Strategies for systemic urban constructed wetlands

Abstract

As a result of ubiquitous impermeable surfaces, conventional water management and stormwater infrastructure, and the resultant degradation of natural hydrologic networks, most American urban areas have suffered severely compromised hydrological function and health, particularly related to stormwater and its storage, treatment, and flow. Negative externalities exist at multiple scales: increased disaster vulnerability, climate change, poor water quality, habitat loss, etc. Because upgrading conventional single-purpose infrastructure has become an increasingly cost-prohibitive option, urban areas are finding that reincorporating natural systems can be more effective. In the last 20 years, constructed wetlands have arisen as a promising multi-purpose solution to stormwater problems. Constructed wetlands are artificial systems designed to mimic natural wetlands by using the same physical, biological, and chemical processes to treat water. They are relatively large, but their size gives them high ecological potential and numerous other benefits, such as flooding protection and recreational spaces, while having low life-cycle costs. Since the effectiveness of constructed wetlands comes from mimicking natural wetlands, then the analogy to nature should be extended as far as possible. In nature, wetlands are a system connected to a regional hydrologic network. Therefore, constructed wetlands distributed systemically throughout a watershed have potential to deliver more networked benefits than the current practice of dispersed and disconnected wetlands for individual sites. Yet little research exists examining the implications of urban constructed wetlands in design and planning terms, at multiple scales. In fact, few urban constructed wetland projects for stormwater exist in the first place. This thesis proposes a framework for understanding the potential of systemic constructed wetlands as landscape infrastructure in urban areas. Based on an understanding of science, engineering, and urbanism, this thesis identifies the urban zones of greatest potential for stormwater constructed wetlands and suggests the benefits that could arise out of an urban constructed wetland system, beyond simply water treatment.