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+--- Thread: Bridges and underpasses etc (/showthread.php?tid=8094)
Bridges and underpasses etc - NorthernRaider - 15 December 2015
Bridges and underpasses etc
Since the floods the other year down south, and the previous severe flooding in Cumbria a couple of years ago where the police officer lost his life I have been paying a lot more attention to structures like bridges, overpasses, cuttings etc in relation to us (a) bugging in or out (b) getting around after TSHTF.
Now I am not evening beginning to suggest we have to make major changes to our preferred routes to or from our chosen safe locations, I am just suggesting we need to pay a bit more attention to the infrastructure along those routes.
Much heavier short term rain storms coupled to reduced maintenence on our road infrastructure, plus aging infrastructure plus heavier vehicles than ever before plus ever more vehicles using our roads is an issue that is I believe a recipe for trouble.
Lack of dredging of waterways, lack out removing silts from some bridges and underscouring of other bridges foundations, rare or non existant cleaning of drains, gullies, storm drains etc added to ever more houses being built and ever more people turning their gardens which could soak up water into car parks where water just runs off is creating more and more problems for us to consider.
The point is guys our chosen routes to or from our chosen safe locations should be as safe and reliabley accessible as possible with the least hazards, YET we see more and more stories of these sudden deluges displacing manhole covers because the flood water is not rising gradually but surging back through the under maintained drains and litterly blowing manhole covers off their flanges. This is an absolutely deadly threat to preppers forced to wade through flood water enroute to their destinations.
Then we come to underpasses which appear to flood of a very regular basis and one engineer tells me that some times its quite simply the drains installed when the underpass was built just cannot cope with these torrential deluges we now get, and of course like much of the infrastructure they to suffer from a lack of decent maintainance.
Years ago I used to see gully sucker crews using the vac pipe to suck out the water and free leaf debris, THEN they would use hand tools to clear out the compressed debris in the drains sump chamber, THEN the guys would use rubber gloved hands to ensure all the drains bits were free and clear flowing. When I was young I believe this was done in some areas twice a year but generally at least once a year. These days they appear to get routine maintainance about every three years unless blocked and that maintenance in itself is usually no more than a quick suck out with the vac pipe. This without including the supposed effects of climate change increase the risk of flooded underpasses and displaced manhole covers.
Other engineers suggest that because of reduced maintenence that if say an underpass near you flooded tomorrow that WITHOUT human intervention the flood water would simply never drain away as the drains become permenantly clogged up, this is an issue we must consider after TSHTF or in a long term societal collapse.
Bridges, many ancient bridges have stood for hundreds of years and in the UK are still vital links between communities, but again reduced maintenence sees some suffering from underscouring of the foundations this causing the bridges to fail, or sedimentation building up causing flood water to over top the bridge causing structural damage to the roadway and exposing the parapets and walls to impact from debris being carried by floodwater. Many of these old bridges have short spans between foundations that actually sit in the river and are thus more vulnerable to flood damage. more modern structures often completely span rivers thus are less vulnerable to scouring of foundations, but can still be damaged by overtopping.
Cuttings, embankments,sunken lanes etc these again can flood in heavy rain even if the drains are kept clear, but the risk of land slips blocking them is also increased as the drainage on the embankment sides to also require maintainance to remain effective.
I could see many routes become impassible within a couple of years of a societal collapse thus requiring survivors to take very long detours or risk dangerous river crossings.
I think a bit of a double check recce of your bug in / out routes is advisable to see if you can tweak your routes just enough to avoid some of the vulnerabilities I mention above.
RE: Bridges and underpasses etc - bigpaul - 15 December 2015
I've been saying this for years but kept being told "oh this will never happen"!
and its not just bridges, drains and underpasses, ROADS themselves-those near rivers, culverts etc-will be undermined and drop off.
don't forget landslips/mudslides and erosion, without human intervention post SHTF these will need to be detoured around.
things will change post SHTF and avoiding action will need to be taken.
RE: Bridges and underpasses etc - SecretPrepper - 15 December 2015
There are loads here that fill with water. I also think they look like ambush points for less desirables to pray on the in suspecting
RE: Bridges and underpasses etc - Lightspeed - 15 December 2015
For me the biggest headache is a scenario of having to return to the house if there is major flooding.
There is one major river between secondary residence and the house. This is fairly shallow but very wide and very fast flowing. The only way across it is by bridge or by raft/kayak.
I have 7 alternate routes that I can take, each using different crossing points, but each bridge is a potentially major pinch point.
Distance from bridges to the house vary from 5 to 20 miles. I have a pre-decided to dump the car and proceed across any of these bridges on foot if need be.
Once across, its all uphill and the river then becomes a useful deterrent to anyone thinking of running to the hills in my direction:-)
RE: Bridges and underpasses etc - T-oddity - 15 December 2015
As a side note to this if you are ever caught by flooding due to a blocked drain, be very wary if you decide to attempt to clear the drain, in the floods in Hull and Grimsby a couple of years back a chap died after attempting to clear a blocked drain and got sucked down and trapped by the weight of water.
RE: Bridges and underpasses etc - Steve - 15 December 2015
(15 December 2015, 21:15)T-oddity Wrote: As a side note to this if you are ever caught by flooding due to a blocked drain, be very wary if you decide to attempt to clear the drain, in the floods in Hull and Grimsby a couple of years back a chap died after attempting to clear a blocked drain and got sucked down and trapped by the weight of water.
Very good point T, well posted.
A drain can be blocked by something as simple as a shopping bag, but once the water starts moving again it has a lot of power.
RE: Bridges and underpasses etc - bigpaul - 16 December 2015
plenty of Rivers and old pack horse bridges in Devon, as we saw with the Boscastle floods it dosent take much to "take out" a bridge.
RE: Bridges and underpasses etc - Midnitemo - 16 December 2015
LS have you considered a snorkel on your 4x4 in combination with a decent winch....just need to reccy some decent anchor points and carry a dry suit or waders if the river is shallow enough or maybe there are disused fords you're unaware of.
RE: Bridges and underpasses etc - Steve - 16 December 2015
If you plan to go wading in your 4x4 make sure the diffs are properly vented, ie the vents are clear and connected to pipes that go above the waterline. Diffs can get hot in poor ground conditions, and suddenly cooling them in water makes the air inside contract which can suck muddy water inside, or even displace the gasket if the vent isn't clear.
RE: Bridges and underpasses etc - Lightspeed - 16 December 2015
Midnite: Its way to fast flowing to attempt crossing in the LR ( even assuming I was in that car when stranded which is unlikely. Literally its white water for most of the year. Its normally 100ft wide and goes to three times that in spate. Large numbers of huge mobile boulders just add to the complexity.
Steve.... Yes agreed. Hot wheel bearings sucking water into themselves when launching dinghies is a tried and tested procedure:-)
Actually I'm not o fan of wading with the 4x4... if the waters that deep a boat is a better solution.