TECHNICAL PUBLICATION 79-1

FLOODPLAIN MANAGEMENT STUDIES

OF THE SHINGLE CREEK BASIN

Steve S. T. Lin

Jim Lane

Thomas McCann

Resource Planning Department

South Florida Water Management District

April 1979

ACKNOWLEDGMENTS

The purpose of this report is to provide a technical summary of the

studies carried out by the District from 1974 to 1979 in developing

a management plan for the Shingle Creek Basin. The studies were

conducted by the authors within the Water Resources Division, Resource

Planning Department. In addition, supportive analyses were carried

out during 1976-77 by Charles Tai, Technical Review Division, Resource

Control Department.

This report was compiled and edited by Susan McCormick, Director, Land

Resources Division, Resource Planning Department.

TABLE OF CONTENTS

LIST OF TABLES . . . . . . . . . . . - * * * . . . ii

LIST OF FIGURES ..... . . . . . . . . . . . . ..

DEVELOPMENT OF THE PLAN . . . . .. ................ .. 1-3

PHASE I STUDY . . . . .... . . . . . . ... . . . . . . 3-7

PHASE II STUDY ....... . . ................ ... 7-11

DISCUSSION OF PHASE I AND II STUDIES . ... . . . . . . . 11-16

PHASE III STUDY ... . . .. . .................. . 17-24

DISCUSSION OF PHASE III STUDIES ... . . . . . . . . . . . 24-25

REFERENCES ... . . . . . .................... . . 26

TABLES .................... ....... 27-37

FIGURES .... ...... ........ . ........ 38-70

LIST OF TABLES

Number Title Page

1 Peak Discharge Under Future Full Development. . . 27

2 100 Year Flood Peak Discharge Along ShingleCreek . . . . . . . . . . . . . . . . . . . . . . 28

3 100 Year Flood Index Flooding Duration Along

Shingle Creek . . . . . . . . . . . . . . . . . . 29

4 Shingle Creek 100 Year Flood Stage ....... 30

5 100 Year Flood Profile With Existing Land Use -No Improvement in Bridge Section - With On-Stream

Retention (Higher Head Weir) In Shingle Creek -

Initial Stage - 58.50 ft. msl .......... 31

6 100 Year Flood Profile With Existing Land Useand No Improvement In Bridge Sections. ReedyCreek Swamp Inflow Included with Initial Stage

of 57.50 ft. msl at Lake Tohopekaliga ...... 32-33

7 100 Year Flood Profile With Existing Land Use

and Improvement in Bridge Sections. Reedy Creek

Swamp Inflow Included With Initial Stage of

57.50 ft. msl at Lake Tohopekaliga . . 34-35

8 100 Year Flood Profile With Existing Land Useand No Improvement in Bridge Section - ReedyCreek Swamp Inflow Included With Initial Stage

of 58.50 ft. msl at Lake Tohopekaliga ...... 36

9 100 Year Flood Profile With Bridge Improvementand By-pass Channel - Initial Stage of 58.50ft. msl ..................... 37

LIST OF FIGURES

Number Page

1 Rating Curve at Sta. 747+00 With and Without

Weir . . . . . . . . . . . . . . . . . . . . . . 38

2 Stage, Storage, and Discharge Relation for Reach

No. 11A with On Stream Structure ... ..... .. 39

3 Comparisons of Inflows and Outflow HydrographsFrom Large Cypress Marsh Under 25 Year Flood

With and Without On-Stream Retention ..... . 40

4 Comparison of Inflow and Outflow Hydrographs

From Large Cypress Marsh Under 100 Year Flood

With and Without On-Stream Retention .... . . 41

5 Comparison of Inflow and Outflow HydrographsFrom Large Cypress Marsh Under 10 Year Flood

With and Without On-Stream Retention . . . . . . 42

6a Water Surface Elevation Line, 100 Year Flood,(With Channelization North of Turnpike) Sta.290 to Sta. 590..... ............. 43

6b Water Surface Elevation Line, 100 Year Flood,(With Channelization North of Turnpike) Sta.590 to Sta. 890 . ............... 44

6c Water Surface Elevation Line, 100 Year Flood,

(With Channelization North of Turnpike) Sta.890 to Sta. 1190 . . ............... 45

