Watercourse Depth

DrWazzock

Member
Arable Farmer
Location
Lincolnshire
We have noticed over the past decade that some of our watercourses have deepened considerably without any intervention from us. This can mean banks and hedges get undercut and collapse.
We have installed small crude dams or weirs in places which has had some success in holding back silt, reducing depth and effectively widening the flow profile and reducing flow speed and erosion. But we have never had to do this before as usually they just fill with silt and eventually need cleaning out. Certain lengths of watercourse still do silt up naturally but by and large they seem to have become self scouring and get deeper and deeper without intervention.
What’s causing this? High winter flows? Reduction of run off and lack of silt? Anybody else seen this?
 

DrWazzock

Member
Arable Farmer
Location
Lincolnshire
Have we become so successful at reducing water erosion off the fields with buffers and management practices that the watercourses depth is taking on a new equilibrium. Ours only seem to stop self deepening when they hit a clay/gravel layer whereas they used to have a Sandy bed which got a bit shallower every year until it needed cleaning out.
Maybe I’m a bit sad but I find it intriguing to know how these things work.
 

robs1

Member
We have a river here that my grandfather put a concrete pad on a cattle drinking place so it was easier for them, it used to be level with the water level but is now at least a foot if not two above the water, I assume rivers just keep scouring their bed especially if flows increase due to building more houses
 

DrWazzock

Member
Arable Farmer
Location
Lincolnshire
Is it someone further down deepening their bit?

(and look at that...a farmer thinking carefully about his watercourse management...it could never happen!)
We have the forestry commission and golf course downstream of us. They have never cleaned out the watercourses so can’t be accused of over deepening them. They are also having the same problems of self deepening and bank collapse and are trying to hold the water back by crude dams and such like. Upstream of us there have quite a few field soil erosion prevention measures in place for a decade now.
I’m wondering if we are actually the effect of a shortage of silt. Lots of winter flow but with less silt added so the watercourses deepen. It could be that was their old natural depth or more likely they were much wider slower and shallower but in any case I think we are seeing maybe unexpected consequences of field run off reduction. If nothing else is done then I think we will the see the evolution of some very deep water courses in terms of bed level below ground.
 

DrWazzock

Member
Arable Farmer
Location
Lincolnshire
The odd thing is we have culvert pipes that have been fixed at a level for 200 years or so and always used them as a guide for the level when cleaning out but now the watercourse bed level is well below the level of these culvert pipes.
 

Hindsight

Member
Location
Lincolnshire
We have the forestry commission and golf course downstream of us. They have never cleaned out the watercourses so can’t be accused of over deepening them. They are also having the same problems of self deepening and bank collapse and are trying to hold the water back by crude dams and such like. Upstream of us there have quite a few field soil erosion prevention measures in place for a decade now.
I’m wondering if we are actually the effect of a shortage of silt. Lots of winter flow but with less silt added so the watercourses deepen. It could be that was their old natural depth or more likely they were much wider slower and shallower but in any case I think we are seeing maybe unexpected consequences of field run off reduction. If nothing else is done then I think we will the see the evolution of some very deep water courses in terms of bed level below ground.

Maybe a tourist opportunity to diversify. The Lincolnshire Grand Canyon? Helicopter flights?
 
All the ditches that run "up and down" the slope here have terrible issues with scouring and deepening, those that run across the slope silt up and need cleaning out. The ditches that have issues with scouring I have either filled up with branches from trees, or piles of stones to trap the gravel as it flows and reduce the scouring, and to be fair apart from taking ages to do has worked well.
 

DrWazzock

Member
Arable Farmer
Location
Lincolnshire
I am surprised no one has mentioned the obvious solution. Offer to re-home some of those beavers they are wanting to relocate! 🤣
Ha ha. To me that’s an extreme solution which would mean an end to farming here.
I am searching for a happy medium. Watercourse bed just below land drain outfalls. A stable level. It’s very good that we are reducing silt input to the watercourses but I think we maybe need small sluices dams or weirs in order to stabilise bed depth. A happy medium.
 
