HR: 09:00h
AN: H51A-05    [PDF]
TI: Effects of Forest Roads on Internal Hydrological Process in Tropical Catchments
AU: * Sidle, R C
EM: sidle@slope.dpri.kyoto-u.ac.jp
AF: Kyoto University, DPRI, Gokasho, Kyoto-fu, Uji-shi, 611-0011 Japan
AU: Negishi, J
EM: artp1469@nus.edu.sg
AF: National University of Singapore, Department of Geography, 1 Arts Link, Singapore, 117570 Singapore
AU: Siew, R
EM: heehahoo@singnet.com.sg
AF: National University of Singapore, Department of Geography, 1 Arts Link, Singapore, 117570 Singapore
AU: Noguchi, S
EM: noguchi@affrc.go.jp
AF: JIRCAS, FRIM office, Kepong, Kuala Lumpur, 52109 Malaysia
AU: Abdul Rahim, N
EM: rahimnik@frim.gov.my
AF: Forestry Research Institute of Malaysia, Kepong, Kuala Lumpur, 52109 Malaysia
AB: Hydrological response within a headwater forest catchment in Peninsula Malaysia was monitored during a series of storms to assess the influence of unimproved logging roads on hydrological pathways. Four small to moderate sized storms occurred on consecutive days in December 2002, producing a sequence of relatively dry to wet antecedent conditions. Storm duration and maximum 5-min intensity ranged from 1 to 2.4 h and 25 to 102 mm/h, respectively; the last storm was the largest. Discharge was measured at two v-notch weirs at natural drainage outlets along the 50 m-section of the road, at another weir at the truncated outlet of a geomorphic hollow along the road cutslope, and at the 13 ha basin outlet. Peak runoff from the road surface corresponded closely (within minutes) to rainfall peaks; at the basin outlet, lag times between rainfall peaks and peak runoff varied from 40 to 66 min. During the first three storms, no discharge was measured from the hollow and most of the road runoff was Hortonian overland flow with runoff coefficients increasing from 36 to 118% (unit contributing area basis) for the sequential storms. During the third storm some subsurface flow was intercepted at the cutslope. Large water storage in the upper catchment prior to the fourth storm facilitated outflow from the zero-order basin that was almost 6 times greater than the unit area discharge of the 13 ha basin. This discharge from the hollow and subsurface flow intercepted at the road cut extended the falling limbs of these hydrographs about 10 h after the cessation of rainfall; road runoff from earlier storms ceased within minutes of the storm end. Discharge from the 50 m road segment contributed 4.4% of the total catchment runoff during the fourth storm; scaled to the entire road system, this constitutes about 60% of storm runoff. For the three smaller storms with drier antecedent conditions, roads contributed 4 to 10% of total basin stormflow. Clearly roads have a major effect on storm runoff generation and hydrological pathways in tropical catchments, especially during wet antecedent conditions.
DE: 1824 Geomorphology (1625)
DE: 1860 Runoff and streamflow
DE: 1866 Soil moisture
SC: Hydrology [H]
MN: 2003 Fall Meeting