6d Water Surface Elevation Line, 100 Year Flood,

(With Channelization North of Turnpike) Sta.1190 to Sta. 1490 . .............. 46

7a Water Surface Elevation Line, 100 Year Flood,

(With Channelization North of Turnpike),Sta.290 to Sta. 590 . ............... 47

7b Water Surface Elevation Line, 100 Year Flood,(With Channelization North of Turnpike) Sta.590 to Sta. 890 . ............... 48

7c Water Surface Elevation Line, 100 Year Flood,(With Channelization North of Turnpike) Sta.890 to Sta. 1190 . ............... 49

7d Water Surface Elevation Line, 100 Year Flood,

(With Channelization North of Turnpike) Sta.1190 to Sta. 1490 . .............. 50

LIST OF FIGURES (con't.)

Number Page

8a Water Surface Elevation Line, 10, 25, and 100

Year Floods, (With Channelization North of

Turnpike) Sta. 290 to Sta. 590 ......... 51

8b Water Surface Elevation Line, 10, 25, and 100

Year Floods, (With Channelization North of

Turnpike) Sta. 590 to Sta. 890 ......... 52

8c Water Surface Elevation Line, 10, 25, and 100

Year Floods, (With Channelization North of

Turnpike) Sta. 890 to Sta. 1190 . ....... 53

8d Water Surface Elevation Line, 10, 25, and 100

Year Floods, (With Channelization North of

Turnpike) Sta. 1190 to Sta. 1490 ........ 54

9a Water Surface Elevation Line, 25 Year Flood,

(With Channelization North of Turnpike) Sta.

290 to Sta. 590 . ............... 55

9b Water Surface Elevation Line, 25 Year Flood,

(With Channelization North of Turnpike) Sta.

590 to Sta. 890 . ............... 56

9c Water Surface Elevation Line, 25 Year Flood,(With Channelization North of Turnpike) Sta.

890 to Sta. 1190 . ............... 57

9d Water Surface Elevation Line, 25 Year Flood,(With Channelization North of Turnpike) Sta.1190 to Sta. 1490 . .............. 58

lOa Water Surface Elevation Line, 10 Year Flood,

(With Channelization North of Turnpike) Sta.

290 to Sta. 590 . ............... 59

10b Water Surface Elevation Line, 10 Year Flood,

(With Channelization North of Turnpike) Sta.

590 to Sta. 890 . ............... 60

10c Water Surface Elevation Line, 10 Year Flood,

(With Channelization North of Turnpike) Sta.

890 to Sta. 1190 . ............... 61

10d Water Surface Elevation Line, 10 Year Flood,

(With Channelization North of Turnpike) Sta.

1190 to Sta. 1490 . .............. 62

11 Stage-Discharge for 200 Foot Weir At Station

747+00 . . .................... 63

LIST OF FIGURES (con't.)

Number Page

12 Stage Storage Shingle Creek Swamp North of

Osceola Co. Line Based on Recent (1978)Topography .. ..... .................. 64

13 Shingle Creek Basin . ............. . . . 65

14 Runoff Hydrograph at End Reach of 14 and 15

With and Without On-Stream Retention Located

at Large Cypress Marsh Immediately North ofCounty Line ....... . .-................. 66

15a Shingle Creek 100 Year Flood Profiles. ... ... . 67

15b Shingle Creek 100 Year Flood Profiles. .. .... . 68

16 Shingle Creek Basin, Flood Hazard Area AfterStructural Improvements . . . ............ 69

17 Backwater Stages at the Reach Between Aldersgate

and Shingle Creek Village Resulting from a 100-Year Flood .... *...... ..................... 70

DEVELOPMENT OF THE PLAN

The initial study in developing the proposed Management Plan for

the Shingle Creek Basin was a report prepared by Reynolds, Smith and

Hills1 in 1974. This report of existing flooding conditions established

the basic methodology for analyzing the hydrology and hydraulics of the

basin.

As part of the Reynolds, Smith and Hills report, the 100-year flood

hazard area along the main channel of Shingle Creek, from its outlet in

Lake Tohopekaliga on the south to the Old Winter Garden Road in the City

of Orlando on the north, was defined and recommendations for further

research and interim management regulations proposed. The 100-year design flood

was computed by means of the hydrometeorological approach, the computation

of design hydrographs from rainfall for 54 sub-basins in the basin, and

the flood routing of these hydrographs through the natural floodplain

under existing and committed land use conditions as of September, 1974.

