Spatial Diagnosis of Rain Gauges’ Distribution and Flood Impacts: Case Study in Itaperuna, Rio de Janeiro—Brazil

Abstract

The global increase of urban areas highlights the need to improve their adaptation to extreme weather events, in particular heavy rainfall. This study analyzes the impacts of in-situ rain gauges’ distribution (by applying the fractal dimension concept) associated with a spatial diagnosis of flood occurrences in the municipality of Itaperuna, Rio de Janeiro–Brazil, performing an investigation of flood susceptibility maps based on transitory (considering precipitation) and on permanent factors (natural flood susceptibility). The fractal analysis results pointed out that the rain gauges’ distribution presented a scaling break behavior with a low fractal dimension ( 0.416 ) at the small-scale range, highlighting the incapacity of the local instrumentation to capture the spatial rainfall variability. Thereafter, the cross-tabulation method was used to validate both predictive maps with recorded data of the major January 2020 event, which indicated that the transitory factors’ flood map presented an unsatisfactory Probability of Detection of floods ( P O D = 0.552 ) when compared to the permanent factors’ map ( P O D = 0.944 ) . These issues allowed to consider the hydrological uncertainties associated with the sparse gauge network distribution and its impacts on the use of flood susceptibility maps. Such methodology enables the evaluation of other municipalities and regions, constituting essential information in aid of territorial management.

Multi-Criteria Decision Method for Sustainable Watercourse Management in Urban Areas

“…Besides, the studied area has been an issue of recurrent floods (also related to the urbanization and consequent occupation of the channel's and main streambanks). Figure 2 displays the flood mapping of the urbanized area of Itaperuna during the major event of January 2020 [19], in which it is possible to identify the case study watercourse been affected. to the urbanization and consequent occupation of the channel's and main streambanks).…”

“…to the urbanization and consequent occupation of the channel's and main streambanks). Figure 2 displays the flood mapping of the urbanized area of Itaperuna during the major event of January 2020 [19], in which it is possible to identify the case study watercourse been affected.…”

“…Figure 3 presents the conceptual framework idealized in this work. [19] and the flood occurrences in the case study watercourse.…”

“…In his review, Keivani [18] highlighted the main challenges of urban sustainability. Some of them are the huge intra-urban inequalities that cities are prone to (social); the severe challenges for sustainable economic growth that cities are faced with [16] (economic); the impacts of the greenhouse gases (GHG) released on the world climate and the impacts of climate change on living conditions due to extreme events and natural hazards such as heatwaves, hurricanes, and floods [3,6,7,19] (environmental); and the consequences of urban form and spatial development on the sustainable development [4,5] (environmental and economic). The main concern is to maximize these three sustainable dimensions, albeit the intrinsic conflicts among them and the commonly required trade-offs [20][21][22].…”

“…In connection with this, this research approached the Cehab's open channel as the case study, located in the center of the urbanized area of the municipality of Itaperuna, in the Northwest region of the state Rio de Janeiro-Brazil, with approximately 100,000 inhabitants [31], inside the Muriaé River catchment [19]. This watercourse is frequently subject to floods (associated with the urbanization), affecting the local population which urgently requires an engineering intervention, as diagnosed by Campos and Paz [19].…”