# (7.1) WATER DATA: Stream Gradient and Stream Velocity

Does Knowing The Stream Gradient Tell You the Approximate Stream Velocity?

An Information, Opinion, & Sources Report

Compiled by Ocklawahaman Paul Nosca

Created: 12 May 2013

Last Revised: 30 May 2015

Although I have yet to discover any scientific data that describes a mathematical formula used to calculate the STREAM VELOCITY (speed of the current) in miles per hour of a flowing river or creek if its STREAM GRADIENT (average elevation decline) in feet per mile is known--these seem to be my findings from personal canoe paddling experience (downstream & upstream) on various north Florida riverine sections containing no: abrupt constrictions of the main channel, "drop and pool" segments, rock shoal rapids, or waterfalls.

STREAM GRADIENT of 1 foot per mile = STREAM VELOCITY of about 1 mile per hour,

STREAM GRADIENT of 2 feet per mile = STREAM VELOCITY of about 2 miles per hour,

STREAM GRADIENT of 3 feet per mile = STREAM VELOCITY of about 3 miles per hour.

As an example, the swiftest segment of the Ocklawaha River (the 18 miles between the Silver River inflow & the Eureka CR-316 Bridge) descends downstream at an average gradient of about 1 foot per mile with an average current speed of about 1 mile per hour. Paddling a canoe upriver against this current is possible--but it slows the actual forward motion of the canoe by 1 mph. It is sort of like trying to walk south at a 4-mph pace while being on a 1 mph north-bound conveyor belt or escalator--the result is that you actually travel south-bound at only 3 mph! I can paddle my canoe on a still-water canal or lake without current or wind pushing against me at about 4 mph maximum.

Bacon and Black (1891) U.S. Army Corps of Engineers navigation survey report:

"Table No I...

Velocity per hour for lower river...miles...0.90...

Maximum velocity per hour...........do.....1.20..."

NOTE: The "lower river" refers to the Ocklawaha (in 1891) from "Silver Spring Run 53.1 miles" downstream to the "St. Johns River 0.0 miles." "Velocity per hour" means the speed of the river current (stream velocity) which was measured by the U.S. Army Corps of Engineers (in 1891) at an average of 0.90 mph with a maximum of 1.20 mph.

Beck (1965) "Streams of Florida" report:

"In my work I have found a descriptive terminology convenient for reporting velocities. Swift flow is that velocity in which Plecoptera are found in Florida. Moderate velocity is any velocity sufficient to maintain a population of Simuliidae (these are confined to running water in Florida). Any velocities below these two loosely defined levels are termed low. We have only recently obtained and started using velocity meters in our biological work. When the results of this work are available it will be interesting to see how well the actual measurements support the observed qualitative terminology."

"The Sand-Bottomed Stream:

"This is the most widely distributed and most frequently encountered type of stream in the state. It has been the most typical lotic feature of the area and is the one disappearing most rapidly with the alteration of drainage patterns. The sand-bottomed stream is a prominent feature of the Central Highlands (see Cooke, 1939, for a discussion of the topographic regions of Florida)...Typical faunal elements are...Plecoptera...Of all the lotic habitats this is the most typically so."

"Chemically and physically the sand-bottomed stream is mildly acid to circum-neutral (pH 5.7-7.4), has alkalinity ranging 5 to 100 mg/L, hardness from 5 to 120 mg/L, color moderate to high, and of moderate to swift velocity. Bottom deposits consist of fine sand with varying amounts of leaf and other organic detritus in the quieter reaches. Areas of limestone outcroppings are frequent. In the western panhandle the sand-bottomed streams are usually swifter and have coarser bottom deposits. Shifting sand bottoms are common. Plant growth may be slight to quite dense and of great variety."

"The Calcareous Stream:

"These streams are predominantly of spring origin and many of the finest examples have been carefully protected because of their beauty. Visitors to Florida find these a major attraction; a number of the larger springs and their runs have been developed commercially, and the natural aspects of most have been carefully preserved. These are, indeed, a striking sight with their cool, very clear waters, dense and varied growths of submerged plants, and banks shaded by large, moss-hung trees. The beauty of these streams is actually a limnologic feature in that it is the result of two factors; the clarity of the water itself and the high concentrations of phosphorous."

"Widely distributed in Florida, the calcareous stream is found in the Central Highlands..."

"The fauna of these streams is...represented by...and occasionally simuliids and Plecoptera."

"The waters are alkaline (pH 7.0-8.2), the alkalinity ranging from 20 to 200 mg/L, hardness from 25-300 mg/L (omitting the oligohaline and mesohaline springs of Whitford (1956)). The water is normally clear (some examples have a slight turbidity from small amounts of Montmorillonite clay in suspension) and generally low in color. Velocity ranges from low to swift."

"Bottom materials consist of sand, clay, limestone, and quite heavy deposits of organic detritus in the slower reaches. Submerged plant variety appears to be a function of bottom material."

The existence of the larvae of stoneflies (Order Plecoptera) in a Florida stream is an indication that its current flows swiftly and its water quality is good to excellent.

Specimens of the Order Plecoptera, Family Perlidae, Species Neoperla clymene have been collected from the Ocklawaha River basin.

NOTE: When the velocity (downstream current speed) of a river or creek exceeds 3 miles per hour it becomes nearly or actually impossible to paddle a canoe upstream against the current and make any forward progress. Fast-water portions of Georgia’s Chestatee River plus Florida’s Juniper Springs Creek, Chipola River, Aucilla River, and Suwannee River have defeated my upstream paddling attempts!

Bacon, J. H. & W. M. Black. 1891. "Report of the Chief of Engineers, U.S. Army; Appendix O - Report of Captain Black (page 1623); Improvement of the Ocklawaha River, Florida; Report of Mr. J. H. Bacon, Assistant Engineer, United States Engineer Department, St. Augustine, Fla., May 11, 1891." U.S. Army Corps of Engineers.

Beck, W. M. 1965. The streams of Florida, Bulletin of the Florida State Museum Biological Sciences. Vol. 10, No. 3, pp. 91-126, University of Florida, Gainesville, FL.

http://ufdc.ufl.edu/UF00000096

Pescador, M. L.; A. K. Rasmussen; & B. A. Richard. 2000. A guide to the stoneflies (Plecoptera) of Florida. 94 pp. Division of Water Resource Management, Florida Department of Environmental Protection, Tallahassee, FL.

http://www.docstoc.com/docs/109647233/Untitled---Florida-Department-of-Environmental-Protection-_FDEP