Committed land use was defined as "that land for which there is a valid

development contract between a government entity and a developer. A

development contract shall be construed to include land for which there

is an approved PUD final development plan, a subdivision plan, or a

commercial development plan. Land zoned, but for which no development

plans have been approved, will not be considered committed land."2

Detailed documentation on the selection of the 100-year design storm,

the development of design hydrographs for the 54 sub-basins from the

unit hydrograph principle, the flood routing procedure, the backwater

IReynolds, Smith and Hills, Inventory of Existing Flood Conditions,

Shingle Creek, a Preliminary Engineering Report prepared for Orange

County, Osceola County, Central and Southern Florida Flood Control

District, and Division of State Planning as a part of the Project to

Prevent the Eutrophication of Lake Okeechobee, Sept., 1974.

2Ibid., p. A-6.

computation to determine the 100-year flood profile, and the delineation

of the flood hazard area are all included in the report.

Utilizing the Reynolds, Smith and Hills report as the starting point,

subsequent analyses were carried out by District staff in the following

phases:

Phase I:

1. Determination of a new 100-year flood profile and flood hazard

area for the Shingle Creek Basin, using the methodology established in

the RS&H report and a revised 100-year flood stage on Lake Tohopekaliga.

2. Comparison of the 100-year flood hazard area and flood profile

with the results presented in the RS&H report.

3. Delineation of the encroachment line on the floodplain area by

allowing 0.5 ft. rise of water surface above the 100-year flood profile.

Phase II:

1. Development of the design water surface profile assuming

improvements to the existing channel north of the Florida Turnpike.

2. Determination of the effect of improved channelization north

of the Florida Turnpike on the entire Shingle Creek flood hazard area.

3. Delineation of the encroachment line on the floodplain area

assuming 0.5 ft. rise above 100-year flood profile.

4. Determination of flood profiles and encroachment limits under

proposed improvements, including bridges.

Phase III:

1. Development of a refined flood profile for the lower reach of

Shingle Creek.

2. Evaluation of alternatives for detaining flood flows in the

large cypress marsh north of the Orange-Osceola County line.

3. Development and evaluation of alternatives for lowering the

flood profile in the reach below the SCL Railroad bridge.

PHASE I STUDY

Methodology

The information used in Phase I was basically available from RS&H.

Cross-sections along the creek and the bridge sections were obtained from

RS&H, with the roughness coefficient shown on each cross-section. The

runoff distribution along each reach at various inflow points was avail-

able from the RS&H report. Therefore, Phase I primarily involved setting

up an input data system in machine-readable form which met the requirements

of the HEC-2 program. The HEC-2 program computes backwater profiles for

river channels of any cross-section for either subcritical or supercritical

flow conditions. The effects of various hydraulic structures such as

bridges, culverts, weirs, embankments and dams may be used for various

frequency floods for both natural and modified conditions. In setting up

the input job stream for this study, the energy losses due to pier shape,

friction, exit, contraction and expansion, etc. were considered by using

special or normal bridge routine and roughness coefficient cards. A

transition at every 50 ft. above or below a highway bridge was provided.

The selection of a special or normal bridge routine was based on bridge

cross-sectional information. If the bridge geometry could be approximated

by a regular shape such as trapezoidal or rectangular, then a special

bridge routine was used. Otherwise, a normal bridge routine was used for

proper computation of energy losses through the bridge.

The delineation of the encroachment line on the floodplain areas was

determined by using method 4 of the HEC-2 program. This method is based

on an assumption that an equal loss of conveyance occurs on each side of

the channel due to a 0.5 ft. rise of the backwater profile. Normally,

if half of the loss cannot be obtained on one overbank, the difference

will be made up, if possible, by the other overbank. No encroachment

is allowed to fall within the main channel. The cross-sections were

plotted on USGS Quad Sheets using a 5 ft. contour interval map, with the

encroachment station for each cross-section available on the computer

output. Using a 5 ft. contour interval map, the encroachment line was

then linked together. The elevation shown on the cross-sectional map was

also used to help judge the reliability of the contour map.

