Abstract
Stormwater sediments of various sizes and densities are recognised as one of the most important stormwater quality parameters that can be conventionally controlled by settling in detention ponds. The bottom grid structure (BGS) is an innovative concept proposed in this study to enhance removal of stormwater sediments entering ponds and reduce sediment resuspension. This concept was studied in a hydraulic scale model with the objective of elucidating the effects of the BGS geometry on stormwater sediment trapping. Towards this end, the BGS cell size and depth, and the cell cross-wall angle were varied for a range of flow rates, and the sediment trapping efficiency was measured in the model. The main value of the observed sediment trapping efficiencies, in the range from 13 to 55%, was a comparative assessment of various BGS designs. In general, larger cells (footprint 10 × 10 cm) were more effective than the smaller cells (5 × 5 cm), the cell depth exerted small influence on sediment trapping, and the cells with inclined cross-walls proved more effective in sediment trapping than the vertical cross-walls. However, the BGS with inclined cross-walls would be harder to maintain. Future studies should address an optimal cell design and testing in an actual stormwater pond.
Highlights
Progressing urbanisation leads to profound changes of the urban water cycle manifested by increased surface runoff and deterioration of runoff quality by discharges of various pollutants, including stormwater sediments (Walsh et al )
For model construction and testing, the following steps were taken: (i) a scale model was designed assuming a geometric scale 1:10 applied to hypothetical prototype dimensions, (ii) model sediment was chosen, and (iii) sediment trapping experiments were conducted in the model for selected flow rates, sediment fluxes and bottom grid structure (BGS) cell designs
The presentation of results starts with the hydraulics of the BGS tank followed by sediment trapping
Summary
Progressing urbanisation leads to profound changes of the urban water cycle manifested by increased surface runoff and deterioration of runoff quality by discharges of various pollutants, including stormwater sediments (Walsh et al ). In this context, stormwater sediments represent a broad spectrum of particle sizes, including total suspended solids (TSS) and bedload sediment, and impact both the water quality in the receiving waters and operation of drainage systems. Bedload sediment size classes comprising sand and. Tens of thousands of stormwater detention ponds have been built worldwide for controlling runoff peaks by storage and removing stormwater sediment by settling
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