This is not your usual type of geocache. For one thing, there is no physical geocache for you to find. Rather, this is a special type of virtual cache known as an EarthCache. To claim a find on this Earthcache, you must message or email the cache owner with the answers to the questions below, preferably before you log the find.
The Geological Society of America defines an EarthCache site as “a specific geological location that people can visit to learn about a unique geoscience feature or aspect of Earth. Visitors to EarthCache sites can see how our planet has been shaped by geological processes, how we manage resources, and how scientists gather evidence. . . . [A]n EarthCache adventure is treasure hunting for geological and geographical caches that Earth itself has stored. The treasure is the lessons people learn about our planet.”
An EarthCache teaches an earth science lesson. The cache page must include logging tasks that help teach the same lesson. Geocachers must complete the tasks before they log the EarthCache as found.
For more information on EarthCaches, see the Geological Society of America's website.
Finding this Earthcache:
The given coordinates take you to the base of the South Lighthouse Ravine Trail. It also takes you to an informational marker describing the North Point Lighthouse Regenerative Stormwater Conveyance (RSC), an innovative storm water management system recently installed to restore the eroded lower portion of the South Lighthouse Ravine. The North Point’s RSC consists of a series of step pools designed to slow and/or catch storm water as it descends from the bluffs toward Lake Michigan carrying bacteria and debris as well as causing erosion.
In order to get credit for finding the cache, it is not enough to log it below. You also must answer the following questions and message or EMAIL your answers to the Cache Owner. DO NOT place your answers in your log entry!!!
NOTE: Perfection is not required. A good faith attempt to fulfill the logging requirements should be sufficient.
1. The RSC is designed to reduce the speed and quantity of stormwater flowing through the ravine and entering Lake Michigan. Name three benefits to reducing the flow of stormwater through the ravine.
2. What is the retention capacity (i.e., the amount of water that could be stored) of the North Point Lighthouse RSC?
3. Walk up the Ravine Trail to the wooden bridge. How many Step Pools are in this RSC?
4. What, if any, other erosion management strategies do you see used along the Ravine Trail?
5. Do you think the positive results of RSCs outweigh the potential negative consequences? Why or why not? From your observations of the RSC here, do you note any negative consequences? What are they?
Regenerative Stormwater Conveyance
An RSC is a series of pools and riffles, combined with native vegetation and underlying sand and woodchip beds, designed to convey, manage, and treat stormwater runoff.
RSCs can be used in places where grades make traditional stormwater practices difficult to implement. RSC Systems combine features and treatment benefits of Swales, Infiltration, Filtering and Wetland practices. In addition, they are designed to convey flows associated with extreme floods (i.e., 100-year storm) in a non-erosive manner.
Components of an RSC
The three main components of an RSC are:
•Porous bed material
•Weirs, riffles and pools
•Native plant community
Bed Material
The bed material underlying the RSC generally consists of a porous mix of sand and woodchips designed to facilitate
–Retention and Infiltration of surface stormwater into the ground to recharge the groundwater
–Filtering out sediments and associated pollutants
Weirs, Riffles, and Pools
Weirs are grade control structures (like miniature dams) that hold back streamflow and direct water to the adjacent floodplain where it soaks into the ground. In RSCs, weirs are generally constructed with native boulders and/or rock, incorporate a riffle and are paired with a pool. When the area behind a weir fills, water begins to flow over the boulders and rocks and continues downstream into a pool before flowing over the next weir.
A riffle is shallow, gravel and rock bedded section that withstands fast and turbulent flows. The placement of gravel and rock introduces roughness which slows flow. The longer, rougher and wider the riffle, the slower the flow.
Pools receive water from the upstream riffle and hold it until they fill and water flows over the next weir. During storms, pools reduce energy and slow down flow by holding water and, therefore, the wider and deeper the pool, the slower the flow. Pools and floodplains hold water and allow time for water to slowly seep into the ground.
The combination of these features form the riffle-pool or step pool sequence that effectively serve to slow down flow.
Riffles slow water down:
–Dissipate energy
–Allow sedimentation
–Allow vegetation to flourish
Pools retain water
–Reduce overall retention needs
–Provides time for stormwater to soak into ground, recharging the groundwater
Weirs widen flow path
–Safe conveyance of large flows
–Allows interaction with soil/media
Native Plant Community
A native plant community is an essential component of the RSC. Roots of the plants:
– Provide Soil Stability
– Improve water quality
– Decrease runoff volume via evapotranspiration and Infiltration
Possible Downsides
RSC is relatively new technology and some have noted unintended negative consequences under some circumstances. For instance, while slowing the stream may reduce the quantity of pollutants heading downstream and into the lake, the pooling can cause concentration of those pollutants in the RSC. Others have noted that, slowing and pooling the flow of the stream widens the stream channel, potentially drowning nearby trees.
For more information on the Northpoint Lighthouse RSC:
North Point Lighthouse Backdrop for New Stormwater Management System
A Beacon for the Environment
The cache location has been approved by Brian Russart of the Milwaukee County Department of Parks. Permit # 614.