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However, results of these models also affected by the complexity and quality of topographic and input data. studied the conservation of mass and momentum by coupling of 1D and 2D models for river channels and floodplain, respectively. The use of mixed approach of 1D and 2D numerical models increases the quality of results and also saves time and computer memory, which can be limiting factors for the application of 2D models. Several researchers used 1D and 2D models for floodplain modelling and for river modelling. With the advancement of computational technology, many one-dimensional (1D) and two-dimensional (2D) hydrological models have been developed for both river and floodplain modelling to analyse the behaviour of flooding and to identify the causes and effects of flooding. The spatial distribution of input and model parameters also affects the accuracy of river’s geometry such as selection of their spacing and channel shape. Some studies considered precipitation’s spatial discontinuity and used different occurrence/non-occurrence estimation approach to improve the spatial distribution of precipitation. For example, in complex topography, precipitation has uncertainty in its spatial distribution due to uplifting air masses by the wind. The poor spatial distribution of basic input and model parameters data in hydrological modelling such as precipitation, evapotranspiration, infiltration and runoff can affect the model accuracy. However, hydrological modelling has some uncertainties either in input or model parameter, which affects accuracy and efficiency of a model. The complex processes of river and floodplain due to combination of natural and anthropogenic activities have been assessed by several researchers. It is very important to find accurate causes and effects and to understand the behaviour of flooding according to their specific locations. Hydrological model, a simplified and conceptual representation of complex hydrological processes, provides spatial and temporal changes over large areas and simplifies the complex reality. However, poor disaster management practices, limited financial resources and high population pressure are some common characteristics of less developed countries such as Ethiopia, which affects the monitoring, mitigation and relief operations. In-depth exploration into the causes and effects of flooding would lead to improved flood risk monitoring, prediction, mitigation and relief operations. Once the river water has overflowed or breached the levees, water races through the almost level flood plain submerging the cultivated fields and villages along its way causing enormous damage to lives and properties. Due to heavy rainfall in a short period of time, rivers are unable to transport the increased volume of water and other materials along its course that results in over-bank flow causing inundation of neighbouring lands. įlooding is mainly caused as a result of increased settlement along levees, unexpected high rainfall, deforestation, sediment deposition and river channel changes. According to the United Nation’s report, floods accounted for 47% of all weather-related disasters since 1995, affecting 2.3 billion people, killing 1.57 lakhs and incurring damages of about US$19.3 billion and US$0.83 billion in Asia and Africa, respectively. As an example, environmental damage includes contamination of water supplies and destruction to natural habitats by chemical waste and oil spills from vehicles and industrial facilities. Economic loss includes damage to businesses, residential properties, roads, bridges, buildings and automobiles. Every year, flooding incurs loss of life, economy, environment and agriculture. Flooding is one of the main natural hazards and occurs frequently all over the world, especially in Asia and Africa than other countries. Natural hazards are inevitable, unfortunate events resulting from combination of natural, geological and anthropogenic disturbances.