Title: Mean Annual Flood
Full Citation
Permanent Link: http://ufdc.ufl.edu/UF00052647/00001
 Material Information
Title: Mean Annual Flood
Alternate Title: Memorandum from MGG to JWC re Mean Annual Flood, responding to the question: "Is the mean annual flood part of the stream?"
Physical Description: 4p.
Language: English
Publication Date: July 24, 1973
Spatial Coverage: North America -- United States of America -- Florida
General Note: Box 5, Folder 11 ( SF MEAN ANNUAL FLOOD ), Item 11
Funding: Digitized by the Legal Technology Institute in the Levin College of Law at the University of Florida.
 Record Information
Bibliographic ID: UF00052647
Volume ID: VID00001
Source Institution: University of Florida
Holding Location: Levin College of Law, University of Florida
Rights Management: All rights reserved by the source institution and holding location.

Full Text

July 24, 1972





Is the mean annual flood part of the stream?


For the purpose of determining ownership, there is no basis
in law, at this time, to support the proposition that the stream
and therefore the stream bed, is defined by the mean annual flood.


By the authority of g253.12(1), Florida Statutes, the state

is vested with title to the land underlying all navigable streams,

lakes and rivers. This land is deemed to be public property,

and although rights therein may be given, title cannot be granted

away. Holland v. Ft. Pierce Financing & Construction Co., 157

Fla. 649, 27 So. 2d 26 (1946).

To determine the nature and extent of ownership and to resolve

the questionepresented it is necessary first, to determine the

limits of a stream, and second, to determine the extent to which

the term "mean annual flood" comports with those limits.


I Florida case law states that the bed of the stream is

that "land below the ordinary high water mark." United States

v. Ray 423 F 2d 17 (C.A. Fla. 1970) at 20. ThAs, the limits

of a stream may be found by locating the high water mark.

The definition of "high water mark" was first articulated

by the Supreme Court of Florida in Tilden v. Smith. 94 Fla. 402,

113 So. 708 (1927). The Court adopted the Minnesota definition

stating at 712#

'" (the) high water mark..., a line between
a riparian owner and the public, is to be de-
termined by examining beds and banks, and
ascertaining where the presence and action of
the water are so comaon and usual, and so long
continued in all ordinary years, as to mark
upon the soil of the bed a character distinct
from that of the banks, irjweepeet to vegetation,
as well as respects the nature of the soil itself.."

The Court also noted a New Hampshire case, Dow, v.

Electric Co. 69 N. H. 498, 45A. 350, which stated:

'"The high-water mark on fresh water rivers
is not the highest point to which the stream
rises in times of freshets, but is the 'line
which the river impressed upon the soil by
covering it for sufficient periods to deprive it
of vegetation and to destroy its value for

From these descriptions it can be seen that the high water

mark is the product of a constant, sustained flow. It results

from the regular and continuous action of the stream; it is not

the line reached by the water at flood stages, nor is it the line

ordinarily reached by annual swellings of the stream possible

caused by a wet season. (See also, Maloney, Water Law and

Administration, University of Florida Press, 1968, pp 68-72)

Thus, the boundaries of a stream, marking the extent of

state ownership, should be clear upon inspection.

II Before diving into the mean annual flood, it is well

to keep in mind the common definition of "flood," or "flood

waters." This term is defined as "waters above the highest line

of the ordinary flow of the stream." Fla. Jor, Waters and

Watercourses, 553.

The "mean annual flood" is defined as "the flood having

a recurrence interval of 2.33 years." U. S .geological Survey Water

Supply Paper 1543-A at 5. The recurrence interval is equal to

the "average interval of time within which a flood of a given

magnitude will be equaled or exceeded once." Id. at 5. Briefly,

the mean annual flood is found by measuring and recording the

annual floods of a particular watercourse over a given interval

of time. This data is then weighed against known topographic

features and a curve is constructed.

One study has indicated that twelve years of record are

required to define the mean annual flood within 25 per cent.

Geological Survey Water Supply Paper 1543-A at 24.

The mean annual flood point is measured in cubic feet

per second. Thus, with this known volume it is not difficult to


determine the corresponding points on each side of the stream.

It should be noted that these points will be outside

the points designating the high water mark. Thus, at present,

there is no basis in law for holding that the state owns out to

the mean annual flood point, or stated another way, that the mean

annual flood is part of the stream.

It is not probable that mean annual flood will become a

standard in this regard in the near future. In many cases, topo-

graphic maps are not available for computing necessary topographic

characteristics for many parts of Florida. geological Survey

Supply paper 1543-A, at 30.

As an aside, the significance of the mean annual flood

is found in flood frequency analysis, a procedure useful in flood

plane zoning. using these techniques accurate estimates can be

obtained describing the extend of flooding of a particular water-

course over a number of years.


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