Impact Quantification of Decentralization in Urban Growth by Extracting Impervious Surfaces Using ISEI in Model Maker

Nana Yaw Danquah Twumasi,Chikondi Chisenga,Neema Nicodemus Lyimo,Orhan Altan,Nayyer Saleem

doi:10.3390/su12010380

Abstract

Decentralization problems in Africa have caused some infrastructure disparity between country capitals and distant districts. In Ghana, less public investment has created a gap between implementation results and theoretical benefits. Spectral indices are a good approach to extracting impervious surfaces, which is a good method of measuring urbanization. These are restricted by complexity, sensor limitation, threshold values, and high computational time. In this study, we measure the urbanization dynamics of Wa District in Ghana by applying a proposed method of impervious surface extraction index (ISEI), to evaluate the decentralization policy using Landsat images from 1984–2018 and a single S2A data. Comparing our proposed method with five other existing indexes, ISEI provided good discriminated results between target feature and background, with pixel values ranging between 0 and +1. Other indexes produced negative values. ISEI accuracy varied from 84.62–94.00% while existing indexes varied from 73.85–90.00%. Our results also showed increased impervious surface areas of 83.26 km2, which is about 7.72% of total area while the average annual urban growth was recorded as 4.42%. These figures proved that the quantification of decentralization is very positive. The study provides a foundation for urban environment research in the context of decentralization policy.

Highlights

Detailed acquisition of global and synoptic information about the Earth and its environment is possible with Earth-orbiting satellite sensors
We develop an impervious surface extraction index (ISEI) that can be applied in Ghana or similar environment to achieve the objectives of this study
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Summary

Introduction

Detailed acquisition of global and synoptic information about the Earth and its environment is possible with Earth-orbiting satellite sensors These satellite sensors provide a platform for assessing, evaluating, and determining features of spatial phenomena for effective urban planning, expansion, and monitoring studies [1,2,3]. Annual, and longer-term observation such as urbanization and urban growth [5], urban expansion and urban sprawl [6,7], can possibly be monitored These phenomena are driven by the rising percentage of the urban population of which it is estimated that the world’s urban population will be 2.5 billion by 2050, with almost 90% of this growth occurring in Asia and Africa [8]. Another fusion involved synthetic aperture radar (SAR) and optical data at the decision level [22] yielded better accuracies

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Results

Discussion

Conclusion