Impacts of Rapid Land-Use Change on the Meandering Dynamics of the Kinabatangan River, Borneo

PhD Researcher: Alexander Horton

Supervisors: Jose Constantine, Tristram Hales, Michael W. Bruford and Benoit Goossens

Institution: Cardiff University

Sponsor: NERC

Status: Completed

Research questions:

• Does forest clearing have an effect on rates of river migration?
• What are the long-term economic benefits of a riparian corridor for mitigating the effects of increased river migration due to forest clearing?
• What are the specific mechanisms that drive riverbank retreat before and after forest removal?

The first two sections generated some interesting results, which we hope will have a positive impact on the way in which the land close to the river is managed.

To answer the first question, we utilised the historic Landsat imagery, which provided a record of the fluvial response to extended forest clearing. By tracking the migration of the river over time and comparing rates of river movement along sections of the river that have been cleared of the forest before and after the event, we have been able to demonstrate that natural riparian forest has a significant effect on rates of riverbank retreat and that the removal of forest from the riverbanks dramatically increases the rates of riverbank erosion.

Having generated average migration rates associated with forested riverbanks, sections of the river with an intact riparian corridor (10m – 100m wide), and cleared sections of the river, we were able to develop a model that predicts the future position of the river with different land cover scenarios. We then limited our model to the portions of the river that flow through areas of unprotected forest, which will likely be converted to palm oil plantations in the future and ran the model with differing widths of the riparian corridor along the river’s banks. The results suggest that it would be economically beneficial in the long term (>25 years) to leave a 20m wide riparian forest corridor along the river to protect palm oil plantations from losing land to the river. Our results also suggested that the longer the economic projection, the wider the initial corridor should be to maximise yield close to the river so that after 75 years, it is more profitable to leave a 50m wide corridor than it is to clear the forest to the river’s edge.

This project produced a body of research which demonstrated the importance of maintaining a forested riparian corridor in order to mitigate the effects of forest removal on the meandering dynamics of the Kinabatangan River.

Publications:

Horton, A.J., Constantine, J.A., Hales, T.C., Bruford, M., Goossens, B., 2017. Modification of the mechanisms driving river meandering caused by tropical deforestation. Geology G38740.1.