navigation conditions, columbia lock and dam

NAVIGATION CONDITIONS, COLUMBIALOCK AND DAM, CHATTAHOOCHEE

RIVER, GEORGIA AND ALABAMAHydraulic Model Investigation

TECHNICAL REPORT NO. 2-571

July 1961

ARMY-MRC VICKSBURG, MISS.

PREFACE

A hydraulic model investigation of the proposed Columbia Lock and

Dam, Chattahoochee River, was authorized by the U. S. Army Engineer Dis-

trict, Mobile, in a letter dated 3 September 1958 to the U. S. Army Engi-

neer Waterways Experiment Station. The study was conducted in the Hy-

draulics Division of the Waterways Experiment Station during the period

September 1958 to June 1959.

During the course of the study Messrs. R. L. Bloor and J. H. Douma

of the Office, Chief of Engineers; Messrs. C. P. Lindner and L. R. Leach

of the U. S. Army Engineer Division, South Atlantic; and Messrs. G. W.

Gaines, W. C. Knox, A. M. Cronenberg, F. F. Escoffier, A. F. Baer, A. W.

Kerr, and Claude Colquitt of the Mobile District visited the Waterways

Experiment Station at different times to observe certain model tests and

discuss test results. The Mobile District was kept informed of the

progress of the study by monthly progress reports and special repqrts at

the end of each test.

The investigation was conducted under the general supervision of

Mr. E. P. Fortson, Jr., Chief of the Hydraulics Division, and Mr. G. B.

Fenwick, Chief of the Rivers and Harbors Branch, and under the direct

supervision of' Mr. J. J. Franco, Chief of the Waterways Section. The

engineer in immediate charge of the model was Mr. J. E. Glover, assisted

by Messrs. Lloyd Woods, 0. H. Rhodes, and A. E. Hullum. This report was

prepared by Messrs. Glower and Franco.

Col. Edmund H. Lang, CE, was Director of the Waterways Experiment

Station at the time of this investigation; Mr. J. B. Tiffany was Technical

Director.

iii

CONTENTS

PREFACE

SUMMARY

PART I: INTRODUCTION..

The Apalachicola, Flint, anColumbia Lock and DamPlanned Method of OperationNeed for, Scope, and Purpos

PART II: THE MODEL.......

DescriptionScale RelationsAppurtenancesModel Adjustment . .

PART III: TESTS AND RESULTS

Types of TestsTest ProcedureOriginal Design......Plans A and AlPlans B, Bl, and B2Miscellaneous TestsPlan CPlan DPlans E and El

PART IV: DISCUSSION OF RESULTS,

Limitations of Model Results . .ConclusionsRecommendations

PHOTOGRAPHS 1-9

PLATES 1-19

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vii

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Chattahoochee Waterway ..... 1

of Model Study..... ......... 2

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CONCLUSIONS AND RECOMMENDATIONS 0

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SUMMARY

Columbia Lock and Dam, proposed for construction on the Chattahoo-chee River, will provide a navigable pool extending upstream 28.7 miles tothe Walter F. George Lock and Dam. The model investigation was concernedwith the study of navigation conditions in the lock approaches to determinethe adequacy of the proposed design, and with the development of measuresto overcome or minimize the effects of any adverse conditions. An undis-torted model, scale 1:100, reproducing approximately 1.5 miles of theChattahoochee River including the lock and dam structure was used for theinvestigation.

Tests indicated that, because of the position of the lock and damwith respect to the channel alignment, currents moving from the left banktoward the dam will cross the upper approach to the lock. Downbound towsapproaching the lock would have to maintain sufficient steerageway toovercome the effects of these currents which would tend to rotate the towin a clockwise direction as the bow of the tow entered slack water or movethe tow riverward of the lock guard wall as the tow moved across the cur-rents. Navigation conditions in the upper approach can be improved by:extending the proposed excavation along the left bank landward so thattows can negotiate the turn into the approach farther upstream beforelosing steerageway due to reducing speed to enter the lock approach; ex-tending the guard wall upstream to provide greater protection from cross-currents for tows attempting to maneuver within the approach; installingports in the upper guard wall; and installing a training dike to deflectflow into the upper lock approach.

No navigation difficulties are expected in the lower lock approach.

vii

-N- GULF

it OF MEXICO

SCALE IN MILES

100 0 100 200

Fig. 1. Location map

NAVIGATION CONDITIONS, COLUMBIA LOCK AND DAM

CHATTAHOOCHEE RIVER, GEORGIA AND ALABAMA

Hydraulic Model Investigation

PART I: INTRODUCTION

The Apalachicola, Flint, and Chattahoochee Waterway*

1. The Columbia Lock and Dam, proposed for construction on the

Chattahoochee River 46.5 miles above its mouth and about a mile south of

Columbia, Alabama, is a unit in the Apalachicola, Flint, and Chattahoochee

Waterway (see fig. 1). In order to develop the full potential of the

waterway, a comprehensive plan providing for flood control, power, and

navigation was authorized in Section 2 of the River and Harbor Act of

March 2, 1945, Public Law No. 14, Seventy-ninth Congress, first session,

and in Section 1 of the River and Harbor Act of July 24, 1946, Public Law

No. 525, Seventy-ninth Congress, second session, and modified by the

resolution of the House of Representatives adopted May 19, 1953. This

project provides for a channel, 9 ft deep and 100 ft wide, from the mouth

of the Apalachicola River to Columbus, Georgia, on the Chattahoochee

River, and to Bainbridge, Georgia, on the Flint River by the construction

of navigation-power dams at the junction of the Flint and Chattahoochee

Rivers (Jim Woodruff Dam) and near Ft. Gaines, Georgia (Walter F. George

Dam); a low navigation dam between the Jim Woodruff and Walter F. George

Dams near Columbia, Alabama (Columbia Lock and Dam); a multipurpose dam at

Buford, Georgia (Buford Dam), on the upper Chattahoochee River; and sup-

plemental channel work in the Apalachicola River. Other flood-control and

power elements of the comprehensive plan have not yet been authorized for

construction. The elements of the plan authorized for construction, with

the exception of the Columbia Lock and Dam, are all in progress or

completed.

