The Development of Numerical Modelling for Sungai Chini, Pahang (Assessment on the Structure of Weir)
Tasik Chini is the second largest natural freshwater lake in Malaysia located in the southeast region of Pahang, Malaysia. The catchments area about 49.8 km2 consists of 12 small lakes and receiving water flow from several river tributaries. Flow from Tasik Chini will then discharge into Sungai Chini before connecting with Sg. Pahang. The total length of Sg. Chini is at 4.8 km and intersects at km 84 of Sg. Pahang flowing towards South China Sea. There were 309 species of plants including aquatic plants, 92 species of birds and 144 species of aquatic life in the area of Tasik Chini. Due to the development of Tasik Chini, the environment has greatly changed the topography and the pattern of land use in the area which contributes to the hydrological imbalance and altering the entire ecosystem of the lake. Thus, there is an urgent need for a concerted research in Tasik Chini. This study aimed to develop a hydrodynamic model for Sungai Chini, Pahang and its feeder rivers to assess the impact of the existing weir under baseline and future scenario for various return periods (10-, 20-, 25-, 50- and 100-year Average Recurrence Interval (ARI)) to the hydrodynamic of Sg. Chini. The methodology of the study comprises of data acquisition and data collection of hydrological data (HEC-HMS times series) and hydraulic data such as water level and discharge data for Sungai Chini and its feeder rivers; setting up of hydrodynamic modelling; model calibration and verification and follow by model simulations and assessment. Two assessments were done on the existing weir under land use and climate change scenarios and assessments on weir modification. Results for assessment on the impact of the combination of landuse change and climate change for various ARIs show a significant increment in both water level and flow for various ARIs under the impact of both landuse change and climate change with increase of 0.932 m (8.451%) to 1.981 m (14.010%) for water level and increase of 2.434 m3/s (12.290%) to 109.474 m3/s (443.448%) for flow. For the assessment of weir modification, three different weir height were tested, namely scenario with existing weir height (1.5m), scenario with decrease of 0.1m weir height (1.4m) and scenario with decrease of 0.25m weir height (1.25m). Results for both 50 and 100-ARI show water level with a slight decrease in trend at upstream of weir and upstream of sg chini, but a slight increase at downstream of weir and downstream of Sg. Chini. However, both water level and flow increase at all locations. From the simulation, appropriate measures for flood and river management has been proposed to minimize the impact of flooding and at the same time to sustain the growth of lotus population at Tasik Chini without disrupting the navigational system along Sungai Chini.
Authors
Abstract
Tasik Chini is the second largest natural freshwater lake in Malaysia located in the southeast region of Pahang, Malaysia. The catchments area about 49.8 km2 consists of 12 small lakes and receiving water flow from several river tributaries. Flow from Tasik Chini will then discharge into Sungai Chini before connecting with Sg. Pahang. The total length of Sg. Chini is at 4.8 km and intersects at km 84 of Sg. Pahang flowing towards South China Sea. There were 309 species of plants including aquatic plants, 92 species of birds and 144 species of aquatic life in the area of Tasik Chini. Due to the development of Tasik Chini, the environment has greatly changed the topography and the pattern of land use in the area which contributes to the hydrological imbalance and altering the entire ecosystem of the lake. Thus, there is an urgent need for a concerted research in Tasik Chini. This study aimed to develop a hydrodynamic model for Sungai Chini, Pahang and its feeder rivers to assess the impact of the existing weir under baseline and future scenario for various return periods (10-, 20-, 25-, 50- and 100-year Average Recurrence Interval (ARI)) to the hydrodynamic of Sg. Chini. The methodology of the study comprises of data acquisition and data collection of hydrological data (HEC-HMS times series) and hydraulic data such as water level and discharge data for Sungai Chini and its feeder rivers; setting up of hydrodynamic modelling; model calibration and verification and follow by model simulations and assessment. Two assessments were done on the existing weir under land use and climate change scenarios and assessments on weir modification. Results for assessment on the impact of the combination of landuse change and climate change for various ARIs show a significant increment in both water level and flow for various ARIs under the impact of both landuse change and climate change with increase of 0.932 m (8.451%) to 1.981 m (14.010%) for water level and increase of 2.434 m3/s (12.290%) to 109.474 m3/s (443.448%) for flow. For the assessment of weir modification, three different weir height were tested, namely scenario with existing weir height (1.5m), scenario with decrease of 0.1m weir height (1.4m) and scenario with decrease of 0.25m weir height (1.25m). Results for both 50 and 100-ARI show water level with a slight decrease in trend at upstream of weir and upstream of sg chini, but a slight increase at downstream of weir and downstream of Sg. Chini. However, both water level and flow increase at all locations. From the simulation, appropriate measures for flood and river management has been proposed to minimize the impact of flooding and at the same time to sustain the growth of lotus population at Tasik Chini without disrupting the navigational system along Sungai Chini.
Citation
IR. LIEW YUK SAN , DATO IR. DR. HJ. NASEHIR KHAN BIN E.M YAHAYA, IR. AZMAN MAT JUSOH, DR. SURIYANI AWANG, Muhammad Saufi Ishak. 2015. The Development of Numerical Modelling for Sungai Chini, Pahang (Assessment on the Structure of Weir). Digital NAHRIM Publication Repository.