Update on Local Flooding Issues Since last FAG 27th July 2016 - - PowerPoint PPT Presentation

Flooding Advisory Group Meeting 2-11-2016

Update on Local Flooding Issues Since last FAG 27th July 2016

Flooding Advisory Group Meeting 2-11-2016

Nationally

Government Report Published 8th Sept 2016.

Can be found at https://www.gov.uk/government/uploads/sy stem/uploads/attachment_data/file/551137/ national-flood-resilience-review.pdf

Analysis ‐ David Shukman, BBC Science Editor Ministers offer communities the prospect of better protection from flooding but the report lays bare the scale of the work needed to achieve

• that. What does not appear in the press

release accompanying the report is what many would judge to be the key finding: that as many as 530 important infrastructure sites across England ‐ water supplies, telecommunications systems and electricity networks ‐ are still vulnerable. The uncomfortable truth is that it's impossible to defend everyone all the

• time. But no one in authority

particularly likes to say so.

http://www.bbc.co.uk/news/science‐environment‐37306094

Press release by the Association of British Insurers (ABI) 29‐09‐2016

The insurance industry has published three "flood risk" symbols it would like estate agents in England and Wales to put on their property particulars. The ABI says the symbols would prompt buyers to investigate flood risks properly. It claims that at the moment, house‐hunters are more likely to ask about parking provision than flooding. "It would be a pointless and fruitless exercise," said property expert Henry Pryor. "You would make a huge proportion of homes unsalable and unmortgageable.“ The ABI said that if estate agents did not take up the idea voluntarily, it might consider asking for legislation to make it compulsory.

http://www.bbc.co.uk/news/business‐37565462

In the News 11th Oct 2016

“Some of these tensions around flood policy are revealed in an unpublicised report to government that ministers plan to launch in coming weeks.” “The Association of British Insurers said even buildings guarded by flood defences should have flood‐proof doors in case embankments are over‐topped.” “The comments add to a complex blame game over responsibility for floods.” “The report's main author, Sir Peter Bonfield, points the finger at householders for failing to improve their homes after flooding”

https://www.gov.uk/government/news/new‐support‐gives‐property‐owners‐better‐protection‐from‐flooding

Actually officially published by Government

• n 28th Oct 2016

The Property Flood Resilience Action Plan, chaired by Dr Peter Bonfield, brings together Government and industry and establishes an action plan to ensure property owners are better equipped to prepare for flooding and get back into homes and business sooner if it does.

https://www.gov.uk/government/uploads/system/uploads/attachment_data/file/551615/flood‐resilience‐bonfield‐action‐plan‐2016.pdf

http://www.bbc.co.uk/news/science‐environment‐37840482

And being right up to date – today 2nd Nov 2016 - The Environment, Food and Rural Affairs Committee has published its Second Report

The committee's chairman, Neil Parish MP, said: "We propose a radical alternative to the current fragmented, inefficient and ineffective flood risk management arrangements The government said it saw no need for organisational change The full report can be found at:‐ http://www.publications.parliament.u k/pa/cm201617/cmselect/cmenvfru/1 15/11502.htm

(* see full report but reason is to “encourage” the uptake of more sustainable drainage systems (SuDs))

Resilience must be improved: it is impossible to protect all properties from flooding at all times so the Government must improve help for communities and individuals to cope with and recover from flooding:

• The Government must make developers who fail to comply with planning requirements

liable for the costs of flooding;

• Water companies should be made statutory consultees on planning applications, and

the right to connect surface water to a sewerage system should be removed;*

• Unless a voluntary code is finalised this year, the Government must amend Building

Regulations to make use of flood resistant materials in new buildings mandatory;

• The Government should develop by the end of 2017 a grant scheme to support those

small businesses unable to secure affordable insurance to install resilience measures.

Some of the key recommendations

Flooding Advisory Group Meeting 2-11-2016

Locally Since last FAG 27th July 2016

.

Council’s New Flood Response Plan was “signed off” in July

• 2016. This replaces

the earlier 2011

• plan. (Additional

coverage for SW incidents.) This is a restricted document

.

Echo Article 26-9-16

Matt Wheeldon, director of assets and compliance for Wessex Water, said: “We frequently hear from customers who have flushed wipes which have then caused a blockage. “As a result they have had their garden flooded with sewage and, in worst case scenarios, their homes flooded.”