* Prototype information obtained principally from: Design Memorandum No.3, Columbia Lock and Dam, Chattahoochee River, Georgia and Alabama,U. S. Army Engineer District, Mobile, Alabama; House Document No. 342,76th Congress; and House Document No. 300, 80th Congress, 1st session.

Columbia Lock and Dam

2. The Columbia Lock and Dam will provide a normal upper pool

elevation of 102.0.* This will provide a 9-ft navigable depth extending

28.7 miles upstream to Walter F. George Lock and Dam; however, some chan-

nel improvement will be necessary at the upper end of the pool. The dam

will consist of (a) a gated section, containing four tainter-gate bays,

each with a clear width of 60 ft, and having a crest elevation of 82.0,

and (b) a 340-ft fixed-crest section with crest at elevation 102.0. The

lock will have clear dimensions of 82 by 450 ft and a maximum lift of

25 ft.

Planned Method of Operation

3. During the greater part of the year when the flow in the Chatta-

hoochee River is low, it is planned to operate the turbines at the Walter

F. George powerhouse only during hours of peak demand. This type operation

will cause flow in the Columbia pool to fluctuate from practically zero to

as much as 30,000 cfs daily. In order to narrow the range of discharge

over the Columbia spillway and build up the tailwater elevation gradually,

it is planned to regulate headwater levels and discharges at the gated

spillway. The pool at the Columbia Lock and Dam will be drawn down to an

elevation not less than 96.0 starting about an hour and a half before the

turbines at the Walter F. George powerhouse are put into operation. The

pool drawdown surge thus created will move progressively up the reservoir,

and about the time it would begin to affect the upper end of the pool,

power operation of the Walter F. George powerhouse will begin and the surge

generated by the turbine discharge will move downstream, counteracting and

quickly reversing the drawdown surge in the Columbia pool.

Need for, Scope, and Purpose of Model Study

4. The original design of the Columbia Lock and Dam was based on

* All elevations are in feet above mean sea level.

sound theoretical design practice and experience with similar structures.

However, navigation conditions vary with location and flow conditions up-

stream and downstream of a structure, and an analytical study to determine

the hydraulic effects that can reasonably be expected to result from a

particular design is both difficult and inconclusive. Thus a comprehen-

sive model study to investigate these effects was considered necessary.

5. The location of Columbia Lock and Dam just downstream of a bend

in the river, and the arrangement of the structures with the lock on the

left bank below the point of the bend were already fixed at the time of

the model study. Therefore, the specific purposes of the model tests were

to demonstrate flow conditions that would occur in the upper and lower

lock approaches at various river flows, and to assist in development of

any modifications--other than relocating or rearranging the structures--

that might eliminate or minimize undesirable conditions.

PART II: THE MODEL

Description

6. The model reproduced a short reach of the Chattahoochee River,

extending from 4000 ft above to 4200 ft below the proposed site for the

Columbia Lock and Dam (fig. 2). The model was of the fixed-bed type with

Fig. 2. Site map

the greater part of the channel and overbank area molded in sand-cement

mortar, and the remainder, consisting of areas along the left bank likely

to be modified during the study, molded in pea gravel to sheet-metal tem-

plates (fig. 3). The dam crest, lock, and guard walls were fabricated of

sheet metal. Piers on the gated section of the spillway were made of Plexi-

glas. The lock and dam gates were simulated schematically with sheet-metal

slide-type gates since their only function was to maintain the upper pool

at the desired elevation without regard to gate opening or stilling basin

act i on.

Fig. 3. The model

7. The model was molded in accordance with a 1953 hydrographic

and topographic survey except for areas proposed for dredging which were

molded to the after-dredged condition. Sufficient overbank area was in-

cluded in the model to contain the maximum navigable pool (a pool eleva-

tion of 114.0 at a discharge of 86,000 cfs).

Scale Relations

8. The model was built to an undistorted scale ratio of 1:100,

model to prototype, to obtain accurate reproduction of velocities, cross-

currents, and eddies that would affect navigation. Other scale ratios

resulting from the linear scale ratios were: area, 1:10,000; velocity and

time, 1:10; discharge, 1:100,000; and roughness (Manning's "n"), 1:2.15.

Appurtenances

9. Water was supplied to the model from a comprehensive circulating

system, and discharge was measured with a venturi meter. Water-surface

elevations were measured by means of 10 piezometers located in the model

channel and connected to a centrally located gage pit. Upper pool stages

were controlled by opening and closing the dam gates; tailwater elevations

were controlled by means of a tailgate located at the lower end of the

model.

