Of all the ‘natural’ hazards to which humans are exposed, floods are probably the most widespread and account for most damage and loss of life (Alexander 1993). Floods also appear to have a special impact on their victims, instilling a fear of the consequences that often exceeds their actual impacts (Green and Penning-Rowsell 1989). They also can have serious secondary impacts on the economy of the regions affected, and they can markedly influence agriculture in disaster-affected areas for some time after the event has passed, by affecting cropping patterns and yields, as dramatically is the case in Bangladesh (Alexander 1993).
Geographers have studied the complexity of such flood hazards for many years and have made significant contributions to their understanding, not least by tackling the interface between physical geography and human geography that is highlighted in the flood situation by the complex relationships between human behaviour and extreme geophysical events.
The foundation of such research was in the ‘Chicago’ school of hazard geography pioneered by White and others (Burton et al. 1978; 1993). This has been followed by the work of Hewitt (1997) and Mitchell (e.g. Mitchell et al. 1989) and elsewhere in the world in Australia (Smith 1999), New Zealand (Eriksen 1986), the UK (Penning-Rowsell et al. 1986; Arnell et al. 1984) and elsewhere (Chan and Parker 1996; Kanti Paul 1997, Pelling 1998).
In addition, geographers have contributed to the hydrology of floods, mainly by evaluating the impact of humans on flood regimes (Hollis 1988), through evaluating spatial flood patterns (Newson 1989) or understanding the geomorphology of floodplain processes (Anderson et al. 1996).
From other disciplines has come the sociology of human group interaction in floods and other extreme events (Torry 1979), the psychology of behaviour under risk circumstances and of risk communication (Handmer and Penning-Rowsell 1990), and the configuration of institutions to tackle such hazard phenomena (Hood and Jones 1996). Many of the key debates centre on whether flood and other risk is socially determined rather than physically based, and whether risk is socially divisive (Beck 1992).
Floods can be classified into fluvial, coastal and those that result from deficiencies in urban drainage. Fluvial floods occur when river discharge exceeds its bankfull capacity. The return period of out-of-bank flood flow is generally 2.3 years (Newson 1989), and the magnitude of floods and their probability of occurrence are strongly connected, although these relationships are regionally specific and depend on climatic conditions and river catchment character (ibid.).
Coastal flooding occurs where tide levels exceed land levels, exacerbated by extreme wave