A recent UN study (2004) fears that the number of people affected by catastrophic floods may increase from the present 1 billion to double this number by 2050. While more than 25 000 people are killed every year by floods and such weather-related disasters, the costs of these disasters range between $50 and 60 billion annually. Of the estimated over 520 million people affected annually worldwide, more than 400 million are directly exposed to flood threats, mainly in Asia. During the period 1987-97 about 228 000 lives were lost in Asia, accounting for 93% of flood-related deaths. The importance of managing disasters due to floods is obvious, given their primary role in exacerbating frequent calamities, loss of lives, property damage, and ruining the economies of the poor and vulnerable in particular. Acknowledging these factors, ICID constituted a Working Group to exclusively address issues related to ''able'' flood management. One of the clear mandates spelt out in its charter also relates to ''flood management techniques''. The Working Group on Comprehensive Approaches to Flood Management (WG-CAFM) has recently brought out a Manual Planning of Structural Approaches to Flood Management.
Flood management (or flood risk management) concerns all actions related to the control of floods, the mitigation of flooding and, after such flood control and mitigatory measures have been implemented, the management of the residual risk of flooding. In order to decide on an optimum solution of flooding problems, it is necessary to know the extent of damage caused by floods of different magnitudes/probabilities. Flooding can be due to many reasons, but the Manual focuses on flooding caused by overtopping of riverbanks and overtopping/ breaching of flood embankments along rivers. A logical method of assessing such damage for use in the selection of a flood protection system is presented in the Manual. Damage assessment, therefore, has been considered as a necessary step for carrying out flood management.
An effort has been made to formulate recommendations for the application of a certain return period as a function of the considerations identified in the Manual. Advantages (and disadvantages) of a standard level of protection have been mentioned. Reasons for adopting a certain level of protection for a certain area (such as loss of human life) are discussed, including related political, economic or psychological considerations. Each of these reasons has been elaborated upon to establish the quantitative and/or qualitative basis on which a decision could perhaps be possible. Some case studies have been presented.
Further, the use of hydrodynamic mathematical models of the deterministic type for carrying out flood management has also been covered. The purpose and effectiveness of certain mathematical models for understanding the flooding phenomenon in order to study and test flood control measures and, finally, to calculate various flood parameters have also been described. Suggestions have been made regarding the application of deterministic models with physically based parameters primarily for regional and/or global flood event analysis. Flood damage assessments in Canada, Australia, Japan, The Netherlands and the Mekong basin are briefly reviewed.
Most sections of this Manual include material on sample applications. These examples have been selected to provide the user with further insight into the associated structural measures, and their practical applications.
Through this Manual the author intends to give planners and decision makers in flood management and flood control, guidelines on the planning and design of flood control projects. Associated examples have been set up to enable the user quickly to assess the applicability of the various measures to his or her situation and to identify appropriate procedures. In all, the Manual covers management strategies for flood mitigation involving structural approaches and complements ICID's Manual, Non-structural Approaches to Flood Management.
It may be recalled that ICID had earlier brought out a Manual Non-structural Approaches to Flood Management (1999). Part I of the early version of ICID Manual contained introductory and general explanatory information;