10. Velocities and current directions were determined in the model

by means of wood cylinder floats weighted on one end to simulate the maxi-

mum permissible draft for loaded barges using the waterway (9-ft proto-

type). A model tow and towboat, shown in fig. 4, were used to determine

Fig. 4. Model towboat and tow

and demonstrate the effects of currents on tows navigating the lock ap-

proaches. The over-all length and width of the towboat with tow simulated

the largest tow for which the lock was designed (78 ft wide by 450 ft

long) with a draft of 9 ft; the dimensions of the towboat itself were not

to scale. The towboat was equipped with twin, screw-type propellers

powered by a small electric motor operating from batteries located in the

tow. The towboat was controlled electronically by remote control and

could be made to run in forward or reverse, at variable speed, and at

various sets of the' rudders.

Model Adjustment

11. Inclusion of the proposed plan in the initial model construc-

tion precluded adjustment of the model to existing prototype conditions.

This type of adjustment was not considered necessary since the proposed

improvements would involve a radical change from existing conditions. The

model surface was of brushed cement mortar, providing a roughness

(Manning's "n") of about 0.0135, which corresponds to a prototype rough-

ness of about 0.029. Based on experience with other models of this type,

brushed concrete gives a very close approximation of the roughness re-

quired to reproduce prototype conditions. Because of the short reach of

river included in the model, any errors in the simulation of prototype

roughness would produce too small an error in the water-surface elevation

to appreciably affect test results.

8

PART III: TESTS AND RESULTS

Types of Tests

12. Tests were concerned primarily with the study of currents and

velocities and the behavior of the model tow in the lock approaches with

various riverflows, dredging plans, and alterations of the lock guard

wall simulated. Also included in the testing program were studies to de-

termine the velocities of currents impinging on the riverbank opposite the

lock discharge outlet during lock emptying, currents around the landside

lock wall during lock filling, and the effect of flow through the gated

spillway on navigation conditions in the lower lock approach. The model

scale was not sufficiently large to permit a study of the discharge coef-

ficients of the spillways or the effectiveness of the stilling basin.

These features were studied on larger-scale section models, and results

of these tests will be presented in a separate report.

Test Procedure

13. Tests consisted of reproducing selected, representative river-

flows (both controlled and uncontrolled) and determining current veloc-

ities and directions and their effects on the model tow. Controlled river-

flows were reproduced by introducing the proper discharge, setting the

tailwater elevation for that discharge, and manipulating the dam gates

until the required upper pool elevation was obtained. Except in certain

instances, all controlled-riverflow tests were conducted with all dam

gates opened the same amount. Uncontrolled riverflows were obtained by

introducing the proper discharge with the dam gates open full, and

manipulating the tailgate until computed tailwater elevation for that

flow was obtained. Lock-emptying discharges were simulated by filling the

lock and adjusting the lock-emptying valve until the rate of emptying was

the same as the computed rate. All flows were permitted to stabilize be-

fore any data were recorded. Representative flows selected for testing

and/or demonstrations included the following:

a. Flow of 20,000 cfs with upper pool at elevation 96.0 (normal

All of the

stages.

hinged-pool operation). Peak flow from all units atWalter F. George powerhouse regulated by operation ofspiliway gates. This flow was also tested with anormal upper pool elevation of 102.0.

b. Flow of 32,000 cfs with upper pool at elevation 96.0(hinged-pool operation). This is the maximum capacityof the Columbia spillway with all gates fully open andpool at lowest elevation permissible.

c. Flow of 32,000 cfs with normal upper pool elevation of102.0. This is the normal condition with peak flow fromthe Walter F. George powerhouse and local inflow.

d. Flow of 45,000 cfs with normal upper pool elevation of102.0. This is the capacity of the Columbia spillway withall gates fully open. This condition is expected to occurabout two or three times a year for periods of about fourdays.

e. Flow of 86,o000 cfs with upper pool elevation 114.0. Thisis the maximum flow at which navigation through the lockis feasible. It is expected to occur about once in threeyears for a duration of about 10 days.

above-listed flows were reproduced in the model as constant

14. Velocities were determined by timing the travel of the floats

described in paragraph 10 over a measured distance; current directions

were ascertained by plotting the paths of the floats with respect to

ranges established for the purpose. In plots of currents in turbulent

areas or where crosscurrents existed, only the main trends are shown for

clarity. The model towboat and tow were observed to determine the effects

of currents on their behavior and the maneuvering required to overcome the

effects of adverse currents in approaching the lock. Some of the current

patterns were determined by taking vertical, time-exposure photographs of

the movement of the wood floats. To obtain current velocities, an

electronic flash was operated during the time exposure, thus superimposing

the location of the floats on the photographs at known time intervals.

The distance between the float locations as defined by two successive

flashes and the time interval were used to compute velocities. Velocities

obtained during lock emptying were, verified by setting a constant lock dis-

charge equal to the maximum instantaneous lock discharge and measuring ve-

locities along the riverbank opposite the lock discharge outlet with a ve-

locity meter.

9

10

Original Design

Description

15. The original design proposed for the Columbia Lock and Dam is

shown in fig. 5. The essential features of this plan were:

a. A lock near the left bank with clear chamber dimensions of450 by 82 ft and with tops of the lock walls at elevation115.0.

b. A 500-ft-long upper guard wall and a 370-ft-long lowerguard wall.

c. An approach channel from the lock to a point about 2400 ftupstream obtained by dredging the left bank to a bottomelevation of 83.0.

d. A lower approach channel obtained by dredging the left bankto a bottom elevation of 64.0 for a distance of about 2300ft from the lock to where the approach channel joined thenavigation channel which was dredged to a bottom elevationof 67.0.

e. A 620-ft-long dam, of which 280 ft was gated spillway witha crest elevation of 82.0, and 340 ft was fixed-crestspillway with a crest elevation of 102.0. The gated spill-way was equipped with four tainter gates, each 60 ft wideby 21 ft high.

f. An upstream approach to the gated spillway excavated toelevation 77.0, and an exit area below the spillway ex-cavated to elevation 72.0.

