Urban flooding in Dhaka, Bangladesh, is intensified by rapid urbanization, loss of permeable land, and constrained drainage. This study evaluates the Hatirjheel–Gulshan–Banani lake system using low-impact development (LID), water-sensitive urban design (WSUD), and sponge city principles. Multi-year satellite mapping was retained to describe urbanization between 2010 and 2024; however, the hydrological contribution of LID was assessed through a paired single-year analysis, holding urbanization constant. The runoff assessment used the 2024 land-use condition reported for the local drainage system: 56.43% built-up land, 32.11% open and cultivated land, and 11.46% water bodies and wetlands, producing an existing composite runoff coefficient of 0.534. The LID scenario kept the same land use, catchment areas, and rainfall intensities, but assumed that 30% of existing built-up surfaces received permeable or vegetated treatment with a planning-level treated-surface coefficient of 0.25. The resulting composite coefficient was 0.475. For the five-year design event, estimated peak discharge decreased from 87.89 to 78.14 m³/s in the 19.00 km² Hatirjheel sub-catchment and from 53.16 to 47.26 m³/s in the 8.27 km² Gulshan–Banani sub-catchment, corresponding to an 11.1% reduction in each case. A sensitivity range for treated-surface coefficients of 0.20–0.35 yielded peak-flow reductions of 7.9–12.7%. The result is therefore presented as a planning-level scenario estimate rather than measured field performance. The study identifies permeable paving, vegetated swales, bioretention, pocket wetlands, rainwater harvesting, and restoration of lake-canal connections as locally appropriate measures. LID should complement, rather than replace, conventional drainage and regular maintenance.