Visiting neighbors are calling Act 3 a sensation! Weirs of all shapes and forms are appearing everywhere. Beautiful sandstone boulders entered from stage right and stage left and were placed strategically at elevation changes. These bou
l
ders are huge showy things, but we all noted that the cobble weir groupings are lovely too. Here are both on display at the top of the regenerative stream cha
n
nel.
Some visitors have asked why we have installed "dams". The weirs, which are actually made to seep and flow, are unlike dams that don't allow such actions. There is a reason boulders, cobble, woody materials, and sand are not the mat
e
rials used by dam builders. Together, these materials invite water to seep and flow! Dams only allow water to flow on demand.
Weirs are an important aspect of ecosystem restoration. The step pools in b
e
tween the weirs are flushed gently with fresh water as natural healthy streams flow. These shallow step pools between elevation changes are where nature is allowed to "clean house". For example, step pools produce clean water habitat for mosquito predators to breed. All agree that if a preponderance of mosquitoes equals an ecosystem out of balance then St. Luke's woodlands would be consi
d
ered stratospheric on a balance measurement scale. Here is a photo of poor starved St. Luke's nearly dry stream channel producing mosquitoes at record le
v
els. This photo says, "Help me, please!"
Hurray for the arrival of weir construction getting us closer to the flow of water. Why can't the water just flow? If you've ever walked a natural stream, you'll see riffles made of cobble and woody material between pools of slower moving water. Clean water is created by slowing the speed, and weirs act like speed bumps. In storms, the weirs slow the force of water, distributing overflow into step pools, which also distribute overflow into the stream valley providing water into the stream banks where thirsty native plants await with large fibrous roots. The flow is managed for maximizing infiltration and controlling speed. To understand the weirs and step pools better, here is the first of a series of diagrams downloaded from DNR's Bay restoration materials. Information courtesy of DNR and our d
e
sign/build firm principal, Keith Underwood.
As it turns out, weirs in wetlands are made of different materials, which explains the many very long, straight logs that were delivered. These logs serve as weirs in wetland elevation changes. In this photo, I am standing in the future wetland at the weir made of sand and logs.
Further up the elevation from the stream valley, there are other weirs in various stages of creation. These weirs in bioswales will slow down stormwater, increa
s
ing the rate of infiltration in the sandy cobbled trenches. By doing so, we increase the opportunity of ground water seepage and even perhaps regenerate old springs that probably existed here long ago watering cattle and horses and b
e
fore that feeding the pre-colonization landscape. Here is a diagram of desirable upland low lying areas that promote ground seepage.
It is fascinating to see the treatment train of best management practices in Bay restoration taking shape. Here are three photos showing the evolution of bio
s
wale weirs under construction.
Next up is more stream channel to be built so that means more weir construction. Stop by to see artistic naturescaping with a super huge sculpting tool.