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February was almost exactly average in Bournemouth but across the Wessex region it was well above average

(Interestingly Sept was dryer than average across the whole Wessex Region)

July and June 2016 Rainfall

With 6.6mm of rain in the whole of July 2016 (at Kings Park Met station), this was our third driest July on record, after those of 1934 (3 mm.) and 1911 (5.6 mm.)

UK climate anomaly maps relative to 1961-1990 average available at:-

http://www.metoffice.gov.uk/public/weather/climate-anomalies/#?tab=climateAnomalies

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With only 6.6mm of rain in the whole of July 2016 (at Kings Park Met station) August came in with over an inch of rain on the first day. On the 1st August we had four times more rain than the whole of July. It was a very long duration - 23 hours and only a peak of 4.4mm an hour so little or no effect.

.

. But by the 16th August we were getting headlines of:-

(An ‘absolute drought’ - a period of 15 days on none of which more than 0.25mm of rain falls )

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And then on to Sept

. First “event” was on afternoon of Saturday 3rd Sept with 20.2mm recorded on TH rain gauge although no reported flooding.

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13th Sept 2016 – Nationally hottest day of the year? (not in Bournemouth – 19th July 2016)

2nd Event 13th Sept 2016.

Minor Highway flooding in:- Wallisdown Road Braidley Road St Lukes Road South Kinson Drive Maxwell Road Also Lower Gardens THERE HAD BEEN NO FLOOD WARNINGS ISSUED

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. Second “event” was on morning of Tuesday 13th Sept with “only” 11.2mm recorded on TH rain gauge.

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we have to go back to 19 September 1926 to find a temperature above 30C that late in the month (31.7C Heathrow, London).

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3rd Event 16th Sept 2016

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First Flood warnings issued 15.00 on Wednesday the 14th Sept

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First thing on Thursday 15th Sept out sweeping high risk areas including East Avenue, Glenferness Avenue, Elgin Road, Kinson Road (nr old baths). This is Maxwell Road at 8.30 in morning.

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Later on during the Thursday 15th Sept

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This was updated at 23.00 hours on Thursday 15th Sept

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We normally get 65.4mm

• f rain in the

whole month

• f September

(Kings Park Av 1975-2015)

Rain Gauge Locations

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First alarm from BBC rain gauges was at 00:045 GMT (01:45 BST)

Flooding in Winton

Flooding in Winton

Flooding in St Lukes Road

Flooding in East Avenue

Flooding in East Avenue

Flooding in Maxwell Road

Lower Gardens – YouTube footage -https://www.youtube.com/watch?v=iWKjuK3HoTQ

Lower Gardens – WW Cleaning team in operation

Lower Gardens – Crazy Golf (probably 4 or 5 hours after rain)

Lower Gardens – cover blown

Damage to the Bourne Stream Outlet screen

Damage to stream bank in upper Gardens

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Significant Flooding in:- Columbia Road / Heaton Road Area Wimborne Road (Winton High Street) St Luke’s Road Lower Gardens Also flooding in:- Acton Road Surrey Road Branksome Wood Road Stanfield Road Trafalgar Road Maxwell Road Queens Park Avenue Cooper Dean Rdbt Mandale Road / Nutley Close / Poole Lane Howeth Road East Howe Lane Millhams Road Boscombe Chine

Legend is number of “dots” - we actually have reports of 34 properties flooded internally Extent of reported / observed flooding for 16th Sept 2016 (as at 2-11-2016)

Reported flooding for 16th Sept 2016 as at 27/10-2016 and Predicted 1 in 20 yr 50mm SW flooding extent

All Rain Gauges Daily Totals Sept 2016

Rainfall is for historical reasons recorded daily from 9.00 GMT to 9.00 GMT the next day. So if it rains between midnight on the 15th and 9.00 GMT (8.00 BST) on the 16th that gets counted as raining on the 16th Town centre seems worst affected

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And into October

16th October 2016

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No Flood warnings issued.

(Although flood alert issued 12:57 15/10/2016 for possible flooding due to high tides at Christchurch Harbour

Howeth Road

Lower Gardens

Maxwell Road

.

Why?

.