Assumptions

The following assumptions were made during the process of this study:

1. The bridges and waterways were not obstructed by trees, brush

or other debris during the flood period.

2. All bridges over Shingle Creek were of sufficient strength to

resist such a major flood.

3. A transition at 50 ft. above or below every bridge was either

provided or based on the extension of the last cross-section available.

A deep canal section below the channel bottom in the vicinity of the B-2,

B-3, Bee Line connector, and Conway Road bridges was assumed to be main-

tained in its existing condition. However, such an assumption was not

necessary under the Phase II study due to the channel improvements proposed

for this portion of the creek.

4. Outflow from Turkey Lake, Clear Lake, and Lake Mann would not

occur until sometime after 30 hours due to high tailwater conditions in

Shingle Creek. Therefore, it was assumed that the outflow from these

lakes would not contribute to the peak flow in Shingle Creek.

Results

1. Flood Profiles. As mentioned previously, the source of data

for the HEC-2 program was the same for both the RS&H and District studies

except for some minor adjustment of cross-sections that did not extend

completely across the floodplain and the transitional sections upstream

and downstream of the highway bridges. In general, the results from both

computations are very close except at the locations of highway bridge

crossings. The special bridge and normal bridge routines that were used

in this study depend on the available existing geometry of the bridge

cross-sectional information. The special bridge routine was used on all

bridges by RS&H. However, the differences between the two are within 0.5

ft. except for the State Road 530 bridge near Section 7. A transitional

cross-section at a distance of 50 ft. from that bridge was assumed by using

the same cross-section as Section 6 in this study, instead of the Section

7 used by RS&H, with the result that the net area under the bridge was

2,277 sq. ft. instead of the 1,462 sq. ft. used by RS&H. Due to these

differences in bridge sections, a greater difference in the backwater

computation resulted. However, the backwater profiles became close again

for the following reaches, with a computed stage at the upper end of 97.90

ft. msl as compared to the 97.50 ft. computed by RS&H.

The backwater computation indicates that a number of bridges will be

submerged during a 100-year flood. These bridges are at Taft Vineland

Road, Sand Lake Road, Americana Boulevard, and McLeod Road (State Road 446).

A number of bridges will be partially submerged. They are the Old Tampa

Highway, SCL Railroad, Powerline Road, Road "E" Bridge (B-2), Road "D"

Bridge (B-3), Florida Turnpike, Oak Ridge Road and Abilene Trail. In

other words, twelve of the nineteen existing bridges crossing Shingle

Creek will be either completely or partially submerged under this 100-year

flood. Those bridges with timber piles, such as State Road 531, Old

Tampa Highway, and the SCL Railroad, may not be able to resist such a

large flood since the flow velocity under this bridges is much greater

than a permissible velocity of 2.5 ft/sec. The mean velocity in the

floodway areas would not generally exceed 2.5 ft/sec.; however, the mean

velocity in the main channel slightly exceeded 2.5 ft/sec. in the reach

near Oak Ridge Bridge (i.e., Stations 1207+20 through 1231+20).

2. Flood Hazard Area and Encroachment Line. The outline station

of the flood stage along Shingle Creek and the encroachment station on

every cross-section are available from the computer output. They were

also plotted on the USGS Quadrangle sheets along with the location of

each cross-section. With the aid of contours and elevations from the

cross-sections these points were linked together. However, a field trip

was taken to assist in the process of delineation of the encroachment

line at the following locations (where information wasn't available on

either the contour maps or the cross-sections): (a) the area near Lake

Tohopekaliga, (b) the swampy area north of the SCL Railroad and west of

the Kissimmee Airport, (c) the swampy area south of Taft Vineland Road,

and (d) the urban area along the existing channel from Lake Clear to

Shingle Creek. (The Reedy Creek Swamp area was excluded in this study.)

The outline limit of the floodplain area is approximately the same

as the flood hazard area shown by RS&H except in the following locations:

(a) the area near the Oak Ridge bridge where a portion of the currently

developed area would be within the floodplain, particularly the area

east of Shingle Creek, (b) the area east of Interstate 4 bridge crossing,

and (c) the area near the WLOF Radio Towers. (This may be caused by

different assumptions in the extension of cross-sections.)

