A practical method for rehabilitation of stormwater collecting system by node flooding detection and regional hydraulic redesign: a case study of eastern Tehran metropolis.

This study investigates the effect of structural modification actions on the existing stormwater collecting system in Eastern Tehran to increase the hydraulic capacity and create suitable conditions for the passage of runoff in the critical points of the canal. First, the hydraulic conditions within the stormwater collecting system were simulated using the Stormwater Management Model (SWMM) model before/after the modification to investigate the rehabilitation results. Three critical locations along the main canal were recognized as the most vulnerable points. Then, based on field visits and brainstorming sessions, rehabilitation methods were presented, and three practical solutions, including canal deepening, canal widening, and their combination, were investigated for each. Then, local investigating based on the rehabilitation alternatives for each critical location was conducted using the HEC-RAS. Finally, the SWMM model was used again to evaluate the overall operational performance of the stormwater collecting system after the rehabilitation. The results revealed that it is necessary to implement two alternatives of deepening and widening to provide adequate transmission runoff capacity during rainfalls with various return periods. More specifically, the localized redesign of the eastern flood diversion canal had an acceptable improvement in reducing flooding problems so that for floods with a return period of 10 years, the number of node flooding dropped from 4 to 0, inundated areas from 17% to 0, and the overflow volume from (10-45) to 0. Moreover, the proposed local rehabilitation reduced the overflow volume from (30-65), (43-74), and (70-92) in the status quo to (4-12), (11-27), and (24-36) for rainfall with 25, 50, and 100-year return periods.

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.

Developing an integrated risk management framework for agricultural water conveyance and distribution systems within fuzzy decision making approaches.

Irrigation canal networks, as the primary agricultural water conveyance and delivery systems, are exposed to a variety of hazards affecting the water distribution processes. This study, for the first time, develops a comprehensive risk management framework for the canal network through a Fuzzy Hierarchical method. In this regard, the risk is analyzed by a combination of probability, consequence, and vulnerability against identified hazards based on the hierarchical framework. The developed model is based on fuzzy numbers to consider the uncertainties arise from experts' opinion. To aggregate the calculated risk in the hierarchical framework, the Fuzzy Simple Additive Weighting (FSAW) approach was employed. To enhance the reliability of the water distribution system and decrease the risk of failure, six risk management alternatives are proposed based on the risk assessment results and the most significant hazards. To prioritize managerial scenarios, two sets of criteria were selected including quantitative criteria (consisting of cost of operation and risk reduction) and a qualitative set (compromising social and operational criteria). The risk management scenarios were prioritized based on two rational multi-criteria decision-making (MCDM) methods of a Technique for Order Preference by Similarity to Ideal Solution (TOPSIS) and Simple Additive Weighting (SAW). Regarding different degrees of importance of the criteria, a pair-wise comparison was conducted by a group of experts to determine the relative weight of the criteria. According to the risk assessment results, the riskiest hazards are poor maintenance, seepage, unexpected event, drought, and vandalism of the structure. Moreover, employing the MCDM model in risk-based decision-making reveals that "maintenance improvement" is ranked as the first scenario, with score values of 0.851 and 0.237 employing the SAW, and TOPSIS approaches, respectively.