Abstract
AbstractWith increased intensity rainfall events globally and urban expansion decreasing permeable surfaces, there is an increasing problem of urban flooding. This study aims to better understand rainfall infiltration into a Sustainable Drainage System (SuDS) permeable pavement, compared with an adjacent Green Area of made ground, in relationship to groundwater levels below both areas. Both areas were instrumented with soil water content and matric potential sensors and four shallow boreholes were instrumented with groundwater level sensors. Surface infiltration rates were measured using a double‐ring infiltrometer. Results showed that average infiltration rates of the SuDS (1,925 mm/hr) were significantly higher than the Green Area (56 mm/hr). The SuDS was well designed to transfer rainfall rapidly to the aquifer below, where groundwater levels rapidly rose within 1 hr of a 1 in 30 year event (32.8 mm/hr). In comparison, soil compaction of the made ground Green Area decreased infiltration rates, but still enabled the majority of rainfall events to infiltrate. The aquifer below the Green Area responded more slowly, as lower matrix potentials facilitated water retention in the soil profile, slowing water draining to the aquifer. This work reiterates the importance of ensuring a 1 m separation depth between the base of the SuDS infiltration zone and aquifer depth.
Highlights
Record-breaking rainfall events have significantly increased globally (Allan & Soden, 2008; Lehmann, Coumou, & Frieler, 2015) and in combination with urban expansion and decreasing permeable cover, there is an increasing problem of surface water urban flooding (Adelekan, 2010; Du, Van Rompaey, Shi, & Wang, 2015)
By comparing these two sites: (a) a permeable pavement of open joint inter-locking pavers and (b) re-made ground of crushed bricks covered by a layer of sand, clay and grass, we aim to develop a better understanding of surface infiltration rates, ground water retention and groundwater level response to local rainfall events in relationship to flood mitigation of urban environments
Sustainable Drainage System (SuDS) and Green Area sites, because previous analysis of surface water flooding in the UK were associated with rainfall intensities of less than 1-in-10 year return periods (Hurford, Parker, Priest, & Lumbroso, 2012)
Summary
Record-breaking rainfall events have significantly increased globally (Allan & Soden, 2008; Lehmann, Coumou, & Frieler, 2015) and in combination with urban expansion and decreasing permeable cover, there is an increasing problem of surface water urban flooding (Adelekan, 2010; Du, Van Rompaey, Shi, & Wang, 2015). A typical grey structure in SuDS design is to install permeable pavement systems, which are designed to increase rainfall infiltration, to reduce greenfield runoff rates and retain surface contaminants, such as hydrocarbons, heavy metals and nutrients. The Green Area is typical of made ground developed from crushed building bricks mixed with local sandy loam and covered by a perennial clover/grass mix By comparing these two sites: (a) a permeable pavement of open joint inter-locking pavers and (b) re-made ground of crushed bricks covered by a layer of sand, clay and grass, we aim to develop a better understanding of surface infiltration rates, ground water retention and groundwater level response to local rainfall events in relationship to flood mitigation of urban environments
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