The given charts depict two different ways of protection for homes which are at risk of being flooded, and both of the houses are raised above ground level. The main difference between the two protection plans is whether there is a stopbank or not
In the first diagram, the function of a stopbank as a barrier against flooding from nearby rivers is illustrated. This barrier, depicted as a mound near a drain/river, exceeds the predicted height of a 100-year flood. Additionally, the houses can be built on stilts to prevent flooding from rainwater, and there is a floodgate beneath the stopbank opened to allow the internal winding to drain off into the river.
In contrast, the second illustration portrays the dire consequences of a house lacking such protection, directly exposed to overflowing water. In this case, buildings are also raised on stilts. The height of the stilts is 300mm above the 100-year flood level which is called freeboard. This measurement can secure the house against the flood.