Development of Percolating Sediment Trap for Urban Drainage

Urban development often increases surface erosion and runoff which may ultimately cause silting and flooding problems in the downstream areas. The sand from the erosion is controlled by sediment traps located at specific locations particularly at the junction or intersection between drains. The sediment trap reduces the water flow in the drain thus allowing suspended materials to settle and remain in the trap until it is removed during maintenance work. The problem with the sediment trap is that it also retains water that may provide an opportunity for mosquito breeding. Intermittent rain with the interval of three or more days under hot and humid tropical climate is an ideal condition for mosquito breeding of sufficient time in the stagnant water to complete the life cycle. This paper presents research findings as a control mechanism for silt but will not allow stagnation of water. A model sediment trap with a dimension of 15 in x 15 in x 16 in was developed with three different sizes of bottom openings 3 in, 4 in and 5 in diameter. The traps were designed to meet the criteria for minimum sump invert level of 15 cm below the drain invert level and were tested on the soil of Bandar Seri Iskandar consisting of sandy loam soil, loamy sand soil and mining sand. The soil hydraulic conductivity is 1.03 x 10-4 cm/s, 1.58 x 10-4 cm/s and 2.0 x 10-2 cm/s, respectively. It was found that the traps were able to percolate all the retained water in less than three days. The application of this sediment trap in urban drainage is expected to be able to control water stagnation and mosquito breeding in storm water infrastructures.