Proforma E for Oxford

Tasks to be completed Elaboration/Rationale Oxford example (for details of the “shortlist” of the 6 options, see above)
Option number Option 1 Option 2a Option 2b Option 3 Option 4 Option 5
Discount the annual average damages (from Task 11) over the life/lives of the proposed interventions (e.g. multiply the annual average by 29.9 for a discount rate of 3.5%). The result is the ‘present value’ of those damages (see the Table in Annex C11, final column, for an example).  We need to bring all costs and benefits to present (day) values, in order for the comparison to be appropriate/valid. Discounting is a complex issue, explored somewhat in Annex E1. PV monetised flood damages (£m) 

And PV of damages avoided (£m)

1,237.4 

 

 

 

 

 

0

315.2 

 

 

 

 

 

922.2

297.8 

 

 

 

 

 

939.6

267.9 

 

 

 

 

 

969.5

122.1 

 

 

 

 

 

1115.3

89.8 

 

 

 

 

 

1147.6

Discount the estimated recurring maintenance costs of each intervention, to get a full present value of the costs of each intervention.  Ditto This is already done in the costs given above.
Make up a table of interventions (in ascending order of cost), showing (a) the present value of all damages to be avoided and (b) the present value of all costs  We need to investigate the benefits of successive increases in expenditure on more ambitious schemes/interventions to identify the ”best” scheme economically and in terms of what standard of protection it delivers See Annex E17 for a full sized table
Calculate the ratio of benefits to costs See Annex E17 for a full sized table
Calculate the value of benefits minus costs
Option Benefit minus Cost (£) ID
1.     Do nothing 0.0 1
2.     Do minimum 904.8 2a
3.     Do minimum (“extend”) 918.2 2b
4.     Defences (at Gandpont, etc.) 944.4 3
5.     Channel and medium sized culverts 1002.0 4
6.       Channel, medium culverts and defences 1030.6 5

 

                                                                                        

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