German flood protection is planned around a defined flood, the HQ100. It is a flood that occurs at a given place statistically once in a hundred years. Under the Water Resources Act, the states must designate by regulation the areas such a flood would cover. In 2004, Bavaria introduced a Klimaänderungszuschlag, a climate change surcharge, for planning flood defenses. It is a flat 15 percent added to the HQ100.