Data_Sheet_2_Role of Neighborhood Design in Reducing Impacts of Development and Climate Change, West Sherwood, OR.docx

We used the EPA SWMM-5. 1 model to evaluate the relative impact of neighborhood design and constructed Low Impact Development (LID) features on infiltration, evaporation, and runoff for three future scenarios. In the Current Course (CC) future, current regulations and policies remain in place under lower rates of climate change and population growth. In the Stressed Resources (SR) future, rapid rates of population growth and climate change stress water systems, and conventional development patterns and management actions fail to keep pace with a changing environment. In the Integrated Water (IW) future, with the same rapid rates of climate change and population growth as the SR future, informed water management anticipates and adapts to expected changes. The IW scenario retains public open space, extensive use of constructed LID features, and has the lowest proportion of impervious surface. Neighborhood designs varied in the number of dwelling units, density of development, and spatial extent of nature-based solutions and constructed LID features used for stormwater management. We compared the scenarios using SWMM-5.1 for a set of NRCS Type 1a design storms (2-yr, 25-yr, 20% increase over 25-yr, 30% increase over 25-yr) with precipitation input at 6-min time steps as well as a set of 10-year continuous runs. Results illustrate the importance of neighborhood design in urban hydrology. The design with the highest proportion of impervious surface (SR future) produced runoff of up to 45–50% of precipitation for all variations of the 25-year storm, compared to 34–44 and 23–39% for the CC and IW futures, respectively. Evaporation accounted for only 2–3% of precipitation in the 25-year design storm simulations for any scenario. Results of continuous 10-year simulations were similar to the results of design storms. The proportion of precipitation that became runoff was highest in the SR future (33%), intermediate in the CC (16%), and lowest in the IW future (9%). Evaporation accounted for 6, 11, and 14 of precipitation in the SR, CC, and IW futures with LID, respectively. Infiltration was higher in scenarios with LID than for the same scenario without LID, and varied with the extent of LID employed, accounting for 59, 71, and 74% of precipitation in the SR, CC, and IW scenarios with LID. In addition to differences in performance for stormwater management, the alternative scenarios also provide different sets of co-benefits. The IW and SR future designs both provide more housing than the CC, and the IW future has the lowest cost of development per dwelling unit.

本研究采用美国环境保护署（EPA）的SWMM-5.1模型，对三种未来情景下，邻里设计及构建的低影响开发（LID）特征对渗透、蒸发和径流的相对影响进行评估。在当前趋势（CC）的未来情景中，现行法规和政策在较低程度的气候变化和人口增长下维持不变。在资源压力（SR）的未来情景中，人口增长速度和气候变化迅速，水资源系统受到压力，传统的开发模式和管理工作难以适应不断变化的环境。在综合水资源（IW）的未来情景中，与SR未来情景具有相同的气候变化和人口增长速度，信息化的水资源管理预判并适应预期的变化。IW情景保留了公共开放空间，广泛使用构建的LID特征，且不透水表面的比例最低。邻里设计在住宅单元数量、开发密度以及基于自然的解决方案和构建的LID特征用于雨水管理方面的空间范围上存在差异。本研究利用SWMM-5.1模型，针对一套NRCS类型1a设计风暴（2年、25年、25年基础上增加20%、25年基础上增加30%），以6分钟的时间步长输入降水数据，以及一组10年的连续运行数据，对情景进行比较。结果表明，邻里设计在城市水文学中的重要性。具有最高比例不透水表面的设计（SR未来情景）在所有25年风暴的变体中，产生的径流高达45-50%的降水量，而CC和IW未来情景分别为34-44%和23-39%。在25年设计风暴模拟中，蒸发仅占降水的2-3%。连续10年的模拟结果与设计风暴结果相似。降水量转化为径流的比例在SR未来情景中最高（33%），在CC情景中居中（16%），在IW未来情景中最低（9%）。在SR、CC和IW未来情景中，LID分别使蒸发占降水量的6%、11%和14%。在LID应用程度不同的情景中，渗透率高于未使用LID的相同情景，渗透率随LID应用程度的增加而增加，在SR、CC和IW情景中LID使降水量占比分别为59%、71%和74%。除了在雨水管理方面的性能差异外，不同的情景还提供了不同的协同效益。IW和SR未来情景的设计比CC提供了更多的住房，IW未来情景的单位住宅开发成本最低。