Topographical thresholds for ephemeral gully initiation in intensively cultivated areas of the Mediterranean

被引:113
作者
Vandekerckhove, L
Poesen, J
Wijdenes, DO
de Figueiredo, T
机构
[1] Katholieke Univ Leuven, Lab Expt Geomorphol, B-3000 Louvain, Belgium
[2] Ecole Super Agr Braganca, P-5300 Braganca, Portugal
关键词
gully; Spain; Portugal; slope gradient; drainage area; rock fragments; impermeable horizon; tillage direction;
D O I
10.1016/S0341-8162(98)00068-X
中图分类号
P [天文学、地球科学];
学科分类号
07 ;
摘要
Ephemeral gullying is an important erosion process in Mediterranean areas suffering from land degradation because of increased drought and human impact. An ephemeral gully is formed when a hydraulic threshold for incision into a resistant soil surface is exceeded. The flow intensity at the soil surface of any landscape position is controlled by topographical parameters, such as local slope (S) and drainage-basin area (A). The objective of this study was to investigate to what extent one could use field measurements of S and A to predict the location of ephemeral gully initiation in intensively cultivated Mediterranean environments. Two relatively homogeneous study areas in Southeast Spain and Northeast Portugal with widespread ephemeral gullying were selected. S and A were measured by standard methods at the initiation point of 50 ephemeral gullies in each study area. The relationship between S and A was statistically investigated. On a double logarithmic scale, the S and A data showed considerable scatter. Orthogonal regression resulted in the threshold relationship S = aA(-b) with b = 0.133 for Spain, and b = 0.226 for Portugal. The analysis also showed that S and A were weakly correlated :For the Spanish dataset, and more strongly correlated for the Portuguese dataset. The correlation was considerably strengthened by including additional information on planform curvature and on tillage direction relative to the gully direction. Greater soil stoniness and the presence of a less permeable horizon generally increased the threshold level in both study areas. The threshold relationships resulting from this study were compared with literature data. The indices A(c)S and ln(A(c)/S) were applied to our study sites but neither relationship individually described the general trend between the data of S and A. Therefore, an alternative index, A(c)(b)S, with 0.133 less than or equal to b less than or equal to 0.226, according to the empirical trend between drainage basin area and local slope, was proposed to describe the topographical threshold conditions for ephemeral gully initiation in similar Mediterranean areas. (C) 1998 Elsevier Science B.V. All rights reserved.
引用
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页码:271 / 292
页数:22
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