Elsevier

Journal of Hydrology

Volume 566, November 2018, Pages 830-845
Journal of Hydrology

Research papers
Evaluating performances of green roofs for stormwater runoff mitigation in a high flood risk urban catchment

https://doi.org/10.1016/j.jhydrol.2018.09.050Get rights and content
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Highlights

  • Evaluation of green roofs for stormwater management at urban basin scale.

  • Green roofs cause peak flow and volume reduction in the urban drainage network.

  • Green roofs are more effective during frequent storms of smaller magnitude.

  • Non-linear reduction of outlet peak flow if network mainly at maximum convey capacity.

  • Effectiveness may increase with spatially heterogeneous implementation.

Abstract

Urbanization modifies the hydrologic cycle, resulting in increased runoff rates, volumes, and peak flows in the drainage network. In this paper, the implementation of green roofs as source control solutions for mitigating the impacts of urbanization is analysed at the urban catchment scale. The hydrologic-hydraulic response of a 2 km2 urban basin is investigated under various implementation scenarios and rainfall characteristics. In particular, a distributed hydrologic model is employed to assess the impact of 4 spatially homogeneous installations of green roofs (25%, 50%, 75%, 100% of roofs area converted) when forced by 6 storms differing in both duration and return period. In addition, a spatially heterogeneous configuration is tested, with green roofs concentrated where the drainage network is more prone to high degrees of filling. Results show that implementing green roofs at the urban watershed scale can be considered a valuable strategy to reduce both flow peak and volume in urban drainage networks, although the approach is more effective for frequent storms of smaller magnitude. In addition, it is found that the urban system may respond non-linearly to the extent of green roofs implementation in terms of peak flow reduction at the network outlet, and that non-linearity is mainly related to the network being close to its flow convey capability. Finally, planning redevelopment efforts on the basis of local insufficiencies in network convey capacity has the potential of increasing the effectiveness of Low Impact Development solutions.

Keywords

Distributed hydrologic modelling
Low impact development
Urban stormwater runoff management
Flood risk mitigation
Green roofs
LIDs planning

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