1.0 BACKGROUND

1.1 Introduction

Each year, flood events result in significant loss of property, life, and livelihood. Yet at a local scale, floods can be beneficial (groundwater recharge, silt deposits, floodplain fisheries etc). As the economic base in developing countries shifts more to an urban and industrial base, the financial consequences of flood damage increases and demand for flood protection intensifies. Provision of flood protection, either in an urban or rural environment can also lead to cyclical patterns of investment - in the absence of land use controls, population densities in former floodplains can increase, property values rise, and the pressure to provide a greater degree of flood protection intensifies. Even in developed countries with resources for maintenance and more sophisticated flood warning systems, physical flood protection infrastructure cannot always provide full protection, as witnessed by recent floods in the Mississippi, the Netherlands and other parts of Europe.

The effectiveness of physical flood control measures changes in time depending on the level of maintenance and physical processes that affect sustainability, for example changes in river morphology and sedimentation. On the benefit side, large tracts of land are protected from floods by dams and permit forms of economic enterprise otherwise not possible. Although public perceptions may be that physical interventions are sufficient, the reality is that considerable management effort is required and additional attention and resources need to be allocated for non-structural approaches to flood management (flood forecasting, land use zoning, flood proofing, disaster preparedness, flood insurance) either in parallel or independently from structural forms of flood protection through embankments and flood attenuation through storage reservoirs.

The objectives of flood control infrastructure is often couched in hydrologic terms, for instance, providing protection against the 100 year flood which has a particular magnitude. Good quality data are essential to improve the design, but are often not available. As with any other hydrological prediction, there is an element of risk in determining the design flood. Much discussion within technical bodies has focussed on methods of calculating such design floods and reducing the level of risk. In parallel, there has been an increase of attention to flood hazard assessment and risk management. Describing the objectives in terms of the avoidance of certain levels of damage to individual sections of society and the national economy as a whole rather than on the design flood level, may broaden the discussion of flood management options and lead to wider incorporation of the evaluation of options in the planning process.

In addition to uncertainties of hydrological analysis in areas of sparse data, the assessment of reservoir sedimentation and other morphological effects are not precise and can significantly influence the design life of dams and therefore the long term sustainability of flood attenuation dams. Regardless of the level of risk, the downstream areas benefiting from flood protection often undergo more intensive development raising the value of property in the former flood zone. In the event design capacity is exceeded, greater damage would be experienced, raising the question of who bears the flood risk under the new arrangements.

The importance of floods from an environmental perspective is increasingly being realised and studies have been initiated to assess interactive effects of the flood hydrograph and downstream ecology. This raises new questions about operational procedures for dams. The changing environment also affects dams - the effects of global climate change on the frequency and magnitude of extreme events has introduced a new element of risk in the planning and design of flood control and management initiatives which will need to be incorporated .

In many cases, responsibility for water resources planning, land use planning, catchment management, flood forecasting, warning, preparedness, and relief are carried out by separate organisations with limited interaction. Recent events in China have highlighted the need for better implementation of catchment management programs to reduce the intensity of flood events. A more holistic approach to flood management through integration of structural and non-structural measures is closely related to institutional reforms proposed under river basin planning initiatives.

The financing of flood control activities and flood management initiatives are generally achieved through national or provincial budgets as it is often difficult to apportion benefits to individual groups. The nature of the benefit is significantly different to irrigation or water supply in that they are of a preventative rather than creative nature. In many countries, the trend is moving towards to protection of higher value areas – such as urban centres, industry and key infrastructure. In such cases there are possibilities to recur some of the costs from beneficiaries, possibly through betterment taxes. Rural areas and poorer urban areas are unlikely to have the same degree of protection or access to alternative measures.

This paper will address these issues by identifying good practice, assessing the effectiveness of various flood prevention and management options, and determining enabling conditions for a comprehensive package of flood management measures. Specific aspects to be covered include:

• Review approaches to risk assessment and management and how this affects the planning and design process
• Analyse the effectiveness of flood management options and the nature of specific conditions and environment necessary for these (dams, embanking rivers, flood warning, flood proofing, land use zoning, catchment management, restoration of wetlands, disaster preparedness, flood insurance).
• Analyse relationships between operation of dams for flood control and other sectoral objectives e.g. power generation and the extent to which multipurpose objectives are met in practice.
• Policy and institutional factors in the introduction of comprehensive flood management strategies, including risk assessment and financing arrangements
• Review of beneficial aspects of floods and areas of conflict and complementarity with flood protection
• Determine procedures for updating operation based on reassessment of hydrological and morphological changes and demands of other sectors, including the environment
• Good practice for design and management of dams in cases where hydrological data are scarce

Flood control objectives of a dam impose constraints on reservoir. The extent to which the multipurpose objective has been achieved will be reviewed as part of the global review of development effectiveness and, in particular the cross check survey. Specific linkages will also be developed with case studies where flood protection is a stated objective to address issues related to multipurpose operation of the reservoir. These include Tarbela, Grand Coulee, and possibly dams in China and India.

A number of thematic reviews are related to options for flood management including II.1 Ecosystems Functions (the relationship between downstream impacts and flood events and need to simulate flood events in the operational cycle); IV.5 Operation, monitoring and decommissioning (including need to revisit dam operation in the light of changing context); V.1 Planning approaches and V.3 River Basin Planning and Management (the integrated nature of water resources planning), and V.5 Consultation and Participatory Decision Making Processes (involvement of flood affected communities in the planning process)

The output of the study will be linked to two of the wider outputs of WCD, namely (i) the set of criteria, guidelines and standards by providing a more quantitative assessments of the effect and significance of alternative approaches to flood control and management which can be fed into the scope of development approaches to be considered, both for new development and the management of existing dams, and (ii) specific procedures to assess alternatives under the framework of options assessment and decision making