Topic: Ask JP 5


batrabill    -- Nov-19-2018 @ 3:22 PM
  It is a widely held belief amongst boaters that if the Lower Bure was dredged more the water level at Potter Heigham Bridge (to give a specific example) would drop. This would make the area above the bridge more accessible to more boats.

Is that belief true?

What evidence is there of what factors influence the water level at Potter Heigham bridge?

If that is true, why don't the BA devote more resources to dredging the Lower Bure?


Bill


JollyRodger    -- Nov-20-2018 @ 12:33 AM
  Wise question is that Bill. To that I would ask the same of the Upper Thurne especially as by doing that it would increase the flushing effect of the Bure in general.

Jolly Rodger


annville    -- Nov-20-2018 @ 10:51 AM
  Dear Mr Paxman What is the cost of a electric post/tower. Is there a average cost per linear meter for each supply from the grid to each mooring location. and is it the BA's intention to increase the number of electric points/moorings, and what time scale is there to increase them. John


Helmsman1946    -- Nov-20-2018 @ 12:26 PM
  Here is one for a start
http://www.broads-authority.gov.uk/boating/navigating-the-broads/urgent-boating-news/neatishead-electric-installation
Extra points at Reedham Quay (at the end which does not flood) would be hopefully be less costly to install as there is still the redundant electricity supply box which provided power for the crushing skip that was there opposite Middle Hill.

Peter


JP    -- Nov-22-2018 @ 3:17 PM
  Dear batrabill,

The lower Bure is a well-known ‘dredging hot spot’ – we get a large amount of deposited sediments on the series of bends between Acle and Marina Quays.

We have targeted dredging over the last few years to remove these deposits.

2018/19 – 14,000m3 removed from Lower Bure
2017/18 – 5,000m3 Bure Loop
2017/18 – 5,820m3 removed from lower Bure
2015/16 – 12,500m3 removed from Bure at Stokesby.

This focussed dredging has helped bring the Lower Bure up to river specification and removed many deposits which shallowed bends and also we have removed reed encroachments, giving a better line through bends for craft.

As far as we know this work has not had any significant effect on water levels at Potter Heigham (or higher at Hickling where the EA monitor water levels).

Passage through Potter Heigham (ancient monument) is not just restricted via height of the bridge and water depth, but also width. Water flows at this end of the system are less than the lower Bure, but this is affected by many factors, none of which are dredging related.

Broadland Environmental Services Limited (BESL) has done some modelling on this system and from memory the sheer amount of tidal input coming in at Great Yarmouth is one of the biggest factors in holding water further up in the upper reaches of the River Thurne.

We will check this understanding and re-post once we have specific information from the BESL model.

Regards

John



annville    -- Nov-22-2018 @ 3:59 PM
  Why is it that i didn't get a answer to my question from JP.John


JP    -- Nov-22-2018 @ 4:09 PM
  Afternoon John,

I have asked for the information and plan to get back to you tomorrow with the answer.

Regards

John


annville    -- Nov-22-2018 @ 5:57 PM
  Thankyou i felt left out there for a moment no rush. John


batrabill    -- Dec-4-2018 @ 12:27 PM
  John

Quote "We will check this understanding and re-post once we have specific information from the BESL model."

I wonder if you have been able to obtain any useful information on this?



Bill


annville    -- Dec-5-2018 @ 5:50 PM
  Dear Mr Paxman I see that CRT have had funding from Defra to install electric posts to enable boaters to have a alternative to running their engines at moorings. Can you not get funding from Defra to do the same for us. John


VetChugger    -- Dec-5-2018 @ 11:57 PM
  I suspect he may be busy with University Challenge! Now Mr Packman might be a more suitable target!

Trevor


JP    -- Dec-6-2018 @ 7:35 AM
  Good morning batrabill,

As promised we have followed up this matter with Broadland Environmental Services Ltd (BESL) and the company’s hydrological model addresses this issue. This is what it says ...

"Dredging the River Bure
Residents along the River Bure believe that flooding is aggravated by a lack of maintenance of the river channel. They propose that flood levels would be reduced if the river channel was dredged between Bure mouth & Three mile House.

In reality, the bed level near to the Bure mouth is raised and currently prevents extra water (saline water) from entering the system at high tide. If the channel were to be dredged from the mouth of the river, flood levels would in fact become worse.
Dredging the river further upstream from this point would possibly reduce water levels but by such a small amount that the overall effect would be negligible.

Potter Heigham Bridge
Anecdotal evidence suggests that flooding in the River Thurne is exacerbated by the presence of Potter Heigham Bridge.

This is a listed building, therefore no real solution to the problem can be provided. However, the model has been used to investigate this query. The results of the investigation indicate that the water levels on the River Thurne are governed more by water levels on the River Bure than they are by any structures over the river, as the presence OR not of the bridge makes no difference to peak water levels.

Whereas, significantly lowering or raising the River Bure water levels (e.g. through washlands or crest raising) lowers or raises the River Thurne water levels."

Hope that helps.

Regards
John



JP    -- Dec-6-2018 @ 7:36 AM
  Morning John,

Thanks for that news. Can you please see if you can find out if this is from the core Defra grant given to CRT or some special allocation. I will try and do the same using my contacts. Certainly if it is from the latter I will do my best to get some funding for this from the Department.

Cheers
John



JP    -- Dec-6-2018 @ 7:38 AM
  Morning Trevor,

Thanks for the correction – interestingly they have the same origin.

Cheers
John



Paladine    -- Dec-6-2018 @ 8:25 AM
 
Just put the words - Islington Defra electric - into a search engine. This is a scheme to lower urban air pollution (supposedly). It is seen by some in the canal boating world as the thin end of the wedge to ‘gentrify’ an area popular with ‘continuous cruisers’ who don’t actually cruise very continuously.

"..for the avoidance of any doubt, the broads are not legally a national park and do not come under the national park legislation, and nor will they."
Parliamentary Under-Secretary of State for DEFRA (Hansard 2015)


batrabill    -- Dec-6-2018 @ 3:55 PM
  John, appreciate the reply. It's plainly a complex issue.

Quote "The results of the investigation indicate that the water levels on the River Thurne are governed more by water levels on the River Bure than they are by any structures over the river, as the presence OR not of the bridge makes no difference to peak water levels.

Whereas, significantly lowering or raising the River Bure water levels (e.g. through washlands or crest raising) lowers or raises the River Thurne water levels."

This suggests that the flood alleviation work which must have raised the crest level (it seems inevitable that extensive repair of the crests made the average height higher...) may be the main factor in the perceived rise in Thurne level??

Bill


annville    -- Dec-6-2018 @ 6:09 PM
  Dear Mr Paxman Sorry i can't find out where it came from only from Defra, it was for CRT's Eco visitor moorings to enable visitors power for there boats without running their engines and causing pollution, enabling a cleaner environment along the rivers. John


Marshman    -- Dec-6-2018 @ 6:10 PM
  BFAP may have raised the crest level but water rarely , if ever overtops the existing banks, and the raised crest level does not IMHO affect the normal river levels but would only come into play on the very highest of tides and highest predicted floods.

As you say, the whole issue is very complex and many factors are involved - not sure that at normal levels there is much connection between higher crest levels and Potter Bridge except at times of real flooding!


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