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What the report really says - known risks vs unknown risks.



Some self-proclaimed ‘experts’ have been protesting that saltmarsh won’t develop on Hoylake beach, and that the latest report states sand dune development is more likely.


Let’s review this further…


Extract from the technical report -Section 4.1.2 says...


'How the zonation of the saltmarsh will actually develop over time is uncertain, as saltmarsh zones vary in location and land cover; however, given the continued increase in beach levels over the next 50 years, more distinct low, middle, and high marsh zones (and comprising species) would likely develop as the vegetation migrates seaward.'


'The presence of sand dune vegetation can further increase the accumulation of sand as it is trapped around both living and dead plant matter. Whilst this, and the development of saltmarsh, may reduce wind-blown sand nuisance, sand dune development has the potential to result in higher beach levels than that predicted by this study.


Should dune height exceed that of the existing sea wall, there is the potential that the dune could migrate landwards, affecting local roads and houses.'




Extract from the technical report - Section 4.2 says...


‘For the ‘Do Everything’ scenario, Hoylake Beach would be managed over the next 10, 20 and 50 years, so that all vegetation is removed, i.e. there would be no ecological change.’


‘The changes in beach levels would be similar to the ‘Do Nothing’ scenario because the supply of sand would remain the same and the clearing of vegetation (by whatever means is determined) would be completed without removal of the sediment.


Whilst the removal of sand dune vegetation would reduce the rate of sand accumulated by dune formation, meaning that the higher beach levels resulting from dune formation would be less likely to occur, wind-blown sand nuisance would likely increase due to the non-vegetated beach providing a larger source of sand. '


There are online groups with misplaced confidence who have demanded that everyone should ‘follow the science’ including Councillor Pat Cleary (for Birkenhead & Tranmere) and leader of the Green Group , who wrote the following on his blog dated 19 October 2021. (click here)


Cllr Cleary's Blog Extract:


‘Rewilding Hoylake Beach is not only good for nature, it's essential for the future of Hoylake town

Sadly, last night's meeting of Wirral Council did not debate motion #2 on Hoylake Beach:

If it had, I would have laid out the following arguments why leaving the beach alone is critical for the future wellbeing of the town itself, never mind the many benefits for nature which are already apparent since the regressive spraying/raking policy was abandoned. The Green Group rejects the basis of this motion. It is scientifically inaccurate and if adopted would be damaging to the people of Hoylake and beyond, ruinous for wildlife and extremely expensive for Wirral Council.


This is fantastic news for Wirral – for our wildlife, our residents and the

future financial wellbeing of Wirral Council.


Dunes will defend us from sand storms and sea storm surges without the need for expensive, artificial defences such as currently being implemented for West Kirby at a cost of millions of pounds. This is because the beach at Hoylake is rising rapidly over time. At present, nearly all of the sand that could reach the promenade is stopped by the sea wall. If, as beach levels continue to rise, we don’t allow sand dunes to form, then we can expect disruptive amounts of sand several times a year. The clean-up costs to the council would be measured in hundreds of thousands of pounds, even before you consider the damage to property.


Our response to the above blog:


Dear Pat,


Please assure us you have read the section 4.1.2 of the report where it states:


‘sand dune development has the potential to result in higher beach levels than that predicted by this study. Should dune height exceed that of the existing sea wall, there is the potential that the dune could migrate landwards, affecting local roads and houses.'


Or Section 8.1 in the report where it states the following:


‘however, there is also a risk that a developing dune system could form a barrier against any overtopped water flowing back to the sea and could thus enhance flooding in some locations.’



We wonder if you view the Royal Haskoning report as also being ‘scientifically inaccurate’ too?



Section 6 - Flood Risk Assessment says



‘In the 'Do Nothing' scenario the developing dune system could start to have a flood defence system function, should the dunes potentially grow higher than the sea wall.


This would however not affect the scale of the flood zone because that would require a continuous, uninterrupted row of dunes; any gap in the alongshore arrangement of the dunes would lead to a breach, in which case the risk of still water level flooding is similar.


Therefore, in both scenarios, changes in future flood risk are expected to be similar, and still water level flooding will continue to be the dominant source of flooding.


Should the ‘Do Nothing’ and/or ‘Do Everything ‘scenarios affect groundwater levels, e.g. through changes in beach levels, this has the potential to affect groundwater flooding behind the sea wall.’


So, if the dunes grow higher they might provide flood protection, BUT this would lead to higher beach levels and if they exceed the height of the sea wall there is potential for the sand to migrate landwards affecting local roads and houses creating further surface water flooding and drainage issues.



Will Wirral Borough be liable to the North promenade home owners if their “Do Nothing” approach actually increases the risks of flooding to their homes?



So, in conclusion there are no stark benefits from raking or rewilding the beach with regards to flood protection although in section 9.1 the report does add the following:



Section 9.1 - Conclusions


‘however, there is also a risk that a developing dune system could form a barrier against any overtopped water flowing back to the sea and could thus enhance flooding in some locations.’



Wait! … let's get this straight!


Sand dune development has the potential to not only increase the levels of the beach AND migrate landwards (bringing more sand closer) but could ALSO form a barrier to any overtopped water from flowing back into the sea and could therefore enhance flooding.


Whereas raking the beach will see an increase in wind-blown sand nuisance only.


One can’t help but wonder how these potential dunes might impact upon ground water flooding.

Will water flowing from the drains /roads also get trapped, creating an even bigger mess to clean up including increased surface water flooding?



It’s fairly reasonable to conclude that under the ‘Do Nothing’ scenario and allowing nature to take its course, we will see an increase in uncertainties and unknowns?


In summary, under the 'Do Nothing' scenario, sand accretion and dune development has the potential to see;


- higher beach levels than predicted


AND


- the potential dune height (should they develop) could exceed the sea wall, affecting local drainage, roads and houses, thus increasing surface water flooding risks.


How will Wirral Borough Council predict the cost of clearing up this mess?



Whereas in the ‘Do Everything’ (back to maintaining the beach) we have an increased chance of predicting certain outcomes.


- We have experience of beach maintenance plans, whereby costs can be quantified, budgeted for and understood.


- The sand mesh barriers originally erected along the promenade railings (now in disrepair) if replaced, should prevent some windblown sand.


- The raking machine purchased in 2019 (paid for by Wirral tax payers. ) just before the beach management plan was stopped, barely used and remains dormant.


At least the ‘Do Everything’ option means no risk of sand dunes growing higher than the sea wall, and more importantly no enhanced flooding risks in some locations, as stated within the report.

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