Area of all adopted roads and pavements in Bournemouth 6,862,308m2 (This excludes private drives/ forecourts other hardstanding or any roofs) Approx No of Gullies in Bournemouth 22,200number But not all of these are in adopted roads, there are a lot on the prom etc So say 20,000 So each gully drains 343m2 Between 01:00‐01:09 (GMT) on 16th Sept 2016 we had 11.6mm of rain 0.00001933m/s of rain So each gully on average was trying to cope with 0.006633565m3/s = 6.6l/s Modeling gullies can be very complicated. There are lots of different types and some are not well placed. Wapug User Note 40 (by Richard Allitt Asc) suggests a simple rule of thumb of allowing 5l/s which gives good average results That assumes the gullies are not in any way blocked So every second there is at least 1.5l or roughly 3 pints that cannot get into the piped system So in 10 minutes and 22,200 gullies that’s 19603m3 unable to drain into the sewers According to wikipedia an Olympic‐size swimming pool is 2,500 m3 7.8Olympic size swimming pools

Some simple maths shows part of the problem. THIS IS TYPICAL FOR URBAN AREAS and is not unique to Bournemouth and its largely because of how historically they used to design road drainage

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One Possibility Urban heat Island effect

An urban heat island (UHI) is a city or metropolitan area that is significantly warmer than its surrounding rural areas due to human activities (Most of this research seems to be centred on America) “Aside from the effect on temperature, UHIs can produce secondary effects on local meteorology” “The extra heat provided by the UHI leads to greater upward motion, which can induce additional shower and thunderstorm activity”

https://en.wikipedia.org/wiki/Urban_heat_island http://www.metoffice.gov.uk/media/pdf/8/m/MO_PUP_insert_HEALTH.web.pdf http://www.urbanheatislands.com/

Original to FAG 16-11-2015

http://www.ofwat.gov.uk/wp-content/uploads/2015/11/rpt_com_met_rainfall.pdf

Changes in the frequency of extreme daily rainfall amounts for winter and summer have been estimated for 40 towns and cities using modelled rainfall amounts.

The projected changes in return periods should be used with caution.

Graphs showing the changes in return period for rainfall events with present-day return periods of 5, 10, 20, 30, 50 and 100 years are shown here for all locations listed in Table 1. (Present was 2010)

Other local issues

Flooding in Hanlon Close / Grower Gardens.

(Recently reported by our Neighbourhood Development Officer on behalf of elderly residents. Apparently problem had been going on for years! Water was regularly deep enough to get into back gardens). Not a WW SW sewer but a previously unknown Highway drain.

What we found - wood, bottles, cans, balls, crisp packets etc. in a 150mm dia SW pipe!.

Minor Highway Flooding in Millhams /Ringwood Road (July 2016)

Highway Flooding in Wallisdown Road near St Marks Church. The problem has been getting worse over several years. (A soakaway was found in the church ground and cleaned out some 4 years ago.)

Highway Flooding in Wallisdown Road near St Marks Church. Result of Investigation

There are no Surface Water Sewers in this area and the north side footpath was unusable in wet weather. (Previous level survey has shown that the two eastern gullies are draining over 2,000 m2 of road)

Wallisdown Road Works - Aug 2016. New head wall, ditch clearance and soakaway – Funded from Highway Maintenance Revenue Budget – works cost approx. £8,500.00

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Works since last meeting

Planning Applications Continue (record number in May 2016). Draft Section 19 report for event of 23rd June 2016. Wallisdown Road flooding (around St Mark’s Church) traced to failed soakaway and partially filled in ditch (technically a swale). Swale cleared 2nd half of August and new soakaway installed. This was to be funded from LTP but is now revenue funded. Maxwell Road Drainage Works Flood data collection for new Section 19 report on 16th Sept 2016 event. Millhams Recycling centre- Investigations for new site drainage has discovered where existing drains run and why not working. (July 2016). Will include in main part of scheme. Bournemouth Highway Asset Management Plan. (Drainage) Continuing. Design progressing on LTP funded schemes: - Wimborne Road /Winton High Street (around St Peter’s Hill). This will only reduce the extent of the problem. No further progress on Kinson Dam overflow screen (with view to making a bid for Local Levy funding)

Wessex Regional Flood and Coastal Committee - Dates

• 24th October 2016 Edgar Hall, Somerton – Local Levy
• 13th Dec 2016

Venue TBC - Investment & Strategy Group

• 10th January 2017 Venue - Dorchester / Weymouth Area -RFCC
• 28th March 2017 Venue – Taunton Area - I & Str Group
• 25th April 2017 Venue - Shepton Mallet /Frome Area - RFCC
• 20th June 2017 Venue TBC - Investment & Strategy Group
• 18th July 2017 Venue - Yeovil / Taunton Area - RFCC
• 26th Sept 2017 Venue TBC - Investment & Strategy Group
• 17th Oct 2017

Venue – Blandford Area – RFCC

• 12th Dec 2017

Venue TBC - Investment & Strategy Group

Wessex Regional Flood and Coastal Committee Meeting of 24th Oct 2016