Scalable Construction: Engineering of Stream and Wetland Enhancement in Fine-grained Systems

Year: 2023
Presenter/s: Abbey Rhode
Symposium Session: 2023 - 11 Foresight in Adaptive Management
Topics covered: adaptive management and monitoring, floodplain, lessons learned, temperature, urban, water quality, and wetlands


Engineering plays an important role in many stream and wetland enhancement projects, especially in heavily impacted urban and agricultural areas. The traditional approach for cost-effective scaling of engineering is standardized design, but natural systems are difficult to standardize and the Tualatin River basin is dominated by fine-grained sediments which are a departure from the cobble and gravel-dominated streams that typically characterize the Pacific Northwest. These fine-grained streams are particularly sensitive to the impacts of urbanization and the lack of coarse sediment has forced us to reconsider our engineered approaches to streams, starting with acknowledging the limitations of traditional methods. Furthermore, engineered approaches are expensive and time-consuming, with much of that time and effort being spent on understanding and mitigating the risks that our own engineered activities will have on the site, including the significant disturbance required to construct those engineered elements.
This presentation will illustrate how we have been applying our lessons learned from the Tree For All Program to scaling up our engineering approaches to stream and wetland enhancement and the challenges encountered along the way with case studies of past and current work. Much of it begins at the organizational level. By embracing an ethos of innovation, long-term stewardship and adaptive management, engineers are empowered with the flexibility to scale back designs and allow for more uncertainty and change over time. The immediate outcomes following construction are de-emphasized in favor of long-term outcomes which shifts the focus of engineering from fixing a system to buying time for the ecosystem to heal itself. That increased flexibility allows for a more efficient and collaborative design process such as reducing the level-of-effort of desktop design in favor of field-fit design where engineers, ecologists and contractors can customize the design to the site together. However, that openness to change and unpredictability brings new challenges with how we define and demonstrate success or failure which is important for both ourselves as practitioners to be able to adaptively manage our sites and improve our methods, as well as for meeting regulatory requirements.