The Scottish Government

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CHAPTER 1: INTRODUCTION

1.1 Seventy-two flood prevention schemes ( FPS) have been promoted in Scotland under the Flood Prevention (Scotland) Act 1961.

1.2 In May 2004 JBA was commissioned by the Scottish Executive, Environment Group, Air, Climate & Engineering Unit to provide a flood and coastal defence database (an Asset Database) of schemes promoted under the 1961 Act, and to determine the areas benefiting from them.

1.3 All data in the database is geo-referenced (i.e. includes a grid reference) and includes details of the defence, condition, standard of protection provided by the flood defences, flood inundation area, defended areas, number of properties defended, value of benefits and historic flood information.

1.4 The Database is available to users over the web. This provides valuable information that can be used in facilitating flood management, planning and maintaining information on flood risk.

Objectives

1.5 The Scottish Executive ( SE) is investing in improving its understanding of flooding in Scotland. Recommendations made in recent reports on climate change ^1,2 identify a need for a register of fluvial and coastal defences containing detailed records of the assets, the defended areas and number of properties protected.

1.6 The SEPA Indicative River and Coastal Flood Map (2006) was made available on 1 November 2006, showing the 200 year flood outline (0.5% Annual Exceedance Probability), but without account being made for the presence of flood defences. The new maps therefore show locations that currently benefit from flood prevention schemes as being at risk from flooding and the Scottish Executive wish to determine the areas that are currently protected.

1.7 All schemes promoted under the 1961 Act are described as Flood Prevention Schemes. However it should be emphasised that no scheme can completely remove the risk of flooding and there is always a residual risk resulting from failure of the defences or from the design event being exceeded. Therefore the schemes provide management of flooding rather than prevent flooding.

1.8 This project was commissioned to provide a condition and asset database and to establish the defended areas for each of the schemes. Specific objectives were to:

• Construct a database of river and coastal flood prevention schemes together with a map-based ( GIS) interface
• Record the condition of the defences
• Show the area benefiting from the flood defences
• Define defended and undefended areas for a range of return period events
• Establish the current standard of protection
• Determine the number and value of properties benefiting from the defences

1.9 The database includes information on the detailed location, type and condition of defences, the flood outlines, defended areas, defence photos, 'as-built' drawings of the scheme. It also includes details of the scheme including information on the level of protection, construction costs and date of construction, benefits in terms of numbers of properties protected and their economic value, the maintenance regime and current frequency of inspection.

1.10 The database also identifies flood defences that the local authorities have submitted that have not been constructed as a formal Flood Prevention Scheme. It is likely that a number of Coastal Protection Schemes promoted under the Coast Protection Act 1949 ³ , and other works constructed under other statutes, will provide an element of flood protection. The database is therefore able to store and identify schemes by the act under which they are promoted.

1.11 In order to populate the database, over half the schemes were reviewed in detail and reports on each of these individual schemes were provided to the relevant local authority and Scottish Executive.

Study Approach

1.12 Meeting the study objectives has required the following discrete activities:

• Identification and location of flood defences
• Where required surveying the heights and dimensions of the defences
• Recording the condition of the defences
• Identifying the area benefiting from flood defences
• Estimating the flood risk during 100, 200 and 1,000 year floods with and without defences
• Establishing the current standard of protection provided, taking account of freeboard
• Determining the number and value of properties benefiting from each Flood Prevention Scheme
• Constructing a database containing information on Flood Prevention Schemes promoted under the Flood Prevention (Scotland) Act 1961
• Creating a Geographical Information System ( GIS) user interface to the database and making the information available via the internet

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