Have we become so successful at reducing water erosion off the fields with buffers and management practices that the watercourses depth is taking on a new equilibrium. Ours only seem to stop self deepening when they hit a clay/gravel layer whereas they used to have a Sandy bed which got a bit shallower every year until it needed cleaning out.
Maybe I’m a bit sad but I find it intriguing to know how these things work.
IMO certainly around here the flow of silt off land up ditch has increased as soil OM has decreased. We are also having much more severe weather events, with 50 -100 mm of rain over 24 hours, several times in the last 10 years 50mm in 2 hours.
Last October all the ditches here were loaded with my neighbour's soil, he cleans his ditches very frequently but has no buffer strips and works it to death.
I think it is faster flows, not less silt, but it could vary in areas.
 

thesilentone

Member
NFFN Member
Location
Cumbria
I think it depends where you are in the whole 'flow ' of things upstream on a hill, or downstream on a plateau.

Water dynamics go out the window when you get a major deluge. Normally silt is picked up on-route from the faster flowing parts and dumped in the slower flowing areas, which is generally where it meanders towards it's end/estuary.

But, a deluge throws that out the window as the slower flowing areas, then also become fast flowing.

For a water system to operate effectively, the whole system must be in sync, as this starts with the water table level and everything after that.

Our forefathers built a system that worked well, not only have we almost abandoned that system to decay and fall into a state of disrepair, we have not addressed the change of circumstances that climate change and weather patterns are having.

In Germany I have seen several rivers with 'scalloped ' river edges, these are supposed to slow the outer edge of the river flow down, and increase the flow in the center. Aimed to stop silting and bank erosion.

Also, designing rivers and water-courses for the '100 year event ' seems to have gone out the window.
 

Jackov Altraids

Member
Livestock Farmer
Location
Devon
What I think this highlights is the problems with centralised over-generalised policies from people with qualifications rather than experience.
As farmers, we know that every decision we make has different consequences over different time periods and that the success or failure of a decision can be decided by weather events that are largely unpredictable.
Faster flows will be due to more extreme weather events but also because all developments have been required to deal with rainwater as fast as possible. Trying to get farms to 'hold water back' is just a cover for the lack of any contingency in the developed areas.
Silting is a natural process which is vital to the local flora and fauna in some areas while being a risk to the same, in others. Decisions need to be made by local, knowledgeable people.
 

Henarar

Member
Livestock Farmer
Location
Somerset
We have noticed over the past decade that some of our watercourses have deepened considerably without any intervention from us. This can mean banks and hedges get undercut and collapse.
We have installed small crude dams or weirs in places which has had some success in holding back silt, reducing depth and effectively widening the flow profile and reducing flow speed and erosion. But we have never had to do this before as usually they just fill with silt and eventually need cleaning out. Certain lengths of watercourse still do silt up naturally but by and large they seem to have become self scouring and get deeper and deeper without intervention.
What’s causing this? High winter flows? Reduction of run off and lack of silt? Anybody else seen this?
More volatile weather,
we are getting the same thing happening here when there is a good downpour like we had a few days ago
 

Bogweevil

Member
We have noticed over the past decade that some of our watercourses have deepened considerably without any intervention from us. This can mean banks and hedges get undercut and collapse.
We have installed small crude dams or weirs in places which has had some success in holding back silt, reducing depth and effectively widening the flow profile and reducing flow speed and erosion. But we have never had to do this before as usually they just fill with silt and eventually need cleaning out. Certain lengths of watercourse still do silt up naturally but by and large they seem to have become self scouring and get deeper and deeper without intervention.
What’s causing this? High winter flows? Reduction of run off and lack of silt? Anybody else seen this?

I blame direct drilling, cover crops, larger heavier machinery, fewer root crops - inhibits erosion and speeds run off. Rushes/sedges could be the answer:

1635162990936.png
 

DrWazzock

Member
Arable Farmer
Location
Lincolnshire
Trying to get us to “hold water back” or slow it down is all very well on worthless amenity land but makes agriculture as we know it almost impossible. Their plans to spill flow over a wide area to slow it down will also have a limited effect in my view. The town still sits at the neck of a funnel and whether the flow arrives narrow and fast or slow and wide, once the ground is saturated it’s still the same amount of water that has to get through the town. And with all these dams and restrictions, ground will remain saturated for longer and actually have less transient water buffering capacity in my view.
I’d prefer a chain of properly engineered and controlled winter storage reservoirs to take peak winter flows and allow irrigation in the summer but looks like it ain’t going to happen. A return to unproductive swamp and marsh looks more likely.
 

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