Accepted there is a Flood risk from Tame in Mossley
The long term river Tame level data shows the Tame has flood risk levels on a consistent basis. The flood levels were set to 330cm to indicate flood danger.
Flood Danger : The North West river basin district Flood Risk Management Plan 2015 to 2021 [Ref21] says of Mossley :
Quote : 3.Steeper ground in areas such as Ramsbottom, Littleborough, Delph and Mossley leads to fast flowing surface water and rapid inundation, both of which can be hazardous.
Historically, current rainfall levels are low, so flooding could be higher
The long term analysis of North west rainfall shows there is a significant risk of greater levels of rain in the past, in the 1930s and 1940s there could be 5 >150 mm per month, rainfall events per year. This shows flooding incidence are currently low and flooding events of greater magnitude are inevitable.
The flood event on 16-3-2013 coincides with a huge flood reading at Uppermill, which means the maximum flood level reading needs reviewing. i.e Some "flooding/level" incident occurred as it was recorded on 2 independent gauges. This extra high reading isn't recorded as a highest ever level, yet it may have been a real event.
Rate of change of flood levels is increasing
From analysis of the chart of the rate of change of daily maximum river level at Mossley.
It can be clearly observed that the rate of change of the average level has remain steady around 60cm cumulative daily rate of change per week.
Whereas the Maximum Rate of change has linearly increased over the monitoring period, apart from the 2013 flood anomaly.
This shows the rate that the river level goes up - has got higher from 600 (cm Change per day per week) to over 800 (cm/d/w).
i.e. An increase in "Speed of floods" or "Run off" of 125%.
i.e. Since the level of rainfall is currently normal to low, this increase in flood level speed can only be accounted for by a reduction of rainfall soak in the Tame flood plain and surrounding catchment area.
note : This is a daily reading so, "real time" flood speeds may changing by an even greater amount. It is imperative to analyse the real time data for increase in flood angle against rainfall.
The flood in Mossley on 11/9/2017 show that the flood warning level should be decreased to ~80cm and the alarm level be set ~240cm at the Waggon gauge Uppermill.
Quote : 11. Flood risk is increasing, perhaps substantially, so Planners, Emergency Planners, Asset Managers and others will need to mitigate this through a mix of collaborative working, planning policies, use of ‘worst case’ scenarios, development of contingency plans, and some detailed analysis.
In line with Open Condition Monitoring an analysis of public ally available River Gauge information was performed. [Ref14 : OCM ];[Ref22 : Maintenance Techniques and Analysis]
Gauge data for Mossley Tame river was obtained from : [Ref1] : riverlevels.uk
This data contains an average river level for the day and a maximum and minimum level for the day.
The river level data was inspected and a number of incorrect gauge readings were deleted. These were identified by the number 99.9999 and were understood to be when the gauge had failed.
The Flood data for 17/3/2019 raw data was obtained Government flood warning information service. [Ref2]
The data was input into a spreadsheet and various charts were produced to show various aspects of the river level data, see results and spreadsheet charts tab.
Rain data from [Ref3] was checked, analysed and compared with flood levels.
Flood levels are increasing
The recent flood condition of the 17/3/2019 was the latest and also a new daily record level.
Analysis of Mossley Tame River Levels against (hazardous) floods
The Analysis of North West rainfall per month from 2012 to 2019 also shows that the normal level of rain is 100 mm per Month and an increase to 150 to 200 mm per Month can cause flooding conditions. This shows once more a disproportional flooding response from relatively minor, or at least usual, variations in rain fall.
Flood Mossley 11th September 2017 : Max Gauge reading : 240 cm
There was a warning of the flood the previous day ~80 cm level, building up to the flood over 4 days.
This flood shows the high danger of relying on drains and culverts, which get blocked claimed as a partial cause of the flood..
Flood Mossley 21st November 2016 : Gauge reading of 298 cm
Despite major floods - gauge warning level of 330cm was not reached. Previous daily maximum levels of 100cm gave warning of the flood. The flood continued with levels of 200cm.
Ironically the 26th December 2015 flood report was released a few days earlier on the 30th-10-2016 [Ref6]
Quote "The flooding Stalybridge and Mossley was horrendous for the area. A lot of houses damaged by the torrential rain and floods. Was a nightmare"
Quote "A friend has just tweeted that the tunnel near Stalybridge is flooded and so they're stuck on the train there."
[Ref8] Homes were destroyed just downstream of Mossley in Stalybridge.
