Compare the above photo to the photo at the top of the Home Page which was taken from the same approximate location. The photo on the Home Page was taken just after a rain event, while the dry creek bed above is typical of this reach of creek between rain events. Clearly this habitat cannot support a stable community of aquatic wildlife (e.g. fish). A creek in this regions with a watershed of this size (1-square mile) in an undeveloped watershed, would be expected to have much more stable flow. Also Note the abandoned drinking water pipe (~2/3 up from the bottom of the image) that used be be buried under the creek but has been exposed by downward erosion and widening of the creek due to increased erosive flash flows. An active sanitary sewer line has also been eroded out/exposed about 100-feet upstream of that location.
Urban Stormwater Problems:
Urban (and suburban) areas throughout our region (and the world) suffer from many serious stormwater problems. The problems that most impact people's lives in this regions include:
Upland stormwater flooding
Property damage from excessive streambanks erosion
Loss of biodiversity and access to safe and ecologically healthy natural spaces
All of these problems are felt in various places within the Cooper Creek watershed. While addressing these large-scale challenges may seem daunting, it is notable and encouraging that they all have a common underlying cause, and therefore effort to address any one of these problems, if done thoughtfully, may mitigate more than one problem at a time.
A Common Cause:
A common cause of these problems is - the way that human alteration of the landscape has altered how rainwater moves through the landscape - due to lack of planning/investment to preserve or mimic natural movement of water through the landscape. In the Demonstration Watershed, like all of the urbanized world, we have cleared away forests and covered of the land (nearly 50%) with impervious surfaces (e.g. roads, parking lots, and buildings). Beneath the ground we have installed a dense web of pipes - the oldest of which typically consist of short tile segments lined up allowing water (and sewage) to migrate in and out at the joints. The pipes are typically installed within relatively "hydraulically conductive" graveled trenches that may have significant effects on groundwater flows. The many ways that these changes effect how water moves through the landscape are often complex, but the overall role in driving the problems listed above is clear. Some of these problems can manifest quickly when the rain falls on upland areas (e.g. upland stormwater flooding and sewer overflows). Others result from the way that these alterations impact flow patterns in streams. In-stream flow pattern changes fit into two categories:
Peak flow impacts - larger and more frequent erosive flash flows that lead to stream flooding, excessive stream bank erosion, and habitat destruction
Baseflow impacts – reduced groundwater levels resulting in creeks drying out in between rain events - a huge source of habitat degradation and loss; much of this lost groundwater is ending up in sanitary sewers driving sewer overflows.
A catch-all term for these in-stream flow pattern changes is hydrologic alteration.
Climate Change – An Exacerbating Factor:
It is important to note that the two categories of impacts from hydrologic alteration, peak flow impacts and baseflow impacts, also represent the primary ways in which climate changes has, and is projected to continue to, our impact water resources and communities in this region. So, by implementing solutions to mitigate impacts of hydrologic alteration, we simultaneously build resilience in our community against the impacts of climate change.
To mitigate the impacts of hydrologic alteration and climate change, we need to restore or mimic the natural movement of water through the landscape. This can be achieved by incorporating nature-based solutions. By taking a wholistic, nature-based approach to addressing the root cause of all of these problems, we can mitigate the impacts of more than one problem at a time. But important questions remain:
How much hydrologic mitigation is enough to solves various problems in various places?
To what extent is the dense network pipes underlying urban areas, and streams, draining creek flows between rainfalls?
What mitigation techniques are the most effective to solves various problems in various places?
How can existing techniques be improved or thoughtfully places to improve performance or create more co-benefits?
This is where the Demonstration Watershed comes in - we are implementing, and assessing the performance of, cutting-edge hydrologic mitigation projects. Project performance is being assessed for both individual projects, and on a cumulative basis. This work will inform water resource management throughout the regions (while solving problems in the Cooper Creek watershed).