Integrated approach for low impact development locating in dense residential areas based on sustainable development criteria.

The study proposed a practical approach for low impact development (LID) placement in dense residential urban catchments considering social, economic, and technical criteria. The objective is to shift the current technical orientation in LIDs' locating to a practical one with a specific level of residents' cooperation. Four stages were conducted, including (i) acquiring the residents' socio-economic information; (ii) hydraulic simulation of the stormwater collection system in the status quo, (iii) regionalization of the urban catchment using data mining, and (iv) proposing specific LIDs locating scenarios. The field study lasted around four months in a dense residential area with a combination of old/new buildings in the eastern Tehran metropolis. Regionalization was conducted by combining pre-processing/clustering techniques, resulting in six regions (preliminary results) and four regions after the clustering integration in the post-processing study. The regions have different priorities for the LIDs locating, including (i) cooperative cluster, 57 sub-catchments (SCs) and appropriate for rain barrel (RB) and green roof (GR) locating; (ii) semi-cooperative cluster, 12 SCs, appropriate for RB or GR locating; (iii) 15 SCs with infrastructural constraints in the third cluster and appropriate for RB; and (iv) non-cooperative cluster, 34 SCs, inappropriate for LIDs locating. Accordingly, seven locating scenarios were specified, and the developed EPA-SWMM model was modified to evaluate the scenarios for mitigating the study area's node flooding problems. The finding shows that the overflow volume reduced in a range of 36.7-93.1%, 28.3-78.7%, and 16.3-66.4% under the rainfall with 2, 5, and 10 years return periods, respectively.

Simulating the effects of low impact development approaches on urban flooding: a case study from Tehran, Iran.

Low impact development (LID) methods have been shown to be efficient in reducing the peak flow and total volume of urban stormwater, which is a top priority for effective urban stormwater management in many municipalities. However, decision-makers need information on the effects of LIDs and their associated costs before allocating limited resources. In this study, the Storm Water Management Model (SWMM) was used to investigate the effects of five different LID scenarios on urban flooding in a district in Tehran, Iran. The LID scenarios included rain barrel (RB) at two sizes, bio-retention cell (BRC), and combinations of the two structures. The results showed that significant node flooding and overflow volume would occur in the study area under the existing conditions, especially for rainfall events with longer return periods. BRC and combinations of BRC and RBs were the most effective options in reducing flooding, while the smaller-size RB was the cheapest alternative. However, normalized cost, obtained through dividing the total cost by the percent reduction in node flooding and/or overflow volume, was smallest for BRC. The results of this study demonstrate how hydraulic modeling can be combined with economic analysis to identify the most efficient and affordable LID practices for urban areas.