CAUSES OF FLOOD IN OGBARU LGA OF ANAMBRA STATE

Background of the study
Floods are major disasters affecting Ogbaru L.G.A of Anambra state, Nigeria and the world annually especially in most flood plain areas (Action Aid, 2016). Floods do not only damage properties and endanger the lives of human and animals but also produce other secondary effects like outbreak of diseases such as cholera and malaria as well. Flooding is commonly caused by heavy downpours of rains on flat ground, reservoir failure, volcano, melting of snow and or glaciers etc. Flood risk is not just based on history, but on a number of factors: rainfall, river flow and tidal-surge data, topography, flood control measures, and changes due to construction of building and development on flood plain areas (Abowei and Sikoki, 2015).

Flooding is caused by several factors and is invariably preceded by heavy rainfall. The other causes of flooding are moderate to severe winds over water, unusual hightides, tsunamis due to undersea earthquakes, breaks or failures of dams, levees, retention ponds or lakes, and other infrastructure that retains water. Flooding can be aggravated by impervious surfaces or by other natural and man-made hazards which destroy soil, vegetation that can absorb rainfall (Thompson, 2014). Although flooding is a natural occurrence, man-made changes to the land can also be a factor. Development does not cause flooding but can make it worse. In cities and suburbs, pavement and rooftops prevent some rainfall from being absorbed by the soil. Thus can increase the amount of runoff flowing into low lying areas or storm drain system (Adeaga, 2018).

The significance of the year 2012 flood disaster in Nigeria lies in the fact that they were unprecedented in the past forty years. Most parts of the central states of Nigeria and other adjoining states along the river Niger and Benue are devastated by these floods causing huge destruction to the rural and urban infrastructures (farmlands/crops, roads, buildings, damages, bridges, power lines etc.) and socioeconomic lives of the areas (Welch and Symons and Narver, 2017). Floods occur when the soil, stream channels and man-made reservoirs cannot absorb or contain all the water. A flood that occurs suddenly with little or no prior signs, is called a flash flood and is due to intense rainfall over a relatively small area, it us inevitable resulting from the natural rainfall runoff process. It is a natural phenomenon and its magnitude is periodic. The periodicity of flood implies that every year some area surrounding the river (on both sides) is flooded (Aderogba, 2012).

Flood disaster management like other disasters management can be grouped into phases; the preparedness phase where activities such as prediction and rusk zone identification or vulnerable mapping are taken up long before the event occurs, the prevention phase where activities such as forecasting early warning, monitoring and preparation of contingency plan are made before or during the event, and the response and mitigation phase where activities are undertaken after the disaster and these includes damage assessment and relief management (Wright, 2011).

1.2 Statement of Problem
In the last three decades, the impacts of flooding have increasingly assumed from significant to threatening proportions, resulting in loss of lives and properties. Though detailed statistics are not available regarding the losses sustained by the urban dwellers and flood victims, it is obvious from the available record that irreparable havocs have been sustained by the indigenes of Ogbaru Local Government Area due to what has become perennial natural disaster in our cities. Apart from houses that collapse by flooding, schools buildings and bridges sometimes collapse as well. Markets places and farmlands are submerged for weeks and sometimes are washed away. Hence flooding in Ogbaru Local Government Area needs to be assessed.