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. A creek with a drainage area (watershed) of this size, in an undeveloped watershed, would be expected to have much more stable hydrology.
What's Harming the Creek? - In a Nutshell: To answer the question succinctly, Cooper Creek is heavily impacted by Urban Hydrologic Alteration; that is, the duel symptoms of 1) an increased frequency of erosive flash flows, and 2) reduced base flows (the creek is drying out!). The Collaborative is currently primarily focused on mitigating hydrologic impacts - see our Demonstration Watershed & Initiatives pages. For a "deeper dive" on what’s harming our creek, read-on!
What is "stream health”, and how do we know what is harming our creek? There are many reasons to care about the health of our creeks, but how do we know how healthy our creek is? If the health of our creek is impaired, how do we know what is impairing it? When assessing the health of a stream, three main components are typically considered: 1) water quality, 2) physical habitat quality/stability, and 3) biological integrity. It is important to understand that in order for a stream to support a diverse community of aquatic wildlife, the stream must have good water quality and good habitat quality/stability. For this reason, measures of in-stream biological diversity is widely seen as the gold-standard for assessing the “health” of a stream.
Once you have determined the health of a stream (typically measured by indices of fish and macroinvertebrate communities present in the stream), measures of water quality, physical habitat/stability, and watershed characteristics (derived from geographic information systems and modeling) are analyzed to determine the causes of biological impairment.
What is harming Cooper Creek? – Urban Hydrologic Alteration. Cooper Creek, like many of the creeks in urban/suburban parts of our region is impacted by Urban Hydrologic Alteration. Covering the ground with impervious surfaces (e.g. roads, building, parking lots) has increased the amount of, and the speed with which, stormwater is delivered to the creek (see figure below). This has resulted in two categories of problems collectively referred to as urban hydrologic alteration:
1. Increased frequency of erosive flash flows:
Flash flow events that churn up the stream bed, impacts aquatic wildlife (by crushing them and flushing them downstream). In an undisturbed watershed this would naturally occurs at a frequency of maybe once to a few times per year; however, in urban and suburban watersheds these flows occur much more frequently and many important members of the ecological community are unable to recover from these frequent disturbances.
Frequent flash flows also result in excessive streambank erosion that creates a large amount of sediment pollution in the creek (and down stream creeks/rivers) which negatively impact aquatic wildlife in a number of ways. Sediment pollution (primarily from excessive bank erosion) is the #1 cause of “biological impairment” in streams in Ohio and throughout the U.S.
Excessive streambank erosion also leads to loss of property along the creek and damage to public and private infrastructure located along-side the creek.
2. Decreased baseflow – our creeks is drying-out:
Baseflows (the stream flows between rain events) are being reduced or eliminated in response to lowered groundwater levels caused by reduced infiltration (i.e. soaking-in of rainwater into the ground) and by draining of groundwater through deeply buried stormwater and sanitary sewer pipes.
Headwater streams near the top of our watersheds, like Cooper Creek, are disproportionately impacted by urban hydrologic alteration because of their relatively small drainage areas. These creeks also represent critical habitat for amphibians and contribute many critical support functions to wildlife in larger streams lower in the watershed. As headwater streams represent the vast majority of total stream length within our region’s watersheds (85 to 90% of stream miles), the loss of these critical ecosystems on a landscape scale is huge.
Obviously, this huge loss of water resources impacts terrestrial wildlife as well – all plants and animals need water to survive.
Another Important point to make about urban hydrologic alteration, is that hydrology is foundational to all other functions of the stream. It controls the geomorphic processes of the stream which is the primary determinant of physical habitat quality/stability. To illustrate the foundational nature of hydrology in stream ecology one need only point out that if an impacted urban stream is drying out between rain events, there will be no fish present to care about the quality of the water running off the landscape.
There are certainly water quality problems in Cooper Creek as well, and while the Collaborative’s primary focus is currently on the more foundational hydrologic problems, we are concurrently working to address some of the more serious water quality problems as well.
