Flooding occurs in moderate-to-low risk areas as well as in high-risk areas. Poor drainage systems, rapid accumulation of rainfall, snowmelt, and broken water mains can all result in flood. Properties on a hillside can be damaged by mudflow, a covered peril under the Standard Flood Insurance Policy. In high-risk areas, there is at least a 1 in 4 chance of flooding during a 30-year mortgage. For these reasons, flood insurance is required by law for buildings in high-risk flood areas as a condition of receiving a mortgage from a federally regulated or insured lender.