How does climate affect the infiltration capacity of stormwater facilities?
The question of whether and how climate and geographical location can affect the ability of infiltration-based stormwater facilities, such as biofilters, green roofs and grassed swales, to manage runoff volumes has been investigated by Iván Mantilla in his licentiate thesis "Climate and geographical influence on the performance of infiltration-based facilities for managing runoff – Temporal and spatial variability" which he presented on May 3, 2024 at a seminar with Vegard Nilsen from NMBU (Norwegian University of Life Sciences) as discussion leader.
This research analyses the impact of different climatic variables characteristic of four urban areas in Sweden, including precipitation patterns and temperature gradients. To do so, historical meteorological time series data from each urban area were used as inputs for a rainfall-runoff and snowmelt model. The model outcomes aim to provide a better understanding of the most influential factors affecting the runoff volume reduction capacities specific to oceanic, humid continental, and subarctic climatic zones. Results are presented in terms of the annual and seasonal distribution of runoff volume reductions and peak flow attenuations.
To complement these findings, field measurements were conducted to assess the infiltration performance of a grass swale. These measurements aimed to establish a correlation between the hydraulic properties of the swale and the spatial variability of saturated hydraulic conductivity (Ksat) values. In addition, a comparative analysis between point infiltration measurements and a full-scale infiltration test was conducted. This analysis aimed to evaluate the swale's infiltration capacity under a natural rainfall event. Furthermore, this thesis includes the implementation of an outflow control structure in a grass swale, designed to enhance detention capacities and control the release of outflows. Empirical results provide a baseline for the influence of outflow controls, particularly under critical conditions such as high soil water content. The approach aims to demonstrate how a space-efficient solution can offer an adaptive response to the escalating flood risk caused by increased rainfall intensities due to climate change.
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