Felixstowe Dredging

[LONG_KEELER]

Below is a link to possible future dredging to enable larger ships to berth at Felixstowe.

I'm wondering if there is proof that dredging can effect entrances like the Deben, Ore and Stone Point at Walton.

I do remember a few years ago, Stone Point changing quite dramatically for a season or two.

Huge £90m dredging project revealed - this is what it means for ports in Ipswich, Felixstowe and Harwich

Also, are there any previous occasions where Felixstowe Port did a bit of extra dredging just to keep us yotties sweet ?

 

[Leighb]

AFAIR the problems at Stone Point were caused not so much by the dredging per se, but the dumping of the spoil on the seaward side of the Point, a lot of which the tide brought round into the channel!
There is an article about the plans in today’s EADT but more expressing concern about possible erosion of the beaches at Felixstowe.

 

[John 32i]

At least one Shipping Line has started charging a GBP 6 per unit 'dredging surcharge' already.

 

[LittleSister]

I'm wondering if there is proof that dredging can effect entrances like the Deben, Ore and Stone Point at Walton.

It is virtually impossible to categorically prove it either way, but in the wider scale of the vast amount of material washing about the Estuary and North Sea, and the complex processes involved, the effect, if any, will almost certainly be negligible.

The application for the licence to do the work will include a detailed expert assessment of such things.

The East Coast is a highly active (i.e. constantly changing) coast. It only ever looks stable in the light of our short lives (and attention spans).

The Deben, Ore and Walton channel entrances will have been more affected in recent decades by 'natural' processes; changes in agriculture and river water abstraction; urbanisation; and coastal and flood 'protection' works (which will typically have 'negative' effects elsewhere); etc.

 

[johnalison]

It is virtually impossible to categorically prove it either way, but in the wider scale of the vast amount of material washing about the Estuary and North Sea, and the complex processes involved, the effect, if any, will almost certainly be negligible.

The application for the licence to do the work will include a detailed expert assessment of such things.

The East Coast is a highly active (i.e. constantly changing) coast. It only ever looks stable in the light of our short lives (and attention spans).

The Deben, Ore and Walton channel entrances will have been more affected in recent decades by 'natural' processes; changes in agriculture and river water abstraction; urbanisation; and coastal and flood 'protection' works (which will typically have 'negative' effects elsewhere); etc.

That seems a bit over-optimistic to me. The fact that the estuaries are subject to complex influences is clearly true, but this doesn't exclude the possibility that activity in the Orwell might have an effect. I have no doubt that projections will be made about these effects, but I would like to hope that they will not be done by the same people that recommended dumping near Stone Point.
Not being a hydrologist, I would assume that extraction from the Orwell would lead to increased erosion from nearby, presumably Felixstowe, though this might indeed be scarcely noticeable. On the whole, I am in favour of Felixstowe docks being made economically successful, and some changes around the coast might be a fair price to pay for this. I just hope that it is done properly.

 

[LittleSister]

That seems a bit over-optimistic to me. The fact that the estuaries are subject to complex influences is clearly true, but this doesn't exclude the possibility that activity in the Orwell might have an effect.

I didn't claim otherwise.

 

[LONG_KEELER]

AFAIR the problems at Stone Point were caused not so much by the dredging per se, but the dumping of the spoil on the seaward side of the Point, a lot of which the tide brought round into the channel!
There is an article about the plans in today’s EADT but more expressing concern about possible erosion of the beaches at Felixstowe.

Ah yes, it was the spoil.

I suppose there are still areas that would welcome the spoil.

I remember when at W. Mersea, spoil seemed to be welcome. In the winter and I
think packing shed area. Quite an impressive sight.

 

[johnalison]

I didn't claim otherwise.

I'm afraid that when I read your suggestion that the effect, if any, would almost certainly be negligible to mean the the effect would be, er, negligible.

 

[LittleSister]

It is virtually impossible to categorically prove it either way, but in the wider scale of the vast amount of material washing about the Estuary and North Sea, and the complex processes involved, the effect, if any, will almost certainly be negligible.

I'm afraid that when I read your suggestion that the effect, if any, would almost certainly be negligible to mean the the effect would be, er, negligible.

You think 'almost certainly' means nothing?

 

[johnalison]

You think 'almost certainly' means nothing?

I may have misunderstood you, but my reading was that you were suggesting that the proposed dredging in Harwich would 'almost certainly' have a negligible effect. With no pretence to any technical knowledge, I was suggesting that this was an assumption that we shouldn't rely on, especially since previous activities in the region haven't always turned out well, as at Stone Point. I am sorry if this is a misreading.

 

[LittleSister]

That seems a bit over-optimistic to me. The fact that the estuaries are subject to complex influences is clearly true, but this doesn't exclude the possibility that activity in the Orwell might have an effect.

I'm afraid that when I read your suggestion that the effect, if any, would almost certainly be negligible to mean the the effect would be, er, negligible.

I may have misunderstood you, but my reading was that you were suggesting that the proposed dredging in Harwich would 'almost certainly' have a negligible effect.

I am glad that you now seem to accept that I never said it would not have an effect.

As I originally said -

It is virtually impossible to categorically prove it either way, but in the wider scale of the vast amount of material washing about the Estuary and North Sea, and the complex processes involved, the effect, if any, will almost certainly be negligible.

The application for the licence to do the work will include a detailed expert assessment of such things.

