechanisms explaining the effectiveness of buffer strips require further studies under varied pedo‐climatic conditions. Copyright © 2011 John Wiley & Sons, Ltd.     

Laboratory and field studies in the use of the isotope59 fe for tracing soil particle movement

Radioactive ⁵⁹Fe is considered to be one of the most satisfactory isotopes for tracing soil particle movement. Laboratory techniques of labelling and their success are investigated along with the scintillation technique of radiation detection. Following the completion of a field pilot study ⁵⁹Fe-labelled soils were exposed on both vegetated and burnt heather moorland on the North York Moors to monitor relative soil movement.     

Rainfall,runoff and erosion on bare arable soils in east Shropshire,England

The magnitude, frequency, and duration of erosive rainfall on bare arable soils is investigated within an area of sandy soils in east Shropshire. Rainfall parameters are compared with runoff and erosion from ten 25 m² runoff plots, maintained in a bare condition on slopes of varying steepness. On rain-drop compacted (capped) soils measured erosion rates of ≦ 42.7t ha^?1 occur during individual storms. Erosion rates increase markedly with slope and on slopes > ? 13° are largely attributable to rill erosion. Prolonged duration, low intensity events cause relatively little erosion; most is accomplished by short duration, high intensity (> 10 mm h^?1) convective rainstorms. Comparison of measured erosion-producing events and long-term rainfall records indicate that potentially erosive storms are quite frequent, and are most likely to cause erosion in late spring/early summer.     

Controls on the development of continuous gullies: A 60 year monitoring study in the Moldavian Plateau of Romania

Gully erosion is a major environmental threat on the Moldavian Plateau (MP) of eastern Romania. The permanent gully systems consist of two main gully types. These are: (1) discontinuous gullies, which are mostly located on hillslopes and (2) large continuous gullies in valley bottoms. Very few studies have investigated the evolution of continuous gullies over the medium to longer term. The main objective of this study was to quantitatively analyse the development of continuous gullies over six decades (1961–2020). The article aimed at predicting temporal patterns of gully head erosion based on field data from multiple gullies. Fourteen representative continuous gullies were selected near the town of Barlad, most of them having catchment areas < 500 ha. Linear gully head retreat (LGHR) and areal gully growth (AGG) rates were quantified for six decades. Two main periods were distinguished and compared (i.e., the wet 1961–1980 period and the drier 1981–2020 period). Results indicate that gully erosion rates have significantly decreased since 1981. The mean LGHR of 7.7 m yr⁻¹ over 60 years was accompanied by a mean AGG of 213 m² yr⁻¹. However, erosion rates between 1961 and 1980 were 4.0 times larger for LGHR and 5.9 times more for AGG compared to those for 1981–2020. Two regression models indicate that annual precipitation depth (P) is the primary controlling factor, explaining 57% of LGHR and 53% of AGG rate. The contributing area (CA) follows, with ~33%. Only 43% of total change in LGHR and 46% of total change in AGG results from rainfall-induced runoff during the warm season. Accordingly, the cold season (with associated freeze–thaw processes and snowmelt runoff) has more impact on gully development. The runoff pattern, when flow enters the trunk gully head, is largely controlled by the upper approaching discontinuous gully.