Climatologist, Prof. Imo Ekpoh, has blamed the combination of high temperature due to global warming and high tropical humidity for the recurring flood in Calabar and environs.
Ekpoh, a lecturer in the Department of Geography and Environmental Science at the University of Calabar, told the News Agency of Nigeria (NAN) in Calabar Monday that infrastructural development and climate change were other causative factors for the yearly flooding.
He said that in the past such severe flooding used to occur in cycles of 20 years to 30 years.
He said the impact of the flood was then less painful because it allowed time for affected people to recover.
“The level of infrastructure development within Calabar has increased and the town witnessed massive expansion since the city became a state capital in the early 1970s.
“This situation has increased the level of concretisation and asphalting of the land-surface, leading to enhanced runoff from rainfall while diminishing the infiltration rate of the soil. he implication is that more water from rainfall is available on the surface to run as surface flow which we call flood.The infiltration capacity of the soil is reduced due to the preponderance of urban infrastructure such as buildings, asphalted roads, concrete car parks and other paved surfaces,’’ he said.
Ekpoh also said that urbanisation in Calabar has seen people building in flood reception zones or flood prone areas.
“Such enterprise will naturally suffer at the slightest sign of flooding. Of course, it is a common saying that water finds its own level. If construction infringes on a drainage channel, the water will move elsewhere if it cannot uproot the obstruction on its path.’’ he said.
The climatologist also said that the 21st century climate change, associated with global warming had created significant distortions in the local climate pattern in Calabar and elsewhere.
“For instance, intense afternoon thunderstorms that can generate more than 250 milliliters of rain within a day or even shorter duration have become commonplace. This is because global warming has provided the needed thermal energy for increased evaporation along the Atlantic Gulf of Guinea. A combination of enhanced thermal and cyclonic activities, therefore, drives the massive rainfall regime that Calabar has been experiencing lately. This is as against the familiar rainfall regime that should accompany the regular swings of the inter-tropical convergence zone,’’ Ekpoh said.
He said the recent severe floods in Calabar qualified to be called extreme climatic events which should occur in cycles of 20 year to 30 years based on historical records.
“Unfortunately, climate change has conditioned an extreme climatic event into an annual event.
“A combination of high temperatures due to global warming and high humidity mean that the level of chemical reaction has increased leading to intense, deep chemical weathering of the soil.
“This process ensures that silt, sand and clay are in abundance, especially during the rainy season, and they are implicated in the rapid silting of the gutters and natural drains. In addition to natural silting of the drains, most people in the city are still in the habit of disposing wastes into gutters and drains. This leads to the clogging of both artificial and natural water channels,’’ he said.