Persistence of road runoff generation in a logged catchment in Peninsular Malaysia |
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Authors: | Alan D Ziegler Junjiro N Negishi Roy C Sidle Takashi Gomi Shoji Noguchi Abdul Rahim Nik |
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Institution: | 1. Geography Department, University of Hawaii, Honolulu HI, USA;2. Aqua Restoration Research Center, Public Works Research Institute, Kawashima, Kakamigahara, Gifu, Japan;3. Disaster Prevention Research Institute, Geohazards Division, Kyoto University, Kyoto, Japan;4. Forestry and Forest Product Research Institute, Tohoku Research Center, Japan;5. Forest Research Institute Malaysia, Kuala Lumpur, Malaysia |
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Abstract: | Measurements of saturated hydraulic conductivity (Ks) and diagnostic model simulations show that all types of logging road/trail in the 14·4 ha Bukit Tarek Experimental Catchment 3 (BTEC3) generate substantial Horton overland flow (HOF) during most storms, regardless of design and level of trafficking. Near‐surface Ks(0–0·05 m) on the main logging road, skid trails and newly constructed logging terraces was less than 1, 2 and 34 mm h?1, respectively. Near‐surface Ks on an abandoned skid trail in an adjacent basin was higher (62 mm h?1), owing to the development of a thin organic‐rich layer on the running surface over the past 40 years. Saturated hydraulic conductivity measured at 0·25 m below the surface of all roads was not different (all <6 mm h?1) and corresponded to the Ks of the adjacent hillslope subsoil, as most roads were excavated into the regolith more than 0·5–1 m. After 40 years, only limited recovery in near‐surface Ks occurred on the abandoned skid trail. This road generated HOF after the storage capacity of the upper near‐surface layer was exceeded during events larger than about 20 mm. Thus, excavation into low‐Ks substrate had a greater influence on the persistence of surface runoff production than did surface compaction by machinery during construction and subsequent use during logging operations. Overland flow on BTEC3 roads was also augmented by the interception of shallow subsurface flow traveling along the soil–saprolite/bedrock interface and return flow emerging from the cutbank through shallow biogenic pipes. The most feasible strategy for reducing long‐term road‐related impacts in BTEC3 is limiting the depth of excavation and designing a more efficient road network, including minimizing the length and connectivity of roads and skid trails. Copyright © 2007 John Wiley & Sons, Ltd. |
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Keywords: | bulk density Horton overland flow (HOF) interception of subsurface storm flow (ISSF) logging impact recovery runoff generation saturated hydraulic conductivity (Ks) |
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