News:

The Best Fishing Forum In The UK.
Do You Have What It Takes To Be A Member?

Main Menu
Please consider a donation to help with the running costs of this forum.

River Don Trust Habitat Improvement

Started by machar, December 04, 2012, 02:31:15 PM

Previous topic - Next topic

0 Members and 1 Guest are viewing this topic.

machar

The following Press Release has just been issued by the River Don Trust

"The salmon population in the Aberdeenshire's River Don is already taking advantage of a new fish pass, allowing them far easier access to an important tributary for spawning. This follows the installation of a new pass in late summer through a vehicle ford over the Ernan Burn on Edinglassie Estate.

The pass should enable the river's salmon to utilise to maximum extent over three miles of spawning and juvenile habitat.

The area in the upper part of the river's catchment is believed to be particularly important for spring salmon, the most fragile component of the Don's stocks of migratory fish.

Jamie Urquhart, Biologist for the River Don Trust, explained: "The ford in question was clearly a major obstacle for salmon to negotiate as they tried to migrate upstream. Having obtained the necessary consents from SEPA, we carried out the work ourselves, with support and private funding from the Don District Salmon Fishery Board and Edinglassie Estate respectively, using a low-tech, low-cost design employing locally sourced larch timber and locally won stone. This complied with the Estate's wish for a low visual impact whilst maintaining the aesthetics of the upland terrain".

Mr Urquhart continued: "It is pleasing that this month we have already seen several pairs of adult salmon upstream of the pass. Previously this tributary has been stocked with juvenile hatchery fish. Adult salmon homing back to this area should now be able to ascend through the fish pass at will and spawn naturally – a much more desirable situation than trying to replicate nature through the use of hatchery-bred fish. This exercise has established a skill set within the Trust which will serve us well in undertaking further similar works in the future"



Before



and after

Bobfly

The upper ford replacement is really little different from an Irish Bridge with a single pipe channel. The Irish Bridge style always suffers from shifting bedload blocking the pipe entries and whenever the road bed is overtopped in a spate the surface needed to be in concrete to stop it being washed away. In this case there seems to be unbound as-dug or crusher-run material and I wonder how long it will stay since even a minor spate will lead to overtopping. The flow level control weir below the new crossing is not much less of an obstacle than the last ford and as it becomes undercut might develop the same height difference. I wonder how it will all look three years from now.
~  <°))))):><       ~   <°))))):><

Wildfisher

Good work!   :D

Odd though, from the photo that old ford does not look as if  it would be a barrier to salmon other than in very low water, certainly no more than  the new weir downstream of the new bridge.  It is difficult to gauge the scale and water depths  from a photo though.

Malcolm

Quote from: admin on December 04, 2012, 03:08:08 PM
Good work!   :D

Odd though, from the photo that old ford does not look as if  it would be a barrier to salmon other than in very low water, certainly no more than  the new weir downstream of the new bridge.  It is difficult to gauge the scale and water depths  from a photo though.

That was my thought too Fred. They have to ascend a much bigger obstacle on the Endrick.
There's nocht sae sober as a man blin drunk.
I maun hae goat an unco bellyfu'
To jaw like this

Traditionalist

That was not an obstacle to migrating salmon and the "new" installation is likely to cause more problems than the old one.

Wildfisher

Quote from: Malcolm on December 04, 2012, 04:09:51 PM
That was my thought too Fred. They have to ascend a much bigger obstacle on the Endrick.

It may depend on the water depth below the fall Malcolm. if the old pool was shallow during low water the fish may not have been able to get up enough speed to jump over. I'm not sure how they do that though, so that could be nonsense.  :lol:   Anyway, in high water than old weir would vanish I think and the fish would have swam over it easily. Like Vaughan I do wonder if that bridge will still be there after a big flood. It looks like it will block easily too as there does not seem to be a lot of "headroom" underneath. Again it is hard to say from a photo.

Wildfisher

Quote from: Bobfly on December 04, 2012, 03:07:47 PM
I wonder how it will all look three years from now.

I have seen work like this carried out  on another stream  up in the north west where they have created pools using  boulders graded down stream to allow the fish to swim up into the pools. A member of this forum was involved with the planning and implementation of this and after many winters and spates they are still there. It is pretty impressive work, very natural looking,   that was done without fanfare and has greatly improved the habitat for all animals and fish, not just salmon or making vehicle access more  reliable for grouse shooters in wet weather.   The hideous and unnatural burnt patterns and eroded bulldozed tracks on the hill in the above photos may indicate this is the principle use of the land.

Bobfly

Infilling with large rocks set into the stream bed to make boulder cascades would be a reliable and simple way of dealing with the previous ford, which was not much of a barrier in the first place if fish movement was at higher flows. I have a hatred of Irish Bridge types of culverted fords as they always always give trouble by blocking up at the intakes and scouring down at the outfalls. A complete menace when there is any likelihood of branches or debris coming down as the culverts block straightaway and you then have a higher barrier dam structure across the stream than the level of the original fords.
~  <°))))):><       ~   <°))))):><

Traditionalist

Quote from: Bobfly on December 05, 2012, 12:16:02 PM
Infilling with large rocks set into the stream bed to make boulder cascades would be a reliable and simple way of dealing with the previous ford, which was not much of a barrier in the first place if fish movement was at higher flows. I have a hatred of Irish Bridge types of culverted fords as they always always give trouble by blocking up at the intakes and scouring down at the outfalls. A complete menace when there is any likelihood of branches or debris coming down as the culverts block straightaway and you then have a higher barrier dam structure across the stream than the level of the original fords.

Agreed, fish movement on such a stream will only be at higher flows anyway. What has been done is a "change" not an improvement and it will likely cause more problems than it purportedly solves.

Billy

Scouring may be a problem but only time will tell and it should be fairly easy to clear away.

No chance of trees and branches blocking the culvert looking at the landscape above the bridge. I can see they have tried to replace one slightly large obstacle with two smaller ones and it will help in lower water.

As previously said I would like to see it in a couple of years and it has created a couple of nice pools which will help the trout as well.

Billy

Go To Front Page