In 50 words what does this mean? In the scenario for 2100 ( 1m), a major flood event would typically surpass our 7.04m threshold once every 500 years. This is because the water level for a flood event that returns every 500 years is 7.018m (figure 2), just under our threshold. This implies that the probability of a flood surpassing 4m is relatively low unless we consider a long-term risk of 500 years. Considering a 100-year lifespan, the design risk associated with water levels exceeding 4m is less than 18% (figure 3)