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- Info
Wetland networks for stormwater management in subtropical urban watersheds
| Author: |
Tilley, David R.; Brown, Mark T. |
| Date: |
1998 |
| Periodical: |
Ecological Engineering |
| Abstract: |
A quantitative method suitable for planning wetland stormwater treatment at the regional, multibasin scale was developed based on simple zero order kinetics (uptake rates) and average nutrient loading conditions. The method was applied to urbanized watersheds south of Miami, FL and yielded a hierarchically organized network of wetlands for processing storm waters. Coastal watersheds in Dade county, FL, varying in intensity of development from heavily urbanized to almost completely undeveloped and ranging in size from 38600 ha to 700 ha were analyzed. Watersheds were divided into three spatial scales: basin ( > 1000 ha), sub-basin (1000-100 ha) and neighborhood (100-10 ha). The methods used to calculate wetland area were based on: (1) reducing nutrient and sediment concentrations to background levels of the receiving water body (Biscayne Bay); and (2) retaining storm runoff to attenuate pulses of freshwater discharge. At each spatial scale, the wetland area needed to treat nitrogen, phosphorus, suspended sediment, biological oxygen demand and the water quantity was calculated. The constituent requiring the largest treatment area determined the amount of wetland area necessary. Results indicated that at the neighborhood scale, phosphorus runoff, generated by a 5-year 24-h design storm, required the largest wetland treatment area, needing between 2.3 and 10.8% of total basin area. At the sub-basin scale, the loading of total suspended solids, derived from land use specific criteria, needed the largest treatment area, ranging from 0.2 to 4.5°/0 of basin area. The basin scale treatment, based on retaining drainage canal discharge for at least 72 h, needed between 0.1 and 2.5% of basin area. This methodology is useful for feasibility analysis and leads to design principles for planning basin-scale, stormwater management systems in urbanized watersheds. |
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