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Design Guidelines for Urban Stormwater Wetlands
18. Edward L. Thackston, F. Douglas Shields, Jr., and Paul R. Schroeder, “Residence Time Distributions of Shallow Basins,” Journal of Environmental Engineering 113, no. 6 (December 1987): 1319–32; J. Savickis et al., “Effect of a Meandering Channel on Wetland Performance,” Journal of Hydrology 535 (April 2016): 204–10; Arash Farjood, Bruce W. Melville, and Asaad Y. Shamseldin, “The Effect of Different Baffles on Hydraulic Performance of a Sediment Retention Pond,” Ecological Engineering 81 (August 2015): 228–32; Anne F. Lightbody, “The Physical Role of Transverse Deep Zones in Improving Constructed Treatment Wetland Performance” (Massachusetts Institute of Technology, 2007).
water exit too quickly to be sufficiently treated, rendering most of the wetland area unused. Engineers have devoted a lot of time to researching optimal configurations of wetlands that diminish shortcircuiting, for example, proposing long aspect ratios, placing deep zones perpendicular to water flow, or creating sinuous channels.18 In these studies, however, ecology and urbanism were not considered jointly with hydraulic performance. Other engineers have also found simple islands helpful in improving water circulation, but have stopped short of making more elaborate studies.19 Given the promising results of the island cluster in our initial research, our subsequent experiments explored more complex designs for island clusters near inlets. Our preliminary island cluster was made of perfectly extruded circular shapes. For phase two of our research, we chose a geometric, faceted island shape because it was easier to model and faster to fabricate (Figure 2.6 on page 19). However, designers can play with shape and curvature to a certain degree without significantly altering performance, so long as the geometry at the scale of the cluster remains similar. This margin of design is the key to embedding multifunctionality in our forms,
19. Jonas German and Henrik Kant, “FEM-analys av strmningsförhållanden i en dagvattendamm (FEM-analysis of the hydraulic conditions in a stormwater detention pond),” Vatten 54, no. 3 (1998): 183–90; J. Persson, N. L. G. Somes, and T. H. F. Wong, “Hydraulics Efficiency of Constructed Wetlands and Ponds,” Water Science and Technology 40, no. 3 (January 1, 1999): 291–300; J. Persson, “The Hydraulic Performance of Ponds of Various Layouts,” Urban Water 2, no. 3 (September 2000): 243–50; Åsa Adamsson, Lars Bergdahl, and Maria Vikström, “A Laboratory Study of the Effect of an Island to Extend Residence Time in a Rectangular Tank,” in Ninth International Conference on Urban Drainage (Portland, Oregon: American Society of Civil Engineers, 2002), 1–10; S. Khan, B. W. Melville, and A. Y. Shamseldin, “Retrofitting a Stormwater Retention Pond Using a Deflector Island,” Water Science and Technology 63, no. 12 (June 1, 2011): 2867–72.