降低污染和洪水威胁:以美国特拉华州威尔明顿市布兰迪万溪周边环境修复为例

Reducing Threats From Contamination and Flood Damage: Restoring the Brandywine Creek Edge in Wilmington, Delaware, USA

近年来,人们愈发关注公共卫生,以及因洪水灾害和环境污染而产生的有毒物质的迁移与转化问题。设计规划人员也一直在努力探索能够有效应对此类问题的解决方案,期望通过合适的定量方法评估相关方案的影响。本文以美国威明顿市布兰迪万溪周边一处面积约为52.6hm~2的场地为例,识别了场地所在街区当前面临的问题和需求:自20世纪中叶以来,场地经历了高度的工业化发展,除洪水威胁外,附近工业用地、棕地及合流污水管道中的污染物也会随洪水迁移至场地中,极大影响了人们的健康和生活质量。鉴于此,项目团队开发了一套分阶段实施的总体规划方案,以期减少雨洪径流并去除污染物,同时将场地中现有的棕地改造为环境优美的绿地,鼓励更具韧性的场地开发举措。具体设计策略分为地形重塑、引入绿色基础设施和清除污染物三个步骤。方案计划将场地划分为废水处理及颜料制造区、商业区、艺术家聚集区和滨河绿地四个区域,各区域采取不同的污水处理和洪水缓解策略。此外,项目还期望通过增加住宅类型及居住人口的多样性,增进公众与布兰迪万溪的互动。而后,项目应用长期水文影响评价(L-THIA)模型来衡量设计方案的影响和绩效。L-THIA模型是一种空间建模工具,可以估算以往或未来开发方案中雨水补给、雨水径流和非点源污染量的变化。项目利用L-THIA模型评估土地利用现状、城市现行土地利用规划及本研究中提出的总体规划方案的土地利用和污染物清除情况,即将不同区域的土地利用类型及其面积和相关土壤类型输入L-THIA模型中,估算不同污染物的负荷。结果显示,相较土地利用现状,本项目提出的总体规划方案能够更有效地减少雨水径流和污染负荷--雨水径流将减少约24.35%,污染物去除量将增加38.08%。

Located in Wilmington, Delaware, along the shoreline of the Brandywine Creek in the Greater Philadelphia/Delaware River Watershed, this project responds to a specific and critical need for the site as prioritized by multiple stakeholders. The project applies an innovative approach for quantifying increased flood resilience while simultaneously reducing contamination levels through the implementation of green infrastructure. To solve joint issues related to increased flood risk concurrent with higher potential for exposure to environmental contaminants transported in flood waters from adjacent industrial sites, brownfields, and combined sewer overflows, the research team develops a phased approach to decreasing stormwater runoff and pollutant loads on a 130-acre(52.6 hm~2) site along the Brandywine Creek, applying the Long-Term Hydrologic Impact Assessment(L-THIA) model to quantify design impacts and performance of a master plan. Overall, the proposed master plan can reduce stormwater runoff and pollutant loads to levels significantly less than existing conditions or the current land use plan. Further, this research is unique in that it uses outputs from the L-THIA to compare existing conditions, effects of the current comprehensive plan, and impacts related to the proposed neighborhood-scaled master plan to evaluate the effectiveness between each scenario.