The degree of protection required by this subchapter is considered reasonable for regulatory purposes and is based on available information derived from engineering and scientific methods of study. Larger floods may occur or flood heights may be increased by human-made or natural causes. This subchapter does not imply that development either inside or outside of the floodplain will be free from flooding or damage. This subchapter does not create liability on the part of the village or any officer or employee thereof for any flood damage that results from proper reliance on this subchapter or any administrative decision made lawfully thereunder.