Floods at Sidford (and Sidmouth), 24 November 2012.
Following a very wet autumn and a minor flooding event along the river Sid on 21 November 2012, the bed of the river at Sidford was higher than is normally allowed by the Environment Agency (EA). The video link above shows the main ford in Sidmouth town centre.
Because of the flood on 21 November, there had been no suitable opportunity to dredge the river at Sidford in time to prevent the more severe flooding of 24 November. Dredging involves the removal of maybe 100+ tonnes of rocks and gravel that deposit on the downstream side of Sidford Bridge in the area where, hundreds of years ago, there used to be a ford over the river (hence Sid-ford!).
Press reports include mention of up to 600 tonnes being removed after the flood of July 2012 - this may include material from elsewhere along the Sid. Once numerous houses had been built on the flood plain, the river could no longer be allowed to build up its bed and flood areas of what had become a sizeable village - so dredging around the bridge became necessary. Fifteen and twenty years ago this operation was undertaken about once a year but it is now becoming a more regular feature of village life. The last few photos on this page are of the Sid as it approaches the sea at Sidmouth.
|On the evening of 24/12/2012
there was a severe downpour at the end of a very wet day. The ground was completely
saturated and the riverbed just south of Sidford Bridge was unusually high. This led to
the most severe flooding seen in 30 years.
The river is shown dark blue. When it overtops its banks to the north, water flows as shown in red. Often, no properties are affected. If flooding is more severe, water flows down driveways (purple arrows) and back to the river alongside houses and garages. In very severe floods, water flows as shown in light blue also.
The key lesson from these floods for my home is that only a slight flow of water across the top of my driveway is sufficient to fill the area in front of my garage to a depth of 300mm if the flood relief channel alongside the garage gets blocked with debris.
Only when the depth exceeds 300mm does water flow north across my front lawn and back to the river.
Unfortunately, I had decided to spend the evening in Exeter. It took me two hours to drive home, one hour to Newton Poppleford (where the A3052 was closed by 900mm of water) and a further hour to drive via Halfway House on the A3052 to the (flooded) A30 and via Sidbury - again flooded to about 200mm but I made it home to find the scenes shown below. At the height of the flood (around midnight) Sidbury was completely cut off. My home was perfectly safe - I have protected it against far worse events than this, but the garage had a few mm of water covering the front half.
Far more water had collected in front of my garage door than should have occurred - this was owing to apparently insignificant things such as a self-seeded sapling in the wrong place, an old fence post, and a tyre and two blocks of wood that I had left on my driveway.
Students from University of Exeter produced a video showing the Exe at its highest level for many years. Figures supplied to me by the EA include that the River Exe achieved a peak flow of 420 cumecs (cubic metres per second) - someway short of the design figure for existing city defences. However, the currently projected figure for peak flow in a 1 in 100 year event is above the design figure - and so Exeter has been made a priority for additional flood defence work. A computer simulation undertaken by the EA of what could happen in Exeter in a 1 in 100 year flood is also available on youtube.
Whilst much of the publicity centred upon Exeter, the whole of Devon and neighbouring counties were also badly affected. Residents of Sidmouth who live along the river have told me it was the most severe flood in at least 30 years.
Unlike the flood of 7 July 2012, this one occurred at night - when I was at a dance in Exeter.
These photographs are mostly from the day after - 25 November 2012.
Water had overtopped my driveway and completely inundated the front garden.
Piles of twigs can be seen against the front of the caravan. The paving slabs are covered in about 6 to 10mm of mud.
The old car is a 1985 Saab 900i. I bought it in 1988 and ran it until 2007 when the gearbox finally expired after 250,000 miles.
After being cannibalised for parts, it was finally scrapped in 2018.
The driveway was a complete mess with large accumulations of mud and piles of twigs and leaves. The single 110mm surface water drain was completely blocked.
The garage carpets were sodden.
Electrical power had become disconnected because the freezer in the garage had been under a few mm of water - just enough to inundate an electrical junction box.
The peak flood was at around midnight. By the time I arrived home at 1am the water had drained sufficiently to permit power to be restored - the earth leakage trip now sensing that all circuits were again safe.
All of the pathway had been covered in mud - the first job was to hose down a walkway to the front door.
This whole area had been a mass of swirling water - up to 300mm deep.
Just a pity I wasn't home to see it!
With carpets removed it was clear that half to 2/3 of the garage floor was covered with a thin layer of silt.
