Drainage law regulates surface water and sets guidelines for diversion and obstruction of natural run-off on property. Under the civil law doctrine, drainage law is referred to as the natural flow rule, meaning lower land owners are obligated to accept water that flows naturally from higher property. In some regions, drainage laws in cities allow a property owner to deal with water on his or her property under local ordinances.
Civil law typically prohibits a land owner from changing the natural course of storm water by altering the direction of the flow. Upper property owners may not make changes that increase the amount of run-off to nearby land. The law generally prohibits storing water in a pond or basin for later release that might cause flooding.
In most areas, governments are subject to drainage law and must accept responsibility for damage caused by public works projects that divert the flow of water. Public agencies might be immune to liability if a development project caused the damage. The immunity might apply even if the agency approved permits for construction that caused flooding.
Engineers who design development projects typically assume responsibility for following drainage law. They may not block the natural flow of water, increase the amount of run-off, or increase the velocity of the flow. During construction, the developer generally must address erosion and sediment control to comply with environmental drainage law. If a development harms other property, the builder might be ordered to pay for damages.
Some exceptions to civil drainage law might exist in agricultural areas that produce food. Heavy rainfall that floods fields might make it impossible for farmers to sow fields and meet harvesting timelines. This is a major problem in some agricultural regions, where land owners may be permitted to drain excess water from cropland.
In some urban areas, drainage law includes the natural enemy doctrine and the reasonable use doctrine. The natural enemy doctrine gives a land owner the absolute right to dispose of water that could cause damage to his property, such as flooding a basement. This excess water may be diverted into the city’s storm water system in most regions.
The reasonable use doctrine is more difficult to interpret, and is usually decided by a court if problems arise. This drainage law permits obstructing or diverting excess water if the action is reasonable. A land owner can only be held liable for damage to nearby property if his or her activity is considered an unreasonable solution. A judge or jury commonly looks at all the facts to determine if the reasonable use doctrine applies to individual cases.