Research on Water and Sediment Discharge Mechanisms in Tropical Monsoon Evergreen Forest Catchments

Forestry Administration, Cambodia

FY 2016–2020 Grant-in-Aid for Scientific Research (KAKENHI)

KABEYA, Naoki (Kyushu Research Center)

Deforestation is a serious problem in Southeast Asian countries, as the resulting increase in soil erosion may cause stream beds to rise and increase the risk of flooding. Although Cambodia has a relatively high forest coverage compared with its neighbors, many of its forests are rapidly decreasing in area as a result of development.

This research aims to clarify the effects of land-use change on the water and sediment discharge characteristics in an evergreen forest watershed in Cambodia.

We are conducting a field survey and slope experiment in a tropical monsoon evergreen forest watershed in Cambodia to understand:
1) Differences in the amounts of erosion among different vegetation types.
2) The amount of sediment discharge at the watershed scale.
3) The amount of soil erosion on a forest slope.

We have studied water and sediment discharge arising from land use change in the evergreen forest experimental catchment in Kampong Thom Province, Cambodia. The results of this study show that it is important for preventing soil erosion to conserve vegetation on the forest floor and to recover vegetation after cutting. The annual sediment yield in the O Teak Loork catchment, where forest has been mostly developed, was estimated to be very small values as 1.98 × 0.001 mm/year as that value at Japanese forest sites. As the topography of the study site is very flat, sediment produced by soil erosion will be difficult to transport through a channel.

The study findings verified that vegetation prevents soil erosion in the evergreen forest in Cambodia. This provides fundamental information about soil and water conservation in this area.

Naoki Kabeya, Akira Shimizu, Takanori Shimizu, Shin’ichi Iida, Koji Tamai, Asako Miyamoto: Research on water and sediment discharge mechanism in tropical monsoon evergreen forest catchments (I): installation situation of observation plots, Kyushu Journal of Forest Research 71: 79-82, 2018.03.

Naoki Kabeya, Akira Shimizu, Takanori Shimizu, Shin’ichi Iida, Koji Tamai, Asako Miyamoto: Research on water and sediment discharge mechanism in tropical monsoon evergreen forest catchments (II): a case of sediment yield estimation in a developed catchment. Kyushu Journal of Forest Research 72: 51-55, 2019.03.

Naoki Kabeya, Akira Shimizu, Takanori Shimizu, Shin’ichi Iida, Koji Tamai, Asako Miyamoto: Research on water and sediment discharge mechanism in tropical monsoon evergreen forest catchments (III): the results of erosion pin plot experiment on a forest slope with 10 degrees over three years, Kyushu Journal of Forest Research 73: 75-78, 2020.03.

Naoki Kabeya, Akira Shimizu, Takanori Shimizu, Shin’ichi Iida, Koji Tamai, Asako Miyamoto, Sophal Chann, Makoto Araki, Yasuhiro Ohnuki: Long-term hydrological observations in a lowland dry evergreen forest catchment area of the Lower Mekong River, Cambodia, Japan Agricultural Research Quarterly: JARQ 55: 177-190, 2021.04.