Results

16. Velocities and current directions obtained during the test of

this plan are shown in photographs 1-6 and reveal that high-velocity cur-

rents occurred just riverward of the bend in the left bankline immediately

above the lock. Velocities near the left bank of the bend were 1.3 to 2.0

fps with a 20,000-cfs flow (photograph 1), 3.2 to 4.4 fps with a 45,000-

cfs flow (photograph 2), and 4.0 to 6.5 fps with an 86,000-cfs flow (photo-

graph 3). During low flows, the high-velocity currents moved from along

the left bank to the spillway, passing close to the end of the upper guard

wall of the lock. Dulring~ the higher flows, the high-velocity currents

followed the same general alinment, except that they tended to swing

farther riverward of the end of the guard wall.

1-7. The currents moving from the left bank toward the end of the

guard wall would provide a strong crosscurrent in the path of" a tow

POLI EL 15.0PNORAL UPPER PO

EL 102.0

2 MIRYW R P T7.

FLOOR a 0 Q

TYPICAL SECTION THROUGH LOCK

20 0 20 40 60FT

yi

. ETYPICAL SECTION FIXED-CREST

SPILLWAY

10 0 10 2 0 2.F

LEGEND

8 GAGE NUMBER AND LOCATION- - CONTOURS BELOW POOL ELEVATION

---- CONTOURS ABOVE POOL ELEVATION

PARTIAL PLAN GATED SPILLWAY

30 0 30 60 90FT

," .. ."'EL VA R/ES".:." _:.: .. "'n...w..."..": v

TYPICAL SECTION GATED SPILLWAY

10 0 10 20 0 FT

SCALES IN FEET

ROTOTYPE 200 0 200 400 600 800

MODEL 2 0 2 4 6 a

Fig. 5. Plans and details of~ original design

12

attempting to enter or leave the upper lock approach. A downbound tow

attempting to turn into the lock approach would have its stern in high-

velocity currents with its bow in relatively slack water, and thus there

would be a strong tendency for the tow to be rotated counterclockwise.

Since the turn has to be made a short distance above the end of the guard

wall at a point where the speed of the tow should be reduced for entrance

into the lock approach, it would be difficult for the towboat to develop

sufficient steerage to overcome the effects of the crosscurrents, and the

tow would be in serious danger of hitting the end of the upper guard wall.

Since currents do not follow the left bank into the approach to the lock,

tows could not be made to enter the lock approach by flanking. Upbound

tows would tend to have their bows forced riverward by the high-velocity

currents from along the left bank. However, upbound tows could be under

full power and thus could develop sufficient steerageway to overcome the

effects of these currents.

18. In the lower lock approach, a fairly large eddy developed with

upstream currents of about 2.0 to 2.8 fps close along the left bankline.

River currents at the head of the eddy were generally less than 1 fps,

and occurred some distance downstream of the end of the guard wall (see

photographs 4-6). Tows could avoid the upstream currents close to the

left bank and approach the lower guard wall with practically no

difficulty.

19. Currents resulting from a lock-emptying operation with mini-

mum tailwater elevation (no flow over the spillway) impinged on the

right bank as shown in photograph 7. Maximum velocities measured along

the right bank opposite the lock-emptying outlet were in the order of

5 to 6 fps.

Plans A and Al

Description

20. Plan A, as shown in plate 1, was designed to improve navigation

conditions in the upper approach, and was the same as the original design

except for the following:

a. Additional dredging of the left bank was accomplished inorder to move the bend in the left bankline farther upstream.

13

This involved removing an additional 150 ft at the pointin the left bankline and extending the dredge cut about450 ft farther upstream.

b. Thirteen ports, 25 ft wide and with tops at elevation 93.0,were installed in the guard wall, and concrete sheet-pilecells were placed at the end of the guard wall to form a300-ft extension of the wall with 10-ft openings spaced asshown in plate 1. This modification was made in an effortto reduce the crosscurrents in the lock approach.

c. A training dike, consisting of ten 15-ft-diameter sheet-pile cells spaced on 30-ft centers, was placed opposite andjust downstream of the bend in the left bankline in an ef-fort to deflect flow into the lock approach.

d. A 50-ft wing wall was added at the upstream end of thelandside lock wall, angled 45 degrees therefrom to reducethe danger of tows hitting the end of this lock wall.

21. Plan Al was the same as plan A, except that the training dike

was eliminated. Only preliminary tests were conducted with plans A and Al

installed in the model.

Results

22. Velocities and current directions in the upper lock approach

with plans A and Al installed are shown in plates 2-4. With plan A, cur-

rents along the left bank moved into the lock approach. The eddy preva-

lent in the upper lock approach with the original design installed was

practically eliminated during the 45,000-cfs flow (plate 2) and was re-

duced appreciably during the 86,000-cfs flow (plate 3). The model tow

could not be made to drift into the approach with plan A. However, be-

cause of the location of the bend farther upstream and currents moving

into the lock approach, tows could maintain more speed and steerage and

thus overcome the effects of the crosscurrents, or could be flanked around

the bend and driven into the approach without serious difficulties.