When I built the garage a decade ago, I had the floor laid on a slight slope so it could easily be washed out - a sound idea.
An even better idea would have been not to store so many things on it.
Residents need to learn the importance of clearing road drains of twigs and leaves.
Whilst the road does flood from time to time, the quantities of water involved are often small and could probably be accommodated, at least in part, by the drains, provided these were kept clear.
On the morning after the flood, they were all blocked.
Clearing all drains would be of most benefit to householders at the southern end of the Close - and it was these who suffered the most, owing to their houses having been constructed before Building Regulations required that floor levels be raised 600mm above flood plains.
This house at the end of
Packhorse Close was sold to its new owners earlier in 2012.
Too little, too late.
This is the main road drain at the junction of Packhorse Close to the main A3052.
It is at the lowest point of the road in this area. When the Sid overtops its banks to the north of the bridge there can be up to 400mm of flood water here.
In the floods of July 2012 this drain stayed clear, but in November's floods the river water brought with it far more twigs and leaves. These blocked all the local road drains.
The mass of swirling water around this drain in the July 2012 floods is shown on an earlier webpage.
The visibility splay beside the A3052 was deep in water and debris - the first time this has happened in over 20 years, and according to local people, in well over 30 years.
This may not have happened at all (or have been less severe) if the river bed level had been much lower before the deluge of 24 November.
The ferocity of the water was so great it started to dig at the foundations of this roadside fence.
The river also made some attempt to gouge out part of this defensive wall. The vegetation may grow back and knit the area together before the next flood.
The aftermath - this was becoming a little too frequent in 2012 but as of 2017 no further floods on this scale have occurred.
This is the critical flood relief channel down the side of my garage. It is the only escape route for water that overtops the head of the driveway (by the road) once the single surface water drain becomes blocked.
However, on this occasion (and in my absence) the flood water picked up a spare tyre and wheel that had been propped against the conservatory door and wedged it in the location shown. Twigs and leaves then built up both around this and around the self-seeded ash sapling.
But worse was to come.
The flood water also picked up two wooden blocks (shown red) that had been left on my driveway and wedged them firmly against an old fence post that I had left in place to mark the line of the original boundary fence, before I built my garage.
The resulting log-jam caused a build up of other debris and the relief channel became severely restricted. Flood water in channels such as this is conveyed by only a small pressure head - often only a few cm of water - and even slight impediments to flow may not be swept aside.
This is the principal lesson for the future - ensure that this flood relief channel stays clear.
The post has since been cut down.
|Thus, more water than should
have collected on the driveway built up to a 300mm depth, testing both the conservatory
door and the high quality (German) garage door - and both held very well.
Despite 300mm of water against it, the maximum depth of water in the garage at the front end was 10mm, tapering to zero about half way to the rear.
The river level at the back of the garage was exactly to the threshold of the rear door - which is also overdue for additional flood defences.
All my airbricks are permanently protected to 1000mm over this height of flood.
When water reaches the level shown here, it starts to flow across the front lawn and down the north side of my house. Thus, this level should rarely if ever be much exceeded.
Famous last words?
Large areas of garden were covered in up to 120mm of silt.
The water flow patterns were quite different from those in July 2012 because the flood water flowed not only through the arches of the bridge and over the garden but quite forcibly down the side and through the hedge.
Much of the extra destruction may have been owing to the river bed having been so high immediately before the downpours of 24 November.
Thus, the EA need to be especially aware of the importance of dredging excess material from the riverbed at Sidford whenever an opportunity occurs.
The excess depth after 24 November was around 600mm. The area was subsequently dredged on 17/18 December 2012.
The drain from my garage roof goes into a single 110mm pipe - the arrangement works well but is here covered in 50mm of silt and leaves.
The working of the drain to discharge water from the roof was unaffected - it just no longer worked as a surface water drain. But such a function is not required in this location, so the mud didn't really matter.
The tide line of twigs on my neighbour's pristine lawn is witness to the peak level of the river - they were away at the time and so missed all the excitement!
Their new garden shed survived but the floor was covered in mud.
|This flood brought down an unusually large quantity of twigs and leaves - naturally enough for autumn.|
The door of my conservatory is a first line of defence against floods on the driveway. I built the whole conservatory to be especially strong and waterproof. With a little extra buttressing the door easily held against 300mm of water.
Probably less than a litre of water seeped through - but even if the door seals gave way under the force of a much greater depth of water, the house is further protected by very strong flood boards to the height of the conservatory windows.
