Urban flood modelling within the DCs
Calibration of flood models
Conclusion – the challenges now for flood modelling?
The prevalence of flooding events and the associated risk in the urban areas is an increasingly important issue of global significance, although it is more critical for the developing countries (DCs), such as Nigeria, where the hazard is often poorly understood and understudied. With current predictions of worsening future scenarios, it is important to pursue integrated flood risk management approaches which incorporate flood modelling. This paper is part of a research programme which is assessing and modelling urban flood risks in the DCs and data poor areas. It focuses on the latest science and philosophy in relation to urban flood risk management in the DCs. It reviews the literature around current flood modelling techniques and provides a comprehensive table of the different approaches alongside the strengths and weaknesses of the different models. Indeed, research in the vicinity of flood modelling has been extensive, and over the years has resulted in the development of a wide variety of schema, datasets and methodologies for simulating flood hydrodynamics. However, the actual potential of these developments has not been demonstrated in the management of flood risk within the DCs. To date, a perfect model or generic technique which can capture every aspect of flood hydrodynamics in an optimal fashion within the diversity of study locations is still unrealistic. Thus, to bypass the present flood modelling challenges within the context of the DCs, extensive calibration of state-of-the-art flood models is of significance. Additionally, researchers within the DCs should be fascinated by the prospect of developing bespoke flood models based on simple mathematical formulations which are easy to parameterise using global, open source and freely- accessible datasets.
The rate at which flooding occurs in recent times has been unprecedented, with the implication that only few coastal, rural, and urban environments still have their natural states unaltered [67,133,151]. This situation is of global significance, although it seems that the perception of flooding in the developing countries (DCs) for example Nigeria, is being nuanced by obvious limitations in research, economy and policy framework . During flooding, water largely covers land areas not usually covered by water, destroying farmland and critical infrastructure, displacing human populations, disrupting economic activities, and in the worst cases, leading to epidemic and death (, pg.309). These incidences, especially those relating to fluvial and coastal flooding often were due to sea-level rise, ice melt, overtopping or destruction of water defences and coastal tsunamis [35,93]. However, pluvial flooding, the focus of this review, appears to be widespread in recent times especially within the urban areas where its impacts are increasingly a major source of concern for urban residents and policy makers [38,75,90,152].
Pluvial flooding is basically due to increased frequency and intensity of rainfall, although there are a number of other potential causative factors which have been identified. In Dawson et al.  and Adeloye and Rustum  pluvial flooding was problematised on the basis of land use change, geomorphology, failure of urban drainage facilities and poor urban planning. Mark et al.  perceived pluvial flooding with regards to the scale of its impacts which in fact seem to correlate positively with the large number of human population and development assets within the urban areas. The study demonstrates that urban areas are the hotspot of large-scale flooding impacts to the same degree that they are typically fundamental to any nations’ sustainable development. Along with the much-discussed global climate change, which triggers heavy storms in recent times, current knowledge of rapid urbanisation and demographic pressures which characterise the DCs underscores the inclusive nature of urban pluvial flooding, and the primacy of galvanizing discussions for the management of its threats within the DCs [58,156,164,168].