23. Removal of the training dike in plan Al reduced the currents

moving toward the landside of the guard wall and increased the size and

length of the eddy along the left bank (plate 4). Because of the currents

moving toward the riverside of the guard wall, there was very little flow

through the ports in the guard wall. With this plan, tows could not be

flanked around the bend in the left bank. To enter the lock approach,

tows had to move with more power and steerage to overcome the effect of

the crosscurrents than with plan A.

14

Plans B, Bl, and B2

Description

24. Plan B was designed to improve navigation conditions in the

upper approach without the use of a training dike which might be ob-

jectionable to navigation and would increase cost of the project. The

features of this plan, shown in plate 5, included the following:

a. The excavation along the left bank was modified to movethe bend in the bankline farther upstream than in theoriginal design.

b. The exit from the stilling basin was excavated to eleva-tion 64.0 for a distance of 100 ft downstream of the basin.

c. The lock-emptying outlet was pointed more downstream so asto form a 60-degree angle with the lock wall instead of the80-degree angle utilized in the original design.

d. A 188-ft wing wall with three 10-ft openings spaced on 44-ft centers was added to the upper end of the upper guardwall. The wing wall was placed at a 15-degree angle withthe main wall.

25. Plan B1 was the same as plan B except that the wing wall was

276 ft long with five 10-ft openings spaced on 44-ft centers.

26. Plan B2 was the same as plan Bl except that 13 ports, 3 ft

high by 25 ft wide and spaced on 35-ft centers, were installed in the

upper guard wall. The tops of the ports were at elevation 86.0.

Results

27. Upper approach. Velocities and current directions (shown in

plates 6-10) and observations of the model tow indicated that the modifica-

tions incorporated in plan B effected some improvements in navigation con-

ditions in the upper lock approach over those obtained with the original

design. The modifications of plan B did not appreciably affect the cur-

rents moving from the left riverbank toward the end of the wing wall, and

downbound tows would still encounter difficulty negotiating the bend along

the left bank upstream of the lock. During lower flows, tows would en-

counter essentially the same conditions as with high flows, but because of

the lower velocities, the effects of the adverse currents could be over-

come with less difficulty.

28. The increase in the length of the wing wall in plan Bl made

15

little difference in direction or velocity of the currents moving from the

point of the bend toward the end of the wing wall (see plate 11). Naviga-

tion conditions were somewhat better, however, because of the greater

maneuver area provided by the longer wall, and tows would be provided

greater protection from currents moving toward the spillway.

29. Installation of ports in the guard wall in plan B2 permitted

some flow landward of the guard wall and reduced considerably the in-

tensity of crosscurrents at the end of the wing wall (plate 12). Tests

with the model towboat and tow indicated that tows could navigate the

reach from the bend to the lock with less difficulty than was encountered

with either plan B or Bl. The flow through the ports was not sufficient

to permit tows to be flanked around the bend along the left bank and into

the approach. However, tows could drive into the lock approach with less

power and steerage than with plan Bl.

30. Lower approach. No serious navigation difficulties were en-

countered in the lower approach to the lock with either plan B, Bl, or B2

installed. The intensity of the eddy in the lower lock approach below the

end of the guard wall was generally low. The upstream currents along the

left side of the eddy were close to the left bank, either out of the

navigation channel or in a position where they could be easily avoided.

Crosscurrents at the upstream and downstream ends of the eddy were less

than 1 fps and would not have any appreciable effect on the movement of

a tow.

Miscellaneous Tests

Effects of spillway gate openings

31. Tests on a model of a section of the gated spillway, which were

in progress at this time, indicated that during certain controlled river

discharges, waves would be generated in the stilling basin and might ex-

tend into the lock approach. The conditions were set up in the navigation

model with plan B installed, and the highest waves were obtained with a

discharge of 36,000 cfs, a tailwater elevation of 97.8, and the four

spillway gates open 10 ft. These waves extended downstream into the lower

lock approach, where their maximum height was about 0.5 ft. The waves

16

bending around the end of the lower guard wall would tend to move the bow

of a tow landward as the tow approached the lock wall. The height of the

waves was reduced to about 0.2 ft by opening the two center spillway gates

4.0 ft and the two end gates 14.5 ft, and the tendency for tows to be

moved landward was practically eliminated. The effects of the waves on

current directions in the lower approach are shown in plate 13.

Headwater-tailwater relation

32. The headwater-tailwater rating curve, shown in plate 14, in-

dicates that the swellhead over the dam will vary from about 1.3 ft at a

discharge of 45,000 cfs to about 0.7 ft at a discharge of 86,000 cfs.

Lock-emptying operations

33. A typical flow pattern obtained during lock-emptying opera-

tions at minimum tailwater elevation and no river discharge is shown in

photograph 8. The direction of flow from the outlet was diverted toward

the right bank where a clockwise eddy formed upstream and a counterclock-

wise eddy formed downstream of the point of impingement. The flow pat-

tern and the maximum velocity measured along the right bank opposite the

outlet were about the same as in the original design. Velocities along

the right bank were in the order of 5 to 6 fps. The flow pattern during

lock emptying would be altered considerably with discharge through the

dam gates, and the impingement of currents against the right bank would

be reduced.

Lock-filling operations

34. Lock-filling operations were simulated in the model by opening

the upper lock gate in accordance with a lock-filling curve furnished by

the Mobile District. Currents, indicated by floats as shown in photograph

9, indicated that an eddy would form just downstream of the end of the

landside lock wall, but that it would not be of sufficient intensity to

affect appreciably the capacity of the lock intake manifold. It should

be realized that if the lock is filled by means of an intaike manifold in

the landside wall, the current pattern during a lock-filling operation

might be somewhat different, and the intensity of the eddy might be

reater than indicated in this test in which filling was accomplished

thrug the lock gate.

