Hydrological investigation on infiltration capacity in urban areas

Urban flooding is a growing concern globally, exacerbated by climate change and rapid urbanization, which often results in inadequate infrastructure. This study focuses on the flood risks associated with the Kærby neighborhood in Aalborg, Denmark, utilizing hydrological investigations to understand water behavior in the area. The research aims to assess infiltration rates, surface runoff potential, and soil saturation levels, employing tools such as the capillary zone test and double-ring infiltration test to provide insights into the area’s flood vulnerabilities. Soil particle size distribution (PSD) is crucial in influencing water infiltration and retention. This study analyzes topsoil and subsoil samples, identifying the predominance of sandy textures with a high proportion of coarse grains, which suggests good drainage characteristics but also points to potential challenges with water retention. Furthermore, the study explores the behavior of water retention at three moisture levels, revealing the intricate relationship between soil texture, capillary rise, and water absorption. Soils with higher fine content exhibit greater water retention, while sandy soils demonstrate faster infiltration but lower water retention capabilities. The research also highlights the significance of capillary rise in influencing water availability and its potential role in exacerbating flooding in urban settings. Through a series of capillary rise tests, the study illustrates how soil textures and compaction levels directly affect the upward movement of water, particularly in areas with fine-grained soils, where capillarity is pronounced. This behavior suggests that regions with high capillary action could be at an elevated risk of waterlogging during periods of heavy rainfall. Field investigations conducted using a double-ring infiltrometer further emphasize the interaction between the capillary water table and soil infiltration rates. Two sets of infiltration tests, run under different conditions, reveal that soils closer to the water table exhibit higher infiltration rates initially but stabilize more quickly, indicating saturation due to capillary forces. This interaction between the water table and soil capillarity has significant implications for urban water management, particularly in flood-prone areas like Kærby. The study concludes by addressing the heightened flooding risk in Kærby, where fine-grained soils with high capillarity, combined with frequent heavy rainfall and shallow water tables, create an environment prone to rapid saturation and surface runoff. These findings underscore the need for improved flood management strategies, including infrastructure upgrades and more effective urban planning that takes into account the hydrological characteristics of the soil and the rising water table. Ultimately, this research provides valuable insights for policymakers, urban planners, and engineers tasked with mitigating flood risks in urban environments. The detailed analysis of soil behavior and water movement in Kærby offers a foundation for developing resilient flood management systems that can cope with the increasing challenges posed by climate change and urban expansion.