No anti-flood system is 100% waterproof.
If the flooding lasts / in case of a long distance protection, it is strongly recommended to be equipped with water pumps to prevent the accumulation of water downstream of the dam.
In general, provide a pumping capacity of 10 litres / minute (infiltration, rainwater discharge networks) for each linear meter of protection.
Prefer several “small” pumps rather than a single high capacity one.
It is also advisable to have a stand-alone generator.