Anand Nainar (2017) Hydrological and suspended sediment dynamics in catchments of differing land-use history in the tropics - an experiment in Sabah (North Borneo). Doctoral thesis, Universiti Malaysia Sabah.
![[img]](https://eprints.ums.edu.my/style/images/fileicons/text.png) |
Text
24 PAGES.pdf Download (832kB) |
|
Text
FULLTEXT.pdf Restricted to Registered users only Download (25MB) |
Abstract
Land use change has been the main driver of adverse changes in hydrological and suspended sediment characteristics especially in the tropics. Several notable studies on the hydrological and erosional impacts from logging and agriculture were done in Southeast Asia and Sabah, especially during logging operations around the Danum Valley. However, paired catchment studies are few - especially those investigating a few land use on a scale of increasing disturbance while taking into account the history of the land. This study was conducted for that purpose. Five different catchments from the Kalabakan and Segama area with increasing historical land-use disturbance were selected - primary forest (PF), virgin jungle reserve (VJR), twice-logged forest {LF2), repeatedly-logged forest {LF3) and an oil palm plantation (OP). Streams in each catchment has been instrumented with a depth sensor, turbidity sensor, conductivity sensor, temperature sensor and a tipping bucket rain gauge all connected to a "Campbell CR850" solar powered datalogger that records data every 5 minutes. Values of water depth, turbidity and conductivity were converted to discharge (Q), suspended sediment concentration (SSC) and total dissolved solids respectively. For computation of annual yields, data gap predictions were attempted using relationship curves derived from intracatchment and inter-catchment regression of stream variables. However, it was found that the regression relationships were unsuitable and hence three-month yields were presented instead. Three-month water yield was found to be highest in the LF3 and lowest in the OP. Mean suspended sediment concentration is highest in the OP and lowest in the LF3. Three-month sediment yield is highest in the OP and lowest in the LF2 (most likely caused by better interception, better hydrological characteristics and sediment exhaustion). At the event scale, subsurface flow was found to be highest in the PF and lowest in the OP. Peak discharge has no significant difference between the catchments. Water yield is highest in the LF3 and lowest in the OP. The baseflow, peak and end SSC at the event scale are highest in the OP and lowest in the PF. Clockwise hysteresis was found to be the dominant type in the PF, LF2 and LF3 ( 40.00%, 40.00% and 53.33% occurrence respectively) indicating source of sediment within the stream channel. The VJR has anticlockwise hysteresis as the dominant type ( 46.67% occurrence) whereas the OP has similar counts of clockwise, anticlockwise and anticlockwise figure-eight - VJR has distant sediment source while OP has multiple sources of sediment. The modified Lawler hysteresis index [Himean] that was used to quantify the magnitude of hysteresis shows no significant difference between the different land. uses. The classification of hysteresis patterns in the tropics, especially figure-eights and complex hysteresis are mostly generalised. With high intra-event variability, each hysteresis requires a separate analysis to best describe its pattern and to derive a "story" of sediment delivery. Key findings that are directly applicable to management practices: (i) suspended sediment concentration is highest in the oil palm plantation but sediment yield can be greatly minimised with careful selection of areas for oil palm cultivation (lower rainfall and relief); and (ii) there is still a high value in repeatedly logged forest from a water and soil conservation aspect. The common practice of converting repeatedly-logged forest into plantations based on the assumption that there is little ecological function left has to be re-considered.
| Item Type: | Thesis (Doctoral) |
|---|---|
| Keyword: | Land use, Hydrological and suspended sediment, History, Sabah |
| Subjects: | Q Science > QE Geology > QE1-996.5 Geology > QE420-499 Petrology |
| Department: | FACULTY > Faculty of Science and Natural Resources |
| Depositing User: | DG MASNIAH AHMAD - |
| Date Deposited: | 26 Jan 2024 15:08 |
| Last Modified: | 26 Jan 2024 15:08 |
| URI: | https://eprints.ums.edu.my/id/eprint/38025 |
Actions (login required)
 |
View Item |