The provided diagrams illustrate two distinct methods for protecting residential buildings in areas susceptible to flooding. The first approach involves the use of a stopbank, while the second demonstrates the structural elevation of houses.
In the first scenario, where a stopbank is present, a physical barrier is constructed alongside a river or drain to prevent overflow. This setup includes a berm and a floodgate, which helps manage water levels. Despite this protection, the diagram highlights the risk of internal ponding caused by internal runoff from higher ground. Consequently, buildings in these areas are typically raised on stilts to remain above the water level.
Alternatively, in areas without a stopbank, buildings are directly exposed to the 100-year flood level of the adjacent river or drain. To mitigate this risk, the houses are constructed as raised buildings. A critical feature of this design is the inclusion of a 300 mm freeboard. This space acts as a safety buffer, ensuring that the house floor level remains significantly higher than the projected 100-year flood or ponding level, thereby preventing water from entering the living space during extreme weather events.