Dynamic Modeling of Sediment Budget in Shihmen Reservoir Watershed in Taiwan

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.

Modeling Sediment Yields and Stream Stability Due to Sediment-Related Disaster in Shihmen Reservoir Watershed in Taiwan

“…The sum of the water depths in the three tanks is called the Soil Water Index (SWI), i.e., H 1 + H 2 + H 3 . The Tank model is suitable to simulate surface runoff, reservoir flood discharging and flood diversion [26].…”

“…The geological data with a scale of 1:50000 published in 2000 was provided by the Central Geological Survey Bureau, Taiwan. There are twelve geological conditions in the Shihmen Reservoir watershed [26]. The coefficients for the variables are determined from the landslide inventory during heavy rainfall events.…”

“…Landslides play an important role in determining sediment yield from a watershed [19,20]. Several studies attempted to establish the landslide component on total sediment yield [21][22][23][24][25][26]. For example, Burton and Bathurst [21] developed a physically-based model-SHETRAN to estimate the landslide-related sediment yield.…”

“…Hsu et al [23] integrated the HSPF, TRIGRS [24], and FLO-2D [25] models to estimate the sediment yield from soil erosion, shallow landslide, and debris flow. Chen et al [26] proposed an integrated model of Grid-based Sediment Production and Transport Model (GSPTM) at a watershed scale to evaluate the dynamic of sediment production and transport in the Shihmen Reservoir watershed in Taiwan. In their model, rainfall-runoff processes, landslide potential, sediment production from landslide and soil erosion, debris flow and mass movement, and sediment transport were included.…”

“…This study aimed to estimate sediment yields and assess stream stability due to sedimentrelated disaster in a large-scale watershed (>100 km 2 ). An integrated model originally proposed by Chen et al [26] was adopted, but two hydrodynamic and sediment transport models were added in the model to better quantify the flow field and calculate suspended sediment concentration, sediment yields and sediment erosion and deposition patterns in streambeds. To identify the unstable reaches in streams, an evaluation system based on the integrated model that can provide the bed erosion and deposition patterns, flow-induced shear stress on the bed and bank of streams, and possibility of slope failure near the streams was developed.…”