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Floods have potential destructive effects on socioeconomic facilities and cause serious risks for people. During the last decades lots of efforts have been carried out 10 overcome the difficulties caused by this natural phenomenon. In the past, most of the studies have been focused on developing mathematical models to forecast flood events in real -time to provide precautionary activities. The models are various from simple structures to models with high complexity and according to the climate conditions of the catchment under study, most appropriate model must be selected to predict flood events by using the existing recorded data from the catchment Rainfall-runoff model is the main component of a real-time flood forecasting model and transforms rainfall to runoff. The model commonly consists of a number of mathematical equations and parameters which are interconnected together for simulating runoff over a catchment. Since a model is a simplification of the real hydrological system, errors In simulation are unavoidable and influence on the simulation accuracy. Hence. the model should be selected properly and requires to be updated continuously to cope with probable hydrological changes which could create errors on model simulations. The current research focus on real-time flood forecasting by improving and developing rainfall-runoff models and indicating solutions to update the model to cope with frequent hydrological changes which can reduce the model performance. The research was started by evaluating optimisation schemes to derive the model parameters and an optimisation method was proposed based on Genetic algorithm concept. On the second stage, a new rainfall -runoff model called ERM, was introduced and suggested as a reliable model to use In rainfall -runoff modeling. Moreover, the adaptability of the ERM model parameters to cope with different errors occurred in terms of modeling was considered. Finally, in the last part of the thesis, the ERM model was coupled with a well-known numerical filter called the Kalman Filter and a real-time flood forecasting model was introduced.

Differential impacts experienced in relation to environmental hazards in developed and developing countries provide further challenges to actions taken in response to climate change. Whilst developed nations are viewed as more responsible for climate change, it is likely that the impacts will be felt more severely in developing nations. Furthermore, within nations, it is likely that already vulnerable groups (such as the poor) will be worst affected and least able to adapt to or cope with changes. A primary driver for this comparative study is to investigate the adaptive capacity of people at the local level in response to flooding in a developed and developing country context. Investigation into what facilitates the capacity to adapt to climate change i.e. the definition of differences, or similarities in adaptive capacity between people living in developed and developing countries are therefore key tenets of this project. Thus, capacity to adapt is built on more than just economic circumstances, which has implications for adaptation policy and the 'poorest are the most vulnerable' discourse. This project adopts an inductive, qualitative, community level approach to research, in order to identify and categorise adaptive actions taken in response to flooding in Belfast and Chennai case study areas, and to assess the effect of social capital! actor agency on the adaptive capacity of people at the local level. This research affirms that response to flooding that makes a positive difference requires human agency. Social capital is a key aspect of human agency and was found to be imperative in affecting adaptation and adaptive capacity in the case study areas. Social capital is therefore an integral part of adaptation and adaptive capacity. Human agency, however has been found to be influenced by perceptions of risk. Perceptions of risk have been shown to vary across cultural contexts, with a sense of injustice affecting what actions people pursue to adapt to change, and to reduce risk. Willingness to act and to bring about change was therefore not necessarily tied to objective limits (such as lack of economic capital), but also to more subjective social limits that shapes adaptation and adaptive capacity.

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This thesis is concerned with the study of flood plains and the flood hazard in England and Wales. Flood plains form an important resource which is only successfully utilised by the reduction of the flood hazard. The extent of the flood hazard in a study area, the problem of assessing flood damage, and the perception of the flood hazard and adjustment to it, are all investigated in order to suggest ways in which floods may be reduced. The flood hazard is a widespread phenomenon affecting most parts of the study area of this dissertation which consists of the Severn, Wye and Usk catchments, and a group of catchments in Glamorgan. Most major settlements extend into flood risk areas, and require flood alleviation programmes. Flood damage assessment is found to be a major problem which adversely affects our ability to optimise flood plain resource use. The assessment of potential flood damages based directly upon actual damage data is found to be impracticable. Instead, standard flood damage information, based upon actual flood damage data, is developed for residences. This allows the computation of potential residential flood damage. The important problem of flood hazard adjustment is considered in a study of the preconditions of flood hazard perception and individual and community adjustment at study sites. The adjustment process is found to be conditioned by flood experience, spatial variations in the hazard, access to information and adjustment evaluation, whilst personality traits do not appear to be directly important. At the community level, unconventional combinations of adjustment are found to be of value, although low levels of public awareness of flood risk pose a serious problem. Flood hazard reduction can be improved in this country by explicit management of flood plains, by improved economic analyses, and by the application of behavioural principles.

The development of suitable long term flood risk intervention strategies is a challenge. Climate change alone is a significant complication but in addition complexities exist trying to identify the most appropriate set of interventions, the area with the highest economical benefit and the most opportune time for implementation. All of these elements pose difficulties to decision makers. Recently, there has been a shift in the current practice for appraising potential strategies and consideration is now being given to ensure flexible, adaptive strategies to account for the uncertain climatic conditions. Real Options in particular is becoming an acknowledged approach to account for the future uncertainties inherent in a flood risk investment decision. Real Options facilitates adaptive strategies as it enables the value of flexibility to be explicitly included within the decision making process. Opportunities are provided for the decision maker to modify and update investments when knowledge of the future state comes to light. In this thesis the use of Real Options in flood risk management is investigated as a method to account for the uncertainties of climate change. Each Intervention strategy is purposely designed to capture a level of flexibility and have the ability to adapt in the future if required. A state of the art flood risk analysis tool is employed to evaluate the risk associated to each strategy over future points in time. In addition to Real Options, this thesis also explores the use of evolutionary optimisation algorithms to aid the decision making process when identifying the most appropriate long term strategies. Although the risk analysis tool is capable of quantifying the potential benefits attributed to a strategy, it is not necessarily able to identify the most appropriate. Methods are required which can search for the optimal solutions according to a range of performance metrics. Single and multi-objective genetic algorithms are investigated in this thesis as a method to search for the most appropriate long term intervention strategies. The Real Options concepts are combined with the evolutionary multiobjective optimisation algorithm to create a decision support methodology which is capable of searching for the most appropriate long term economical yet robust intervention strategies which are flexible to future change. The methodology is applied to two individual case studies, a section of the Thames Estuary and an area on the River Dodder. The results show the inclusion of flexibility is advantageous while the outputs provide decision makers with supplementary knowledge which previously has not been considered.

Reflecting on fieldwork carried out in the UK insurance sector, the thesis explores the role played by various types of actuarial and hydrological expertise in the performance of flooding as a matter of sustained public concern. In doing so, the question is raised: what analytical status to give the concept of risk when accounting for the epistemic doings involved in bringing yet unrealised future floods to bear on the present? Contrary to most other European countries the provision of flood insurance in the UK is left to the market and organised via an agreement under which insurers pledge to provide cover in areas protected by the Government to a standard of 1:75 years (the average return period between floods). What should be taken into account when mapping out this 1:75 year flood zone is subject to debates constantly revitalised by flood events with changing characteristics as well as new ways of modelling and anticipating what has yet to take place. How should we understand the knowledge claims hardwired into these debates through the involvement of actuarial and hydrological expertise? The thesis will argue that a reorientation of flood risk away from a status as the (multiple) object of these claims towards a status as an event in which a diverse variety of other things are brought into being (maps, futures, frequencies, anxieties, publics, geographies, things which are not necessarily very well understood as risk per se), will give rise to more productive and eventful questions. In the terminology of Isabelle Stengers, to risk is to create the possibility of bringing new things to life – the risking of floods seems to be constantly exciting such creativities.