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[en] Despite of the fact that many soil erosion models have been developed in the past more than 5 decades including empirical based models like USLE and RUSLE and many process based soil erosion and sediment transport models like WEPP, EUROSEM and SHETRAN, the application of these models to regional scales remained questionable. To address the problem, a process-based soil erosion and sediment transport model has been developed to estimate the soil erosion, deposition, transport and sediment yield at regional scale. The soil erosion processes are modeled as the detachment of soil by the raindrop impact over the entire grid and detachment of soil due to overland flow only within the equivalent channels, whereas sediment is routed to the forward grid considering the transport capacity of the flow. The loss of heterogeneity in the spatial information of the topography due to slope averaging effect is reproduced by adapting a Fractal analysis approach. The model has been calibrated for Nan river basin (N.13A) and validated to the Yom river basin (Y.6) and Nam Mae Klang river basin (P.24A) of Thailand, simulated results show good agreements with the observed sediment discharge data. The developed model with few new components can also be applied for predicting the sediment discharges of the river Indus. (author)
[en] All earth dams require protection against erosion due to wave action on the upstream slope and protection against runoff from rain, snowmelt or wave splash on the downstream shell. Erosion protection is a major cost factor in embankment dams, typically varying from 5-15% of the dam cost, although it can approach 50% of embankment cost for long low dikes. The most common type of erosion protection is dumped rock riprap. Current practice in riprap design is based on rational analysis of factors affecting riprap stability, and the performance of existing riprap protection. Historical development of riprap design is reviewed, beginning with U.S. Army Corps of Engineers dams in the 1940s. Riprap design parameters are based on slope steepness and severity of wave action, which depends on reservoir geometry and location. A common cause of riprap deterioration is loss of underlying bedding as a result of inadequate design or segregation of riprap and bedding during construction. The most common form of riprap failures include: loss of filter material through riprap if it is too fine; inadequate rock size to resist wave action, resulting in beaching; segregation during construction, resulting in pockets of undersized rock which can expose the underlying filter, and pockets of oversized rock through which bedding can wash out; breakdown of poor quality stone due to prolonged exposure and wave action; and failure to extend the primary riprap far enough downslope to be below the level of wave action at low reservoir levels. 26 refs., 8 figs
[en] In this article the actions systems for struggle against erosion is described. In the basis it is stated should to have zone character to take into account determining ability to live of plants of a parity of heat and moisture, type of ground, a relative role in erosive process of rain waters. On a zone background the differentiation and specification of systems of actions is made depending on lithology integumentary breeds, a relief, a stage of development of erosion, character of territory use.
[en] A complex methodology for torrents and erosion and the associated calculations was developed during the second half of the twentieth century in Serbia. It was the 'Erosion Potential Method'. One of the modules of that complex method was focused on torrent classification. The module enables the identification of hydro graphic, climate and erosion characteristics. The method makes it possible for each torrent, regardless of its magnitude, to be simply and recognizably described by the 'Formula of torrentially'. The above torrent classification is the base on which a set of optimisation calculations is developed for the required scope of erosion-control works and measures, the application of which enables the management of significantly larger erosion and torrential regions compared to the previous period. This paper will present the procedure and the method of torrent classification.
