Increased Paved Surfaces as Major Factor of Urban Flooding in Humid Tropics: An Example from Calabar, Cross River State, Nigeria

Urban flooding is a major hydrological hazard in most cities of the humid tropics due to high 

amount of rainfall, unlike in Polar Regions. However, recent increase in flooding menace has 

been attributed to human activities. This paper presents new insights on the condition of the 

built-up surface as the major factor of flooding in humid tropical cities using geospatial 

technology, with Calabar as an example. The study area was first classified, using the 

unsupervised algorithm into paved and unpaved surfaces. Nine (9) locations were then selected 

randomly for in-depth study. Data were obtained mainly through satellite remote sensing and 

direct field methods. In all the 9 sampled plots, the unpaved surfaces were below the 

recommended Land Use Act of 1978 benchmark of not less than 36% of the total area. It was 

further proven statistically that there is a significant difference between the observed unpaved

surfaces and the recommended minimum limit with 𝓧

2

cal (66.54) >𝓧

2

tab (15.507). This has 

reduced infiltration component of the hydrological cycle, thereby becoming a major contributor 

to increased runoff and eventual flooding. It is recommended that people‟s connection to nature 

through land development should not impact negatively on thelocal hydrological cycle in the 

different environments, whether at the poles or Equator, to avoid untold flood impact.