Assessment of soil erosion and sedimentation under land use and climate change scenarios in the Upper Nan River Basin, Thailand | |
| Author | Pheerawat Plangoen |
| Call Number | AIT Diss. no.WM-14-01 |
| Subject(s) | Land use--Evaluation--Thailand--Nan River Basin Climatic changes--Evaluation--Thailand--Nan River Basin Soil erosion--Evaluation--Thailand--Nan River Basin Sedimentation--Evaluation--Thailand--Nan River Basin |
| Note | A dissertation submitted in partial fulfillment of requirement for the degree of Doctor of the Engineering in Water Engineering and Management, School of Engineering and Technology |
| Publisher | Asian Institute of Technology |
| Series Statement | Dissertation ; no. WM-14-01 |
| Abstract | Soil erosion patterns and rates are expected to change in future periods mainly because of changes in climate and land use. High intensity rainfall, resulting from expected changes in temperature and atmospheric CO2concentrations, will have significant impacts on soil erosion rates.Additionally, potential change in land use/land cover (LULC) such as vegetation covers will also affect soil erosion. The main objective of this study was to evaluate the impacts of climate and land use change on soil erosion and deposition in the Upper Nan River Basin in the north of Thailand. The present study evaluated rainfall erosivity under future climate projections, predicted land use change, estimated the erosion and deposition of soil under future climate and land use change, and proposed the conservation measures for the areas identified under high risk in future. Future climate data from general circulation models (GCMs), HadCM3, NCAR CSSM3 and a regional circulation model (RCM), PRECIS for four SRES scenarios (A2, A1B, B2 and B1) was downscaled using a statistical downscaling model and the change factor method. Cellular Automata/Markov Change Prediction (CA_Markov) was used to characterize future land use changes. In addition, soil loss modeling using the Revised Universal Soil Loss Equation (RUSLE) and sedimentation modeling was carried out to estimate soil loss and net soil loss under climate change, land use change and a combination of the two changes. To reduce soil loss in high risk areas, four vegetative cover scenarios were considered: vegetative cover in 2020 (LS0), replacement of 50% upland crop by orchards (LS1), replacement of 50% upland crop by forests (LS2) and managing upland crop areas using a mixture of soil erosion control measures (LS3).Results indicate that the average value of soil loss, as determined by the RUSLE modelunder climate change projections from all the GCMs and scenarios, is 157 Mg ha−1y−1for 2016–2025 (2020s), 195 Mg ha−1y−1for 2026–2035 (2030s) and 192 Mg ha−1y−1for 2036–2045 (2040s) as compared to 142 Mg ha−1y−1for the base period in the 1990s. The net soil loss (erosion and deposition), is estimated to increase by 44%, 32% and 34% in 2020s, 2030s, and 2040s respectively as compared to the base period value. The rate of soil loss under the impact of land use change, as determined by the RUSLE model, is determined to be 37 Mg ha−1y−1in the 2020s, 42 Mg ha−1y−1in the 2030s and 39 Mg ha−1y−1in the 2040s, as compared to 142 Mg ha−1y−1for the base period. Similarly, net soil losses estimated by the sedimentation model decrease dramatically by -81%, -74% and -68% in 2020s, 2030s, and 2040s respectivelyfrom baseline value of 24,037 Mg y−1. Land use is the most crucial element in the soil erosion model. However, land use change factors are the most difficult to predict with confidence in practice. In this study, high erosion and deposition zones were identified in areas along the Nan river. Accordingly, improvement in vegetation conditions through measures like vetiver grass cultivation is recommended to farmers in slope areas in order to reduce soil loss. There is a decrease in rate of soil loss under combined impact of climate and land use change as estimated by the RUSLE model: 124 Mg ha−1y−1for 2020s, 120 Mg ha−1y−1for 2030s and 130 Mg ha−1y−1for 2040s, as compared to 142 Mg ha−1y−1for the base period.Net soil loss, as estimated by the sedimentation model under climate and land use change projections also decreases in the futureperiods. The analysis of a combination of climate and land use change revealed that land use planning should be adopted to mitigate soil erosion and deposition in the future in the study area.The analysis of soil loss under various land use scenarios indicated that the annual soil loss will reduce to 125, 105 and 52 Mg ha-1yr-1under LS1, LS2 and LS3 respectivelycompared to 192 Mg ha-1yr-1in LS0. These scenarios were planned to reflect individual but feasible changes in the covers of upland crops, orchards and forest plantation with the aim to reduce average annual soil loss. The selection of the recommended vegetative covers must be carried out keeping in mind the time required for this vegetation to provide full soil protection, as well as the impact incurred when establishing a particular vegetation cover. Overall, soil erosion is estimated to reduce to acceptable levels with maximum reduction in Scenario LS3 than in scenarios LS1 and LS2. Thus, LS3 is recommended as the most adequate of the three scenarios considered for the Upper Nan River Basin. |
| Year | 2014 |
| Corresponding Series Added Entry | Asian Institute of Technology. Dissertation ; no. WM-14-01 |
| Type | Dissertation |
| School | School of Engineering and Technology |
| Department | Department of Civil and Infrastucture Engineering (DCIE) |
| Academic Program/FoS | Water Engineering and Management (WM) |
| Chairperson(s) | Babel, Mukand S.; |
| Examination Committee(s) | Shrestha, Sangam ;Tripathi, Nitin ;Clemente, Roberto s.; |
| Scholarship Donor(s) | Siam University, Thailand; |
| Degree | Thesis (Ph. D.) - Asian Institute of Technology, 2014 |