Inlet and Sewer Traps for Sediment Control in Stormwater Drainage - A Malaysian Case Study

The city of Alor Setar in Kedah, is an important developing centre of business and communications for the Northwest of Malaysia. However, the capacities of the existing storm drains in Alor Setar are severely restricted as a result of sediment deposits washed-in during high intensity rainfall events. These deposits result in stagnant, polluted areas of water within the catchment and a loss of hydraulic capacity needed to deal with large storms. Methods of sediment deposition prediction have been applied to UK catchments with limited degrees of success. The application of these methods has been used to propose an improved sediment management strategy for Alor Setar. The methods involve the development of a simplified hydraulic model of the test catchment and the prediction of areas within the system where deposits are most likely to occur. Using this formation options for invert trap placement can be developed in order to determine their most effective locations. Further analyses are also proposed in order to determine the fill rates of these traps throughout an average year. A proactive maintenance plan can therefore be developed in preference to the reactive maintenance methods currently employed This planned programme of maintenance should ensure that best use of traps is made at all times in order to protect the system from flooding and pollution problems.