Proforma B for Oxford

Tasks to be completed Elaboration/Rationale Oxford example
For the site (in the past): Collect information on flood extent/history in the past (maps of flooding; numbers of properties affected, and their types [e.g. residential; non-residential etc]; photos; etc) It will be useful to know the extent to which the study location has a history of flooding, to inform both our assessment of damages and our elaboration of potential risk reducing measures.  For example, it will be useful to know whether the area is affected very rarely by major events or regularly by minor floods.  < Environment Agency flood map (blue = 100 yr simulation) 

 

 

 

 

 

Flooding in > 1947

For the site (in the past): Collect information on any flood damages and/or disruption to economic activities (i.e. traffic; railways; agriculture) in the past It will be useful to have an idea of the kind of damages that are caused in this location, not least so we can concentrate on those areas where damage is greatest. The local picture of the 2007 flood in Oxford:•       Circa 2,000 homes, and•       Circa 200 businesses affected

•       Nursing homes evacuated

•       Oxfordshire clean-up cost £34 million

•       Schools’ repair and associated costs were £632,000

•       Tourism bookings 40% down

(John Kelly, 8.1.2008)

For the site (in the past): Collect details any injuries and loss of life in floods in the past here. It is important to stress within the case studies that economics using money values is not the whole story.  Many “intangible” impacts from floods, and injury and loss of life are two of these. Loss of life in floods in Oxford is rare, mainly because the River Thames rises slowly at times of flood, and there is plenty of warning given by the Environment Agency.  Nevertheless there are cases of loss of life during floods when people accidentally entered the flood waters by not judging their depth or severity.  The example here is a case in point where a cyclist missed the to pass and unfortunately was drowned in the rapidly moving flood waters
For the site (now and in the future): Collect data on Flood hydrology (flows; flood return periods; flood extents, etc) for the site Any assessment of the benefits of flood risk reduction requires the assessment of the impact in the future of a range of events of different return periods.  Taking a single event is likely to lead to gross errors.See Annex B4
For the site (now and in the future): Collect data on modelled or estimated future flood extents (geographical areas) by return period (e.g. for the  2, 5; 20; 50; 100 year floods) Each of the floods of different severities in the future, the return periods of which are estimated, needs to have a map showing the properties affected.  The rare floods (e.g. 1:100 years) will affect more properties than the more common floods (e.g. 1:10 years).  If this is not the case, the data is likely to be flawed. This is not Oxford, but is the type ofmap that is neededhttp://www.canal.gov.nl.ca/reports/frm/PI_Maps/Badger-FloodRisk-Large.jpg
For the site (now and in the future): Collect data on property numbers and types [e.g. residential; non-residential etc] in each of those areas identified above This is a crucial ingredient, identifying properties and potential damage from events of different return periods.  This is what will be used to calibrate the loss-probability curve (see Annex B4). Table 2.1 Residential and commercial properties at risk (provisional)

Annual chance of flood (% AEP) Residential property* Commercial property* Total*
1 in 5 (20%) 747 312 1,059
1 in 10 (10%) 1,044 397 1,441
1 in 20 (5%) 1,525 467 1,992
1 in 50 (2%) 2,321 574 2,895
1 in 75 (1.33%) 2,533 623 3,156
1 in 100 (1%) 2,695 653 3,348
1 in 200 (0.5%) 3,240 722 3,962
*Figures include properties at risk of flooding above threshold for the Do Nothing option.  This approach is in alignment with current guidance.
For the site (now and in the future): Collect data on population numbers (estimated) in each of those areas. It may be possible to assess the number of properties in the area from the population that lives there, in the absence of better information (i.e. divide population by c. 2.3 to identify the number of households/houses.  In any case this information may be useful for assessing the potential loss of life or injury during floods, related to the population living there.
Annual chance of flood (% AEP) Total population
1 in 5 (20%) 125
1 in 10 (10%) 175
1 in 20 (5%) 235
1 in 50 (2%) 750
1 in 75 (1.33%) 1,100
1 in 100 (1%) 2008
1 in 200 (0.5%) 2,132

 

 

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