EAPSI: Connecting Distributed Impacts in Urban Watersheds to In-stream Hydrology and Water Quality Observations through Refined Landscape Metrics for Optimal Stormwater Handling

雨水通过一个复杂的网络在城市流域中流动，通过渗透径流的透水表面和快速将径流转移到溪流的不透水表面。 不透水区及其与排水管道的连接程度已被证明在改变城市河流的水流动态和水质方面发挥了最大的作用，导致世界各地的条件退化。 这促使人们采用更自然的雨水处理方法，并在整个城市流域采用绿色基础设施做法，从源头上处理径流问题。 由于城市土地成本高，需要指导更好地选择这些设施，以最大限度地提高其效率，满足当地的排水需求，并有助于改善河流条件。 该项目将探索城市排水评估的新方法，这些方法考虑到自然和管道径流路径，并根据不透水表面连通性的措施确定更容易造成河流退化的地区。 将在墨尔本大学的Tim弗莱彻博士和莫纳什大学的大卫麦卡锡博士的指导下，利用包括不透水区及其连通性在内的已建立的空间数据集进行比较和验证，探索方法。 将使用径流和水质数据集探索不同的流径加权方案，时间分析将侧重于小Stringybark实验流域，以评估与绿色基础设施安装相关的不渗透连通性随时间的变化与观测到的流量和水质变化之间的关系。 城市流域不透水面的连通性通常被表示为二元的，而人们已经认识到，连通性实际上存在于一个连续体上，受风暴的具体特征，前期的水分条件，和可变的流路断开。 该项目将利用高分辨率的空间数据，代表海拔，不透水覆盖，和雨水排水网络，建立一个相对的连接指数，提供了一个不渗透性和空间明确的信息，确定城市流域内的关键源区域更紧密地联系在一起的流措施的一个大规模的加权度量。 Python脚本将采用基于网格的流域表面覆盖和径流流径表示，通过调查径流穿过流域的流径不同部分（陆上、不透水、管道、流内）的加权方案来测量连通性。 这些加权方案将被校准，以优化相关的景观度量流中观测线性模型的拟合，并将调查流域之间的参数化差异，以评估它们如何有效地代表物理流域特征和径流传输机制。 这将有助于验证方法，并提供指导，以建立一个可用于未测量流域的工具，以确定任何城市流域内最适合安装绿色基础设施的地区，以减少不渗透的连通性，并通过分布式手段带来积极的变化。 东亚和太平洋夏季研究所计划下的这个奖项支持美国研究生的夏季研究，由NSF和澳大利亚科学院共同资助。

Stormwater moves through urban watersheds via a complex network over pervious surfaces that infiltrate runoff and impervious surfaces that quickly move runoff towards streams. Impervious areas and the degree to which they are connected by drainage pipes have been shown to play the greatest role in shifting streamflow dynamics and water quality in urban streams leading to degraded conditions worldwide. This has spurred the adoption of more natural stormwater handling with green infrastructure practices distributed throughout an urban watershed to handle runoff issues at the source. Because urban land costs are high, guidance is needed to better site these installations in order to maximize their effectiveness to meet local drainage needs and contribute to improvements in stream conditions. This project will explore novel methods of urban drainage assessment that account for natural and piped runoff pathways and identify areas that contribute more to stream degradation based on measures of impervious surface connectivity. Methodology will be explored with the guidance of Dr. Tim Fletcher at University of Melbourne and Dr. David McCarthy at Monash University using established spatial datasets that include impervious areas and their connectivity for comparison and validation. Different flowpath weighting schemes will be explored using runoff and water quality datasets and a temporal analysis will focus on the Little Stringybark experimental watershed to assess how changes in impervious connectivity over time associated with green infrastructure installations relate to observed changes in streamflow and water quality. The connectivity of impervious surfaces in urban watersheds has often been represented as binary while it has been acknowledged that connectivity actually exists on a continuum subject to storm-specific characteristics, antecedent moisture conditions, and variable flowpath disconnection. This project will utilize high-resolution spatial data representing elevation, impervious cover, and stormwater drainage networks to establish a relative connectivity index that provides both a landscape-scale weighted metric of imperviousness and spatially explicit information that identifies critical source areas within the urban watershed more closely tied to in-stream measures. Python scripting will employ a grid-based representation of watershed surface cover and runoff flowpaths that will measure connectivity by investigating weighting schema for different portions of the flowpath that runoff takes across the watershed (overland, impervious, piped, in-stream). These weighting schema will be calibrated to optimize the fit of linear models relating the associated landscape metric to in-stream observations, and differences in parameterization between watersheds will be investigated to assess how effectively they represent physical watershed characteristics and runoff transport mechanisms. This will help validate the methodology and provide guidance to establish a tool that can be used on ungauged watersheds to identify areas within any urban watershed that will be best served by green infrastructure installation to decrease impervious connectivity and impart positive changes in-stream through distributed means. This award under the East Asia and Pacific Summer Institutes program supports summer research by a U.S. graduate student and is jointly funded by NSF and the Australian Academy of Science.