Identification of Waterlogging-Prone Areas in Nanning from the Perspective of Urban Expansion

Abstract

The objective of this study was to discern the spatial and temporal patterns of areas in Nanning that are susceptible to waterlogging, particularly during various phases of urban expansion. Furthermore, this study presents a proposal outlining strategies aimed at preventing and controlling waterlogging. These strategies are based on the integration of the concepts of sponge city and resilient city construction. This study employed remote sensing (RS) and geographic information system (GIS) techniques to provide technical support. The supervised classification method and normalized difference index method were utilized to compare and extract impervious surfaces in Nanning from 2013 to 2020. The present investigation utilized the acquired impervious surfaces to compute the fractal dimension as a weighting factor, incorporating a digital elevation model (DEM) for the purpose of conducting a hydrological analysis in ArcGIS. Based on the findings of the study, several conclusions can be derived. The following conclusions can be drawn from the study: (1) The fractal dimension of Nanning varied over the study period, with values of 1.32, 1.41, and 1.58 in 2013, 2017, and 2020, respectively. The distribution of impervious surfaces showed a decreasing trend from the city center to the periphery. Urban planning and construction activities have significantly influenced the distribution of impervious surfaces, resulting in a progressively more complex and unstable structure. (2) From 2013 to 2020, the urban expansion fractal dimension increased from 1.32 to 1.58, indicating a decrease in the stability of impervious surfaces. The areas with higher concentrations of impervious surfaces coincided with frequent waterlogging-prone areas. Furthermore, the distribution of waterlogging-prone points transformed from a concentrated pattern to a scattered one. (3) In terms of waterlogging prevention and control strategies, the old urban areas are recommended to be transformed into sponge city projects, and the new development areas are planned, designed and implemented with the concept of “resilience”.

Classification and Planning Strategies of Multidimensional Resilience Units for Urban Waterlogging: A Case Study of the Old City District in Shijiazhuang, China

“…Unit resilience clustering analysis reveals that in the old city center, the railway line and surrounding green public spaces are linearly distributed, yet both the unit and adjacent units are low in redundancy. Consequently, these railway-adjacent green spaces can be used as typical pluvial potential spaces, developing linkage potentials with surrounding unit areas, primarily adopting strategies for waterlogging acceptance by connecting units and enhancing regional green infrastructure continuity, in line with the "sponge city" and low impact development (LID) concepts [57]. Additionally, partial LID measures may be adopted to link different parcels within the area, creating a disconnected high-low-high spatial pattern to disrupt the connectivity between surface buildings, thereby increasing surface runoff permeation and reducing the risk of urban waterlogging [58].…”