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The paper reviews the goals of stormwater management adopted in Adelaide and declares a focus on harvesting of stormwater to replace mains water in irrigating areas landscaped with grass, flower beds and shrubs. Four categories of catchments are recognised according to their levels of pollution production - roof runoff and “low”, “medium” and “high” pollution runoff surfaces. Four case study examples of systems involving appropriate treatment trains are described, each one delivering harvested stormwater suitable for irrigation. Two examples are given of large roof areas draining to gravel-filled trenches providing “passive” irrigation to grassed surfaces and two examples of runoff from ground-level surfaces supplying cleansed recharge to small aquifer storage/recovery schemes.

Water Sensitive Urban Design (WSUD) and Low Impact Development (LID) principles were investigated in Dhaka's drainage network using ‘Regime in Balance’ strategy for Average Recurrence Interval (ARI), Y = 100 years. Three feasible alternatives, such as, leaky-well, soak-away and infiltration trench were identified and designed to improve Dhaka's present unsatisfactory stormwater drainage system into one which is sustainable. For selecting the best one, we applied a multi-criteria decision analysis approach and chose the Analytic Hierarchy Process (AHP) model. Eleven criteria under three categories (technical, economic and social) were considered to quantify relative priorities of alternatives. Pair-wise comparisons of alternatives were performed against each criterion and ranked using a scale from 0 to 9. During the process of applying AHP model, consistency of ranking was thoroughly checked and a reasonable level of inconsistency was accepted due to the nature of human judgement. After the analysis, it was found that leaky-well (percentage priority 43%) followed by soak-away (38%) was the most appropriate technology for improving urban stormwater management system in Dhaka, Bangladesh. The proposed model can also be used in better selecting WSUD and LID technologies in other geographic locations.

The contribution of this paper is a comparison of the installation cost of a conventional drainage system consisting of a network of pits and pipes, with that of a hybrid drainage system comprising a network of pits and pipes, supported by allotment scale infiltration measures in a modern greenfield residential development. The case study site is located in Pipers Crest, near Strathalbyn, South Australia. This as-built site consists of 56 allotments, 42 pits (hence 42 sub-catchments), one detention basin and over 1000 m of drainage pipes. In this study, conventional and hybrid (combination of conventional and Water Sensitive Urban Design, WSUD systems) drainage systems were designed to convey minor storm events of 10% annual exceedance probability (AEP), and checked for major storm events of 5% AEP, using the DRAINS model and/or source control principles. The installation costs of the conventional and hybrid drainage systems were estimated and compared based upon cost estimates derived from Australian literature. The results of the study indicate that satisfactory drainage was possible using the conventional or hybrid system when the two systems were designed to have outflow not exceeding the pre-developed flow. The hybrid drainage system requires smaller pipe sizes compared to the conventional system. Also, the size of the detention basin and maximum outflow rate of the hybrid system were smaller than those for the conventionally drained site. The installation cost of the hybrid drainage system was 18% less than that of the conventional drainage system when the objective was to accommodate 10% and 5% AEP storms.

On-site detention (OSD) of storm runoff decreases catchment peak flows through the routing effect of temporary storage; on-site retention (OSR) achieves the same objective by abstracting part of the urban flood wave and passing the retained water to disposal on site. The investigation explored both strategies applied to a set of hypothetical present/re-developed urban catchments ranging in size from 14 ha to 210 ha. Comparisons were made on the basis of site storage required (SSR) to achieve the same global peak flow reductions, environmental aspects and cost. OSR practice was shown to out-perform OSD generally in medium-large catchments with respect to SSR and, hence, cost. The retention option also has clear environmental benefits that fall beyond the scope normally ascribed to OSD practice. The paper cautions against use of OSR in unsuitable circumstances.