There will be more pictures and video to come to document this bold project by Sheffield City Council to uncover a section of stream that used to live beneath a factory floor. They are in the process of creating a "pocket park" that will provide new flood-water storage (when the rivers are in spate) and an improved public park amenity (when the rivers are calm).
The pocket park itself will be excavated out from the current high ground level (and a major construction project is underway at the moment to achieve this).
The Wild Trout Trust were brought in to design in-channel features and riverbed morphology that would maxmise the improvements for the ecology of the stream - including for the prospects of a small and fragmented native population of wild brown trout.
The site after uncovering the stream - but before the in-channel works
Part way through the Pocket Park Construction - new gabion walls and flood defenses
Channel with boulder clusters, log deflector-consolidated point-bars, pool, riffle and meanders plus pre-planted coir pallets and rolls installed by Wharton Landscaping Ltd. on top of berms that were created by redistribution of bed material under WTT direction
Boulder Cluster: for cover against predation, baffling of spate flows, creation of depth variation and substrate retention
Ian from Whartons models the size of rebar pins I used to secure the log deflector(pictured) that is helping to retain the shape of the point-bar made from channel substrate
The head of a 2-m long rebar pin (towards the right) driven into the bed for its full length. To the left is a cut-off end of a pin that was driven half-way before hitting something impenetrable. Bending it over and cutting off provides additional anchoring to each of the main pins when this happens
Boulder Cluster pictured previously (top right of frame) plus log deflector/point bar also pictured previously (top middle of frame) creating and preserving meandering flows into the upstream end of the shaped and planted berms. Big boulders against the wall are helping to protect the upstream end of the berm as well as maintaining meandering flow. Note also the large submerged boulder providing habitat and breaking up flow patterns to produce refuge areas (left of centre frame)
Planted berms on right and left of channel. Narrowed pinch point will promote and retain greater depth of water (offering better protection against low flows during dry summers compared to previous uniformly flat/shallow reach)
Pocket water created by addition of scattered boulders between two planted berms (natural gritstone excavated on site and broken into irregular chunks)
Pocket water detail (facing downstream)
Third planted berm - left of frame (pictured facing downstream)
There is now a great deal more structural variety in the channel. This is true in terms of flow speed and depth and well as in physical structural components (including overhead cover on the undersides of "rock rolls", undersides of boulders and, in future, emergent vegetation). I await the development of this project (including the completion of the pocket park itself) with interest. If the rock-rolls prove to be a great success in protecting the planted coir components - then these might give more town and city councils confidence to try these kind of measures in a wider range of urban streams.
I will post more photos and video on this project as soon as I am able to...
The pocket park itself will be excavated out from the current high ground level (and a major construction project is underway at the moment to achieve this).
The Wild Trout Trust were brought in to design in-channel features and riverbed morphology that would maxmise the improvements for the ecology of the stream - including for the prospects of a small and fragmented native population of wild brown trout.
There is now a great deal more structural variety in the channel. This is true in terms of flow speed and depth and well as in physical structural components (including overhead cover on the undersides of "rock rolls", undersides of boulders and, in future, emergent vegetation). I await the development of this project (including the completion of the pocket park itself) with interest. If the rock-rolls prove to be a great success in protecting the planted coir components - then these might give more town and city councils confidence to try these kind of measures in a wider range of urban streams.
I will post more photos and video on this project as soon as I am able to...
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