Do you remember playing “pooh sticks” as a child?
Most of the best games are simple aren’t they, which we believe is what makes pooh sticks such a joy when anywhere near a river with a bridge. Simply pick up a small stick from nearby, drop your sticks at the same time one one side of the bridge and then rush to the other side, delighting in them appearing, before you begin your tracking adventure along the bank until they get stuck somewhere or you become victorious.
But the same types of tree and shrub debris, coupled with the aforementioned bridges can potentially have devastating effects on local communities – not a chapter you’ll find in any of A.A. Milne’s children’s books about his famous talking bear and piglet, but certainly the reason that the Gridmark Survey team were called into action on a very specific stretch of the Wansbeck river.
As vital as bridges over waterways are logistically, under certain climatic conditions they can also pose a real danger. Morpeth in Northumberland, like many areas in the UK has some low lying land relatively close to the river and is prone to dreaded flood alerts. This calls for careful monitoring by The Environmental Agency, including fixed cameras and a field team who can spring into action when needed.
As you might imagine, other than flash flooding in summer the autumn and winter months provide the biggest challenges with rising rivers. And one of the worst case scenarios is when persistent rain follows a snowfall. The resulting melt water, coupled with the downfall, increases the volume of water and more debris enters the river from the fields and banks. This debris, like a pooh stick can often gather under bridges, stemming the flow and can result in flooding.
There are defences in place at Mitford Dam which are very effective but there is also a seemingly more crude and larger scale defence mechanism known as “The Lowford Tree Catcher” downstream. Whilst this sounds more like a Roald Dahl villain than an A.A. Milne character it is in fact a series of vertical poles which are designed to catch and retain not only larger pieces of debris but a high volume and the river flow continues to stack debris similar to the work of a beaver.
As part of the ongoing management of the river bed the Gridmark team needed to conduct a bathymetric survey on both hard and soft levels of the riverbed as regular flooding events mean that significant portions of the bed have been scoured away by increased flow and in many cases, these underwater ditches are then backfilled with debris.
Part of Morpeth’s charm is its green spaces but as we had to physically navigate the riverbanks the heavy vegetation and forest areas meant that we more than matched a significant cardio session at a gym.
Wading was also quite slow going. Due to the backfilled spaces we mention above being difficult to predict we had to take our time when moving as our footing switched from firm to treacherous often meaning it felt like tip-toeing over a creaky landing when arriving home late as a teenager.
An understandable requirement as part of Environment Agency standards is that all equipment needs to be thoroughly cleaned and disinfected with Virkon before contact with the watercourse.
Due to the densely vegetated riverbank sides, one of the laser scanners was used to extensively scan both riverbanks to extract survey details (trees and ground levels) where manual surveying would have been either extremely difficult or in places impossible.
We love geospatial work near (and in) water as they are always different and we consider ourselves specialists in this type of topographical survey in the North East. This work in Morpeth was no different and we were privileged to be joined for most of the visit by a very busy kingfisher – on more than one occasion we were lucky enough to see it catch, then perch and eat it’s prey, a real treat.
And for the even keener of eye, if you may have also been lucky enough to catch a glimpse of the Lesser Spotted Chris Horn. This remarkable creature is known for its resourcefulness and on this occasion was seen meticulously repairing his waders with a puncture repair kit. A true wonder of the natural world.
If you have topographic survey requirements (or a hole in your waders) 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.
