Abstract
Qualifying sediment dynamic in a reservoir watershed is essential for water resource management. This study proposed an integrated model of Grid-based Sediment Production and Transport Model (GSPTM) at watershed scale to evaluate the dynamic of sediment production and transport in the Shihmen Reservoir watershed in Taiwan. The GSPTM integrates several models, revealing landslide susceptibility and processes of rainfall–runoff, sediment production from landslide and soil erosion, debris flow and mass movement, and sediment transport. For modeling rainfall–runoff process, the tanks model gives surface runoff volume and soil water index as a hydrological parameter for a logistic regression-based landslide susceptibility model. Then, applying landslide model with a scaling relation of volume and area predicts landslide occurrence. The Universal Soil Loss Equation is then used for calculating soil erosion volume. Finally, incorporating runoff-routing algorithm and the Hunt’s model achieves the dynamical modeling of sediment transport. The landslide module was calibrated using a well-documented inventory during 10 heavy rainfall or typhoon events since 2004. A simulation of Typhoon Morakot event was performed to evaluate model’s performance. The results show the simulation agrees with the tendency of runoff and sediment discharge evolution with an acceptable overestimation of peak runoff, and predicts more precise sediment discharge than rating methods do. In addition, with clear distribution of sediment mass trapped in the mountainous area, the GSPTM also showed a sediment delivery ratio of 30% to quantify how much mass produced by landslide and soil erosion is still trapped in mountainous area. The GSPTM is verified to be useful and capable of modeling the dynamic of sediment production and transport at watershed level, and can provide useful information for sustainable development of Shihmen Reservoir watershed.
Highlights
Introduction to Grid-based Sediment Production and Transport Model (GSPTM)Figure 3 illustrates the GSPTM framework, comprising five modules for modeling rainfall–runoff, landslide, soil erosion, runoff-routing, and sediment transport processes, respectively
We used GSPTM to reveal the spatial distribution of landslide mass and corresponding sediment transport in Shihmen Reservoir watershed under an extreme weather event of Typhoon Morakot
In the following, we only present the simulated results of the two watersheds, including landslide prediction, sediment transport and turbidity, and sediment delivery ratio
Summary
States Environmental Protection Agency’s Hydrological Simulation Program-Fortran (HSPF) [10], and Soil and Water Assessment Tool (SWAT) [11] It seems no conventional sediment routing models consider mass input from landslides and correctly reflect the spatiotemporal characteristic of landslide source in a watershed. To simulate watershed sediment dynamics considering landslides, this research proposes an integrated model Grid-based Sediment Production and Transport Model (GSPTM) by incorporating a several individual models for predicting landslide occurrence, and simulating mass production and movement, sediment transport, and river erosion and sedimentation from source area to downstream regions. Details of each model are elaborated below This integrated model was calibrated and tested on a well-documented event of severe Typhoons Morakot, by reconstructing the spatiotemporal distribution of sediment mass in the target area of Shihmen Reservoir watershed. The model is intentionally simplified due to lack of detailed information in a wider watershed, but it intends to provide valuable insights into sediment evolution under any hydrological forcing as a practical reference benefiting assessment of reservoir sedimentation and river channel safety
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