Urban Stream Assessment Frameworks: Stream Flow Impacts, Geomorphic Responses, and Stream Values
Abstract
Urban streams are complex socioecological and hydrogeomorphic systems, often degraded yet highly valued by communities. The linkages between altered flow regimes and stream values (e.g., experiential, aesthetic, and cultural attributes) are often opaque, making it difficult to develop, justify, and fund appropriate restoration approaches and mitigation actions. Drawing upon non-urban analogues, the Urban Streamflow Impact Assessment (USIA) and Urban Stream Assessment Procedure (USAP) were developed in different international settings to explicitly link the severity of impacts on stream values with urban development scenarios and their streamflow and sediment regimes. Despite rapid urban development, increasing interest in urban waterway values, and a plethora of regulated river methods, prior to this study no formal methods were available for linking urban catchment change to the impacts of altered streamflow. The application of USIA and USAP explicitly link altered physical and hydrological processes under urbanization to the stream values lost. Each method emphasized the identification of societal values associated with stream function and developed rational approaches to quantify linkages between values, physical processes, and flow metrics, and in doing so informing target setting for planners and waterway managers. While both methods agreed in their overarching model, significant gaps remained in both. For example, the definition of acceptable deviation from current or reference conditions was a particularly difficult problem which requires both scientific understanding of degradation relationships and a value judgement of what is `acceptable'. Combining social, ecological and hydrogeomorphic science is challenging - it requires additional time, funding, and resources (e.g., professional facilitator), and `leaps of faith' beyond current knowledge. As a result, by identifying the linkages between physical and social sciences these frameworks also identify the research gaps. Implementing integrated process-based stream assessment frameworks that provide a consistent evaluation and incorporates stream values can advance urban catchment and stream planning and management, reduce maintenance, and improve stream health as well as the livability of our cities.
- Publication:
-
AGU Fall Meeting Abstracts
- Pub Date:
- December 2020
- Bibcode:
- 2020AGUFMH053...08M
- Keywords:
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- 0481 Restoration;
- BIOGEOSCIENCES;
- 0493 Urban systems;
- BIOGEOSCIENCES;
- 0496 Water quality;
- BIOGEOSCIENCES;
- 1879 Watershed;
- HYDROLOGY