Lady Close Weir Fish Ladder Hydrographic Survey

Tees River Trust


Scope of Project

If you’ve ever had the pleasure of pootling along a ship canal in a barge, eventually you’ll get to a lock and more often than not they’re accompanied by a local pub.  A very civilised way to spend a Summer evening is to order a drink whilst your narrowboat is either raised up or lowered for the next stage of your journey.

A similar principle can also be applied to help salmon to make their final journey to spawn up river.  But this more frantic rite of passage has become somewhat of an issue in recent years in the River Tees as some of the areas of the riverbed in sections of the Raby Estate have eroded meaning that fewer salmon have been able to get “uphill” seeing a significant drop in numbers year on year.  So the Tees River Trust are working on a project to build “fish ladders” to help the salmon on their way.  

But in order to conduct this work effectively and efficiently a detailed survey of the river both 50m upstream and 50m downstream of the weir, 0.6m of the banks on both sides and 10m from the bank into the adjacent forest was required much to the delight of the Gridmark Survey team who are always enthused to be involved in ecological project work.

Site & Technical Challenges

Raby Estate is renowned locally for its rich variety of indiginous flora and fauna (many of the trees were planted specifically for the estate around 200 years ago) and coupled with an aesthetically idyllic river we knew that we’d be working in an area of natural beauty.  But it did present us with a challenge from the off.  To achieve the levels of geospatial accuracy which we pride ourselves on, we must first establish highly accurate GPS coordinates.  But doing this under the canopy of an established forest with a lot of evergreen trees was a challenge.  So we had to exit the woodland into the main Raby Estate to establish site control co-ordinated to the OS Grid. We then had to traverse into the site location to carry out the survey and establish four PGMs (permanent ground markers) for future reference as specified by the client. 

Due to the vast number of trees on the site we were presented with many “line of site” issues which meant that we had to relocate and set up the survey equipment many times to ensure that we gathered the specified depth of information.

And then of course, there was the river itself.  The riverbed was deep, uneven and fast flowing in places so in line with our RAMS this required a safety person on the riverbank whilst another member of the team was in the river.  The sheer volume of data points requested across the ford area in particular was greater than we would have normally expected and as such took a long time to collect.

Points of Interest

The Raby Estate is a glorious setting and seeing Longhorn Cattle up close and personal was a treat.  We also had good views of both Red Deer and Fallow Deer and were fortunate to not be conducting the survey during rutting season so didn’t need to be on the look-out for testosterone fueled stags.

We look forward to returning to the site as visitors in the near future to inspect the fish ladders which will be created by the Tees River Trust team, knowing that the Gridmark Survey team have played a part in helping the magnificent salmon spawn in the required numbers to help maintain a healthy ecosystem in this famous North East river.

If you have hydrographic or topographic survey requirements and believe that Gridmark Survey might be able to help you with your project please get in touch with one of our friendly team and we can discuss your specific needs.

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