Study on using statistical data, remote sensing, and SCS-CN method to assess urbanization impacts on flow characteristics in Cau river basin, Thai Nguyen province, Vietnam

Abstract

The Cau River basin, particularly the segment flowing through Thai Nguyen province, is undergoing rapid urbanization and industrialization, leading to profound changes in land cover and adverse impacts on the hydrological regime. This paper presents a rapid assessment of these impacts using an integrated methodology that combines the analysis of statistical land use data from 2000-2020, remote sensing spatial data, and the SCS CN method. The results reveal an intense "concretization" process in new industrial centers like Pho Yen and Song Cong, where impervious surface areas have surged by 221% to over 458%, permanently converting more than 10,000 hectares of natural pervious land. This transformation has significantly increased the area-weighted Curve Number (CN) of the sub-basins (by up to 8%), leading to a drastic rise in the effective runoff coefficient (up to 167% for small rainfall events) and a massive increase in runoff volume during major storms. Spatial analysis has identified "hotspots" with the highest flood risk, concentrated downstream of industrial zones and in the low-lying areas of Thai Nguyen City. The study acknowledges limitations regarding hydraulic modeling of pipe networks but confirms that surface runoff generation has exceeded natural capacities.