On the Effectiveness of Domestic Rainwater Harvesting Systems to Support Urban Flood Resilience

Abstract

The effectiveness of domestic rainwater harvesting (DRWH) systems to support urban flood resilience is analysed at the sub-catchment scale, according to a specific DRWH conversion scenario, under 4 degrees of urbanization, 3 drainage network configurations, 4 precipitation regimes and 3 return periods of the rainfall event. At this aim, a suitable modelling framework is implemented: the semi-distributed hydrologic-hydraulic model is undertaken using EPASWMM 5.1.007 where specific tools are developed to simulate DRWH systems at high spatial resolution. The effectiveness of the DRWH systems simulated for the 144 different cases, is analysed at the event scale by using the Volume and Peak Reduction indexes to measure the hydrologic performance. The dimensionless variable, namely the event storage fraction, is defined in order to easily describe the DRWH effectiveness. The event storage fraction is defined as the ratio between the event runoff volume resulting from the impervious surface of the urban catchment in the reference scenario and the storage capacity of the DRWH systems. Modelling results confirm that DRWH catchment-scale applications allow to support specific stormwater control requirements based on peak-flow or volume regulations strategies. Findings of the elaboration reveal for a typical residential catchment in the Italy-France cross-border coastal area, that DRWH effectiveness in supporting the urban flood management becomes significant (i.e. Volume and Peak Reduction indexes greater than 0.2) starting from a storage event fraction of 0.4 that means realizing storage tanks able to contain at least the 40% of runoff volume generated by the targeted event at the sub-catchment scale.

Green Waterfront City, Future Perspectives for Sustainable City in Tidal Flooding Prone Area at Northern Semarang

“…As a result, harvested rainwater could be the primary source of drinking water for the coastal region's residents (Rahman et al, 2021). Furthermore, a study conducted by (Palla and Gnecco, 2022) in the Italy-France crossborder coastal area found that domestic rainwater harvesting is effective in supporting urban flood management, by volume and peak reduction indexes greater than 0.2. It implies the realization of storage tanks capable of containing at least 40% of runoff volume generated by the targeted event at the subcatchment scale (Palla and Gnecco, 2022).…”

Rainwater Harvesting and Treatment: State of the Art and Perspectives

“…Mugume et al [74] showed that RWH systems for UK houses could provide 95% of the users' non-potable water demand, maintaining sufficient attenuation capacity to control stormwater runoff for 1-100 year design storm. Palla and Gnecco [75], analyzed 144 different cases (considering four degrees of urbanization, three drainage network configurations, four precipitation regimes, and three return periods of the rainfall events), concluded that the effectiveness of an RWH system in supporting urban flood management becomes significant when storage tanks can contain at least 40% of the runoff volume. Morales-Pinzon et al [76] showed through a life cycle analysis (LCA) that the introduction of environmental objectives (associated with emissions and the materials used) impact significantly tank size, depending on the type of building.…”

Simulating the effect of rainwater harvesting on flood mitigation: the case of Asunción, Paraguay

“…Despite their effectiveness, a limitation of RWHS is that, in heavy rainfall events, their mitigation capacity is lower because of the storage tank capacity [4]. Other results include decreasing the number of flood events by approximately 50% and retaining 2 40% of the runoff volume generated by the target event [5]. It is relevant that most of the studies mentioned took into account the storm drainage of the cities.…”