ABSTRACT
An increasingly industrialized global economy over the last century has led to a dramatic increment of the impervious area which contributes to the rise of volume and velocity of urban storm water. It results in the rapid discharges into stream and river that caused flash flood events if there is no provision made for collection, storage and proper discharge. Vegetation can help in enhancing the infiltration and surface roughness and reduces the kinetic impact of raindrops thus enhancing the groundwater recharge and reducing flash flood. In addition, the vegetation can also intercept the raindrops and stored on its outer surface for certain period of time. This will further reduced the rate and volume of the stormwater runoffs. Considering the large area covered by these vegetations, a significant effect can be obtained through interception storage on flash flood resulted from rainfall events. However the effects of different characteristics of plants cover on the rate and volume of surface runoff were very limited. Therefore this study focuses on the interception storage performance of local grass species which normally used in Malaysia. Three different types of grass species; Pearl grass (Axonopuscompressus) (dwarf), Philippine grass (Zoysiamatrella) and Cow grass (Axonopuscompressus) were chosen in order to determine their potential in reducing the runoffs. An artificial bed slope were fabricated in the hydrology laboratory of Universiti Teknologi MARA, Shah Alam, Selangor, Malaysia to simulate the rainfall event at site but having control on the rainfall intensity and the plants. Two different rainfall intensities of 17 mm/hr and 166 mm/hr were applied. The grasses were planted in a bed slope with an artificial precipitation. The volume of rainfall was measured as the system is running to determine the water retention capacity. Results showed that rainfall intensity did give significant differences to the percentage reduction of surface runoffs. Laboratory experimental results showed that Philippine grass (Zoysiamatrella) which has the highest dense patch which showed the highest potential of reducing the volume of surface runoff.