17

Plan C

Description

35. Plan C was designed in a further effort to obtain satisfactory

navigation conditions without the training dike of plan A and effect

economies in construction. Plan C was the same as plan A (plate 1) with

the following exceptions:

a. The alignment of the lower end of the dredge cut along theleft bank was modified slightly so that the 400-ft lengthof cut above the end of the lands ide lock wall was thesame as in the original design.

b. The upper end of the dredge cut above the bend was warpedfrom a 1-on-3 to a 1-on-6 slope.

c. The training dike was eliminated, and the 300-ft guard-wall extension was replaced by the 188-ft wing wall ofplan B (see plate 5).

d. Ports in the guard wall were eliminated.

e. The landside wing wall was eliminated.

Results

36. Velocities and current directions for the maximum navigable

flow, shown in plate 15, indicated little difference in the alignment

and velocity of currents from those obtained during the test of plan B

(see plate 10). Navigation conditions were better than with plan B because

the bend in the bank was farther upstream, and because of the increased

maneuver area landward of the guard wall. Therefore, tows could begin

the turn for the approach farther upstream where more speed and steerage-

way could be maintained.

Plan D

Description

37. Plan D involved the modification of the left bank, as in-

dicated by the normal upper pool lines in plate 15. The left bank was

straightened from a point about 800 ft above the end of the landside lock

wall to a point about 1800 ft upstream, where it intersected the existing

bankline. All other conditions were the same as with plan C.

Results

38. Velocities and current directions in the upper lock approach

for the maximum navigable flow (shown in plate 15) revealed that the size

and intensity of the eddy in the upper approach were increased, and cur-

rents from the left bank moved farther riverward of the lock wall than

with plan C. Tows would have less difficulty in negotiating the bend up-

stream of the lock than with plan C, but because of the intensity of the

eddy and irregularities in the alignment of currents within the eddy,

more difficulty would be experienced in maintaining the alignment of the

tow.

Plans E and El

Description

39. Plans E (plate 16) and El included the excavation of the left

bank as in plan B together with modifications of the guard wall as follows:

a. Plan E. The guard wall was 484 ft long and contained 32ports, each 3 ft high by 5 ft wide, spaced on 15-ft centerswith their tops at elevation 86.0. The wing wall was 200ft long, was placed at a 15-degree angle with the guardwall, and contained three ports, each 10 ft high by 20 ftwide spaced on 60-ft centers with their tops at elevation93.0.

b. Plan El. This plan was the same as plan E, except that 16ports on -the downstream end of the guard wall wereeliminated.

Results

40. Current directions and velocities indicated that ports in the

upper guard wall would facilitate the movement of downbound tows approach-

ing the lock, particularly during lower flows (plate 17). During higher

flows (plate 18) the amount of flow through the ports was relatively small,

and the effect of the ports on navigation conditions was not as great as

during the lower flows. Eliminating ports in the lower half of the guard

wall (as in plan El, see plate 19) decreased the flow landward of the

guard wall and increased the intensity of the crosscurrents near the end

of the wall, thus increasing the difficulty tows would encounter in ap-

proaching the lock.

19

PART IV: DISCUSSION OF RESULTS, CONCLUSIONS AND RECOMMENDATIONS

Limitations of Model Results

41. The analysis of the results of this investigation is based

principally on a study of currents and velocities in the upper and lower

approaches to the lock, and the effects of these currents on the behavior

of the model towboat and tow. In evaluating test results, it should be

borne in mind that small changes in direction of flow or in velocities are

not necessarily changes produced by a change in plan, since several floats

introduced at the same point may follow slightly different paths and move

at slightly different velocities. Current directions as shown in the

photographs and plates, except for those obtained during lock-emptying

operations, were obtained with floats submerged 9 ft (prototype) and

should be indicative of currents that will affect the behavior of tows.

Because of the small model scale, it was difficult to reproduce accurately

the hydraulic characteristics of the prototype structures or to measure

water-surface elevations within an accuracy greater than +0.1 ft (proto-

type). For this reason, data showing the swellhead produced by the lock

and dam structure and the amounts of gate openings should be considered

only as approximations. Also, the rate of damping of waves in the model

is greater than would be the case in the prototype because of the effect

of surface tension. The wave heights measured in the model in the lower

approach therefore are probably lower than those to be expected in the

prototype.

Conclusions

42. The results of tests of navigation conditions at the Columbia

Lock and Dam indicate that, because of the arrangement of the lock and dam

with respect to the alignment of the channel, currents moving toward the

dam from along the left bank cross the approach to the lock. In order to

enter the lock, downbound tows must change direction of approach. While

negotiating the turn, a tow would have its stern in high-velocity currents

with its bow in relatively slack water, resulting in a strong tendency for

20

the tow to be rotated counterclockwise and moved toward the dam. The tow

therefore must maintain sufficient speed and steerageway to overcome the

effects of these currents at a time when it should begin to reduce speed

for the approach. Since the location and arrangement of the lock and dam

were fixed by other considerations, the plans tested were designed to

minimize the effects of the crosscurrents and to develop methods which

would facilitate the movement of tows into the lock approach. The re-

sults of these tests are the basis for the following conclusions:

a. No difficulties should be encountered by navigation in thelower approach. With certain tailwater conditions, waveswill develop within the stilling basin of the gated spill-way and extend into the lower lock approach. The waveswill tend to move the bow of a tow landward as it ap-proaches the lock wall. However, the height of the waveswill be generally less than 1 ft, and their effect ontows approaching the lock will be slight. Also, the heightof the waves can be reduced by proper manipulation of thespillway gate openings.

b. It would not be possible for tows to drift into the upperlock approach with any of the plans tested because of theset of the currents and the eddy along the left bank abovethe lock. Also, tows would not be able to negotiate theturn into the upper approach to the lock by flanking, sincecurrents would not follow the alignment of the left bankexcept with plan A, which utilized a training dike to de-flect flow into the approach.

c. Navigation conditions in the upper approach can be im-proved by the following:

(1) Excavation of the left bank so as to place the bendin the left bankline far enough upstream to permittows to negotiate the turn before beginning to losesteerageway following reduction in speed to enterthe lock approach.

