Urban soil infiltration rates on different land use types in southwest Nigeria: actual versus model estimates

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Abstract
As urban development increases and rainfall patterns become more highly variable, rainwater management issues are becoming increasingly prevalent. Given that urban soils may experience greater compaction than non-urban soils, infiltration models may not accurately represent disturbed urban soils, and this might jeopardize computations that rely on these models. Therefore, the objective of this research was to quantify the rates of soil infiltration on various urban land use types and assess the effectiveness of Horton and Green-Ampt infiltration models for application in urban soil environments. At 88 locations (23 commercial, 15 institutional, 36 residential, and 14 urban agricultural locations) spread across Akure metropolis, southwest Nigeria, soil infiltration rates and the soil's characteristics (texture, compactness, and moisture content) were examined. The highest infiltration rates were found in institutional (16.20 ± 9.73 cm hr-1) and urban agricultural (17.51 ± 10.38 cm hr-1) soils; nevertheless, all our data show that Akure's urban soils can infiltrate most rainfall episodes. The modeled and measured infiltration rates compare poorly, with both the Horton and Green-Ampt models underestimating the rates of infiltration of urban soil. When it came to estimating infiltration capacities, both models fared better in moist compared to dry soils and in loamy compared to sandy soils. Regarding the loamy soils, infiltration on the non-compacted soils was more accurately predicted compared to the compacted soils, according to both models, while the reverse was the case for the sandy soils. The models' largely below-average performance in urban soils will probably make projections from the models less reliable. The results of this study demonstrate the necessity of creating more reliable, enhanced infiltration models that work with urban soils.

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