Such a level might be reached in a 1 in 1000 year flood - and half of Sidford would then be underwater.
Part of the mud collected from the front driveway.
This was dumped in my front hedge to help boost defences for next time.
Neighbours opposite deployed conventional defences - I could do the same but this would have adverse consequences for the rest of the Close because so much water flows naturally over my garden back to the river - or at least it did before I built my double garage (with full planning permission!).
With defences of this type being used by an increasing number of residents, keeping road drains clear will be even more important to help limit the amount of water that reaches the bungalows at the end of the road.
|Downstream of Sidford the Sid
flows for a while across its natural floodplain and through largely open country - and
well away from houses. Where footpaths cross or abut the river, some attempt has to be
made to limit its destructive behaviour.
As it nears the sea, the Sid once again needs to be managed more comprehensively in order to limit damage to property.
These boulders were part of the defences at the bottom of Sid Park Road. Similar damage occurred nearby both in July 2012 and in November 2012.
As of 2018 no repairs have been undertaken, probably owing to cutbacks in EA funding.
|This is the footbridge at the
bottom of Sid Park Road, Sidmouth.
A local resident told me that in nearly 30 years he has never seen the water so high as on the night of 24 November. A layer of silt on the bridge surface bears witness to his assertion that it was just lapping over the foot way. Structurally the bridge survived very well.
This photo was taken a week after the November flood. As happened in July 2012 also, The Byes parkland returned to normal very quickly. The only remaining signs were a few broken bridge handrails, areas of silt, some displaced stones and boulders and piles of leaves and twigs.
|Lower down the Sid, the old
footbridge at Lawn Vista suffered considerable damage.
In fairness, it had already been repaired (patched up) several times and much of the wood may have been half rotten.
The flood therefore merely brought forward the date for complete reinstatement of the railings and decking surface.
|Minor damage to embankments could be seen along the last mile of the Sid.|
|In the July floods, a large
brick wall just upstream of the ford was demolished by the force of water.
In November's flood, a section of wall downstream of the Mill St footbridge was demolished.
The damage in this case looks to be as much decorative as it is structural.
It was later rebuilt.
|The pillars of Alma Bridge over
the river Sid as it nears the open sea suffered further damage.
Several 'protest groups' in Sidmouth have seen saving Alma Bridge as supremely important. They argue it is a 'lifeline' for residents living on the east side of town.
In reality it is as much an icon as a useful asset now that the coastal footpath has been diverted away from the crumbling and collapsing cliffs nearby.
As of 2016 it is accepted that the bridge cannot be save and a new crossing further upstream may be constructed - but at what cost and how long will that last before it is compromised?
|This is probably a section of
the garden wall that collapsed into the Sid in July - it has now made progress almost to
the open sea.
At a rough estimate it comprises 100 bricks and mortar with some backing concrete. It is probably made from dense solid bricks so each may weigh about 3 kilo with mortar - so the total weight may be approaching half a tonne.
Bricks are not actually very dense - typically 2000kg/cu.m (kilo per cubic metre) about twice the density of water. Granite boulders, often used for flood defences have a density of around 2700 kg/cu.m.
|In the same week, there were
further large cliff falls to the east of Sidmouth. The cliffs here consist of variously
friable and easily eroded soft material.
Whilst much is made of the need for 'sea defences' to protect these cliffs, much of the erosion and collapse of large sections of cliff is caused primarily by rain water.
Even if sea defences were installed the cliff face would continue to retreat until a stable angle was reached - and by that time the houses on Cliff Road would have lost maybe half or more of their remaining gardens. Even then, erosion would continue. It may be only a matter of time before some or all of these substantial houses become worthless.
The same might be true today for many low lying houses in Sidmouth had not the river Sid been comprehensively 'managed and tamed' over the last 50 years.
|About a week after the floods,
there was a large cliff-fall about 300 metres to the east.
In this photo, the tree that fell down earlier can still be seen. Winter storms and tides will wash all the loose material away.
A local councillor had the idea of dumping a lot of the material dredged from the Sid around the base of the cliffs near Alma Bridge to help prevent erosion.
The material was duly delivered to the end of the Esplanade by the EA - and was washed out to sea before it could even be put into place. It would have lasted maybe a few days or weeks!
Problems along this part of the coast became more severe when EDDC replaced the old wooden groynes that had served well to protect Sidmouth beach. The new rock 'islands' altered wave and water flow patterns to the east - and all the beach shingle disappeared. Predictions that this would happen had been discounted by EDDC.
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