IMPORTANCE OF RURAL ROADS AS SOURCE AREAS FOR RUNOFF IN MOUNTAINOUS AREAS OF NORTHERN THAILAND

Citation
Ad. Ziegler et Tw. Giambelluca, IMPORTANCE OF RURAL ROADS AS SOURCE AREAS FOR RUNOFF IN MOUNTAINOUS AREAS OF NORTHERN THAILAND, Journal of hydrology, 196(1-4), 1997, pp. 204-229
Citations number
69
Categorie Soggetti
Engineering, Civil","Water Resources","Geosciences, Interdisciplinary
Journal title
ISSN journal
00221694
Volume
196
Issue
1-4
Year of publication
1997
Pages
204 - 229
Database
ISI
SICI code
0022-1694(1997)196:1-4<204:IORRAS>2.0.ZU;2-9
Abstract
Unpaved road surfaces have extremely low infiltration rates compared w ith other watershed land surfaces and, therefore, are significant sour ce areas for erosion-producing Horton overland flow. The hydrologic ro le of roads is an important issue in mountainous areas of the tropics where erosion control efforts are predominately focused on deforestati on and agricultural practices. We report on an investigation of soil p hysical properties that control excess rainfall (rainfall intensity in excess of infiltration capacity) on rural roads and surrounding lands in a mountainous watershed in northern Thailand. The results of our d isk permeameter measurements indicate that saturated hydraulic conduct ivity on unpaved roads is about one order of magnitude lower than on a ny other land-surface type. Median saturated hydraulic conductivities were not exceeded by measured rainfall intensity on any land use excep t road surfaces and roadside margins. By simulating excess rainfall, w e found that in contrast with other areas of the watershed, the road s urface tends to generate excess rainfall early in a rain event, and on nearly all of its area. Despite the relatively small areal extent of road-related surfaces ( < 0.5% of basin area), they contribute a large portion of basin-wide total excess rainfall during frequently occurri ng, small rainfall events. However, during larger events, agricultural , secondary vegetation, and forested areas assume greater importance b ecause of their larger areal extent. (C) 1997 Elsevier Science B.V.