[Ref12] Flood damage to school in Greenfield 2017
Flood Mossley 26th December 2015 : Gauge reading of 295 cm
Again, the gauge warning level was not triggered. Warning of the flood was given the day before with max levels of ~140cm
River levels of > 140cm are flood warning levels.
Tame river Mossley , Rate of change of river level, per week 2012 - 2019
Rate of River Level change is increasing
Rate of change of river level, per week chart shows the rate of change of maximum river levels at Mossley. When compared to the rainfall charts, which show low or normal rainfall, the charts shows an upward trend of the change in river levels.
i.e. The river level is going up visibly faster, on the low resolution daily chart.
Simply put, the peaks of river level rise rate are generally increasing, when they should be going down.
This charts shows extracted high levels of river rate of change in level, above 400cm/day, to clearly show how the rate of level change has increased.
This charts shows all the high upward velocity or rate of level level increase events. The events are shown averaged over a month to clearly show how flooding events are getting faster, longer and more frequent.
This chart shows the acceleration of river level, or how quickly the level change speed changes. It shows lower levels of acceleration at firts, increasing through 2015 - 2016, and reamaining high during the relatively low rainfall of 2018 - 2019.
Maximum river events are recent and increasing
It is very concerning to observe that most of the new "Maximum river level recorded events" have happened since December 2015.
Climate change does not account for river changes
The height of floods is historically high, whilst rainfall and level are historically normal to low.
The recent flood level of the Tame at Uppermill and near flood levels at Mossley - March 2019 occurred with ~75mm of rain per month. In the recent past rain levels for Oldham have been >350mm per Month. Viewing the chart of the recent flood it is apparent that any continuation of the rain on that day would have caused a substantial flood, with higher levels than 1m (0.9m warning).
It was only through abnormal luck and shortness of the bad weather that the recent flood levels of the Tame at Uppermill March 2019 did not result serious flooding at Uppermill or Mossley.
Flood hazards and danger in Mossley is High
There is significant danger, buildings have fell down [Ref17] : July 2008 Mill collapses in Mossley.
Quote "Firemen ruled out an explosion, but residents believed the roof has been designed to collect water — and that the building could have collapsed under the weight of recent heavy rain.
Monitor raw data not daily avaerages
Raw data from the Tame may be examined, once it is released, to measure any increase in rate of level increase.
Cross reference real time rain / rate of rain fall
It may also be possible to extract more information from the daily data by cross referencing daily rainfall data, which may show higher levels for the same rain fall as a result of rain fall "soak" reduction and other developments.
Cross reference river levels to building developments
Data could also be cross related to historical developments levels in the area, however requests for development data showed that is not made available..
Review Mossley Waggon gauge river warning and alarm levels
The flood in Mossley on 11/9/2017 and 21st/11/2016 both show that the flood warning level should be decreased to ~80cm and the alarm level be set ~240cm at the Waggon gauge Uppermill.
This chart shows the maximum river levels per day.
These were taken during the heavy rain last Friday, and show a ferocious amount of water coming down the cascade at Ashway in Greenfield.
The cascade feeds the reservoir at Dovestones.
Pictures taken and sent in by Denzil Broadhurst, Deputy Team Leader, Oldham Mountain Rescue Team.
Quote "Firemen ruled out an explosion, but residents believed the roof has been designed to collect water — and that the building could have collapsed under the weight of recent heavy rain.
GMMC122216AB Response attached from the Environment Agency Fri, 5 Apr 2019 11:35 GMMC Info Requests (Inforequests.gmmc@environment-agency.gov.uk)To:you Details
Thank you for your enquiry which was received on 29/3/19.
We respond to requests under the Freedom of Information Act 2000 and Environmental Information Regulations 2004.
Thank you for your comments in relation to the Flood Warning Levels at Waggon Road.
The Micklehurst area of Mossley which experienced flooding during the dates you have mentioned is currently covered by a Flood Alert only (River Mersey Uplands Catchment). This Flood Alert covers an extensive area of the River Tame and is issued when we expect flooding to low lying lands and roads. We issue this Flood Alert based on a river level of 1.65m being reached at the Woolley Bridge monitoring station further upstream on the River Tame.
The Micklehurst area is not covered by a Flood Warning, which would be issued when we expect flooding to properties. This is because there is currently no river level monitoring station on Staley Brook from which we would be able to issue a Flood Warning. As the Waggon Road monitoring station is on the River Tame downstream of Staley Brook we are unable to issue a Flood Warning from there.
