Priyantha Ranjan Sarukkalige

Evaluation of the Impacts of Land Use on Storm Water Quality: Case Study from Western Australia

This study evaluates the impacts of land use on storm water quality. Storm water samples were collected from three main land use areas; residential, commercial and industrial lands around the Town of Victoria Park in Western Australia. Each sample was tested to measure important water quality parameters. Time variation of storm water flow, rainfall intensity and storm water quality clearly showed that the highest concentration of pollutants in storm water occurs during the first flush event. Further analysis shows that the commercial storm water demonstrated the cleanest appearing storm water with lowest amounts of suspended solids whereas the industrial storm water had the dirtiest appearing storm water quality. Nutrients in the residential storm water have the lowest nitrate, ammonia and phosphate concentrations. Overall, the industrial land use site recorded the worst storm water quality. Study further provides recommendations for water quality improvement and management controls.

Numerical Modeling of Flood Vulnerability in Urban Catchments for Flood Forecasting

This study uses two of numerical modeling approaches to represent the urban catchment, and assess the flood risk of an urban catchment; hydrological surface routing approach and hydraulic 2D surface routing approach. Both approaches were combined with 1D hydraulic stormwater drainage network. XPSWMM was used as the modeling tool. This comparison leads to select most suitable approach to assess the possible flood inundations in the study area. Comparison of results of two approaches shows that the both approaches are suitable to represent urban catchment’s hydrological behavior, but the results of hydrological surface routing are more close to observation data. Model was calibrated to one sub catchment and used to generate flood vulnerability maps for whole catchment. These maps will be used as water sensitive urban design guide lines in the future developments of the area, while structural and non structural measures are to be implemented.

Sensitivity Analysis of Catchment Characteristics in Urban Stormwater Management Modeling

Numerical stormwater management modeling helps to understand the urban hydrological catchment behavior. Urban hydrological modeling is a complex process, when considering all the urban hydrological catchment characteristics. Selecting and/or prioritizing catchment characteristics according to their sensitivity on modeling results helps to generate simplified and accurate catchment models. Sensitivities of selected catchment characteristics depend on land use change have been analyzed by hydrological modeling of an urban catchment. Changes to surface roughness coefficients increased the modeled post development peak flow up to 10.3% and 15.5% in 1 year and 100 year ARI events. Changing of infiltration parameters caused to 8.8% and 0.3% changes in peak flows under two scenarios. These results show that the sensitivity of parameters associated with the portion of impervious land use is more significant than the characteristics associated with the pervious land use portion. Results have suggested that the overall land use change is more sensitive to the modeling results of minor rainfall events than the results of major rainfall events. Results will help to decide most sensitive catchment characteristics and applicable range of their values, when modeling similar urban catchments.

Maximize the benefits of water sensitive urban designs in a local government area: Western Australia

Until recently, stormwater management strategies have failed to adequately consider the criticality of spatially varying soil permeability values and their implications on drainage designs. This case study was carried out in new development areas, focusing on identification of soil properties and development of a typology of suitable stormwater management strategies with respect to applicable infiltration capacities. The Guelph Permeameter was used to investigate the in-situ saturated hydraulic conductivities. Test results were categorized into four main permeability groups, very rapid (> 1.56 m/day), rapid (0.48<1.56 m/day), moderate (0.12<0.48 m/day) and slow (<0.12 m/day), based on the theoretical requirements of stormwater management techniques. Finally, with the help of the existing soil maps, the point represent hydraulic conductivity data were been generalized logically in order to develop the hydraulic conductivity maps representing the areal average as an electronic shape files by using a GIS Arc view mapping software. The future development areas under Central Maddington, Kenwick, Central and Outer Beckenham have been identified as low permeable areas which is not suitable for infiltration based stormwater management strategies whereas the Landford, Thornlie, North Huntingdale and Gosnells has been identified as high permeable areas which is highly recommended for infiltration based stormwater management strategies.