Urban water systems face challenges from urbanization and climate change. A study in Turnhout, Belgium, compared different strategies to reduce sewer and river floods. Integrating green spaces for stormwater retention can decrease sewer flood volumes by 30-50% for return periods of 10-100 years. However, this method has limited impact on river floods. Retention basins downstream of stormwater sewers can significantly reduce peak discharges to rivers, but may not lower river flood frequency due to differences in response times. The study emphasizes the importance of integrating urban design with water management to improve flood control in cities.