 

[LittleSister]

ASSESSING THE EFFECTS OF THE PROPOSAL

As there seems a high level of interest, and some scepticism and confusion, about this I thought it might be useful to summarise a bit of what I know about it from skimming some of the documentation. (Note that I have no direct interest or involvement in the applications, and I am not an expert in these matters, but have had fairly extensive peripheral professional involvement in such things.)

In the Environmental Statements and Supplementary Environmental Information which accompany and support the various related applications (and run to hundreds of pages) you can, if you wish, see that the various potential effects have been impressively comprehensively addressed by experts, drawing on years of monitoring and decades of scientific research (the bibliographies alone run to many pages).

Consideration is given to potential effects on commercial and recreational navigation, coastal processes and hydrodynamics, marine water and sediment quality, marine ecology, fish and shellfish resources, commercial and recreational fisheries, marine mammals, ornithology, air quality, marine archaeology, coastal and flood defence, and other human activities. The dredging operation itself, the effects of the deeper channel, and the effects of the spoil dumping have each been addressed separately, but there is a non-technical summary.

However, given the complexities of the processes involved there can never be complete certainty. Hence the potential effects are assessed in terms of expected severity and likelihood, the precautionary principle, and the language in those reports is always carefully suitably qualified.

The proposed spoil dumping ground is an extension to the existing one to the west side of the south end of the Inner Gabbard, over 20NM from the Walton Backwaters, Orwell and Stour. It is a trough between the Inner Gabbard and a shallower ridge to the west. Established research shows the net movement of suspended and bed material in this area is to the north, and the monitoring of the existing dumping which has been going on here for some years is both consistent with that and shows no substantial movement or effects from that dumping.

The disturbance caused by the dredging itself within the harbour area is reckoned likely to lead to some initial reduction in depths. These are only expected to be significant within the dredging area itself, where it will be re-dredged. Outside the dredging area an initial reduction in depth of up to 2mm is anticipated in several patches in the lower reaches of the Orwell and the Stour. The areas anticipated to be affected, and expected depth changes are illustrated on a map.

The 'Harwich Haven Approach Channel Deepening Non-Technical Summary Environmental Statement - 10 - August 2019' states (amongst much else):

The presence of the deepened approach channel to -16m CD is predicted to reduce high water levels by about 1mm to 2mm, extending south of Harwich towards the Walton Backwaters, and by around 5mm to 6mm in the Stour and Orwell. The Stour and Orwell estuaries are mainly bounded at high water by steep rising ground or seawalls. For this reason, changes of this magnitude to the level of high water do not have an impact on the coverage of intertidal mudflats. The tidal range of spring tides is predicted to reduce in the estuaries by between 5mm and 9mm, resulting in an increase in low water of about +5mm. This would result in up to 1.9ha of intertidal habitat becoming shallow subtidal habitat which represents a theoretical loss of 0.1% of intertidal area and about 0.05% loss of intertidal exposure. There would also be a reduction in the rate of sediment accretion within the lower reaches of both the Stour and Orwell estuaries of 0.2ha/yr and 0.4ha/yr respectively. However, these reductions are less than the existing rates of accretion and overall the intertidal areas within the estuaries will continue to increase, albeit at a lower rate.

The presence of the deeper channel would also cause small changes to current speeds within the harbour and approach channel, however changes to wave conditions, the movement of sediment along the seabed and the effect of storm surges were all predicted to be within the natural variability of the area. . .

The deepening of the harbour and channel is predicted to lead to a small rise in the level of low water and a small reduction in the level of high water. These levels are considered so small as to present no change in flood risk and can be compared with the equivalent of one year’s sea level rise, based upon the most recent predictions for the Harwich area. Overall, the potential impact of changes to still water levels on coastal defences, properties, humans and environmental receptors as a result of the proposed works is predicted to be negligible. Predicted changes to wave climate and extreme events (e.g. surges) are also predicted to be of negligible significance on coastal defences, properties, humans and environmental receptors."

I hope that's of some interest.

 

[johnalison]

I am glad that you now seem to accept that I never said it would not have an effect.

As I originally said -

Life can be very confusing. There was I thinking that 'negligible' meant near zero, or too small to be worth considering, and now I find that it means something completely different. We live and learn.

 

[LittleSister]

There was I thinking that 'negligible' meant near zero, or too small to be worth considering. . .

It does of course, but 'It is virtually impossible to categorically prove it either way, but . . . the effect, if any, will almost certainly be negligible' does not mean 'it will be negligible'.

 

[Tomahawk]

Of course this is all to accommodate the next generation of ULCC.

A 25000 TEU ship will make the Emma Maersk look small!

 

[Corribee Boy]

There doesn't seem to be any mention of altered currents in the rivers, and any consequence on erosion rates in the upper reaches, such as at Wrabness Stone and cliffs.

 

[LittleSister]

There doesn't seem to be any mention of altered currents in the rivers, and any consequence on erosion rates in the upper reaches, such as at Wrabness Stone and cliffs.

There is in the extract from the Non=Technical Summary that I quoted in Post #12.

Unfortunately, the documents (including the one I quoted from, and the more detailed and technical environmental assessments from which that was derived) in the application for the dumping ground extension are no longer available on the MMO website, presumably because the decision on that has now been made. (The public consultation period closed some time ago.) They may perhaps be available from the Harwich Haven Authority on request.