Definition
An inundation of water over land not ordinarily covered by it. In legal contexts, "flood" carries significance primarily in three areas:
1. Tort and contract law: A flood is the paradigmatic example of an Act of God — a natural event of such force and unpredictability that it excuses a party from liability or contractual performance that the event made impossible.
2. Property and insurance law: Whether a water event qualifies as a "flood" determines coverage obligations and exclusions under property insurance policies. Policies routinely distinguish flood damage from water damage caused by plumbing failure or storm surge, and the distinction drives litigation.
3. Water and riparian law: A flood event can affect property boundaries through sudden changes to watercourses, interacting with doctrines of avulsion and alluvion. A flood that dramatically and suddenly relocates a river channel may alter ownership boundaries differently than gradual erosion.
Common Language
Modern common usage (Wiktionary): Primarily references the biblical flood of Genesis; secondarily, any large inflow or overwhelming quantity of something.
Historical common usage (Webster's 1913): "A great flow of water... especially, a body of water, rising, swelling, and overflowing land not usually thus covered; a deluge; a freshet; an inundation." Also used for the flowing in of the tide, as opposed to ebb.
The gap between common and legal meaning is less about definition than about legal consequence. Everyday usage treats "flood" as a description of a physical event. Legal usage treats it as a category with doctrinal freight: once an event is classified as a flood, specific rules attach — Act of God defenses become available, insurance exclusions may be triggered, and property law doctrines governing sudden watercourse changes may apply. The classification question, not the physical event, is what courts actually fight over.
Common Confusion
Flood vs. storm surge vs. surface water: In insurance litigation, these distinctions are legally decisive. Courts and policies frequently disagree on whether water driven inland by a hurricane constitutes "flood" or a separate peril. Surface water — rainwater that has not yet reached a natural watercourse — may be treated as a distinct category under both insurance law and water rights doctrine. Researchers should not assume that judicial usage of "flood" is consistent across property, tort, and insurance contexts.
Flood vs. Act of God: A flood is an instance of an Act of God; the Act of God doctrine is the broader legal principle. The terms are not synonymous, though the historical dictionaries treat them almost interchangeably.
Why It Matters in Research
The historical dictionary entries are thin — both Anderson and Bouvier treat "flood" as essentially a cross-reference to Act of God, reflecting 19th-century legal priorities. Researchers using those sources for modern insurance or FEMA-related research will find them nearly useless for current doctrine.
The most consequential modern legal development is the National Flood Insurance Program (NFIP), established by federal statute, which created a standardized federal definition of "flood" for insurance purposes. This statutory definition does not map cleanly onto the common law Act of God cases cited by Bouvier and Anderson. Researchers working on post-1968 flood insurance disputes must consult the federal regulatory framework, not the historical dictionary tradition.
In riparian and property law, flood events connect directly to the avulsion/alluvion distinction. A sudden flood that relocates a boundary river is classified as avulsion, and the prior boundary generally holds. This is the connection Anderson signals by cross-referencing ALLUVION, and it remains live doctrine in states with significant river-boundary property disputes.
Historical case law on flood as Act of God arose largely in the context of common carrier liability — railroads and shippers arguing that flood-caused cargo loss was not their fault. Researchers in that area will find more useful material under Act of God and common carrier than under flood itself.
Jurisdictional variation matters significantly in the insurance context: state courts have split on how to classify hurricane-driven water intrusion, and federal flood insurance policy interpretation is governed by federal common law, not state insurance law, in cases involving NFIP policies.
Historical Dictionary Support
Both Anderson and Bouvier define flood minimally and by reference: Anderson points to Act of God and Alluvion; Bouvier offers a one-sentence definition — "an inundation of water over land not usually covered by it" — and immediately redirects to Act of God, citing an 1847 Delaware case. The substance of what the historical dictionaries treat as flood law is entirely embedded in the Act of God entries.
Webster's 1913 is actually more descriptive than either legal dictionary on the physical phenomenon, capturing the distinction between a rising inundation and tidal flow. The legal dictionaries of the period were not interested in flood as an independent concept — it was a trigger for other doctrines, not a doctrine in itself.
What the historical sources miss entirely: the regulatory and insurance dimensions of flood that dominate modern legal practice. There is no hint in Bouvier or Anderson of coverage disputes, federal flood mapping, or the classification problems that arise when multiple water sources combine during a storm event.
Jurisdictional Note
Federal law governs interpretation of NFIP flood insurance policies, and federal courts apply federal common law to policy disputes, displacing state insurance law. State law continues to govern flood-related Act of God defenses in tort and contract, riparian boundary disputes following flood events, and non-NFIP private insurance flood coverage litigation, where jurisdictional variation is significant.