[en] Kisii District has a topography of undulating hills and is prone to severe soil erosion. The average rainfall is 1900 mm and occurs in biomodal pattern. During a participatory appraisal survey in 1995, farmers indicated that soil erosion in the area had contributed to decline in soil fertility resulting in low crop yields. To address this problem, an on-farm trial was conducted in 1996 at Nyamonyo village to test the effectiveness of four low cost methods of controlling soil erosion. These included maize stover trash line, sweet potatoes,Penicum maximum var. Makarikari grass strip and vetiveria zizanioides (Vertiver) grass strip. A treatment without soil erosion control measure was included. The trial was planted in three farms which acted as replicates. The treatments were planted in runoff plots measuring 4 x 2 m in which had a maize crop were laid down in a randomized complete block design. Surface runoff and eroded soils were collected in 50-l buckets. The experimental site had a slope ranging from 16 to 35%. Preliminary results indicated that maize stover trash line and sweet potato strips were more effective in controlling soil erosion than the grass strips. As the season progressed the grass strips became increasingly more effective in erosion control. The trail is still continuing but results indicate that for short term soil erosion control, maize stover trash lines and sweet potatoes are more effective while Makarikari and Vertiver grass strips are promising as long term soil erosion control measure
[en] IMPAK is quarterly bulletin of the Department of Environment, Malaysia. In this issue, IMPAK's theme is Sustainable Development. It is observed that while definitions of sustainable development appear to differ from one writer to another, they share one common theme, i.e. all contains three fundamental concepts, environment, futurity and equity. Article from DOE news is Bandar Lestari, an environment award with the aims to accord recognition to one urban center that has shown its overall commitment and effort towards achieving environment sustainability in its development. Feature article to support IMPAK's theme are Sustainable Consumption, Where are We Heading? Explanations on correlation between population growth and the economic consumption of the earth resources, New Approaches for the Sustainability of Malaysian Industries suggestion for alternative development strategies with the new environment management system, and the last article is Managing Soil Erosion for Sustainable Farming few approaches to achieve efficient erosion control. Meanwhile Biomass: Renewable Energy Sources in Malaysia fill up the Technical Update section
[en] A greenhouse study examined the influences of various surface covers (a bare control soil and seven rolled erosion control systems—RECS) on surface radiative properties, and soil temperature. In our companion paper we examine relationships with soil moisture, biomass production, and nutrient assimilation. Randomization and replication were key components to our study of microclimate under tropical radiation conditions. The bare Oxisol control soil exhibited the most extreme microclimatic conditions with the lowest albedo (not significantly different from that of P300© North American Green, a dark green polypropylene system), and the highest mean and maximum hourly temperatures recorded at depths of 5 and 8 cm. This hostile climatic environment was not conducive to biomass production or moisture storage and it is likely that the observed soil surface crusts impeded plant emergence. Rolled erosion control systems, on the other hand, generally moderated soil temperatures by reflecting more shortwave radiation, implying less heat energy at the surface for conduction to the soil. The result was that RECS exhibited lower mean soil temperatures, higher minimum temperatures and lower maximum soil temperatures. An aspen excelsior system (Curlex I© Excelsior) had the highest albedo and the soil beneath this system exhibited the greatest temperature modulation. Open-weave systems composed of jute (Geojute© Price & Pictures) and coconut fibers (BioD-Mat 70© RoLanka) were the RECS most similar in temperature response to the bare control soil. Other systems examined were intermediate in their temperature response and surface albedo (i.e., SC150BN© North American Green, C125© North American Green and Futerra© Conwed Fibers). (author)
[en] In this paper, we evaluated the Water Erosion Prediction Project (WEPP) model using 5-yr monitored runoff and sediment data from three different lands cover treatments in the Loess Plateau of China. The results showed that the WEPP model was able to predict 22 out of 37 recorded runoff producing events, and 20 out of 34 recorded sediment producing events. Prediction of annual runoff is more accurate than the prediction of sediment. The correlation coefficients between the annual monitored and simulated runoff ranged from 0.69 to 0.91, and 0.11 to 0.90 for sediment; for the three treatments (bare, corn and grass), the prediction for the grass plot is better than the other two. Soil moisture and storm intensity appeared to have greater effect on both predictability and accuracy of runoff events and sediment yields. For grass plot, Nash-Sutcliffe coefficient was 0.76 in runoff and 0.56 in sediment. WEPP predictions for the grass plot were in agreement with measured values, but no better than using the averaged measured values for the other two treatments (bare and corn plots). Application of the WEPP model should be decided with precautions in the Loess Plateau area. (author)