With reference to the dates of flooding you mentioned:
On 11 September 2017, flooding occurred in Mickehurst Road from a culvert collapse on Micklehurst Brook as described in Tameside MBC’s Section 19 investigation report (https://www.tameside.gov.uk/TamesideMBC/media/PublicHealth/FloodResponseMicklehurstAut17.pdf ). Due to the isolated nature of the event the river level did not reach a level at the Woolley Bridge monitoring station to result in a Flood Alert being issued.
On 21 November 2016 when flooding occurred in the Mossley and the wider River Tame area, we issued the Flood Alert as the river level met the criteria to issue this.
On 26 December 2015, surface water flooding affected one property in Mossley. During this event the river level did not reach a level at the Woolley Bridge monitoring station to result in a Flood Alert being issued. Also the Flood Warning Service only covers areas at risk of flooding from rivers.
Given the evidence above we have concluded that the current level of the Flood Alert is accurate and we are not proposing to amend it at this time.
Please refer to the Open Government Licence which explains the permitted use of this information.
Please get in touch if you have any further queries or contact us within two months if you’d like us to review the information we have sent.
Email: Inforequests.gmmc@environment-agency.gov.uk
[Ref1] : https://flood-warning-information.service.gov.uk/station/5145
[Ref2] : https://riverlevels.uk/tame-mossley-waggon-road#.XJT8lEPLeV4
[Ref3] : https://www.metoffice.gov.uk/climate/uk/summaries/datasets#yearOrdered
[Ref4] : https://tamesidereporter.com/2017/09/mossley-hit-by-flash-floods-again-after-torrential-rain/
[Ref5] : 21st/11/2016 : https://www.bbc.co.uk/news/av/uk-england-manchester-38059186/heavy-rain-and-strong-winds-cause-flooding-in-mossley
[Ref6] : Flood 26th December 2015 : https://www.greatermanchester-ca.gov.uk/media/1261/boxing-day-flood-report.pdf
[Ref7] : http://www.saddleworthlife.com/floods-bring-chaos-to-parts-of-saddleworth/
[Ref8] : Flood November 2015 : https://www.manchestereveningnews.co.uk/news/greater-manchester-news/flooding-millbrook-stalybridge-tameside-houses-12213781
[Ref9] : Flood 2016 : https://www.manchestereveningnews.co.uk/news/greater-manchester-news/flooding-millbrook-stalybridge-tameside-houses-12213781
[Ref10] : Flood 2012 : Dovestones Greenfield : http://www.saddleworthlife.com/13239/
[Ref11] : https://planetradio.co.uk/hits-radio/manchester/news/torrential-rain-causes-flooding-tameside/
[Ref12] : https://www.oldham-chronicle.co.uk/news-features/8/news-headlines/100868/deep-trouble
[Ref13] : Uppermill Flood analysis : https://github.com/wrapperband/Tame-Uppermill-FloodRisk
[Ref14] : Flood Assessment software Open source terrain analysis software : https://github.com/arijitsaha/FloodRisk
[Ref14] : Open Condition Monitoring : https://github.com/wrapperband/Open-Condition-Monitoring
[Ref15] : Related flood danger / cause in hill areas : Wall collapse : http://www.mossleycorrespondent.co.uk/?p=3225
[Ref16] : Related flood danger / cause : Mill Collapse : https://www.flickr.com/photos/21913923@N03/2696179413
[Ref17] : "Mystery" Mill collapses (after heavy rain 20th July 2008) : https://www.oldham-chronicle.co.uk/news-features/8/news-headlines/11932/mystery-as-old-mill-collapses
[Ref18] : Related flood danger / cause : Mill Collapse : http://www.stalybridgecorrespondent.co.uk/2018/02/10/homes-evacuated-following-mill-collapse-in-stalybridge/
[Ref19] : Landslide delays trains Mossley Nov 2012 (During a flood) : https://www.railforums.co.uk/threads/landslide-between-mossley-and-stalybridge-yesterday.74650/
[Ref20] : Concerns of Aberfan-type disaster in Mossley May 2005 : https://www.manchestereveningnews.co.uk/news/local-news/landslide-homes-fear-1149189
[Ref21] : North West river basin district Flood Risk Management Plan 2015 to 2021 : https://assets.publishing.service.gov.uk/government/uploads/system/uploads/attachment_data/file/507122/LIT_10210_NORTH_WEST_FRMP_PART_B.pdf
[Ref22] : Maintenance Allocation Practices and Techniques : https://wrapperband.github.io/Open-Condition-Monitoring/MaintenanceTechniquesAnalysis/
[Ref23] : Gaugemap river level at Mossley Waggon Rd : https://www.gaugemap.co.uk/#!Map/Summary/549/557