Proforma C for Oxford

Tasks to be completed Elaboration/Rationale Oxford example
Undertake research into all the available depth/damage function data that might be used in the appraisal (both Residential and Non-Residential properties)  The potential flood damage in the future at the site in question needs to be quantified.  Then, with adjustments, it can be compared with the cost of preventing that flooding in the future to investigate the worthwhileness or efficiency of that investment. All the data that is required is contained in this Manual and the databases that go with it (all available under license from Middlesex University’s Flood Hazard Research Centre).  Much of this data may be suitable for use in other countries, perhaps adjusted by the ratio of the GDP of the country concerned to the GDP of the United Kingdom.  Some very basic datasets are available free of charge from the following website: 

MCM website (public):

http://www.mcm-online.co.uk/

 

Assign likely future flood damage values (in €) to each property for each return period using whatever data is available, even approximations  The potential future flood damage for every property needs to be assessed for each return period, showing how flood damages increase as the rarer floods  are considered (with longer return periods). This may necessitate quite a lot of judgement and interpolation or extrapolation (perhaps via a model or a spreadsheet). Note that some properties do not flood until quite long return periods. This is normal. Simple example (to be replaced later

Return periods (years)
Property 5 10 25 50 100 200
Return periods event damages (€)
House 1 1000 1500 25000 30000 32000 34000
House 2 0 0 1000 1500 5000 10000
Shop 1 3000 5000 15000 25000 50000 55000
Shop 2 0 1500 5000 12000 17500 22000
Factory 1 0 0 0 30000 150000 250000
etc
etc
…….. continued for every property in the study area
 
Total the damage values for each return period areas for an example) We need to total the potential damages for the whole of the study area so as to get the full picture of the flood risk in the area. Illustrative example from the above table

 

Return periods (years)
5 10 25 50 100 200
Totals € 4000 8000 46000 98500 254500 371000
Tabulate the loss-probability function to calculate future annual average damages for the site as a whole (see Table C11 in Annex C for a detailed example and explanation). The result is the annual average of those damages. This is an essential step. It is a table that incorporates the correct contribution of each of the floods concerned to the annual average: bringing all contributions to be comparable. In effect it defines the loss-probability curve. The annual average damages (AAD), or Total annual benefit, is the area under that curve. See Table C11 in Annex C for the detailed example and explanations). This is not from Oxford but is the type of table used at this stage in the calculations.
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