Flood risks and drainage are key considerations when planning all new suburbs. Today, underground drainage systems are generally designed to cope with frequent storms – those with a 20% chance of occurring in a year. Any excess water travels along planned overland flow paths that carry water away from properties. This prevents them from flooding in the majority of storms – up to those with a 1% chance of occurring in a year. We also look at other benefits when designing drainage systems, including the impact on rivers and creeks.