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| 1 | PROCESSES OF EPHEMERAL GULLY EROSION显示文摘The formation of ephemeral gullies can significantly increase soil loss from agricultural lands and severely impact farm productivity. Erosion prediction technology and conservation management techniques would be greatly improved if the contribution from ephemeral gullies could be more accurately quantified. Field research in Mississippi, U.S.A. and Spain has revealed three categories of ephemeral gullies. Classic ephemeral gullies formed by concentrated flow erosion from runoff occurring within the same field. Drainage ephemeral gullies formed by concentrated flow erosion from runoff originating from areas upstream of where the gully occurs. Discontinuity ephemeral gullies formed in areas where management practices have created a sudden change in slope, such as field boundaries adjacent to roads.Despite the large differences in climate, watershed size, hydrology, and geography, the ephemeral gullies observed in Spain were morphologically similar to those in Mississippi. Using an experimental flume,ephemeral gully erosion proceeded primarily through bed incision, gully widening, and bank steepening,and total sediment load depended upon whether the flow was detachment- or transport-limited. | Javier Casali(Department of Projects and Rural Engineering, Public University of Navarra, 31006 Pamplona, Navarra, Spain) SeaN J. Bennett(National Sedimentation Laboratory, USDA-ARS, P.O. Box 1157, Oxford, MS 38655, USA)Kerry M. Robinson(Plant Science and | 2000 | International Journal of Sediment Research2000，15，1： | 4 |
| 2 | EVALUATION OF TOPOGRAPHIC INDICES FOR EPHEMERAL-GULLY EROSION ASSESSMENT显示文摘Soil erosion by concentrated flows in agricultural areas is an important process affecting soil losses and landscape degradation. The main factors controlling concentrated flow erosion include the erodibility of materials, soil use and management, climate, and watershed topography. In this paper, two topographic indices, closely related with mathematical expressions suggested by different authors, are used to characterize the influence of watershed topography on gully erosion. The AS1 index is defined as the product of the watershed area and the partial area-weighted average slope. The AS2 index is the product of the watershed area and the length-weighted average swale slope. Using different ephemeral gully erosion databases, a high correlation was found between the topographic indices and the volume of eroded soil. The accuracy of different methods for field measurement of ephemeral gullies was evaluated to ensure that the relation between erosion and topographic indices is not affected by assessment errors. The resulting relation are useful to assess soil losses from gully erosion, to identify the most susceptible watersheds within large areas, and to compare the susceptibility to gully erosion among different catchments. This information also can be important to study the response of natural drainage network systems to different rainfall inputs. | J. CASALI L. M. De SANTISTEBAN J. J. LOPEZ J. V. GIRALDEZ J. POESEN J. NACHTERGAELE M. GONI J. LOIZU M. A. CAMPO | 2005 | International Journal of Sediment Research2005，20，4： | 4 |
| 3 | PROCESSES OF HEADCUT GROWTH AND MIGRATION IN RILLS AND GULLIES显示文摘The formation and upstream migration of headcuts significantly increases soil losses and sediment yield from agricultural lands, threatens the structural integrity of earthen dams, and can undermine roads and bridges. Recent research using unique experimental facilities and methodologies has provided new insights on these erosion processes. Under controlled experimental conditions, steady-state soil erosion due to migrating headcuts has been simulated for rills and along crop furrows. During migration, headcut shape, size, rate of movement, and sediment yield remained constant. Downstream of the headcut, a soil bed was constructed where slope was dependent upon the sediment yield from the headcut and the flow transport capacity. Soil erosion processes were also examined in a large outdoor facility simulating gully headcuts. Using a compacted cohesive soil, headcut migration rate was observed to decrease as the average density and average unconfined compressive strength increased. While the flow rate and overfall height were not observed to have a major impact on advance rates, a sand layer at the base of an overfall did have a dramatic influence on advance rates. The erosion processes and flow structure within the large gully headcuts were strikingly similar to those in rills and crop furrows. The commonality of form and process in these soil erosion phenomena suggests that erosion prediction technology and mitigation measures may be developed and widely applied. | Kerry M. Robinson(Plant Science and Water Conservation Research Laboratory, USDA-ARS, 1301 N. Western St., Stillwater, OK 74075, USA)Sean J. Bennett(National Sedimentation Laboratory, USDA-ARS, P.O. Box 1157, Oxford, MS 38655, USA)Javier Casali, and Grego | 2000 | International Journal of Sediment Research2000，15，1： | 1 |
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