Assessment of sediment grain size and hydraulic interactions in urban drainage systems: a case study from Juliaca, Peru

Abstract

Urban drainage systems are essential for the sustainability of cities, significantly impacting water management, pollution control, and urban planning. The city of Juliaca is characterized by a predominantly low slope, ranging from 0.0003 to 0.001 m m^–1, making it particularly susceptible to sedimentation processes within the existing drainage network. The objective of the research was to characterize the sediments in the stormwater drains and to assess the relationship between the granulometric properties and the hydraulic parameters of the drainage system. To achieve this, 12 sediment samples were collected from Zone D of Juliaca at the end of the rainy season and analyzed in the laboratory to determine the granulometric distributions and physical properties. Spearman's correlation coefficient was employed to establish the relationships between sediment characteristics and hydraulic parameters. The results revealed that the granulometric curves exhibited multimodal distributions. Sand was the predominant component in the samples, with an average content of 72.74%, followed by gravel at 21.36%, and silt and clay at 5.90%. The average particle size ranged from 0.159 to 2.132 mm. The drainage system was found to possess considerable hydraulic cross-sectional dimensions, with slope values ranging from 0.0004 to 0.031 m m^–1. The correlation analysis found both positive and negative relationships between particle-size distribution, sediment composition, and slope. However, these correlations were not entirely consistent with established sediment transport principles. This inconsistency is likely attributed to the influx of sediments into the drainage network from unpaved roads, driven by wash-off processes and surface erosion, among other contributing factors.

Keywords: critical velocity, granulometry, hydraulic parameters, unpaved roads, Urban drainage system