1. HR Wallingford Ltd 2002 Overview of the CFMPs and the MDSF Rob Cheetham HR Wallingford LTD

2. HR Wallingford Ltd 2002 INTRODUCTION The following presentation aims to give: a brief overview of Catchment Flood Management Planning (CFMPs) and the Modelling and Decision Support Framework (MDSF) show methods of developing catchment wide rainfall runoff and flow routing models Demonstrate how to carry out socio-economic impact analysis within the MDSF Show how “what-if” scenarios can be developed to address policies

3. HR Wallingford Ltd 2002 PURPOSE OF CFMPs To determine the socio-economic risks associated with flooding; To investigate the efficacy of different flood management in reducing unacceptable risk at a catchment scale; To provide the basis for sustainable flood management policies within each catchment over the next 50 years. PURPOSE OF MDSF To support implementation of CFMPs To provide tools to aid socio-economic and uncertainty analysis Manage data and results of “what if” scenario testing

4. HR Wallingford Ltd 2002

5. MDSF system diagram

6. HR Wallingford Ltd 2002 Import base data

7. HR Wallingford Ltd 2002 Downstream boundary Croal/Tonge confluence Upstream boundary Farnworth GS Section 105 hydraulically modelled reaches Routeing modelling

8. HR Wallingford Ltd 2002 Sub-catchment 1-9 FEH lumped catchment Sub-catchment 1-9i (intermediate sub-catchment) Sub-catchment 1-6 Linked with rainfall runoff model

9. HR Wallingford Ltd 2002 Import water levels and hydrographs

10. HR Wallingford Ltd 2002 External model results

11. HR Wallingford Ltd 2002 Economic damages

12. HR Wallingford Ltd 2002 Social vulnerability

13. HR Wallingford Ltd 2002 Rainfall runoff - routing model generates water levels for present and future conditions MDSF generates flood outlines and socio-economic impacts, thus defining the present and likely future flood risks THESE ARE THE BASE CONDITIONS Policies are developed to address flood risks In the following example, the policy for the Croal catchment is ‘ensure River Tonge water levels do not increase in the future for the 100-year event’ Policy development

14. HR Wallingford Ltd 2002 Flood management options are developed to try to achieve the policy Each option consists of a set of measures Flood management measures include: –On-line/off-line storage –Flood diversion –Channel works/maintenance –Walls and embankments –Non-structural measures Flood management option appraisal Overview

15. HR Wallingford Ltd 2002 Off-line Storage facility River Tonge

16. HR Wallingford Ltd 2002

17. Model used to determine feasibility of options. Objective is to achieve “sufficient and robust” options MDSF used to determine benefits of different options Off-line storage facility for the River Tonge: –Requires modification to achieve stated policy for the Tonge –Difficult to locate within Bolton (consider upstream sites) This is an example only - need to investigate other options Flood management option appraisal Conclusion

18. HR Wallingford Ltd 2002 Overview of the CFMPs and the MDSF Rob Cheetham HR Wallingford LTD