(2) Extension of the guard wall with a wing wall so as toprovide a larger maneuver area and greater protectionfrom crosscurrents for tows moving close to the endof the wall.

(3) Installation of ports in the upper guard wall. Flowthrough ports in the lock guard wall would tend tofacilitate the movement of downbound tows into thelock approach. Because of the location of the lockand dam with respect to the bend upstream, flowthrough the ports would be small unless a favorablehead differential is developed by deflecting flow intothe lock approach by a training dike or dikes, or by

21

extension of the guard wall into the currents movingfrom the left bank toward the gated dam. Normally,as flow through the ports is increased, the speed atwhich a downbound tow would drift toward the guardwall and the difficulty an upbound tow would encounterin pulling away from the wall will be increased unlessthe tops of the ports are well below the bottom of aloaded barge. Since flow through the ports was gener-ally small, no difficulty would be expected with anyof the ports tested in the main wall. Lowering thetops of the ports in the wing wall to elevation 93.0would reduce the difficulty tows would encounter inmaneuvering near the end of the guard wall withoutadversely affecting navigation conditions in otherareas within the approach.

d. No difficulties should be encountered in the upper approachby upbound tows leaving the lock with any of the planstested.

e. Flow from the lock-emptying system will not produce veloc-ities along the right bank greater than those which wouldresult from normal riverflows.

Recommendations

43, Based on the results of this investigation it is recommended

that the following minimum modifications of the original plan be included

in the design of Columbia Lock and Dam:

a. Excavation along the left bankline as provided by plansB and E.

b. Extension of the guard wall with a wing wall about 200 ftlong.

c. Installation of ports in the guard-wall extension (wingwall) and in the main wall.

Photograph 1. Velocities and current directionsin upper lock approach, original design.

Discharge, 20,000 cfs; upper pool el 102.0





Photograph 4. Velocities and current directionsin lower lock approach, original design.Discharge, 20,000 cfs; tailwater el 87.9

Photograph 5. Velocities and current directionsin lower lock approach, original design.

Discharge, 45,000 cfs; tailwater el 100.17

Photograph 6. Velocities and current directions

in lower lock approach, original design.

Discharge, 86,000 cfs; tailwater el 113.3

4,

Photograph 7. Typical flow pattern during lock-emptying operation, orig-inal design. Discharge through dam, none; tailwater el 77.0; upper pool

el 102.0; lock-emptying time, 7 minutes

Photograph 8. Typical flow pattern during lock-emptying operation, plan B.Discharge through dam, none; tailwater el 77.0; upper pool el 102.0; lock-

emptying time, 7 minutes (compare photographs 7 and 8)

Photograph 9. Plan B2:tion. River discharge,

lock-filling time, 7

Typical flow pattern during lock-filling opera-none; upper pool el 102.0; tailwater el 77.0;minutes. Lock filled through upper lock gate

fi :ytt:

/O' 65' /0' 465'

/3 PORTS /0'X25' SPACED ON 35' CENTERS

00 D 30 0 90FT

LEGEND4@ GAGE NUMBER AND LOCATION

CONTOURS BELOW POOL ELEVATION-- " CONTOURS ABOVE POOL ELEVATION

IEL 1150

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TYPICAL SECTION THROUGH PORT

PLAN APLAN A

SCALES IN FEET

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SCALES IN FEET

PROTOTYPE 200 0 200 400 600 800

MODEL 1 0 1 3 4 5 6 7 8

LEGEND

68 --- - FLOAT VELOCITY IN FPS

NOTE; VELOCITY AND CURRENT DIRECTIONFLO~ATS SUBMERGED 9.0 FT.

VELOCITIES ANDCURETDRCIN

DISCHARGI 500 F

. A

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R20

NORMAL UPPER POOL EL 102 . -~~

POOL EL 1140 SL

SCALES IN FEET

4 244 40MODEL o f 4 5s 7 6

LEGEND

---- "-. FLOAT VELOCITY IN FPS

NOTE: VELOCITY AND CURRENT DIRECTIONFLOATS SUBMERGED 1O FT.,EOIISADCRETDRCIN

VELOCIPLAN AAPI ~~DISCHARGI 600 F

AAA AMGuy ___duowearnrvoir Aw %,

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SCALES IN FEET

PROTOTYPE 200 0 200 400 800 800

MODEL I0 l2 3 45 6 7 8

LEGENDAL-.. FLOAT VELOCITY IN FPS

NOTE; VELOCITY AND CURRENT DIRECTIONFLOATS SUBMERGED 9.0 FT.

