The effects of conventional and reduced impact logging on suspended sediment yield in the Sungai Weng experimental watersheds Peninsular Malaysia.

Akkaharath, . and F.S. Lai, . and K.S. Low, . (2007) The effects of conventional and reduced impact logging on suspended sediment yield in the Sungai Weng experimental watersheds Peninsular Malaysia. [Proceedings Paper]

The impact of commercial timber harvesting on catchment sediment yield has always been a major concern among foresters and catchment managers in Malaysia. Concern over the potentially adverse downstream effects for example on the intent of water resource schemes particularly on design quality and flows adopted among others is largerly understandable. Much has been reported on the substantial changes in sediment transport because of soil erosion from exposed land largerly resulting from road and skil trail construction for transportation of timber from affected areas. The Sungai Weng Experimental Watersheds was established to evaluate among other inportant environment effects the conventional logging and reduced impact logging measures on sediment output. This paper reports on suspended sediment yield changes in particular Watershed 2 W2 and W3 due to ground-based timber harvesting from 1997 to 2002. The conventional practice was applied to W3 whereas reduced impact logging RIL guides such as a wider 30m stream buffer strip and 40 sloe limit among others were used in W2. Logging operations in W3 ran from February 1998 until the end of 2000 and in W2 from June 2000 to March 2003. Suspended sediment concentrations varied within the period of study increasing dramatically during logging. For instance the maximum concentration levels sampled in W3 increased from 1980 mgL-1 in 1997 a peak of 92500 mgL-1 in 1999. After logging ceased concentration levels fell to 30200 mgL-1 in 2001 and to much lower 19500 mgL-1 the following year. Peak suspended sediment concentrations were lower in W2 however suggesting at this stage that the extra measures taken to lower logging impact had some influence on sediment yield in the affected basin. In terms of catchment suspended sediment yield the data suggest that conventional logging in the Sungai Weng Experimental watersheds increased by about 42 times over baseline yields during the peak effect period but decreased thereafter as the watershed recovers. The effects of RIL was much lower suggesting that prescribing low harvesting intensity minimizing stand damage and therefore be the main factors in significantly reducing the impact on sediment production among other environmental concerns. The impact from using aerial methods in extracting timber for example would be very much lower.

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Abstract

The impact of commercial timber harvesting on catchment sediment yield has always been a major concern among foresters and catchment managers in Malaysia. Concern over the potentially adverse downstream effects for example on the intent of water resource schemes particularly on design quality and flows adopted among others is largerly understandable. Much has been reported on the substantial changes in sediment transport because of soil erosion from exposed land largerly resulting from road and skil trail construction for transportation of timber from affected areas. The Sungai Weng Experimental Watersheds was established to evaluate among other inportant environment effects the conventional logging and reduced impact logging measures on sediment output. This paper reports on suspended sediment yield changes in particular Watershed 2 W2 and W3 due to ground-based timber harvesting from 1997 to 2002. The conventional practice was applied to W3 whereas reduced impact logging RIL guides such as a wider 30m stream buffer strip and 40 sloe limit among others were used in W2. Logging operations in W3 ran from February 1998 until the end of 2000 and in W2 from June 2000 to March 2003. Suspended sediment concentrations varied within the period of study increasing dramatically during logging. For instance the maximum concentration levels sampled in W3 increased from 1980 mgL-1 in 1997 a peak of 92500 mgL-1 in 1999. After logging ceased concentration levels fell to 30200 mgL-1 in 2001 and to much lower 19500 mgL-1 the following year. Peak suspended sediment concentrations were lower in W2 however suggesting at this stage that the extra measures taken to lower logging impact had some influence on sediment yield in the affected basin. In terms of catchment suspended sediment yield the data suggest that conventional logging in the Sungai Weng Experimental watersheds increased by about 42 times over baseline yields during the peak effect period but decreased thereafter as the watershed recovers. The effects of RIL was much lower suggesting that prescribing low harvesting intensity minimizing stand damage and therefore be the main factors in significantly reducing the impact on sediment production among other environmental concerns. The impact from using aerial methods in extracting timber for example would be very much lower.

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Item Type:	Proceedings Paper
Additional Information:	3 ill. 2 tables. 10 ref.call number: SD235 M3N277 2007
AGROVOC Term:	LOGGING
AGROVOC Term:	SEDIMENT WATER INTERFACE
AGROVOC Term:	WATERSHEDS
AGROVOC Term:	MALAYSIA
Geographical Term:	MALAYSIA
Depositing User:	Ms. Suzila Mohamad Kasim
Last Modified:	24 Apr 2025 05:13
URI:	http://webagris.upm.edu.my/id/eprint/11030

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