VELOCITIES ANDCURETDRCIN

DISCHARG 600 F

LEGEND

4e GAGE NUMBER AND LOCATION- CONTOURS BELOW POOL ELEVATION

-- CONTOURS ABOVE POOL ELEVATION


PLAN S2

SCALEipO 0 10 20 30 FTT

PLANS B,BI, AND B2SCALES IN FEET

PROTOTYPE 29Q 0 200 400 600 X00

MODEL 2 0 2 4 6 S

00

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LEGEND---- FLOAT VELOCITY IN FPS

NOTE : VELOCITY AND CURRENT DIRECT IONFLOATS SUBMERGED 9.0 FT.

NORMAL LOWER A 00L L776 -35 UPPER POOL- EL /020 FT MSL -' - $ ^

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SCALES IN FEET

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I 0 1 2 3 4 5 6 7 8 VELOCITIES AND CURRENT DIRECTIONSPLAN B

DISCHARGE, 20,000 CFS

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I 0 I 2 3 4 6 7 8

LEGENDa-+ FLOAT VELOCITY IN FPS

NOTE : VELOCITY AND CURRENT DIRECTIONFLOATS SUBMERGED 9.0 FT.

VELOCITIES AND CURRENT DIRECTIONSPLAN B

DISCHARGE 30.000 CFS

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PROTOTYPE 20

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38

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NORMAL UPPER POOL EL

NORMAL LOWER POOL EL 770, UPPER POOL EL /020 PT M;SL35 - \ - -

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SCALES IN FEET

0 200 4 1 40 600 800VELOCITIES AND CURRENT DIRECTIONS

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SCALES IN FEET

PROTOTYPE 2000 200dI C40T0 600 800l IRF

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PLAN BDISCHARGE 86,000 CFS

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MODEL

LEGEND

-- - FLOAT VELOCITY IN FPS

NOTE: VELOCITY AND CURRENT DIRECTIONFLOATS SUBMERGED 9.0 FT.

PROTOTYPE zoo

MOEL

DISCHARGE 86,000 CFS

SCALES IN FEET

0 00 400 ago 800

I 2 2 4 s a i a

MODEL STUDY OF COLUMBIA LOCK AND DAMCHATTAHOOCHEE RIVER

VELOCITIES AND CURRENT DIRECTIONSPLAN B I

DISCHARGES 32,000 AND 86,000 CFS

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FLOATS SUBMERGED 9.0 FT.

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SCALES IN FEET

0 200 400 600 800

1 0 1 2 3 4 5 6 7 8

VELOCITIES AND CURRENT DIRECTIONSPLAN 82


mUro

PROTOTYPE 200

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. ' ;GATES I AND 4 OPEN 145 FT

-"'~GATES 2 AND 3 OPEN 4.0 FT

SCALES IN FEET

0 a 00 40

MODEL

LEGEND. FLOAT VELOCITY IN FPS

Q( GATE NUMBER

NOTE: VELOCITY AND CURRENT DIRECTIONFLOATS SUBMERGED 9.0 FT.UPPER POOL EL 102.0 FT MSL

EFFECT OF GATE OPENINGS ONVELOCITIES AND CURRENT DIRECTIONS

PLAN BDISCHARGE 36,000 CFS

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HEADWATER -TAILWATERRATING CURVE

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UPPER POOL EL /14.0 PT MSL

NOTE;$ VELOCITY AND CURRENT DIRECTIONFLOATS SUBMERGED 9.0 FT.

PROTOTYPE

MODEL

PLAN D

SCALES IN FEET

r 0 r 2 a 4 s5Z8_7

VELOCITIES AND CURRENT DIRECTIONSPLANS C AND D

DISCHARGE 88,000 CFS

UPPER POOL EL 10OEO

6--°-.-.F LOA

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SCALE0 0 t0 20 0 FT

PLAN E.SCALE

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TYPICAL SECTION THROUGHWING WALL

SCALE10 0 10 20 30OFT

LEGEND

4 9 GAGE NUMBER AND LOCATIONCONTOURS BELOW POOL ELEVATIONCONTOURS ABOVE POOL ELEVATION

PLAN ESCALES IN FEET

PROTOTYPE 20) 0 200 400 600 5o

MODEL 2 0 2 4 6 a

NORMAL UPPER POOL EL /020

- .o , -°s 2-0

-s -0-C K

0108

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NORMAL UPPER POOL EL /020

LEGEND

°- FLOAT VELOCITY IN FPS

NOTE: VELOCITY AND CURRENT DIRECTIONFLOATS SUBMERGED 9.0 FT.

SCALES IN FEET

P oo o1 200o o 00 400 60 800 VELOCITIES AND CURRENT DIRECTIONSr MODEL I I 2 4 7 PLANE

DISCHARGE 32,00 CFS

K o-"-~ DISCHARGE 45,000 CFS ,"

- -~ NORMAL UPPER POOL EL /G.' ., -1

LEG ND " . - - - -

LEGETY ND RRNTDIECIO

DSHRE8,0CFOATS

SUBMERGED 9.0 FT.

SCALES IN FEET

PROTOTY 20P0 20E40 00 80

I 0 1 2 3 4 5 6 7 8

VELOCITIES AND CUR~RENT DIRECTIONSPLAN E


r

'a

NOTE; VE

FL

MODEL

NORMAL UPPER POOL EL /020 FT MSL

C-j 0~L~ 2

0

LEGENDasw- FLOAT VELOCITY IN FPS


SCALES IN FEET

L 2 I 2 3 4a 5s 8 s

VELOCITIES AND CURRENT DIRECTIONSPLAN El


TUrmom MODEL

eww aww

IPROTTYPE

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navigation conditions, columbia lock and dam

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