Generally, the encroachment line falls within the 100-year flood

hazard area identified by RS&H. That portion between the encroachment

lines along both sides of the main channel is called the designated

floodway. This is the channel of the water course where the greatest

velocities and depths of water occur. That portion of the adjoining

floodplain between the designated floodway and the natural outline of

the selected flood is referred to as the floodway fringe. This portion

of land can be considered for development either by filling to a required

elevation or by applying other flood proofing measures. As a result of

delineation of the encroachment line a substantial floodway fringe is

available. The residential areas which were developed prior to 1970 and

which are currently inside the 100-year flood hazard area are primarily

in this floodway fringe or outside the designated floodway limits.

PHASE II STUDY

Methodology

Phase II was approached in a slightly different fashion from Phase

I. Multiple surface profiles for various discharges, in order to establish

stage-discharge relationships and stage-storage relationships at every

reach, were computed and used to develop storage-discharge relationships

for the proposed channel improvements north of the Turnpike. The following

steps were taken to establish such relationships:

1. The extent of channelization north of the Turnpike was based on

a 30% Standard Project Flood design section which approximates a 10-year

frequency flood for the area.

2. The design sections under the highway bridges were established

by assuming two ft. of excavation at the center portion of the bridge

section, with a 2 horizontal to 1 vertical side slope to the embankment

of the bridge. It was felt that this improvement for the bridge section

would not cause any damage to the substructures of the existing bridges.

3. The storage-discharge relationship was developed by running

the HEC-2 program to obtain multiple surface profiles for Q =

500, 1000,

1500, 2000, 3000, ..., 9000 cfs at different initial stages between 54.0

and 57.5 ft. msl. The amount of discharge at the middle and upper

reach was varied to a combination of 3000, 2000, 1000, 500 and 300 cfs.

The purpose of this was to estimate the variable backwater effects,

channel storage, and return of overbank flow on these reaches.

4. A flood routing computation was performed for all 21 reaches

using the storage-discharge relationship described above. The routing

program developed was based on the modified Puls method for a particular

river reach.

(I1 + 12) (01 + 02)2 At 2 At = S2 - S1

= AS (1)

where,

At = time interval t2 - t1

I1 = inflow at time 1 (rate)

12 = inflow at time 2

01 = outflow at time 1

02 = outflow at time 2

Sl = storage at time 1 (volume)

S2 = storage at time 2

AS = change in volume of storage for the time interval

This equation can be further rewritten in the following manner:

II + 2 Sl 01 - S2 02 (2)2 At 2 At 2

Knowing the relationship between discharge and storage for each reach,

the developed routing program based on Equation (2) was applied to route

the flood, combined with the developed design flood hydrograph from

each subdrainage basin given in the RS&H report. These local design

flood hydrographs were added as local inflow to the reach before flood

routing, or to the outflow from the reach after flood routing.

5. The flows used to determine the maximum water surface elevation

along the creek were determined by using the peak discharge from the

inflow-outflow routed design flood hydrograph discussed in Item 4.

6. Discharge figures close to the previous routed peak discharge at

each reach along the creek were used to run multiple surface profiles.

Then the procedures discussed in Item 3 were used to refine the outflow-

storage relationship for each reach. A new routing process was done in

the same manner as described in Item 4 to compute a new set of design flood

distributions along the creek.

7. The HEC-2 program, utilizing this new set of design flood distrib-

utions at each reach, was then used to compute the backwater profiles. A

new 100-year flood profile and delineation of flood hazard areas were

determined in the same fashion as described in Phase 1.

Results

1. Storage-Discharge Relationship. This relationship was developed

from a multiple run of surface profiles through the HEC-2 program. The

discharges used were 500, 1000, 1500, 2000, 3000, up to 9000 cfs with

different initial stages such as 54.0, 55.0, 56.0, and 57.5 ft. msl at

Lake Tohopekaliga. It was discovered later that the backwater stages for

different initial stages of the same discharge were about the same.

However, the various discharges were tested to estimate the storages due to

variable backwater effects, channel storage, local inflows, etc. A runoff

distribution was first estimated, then a refined storage-discharge relation-

ship was developed through the process described in the general procedures.

The storage of the swamp area in Reach #10B was added to the storage-stage

relationship obtained from the computer output since no survey information

was available. Thus, the computation done by RS&H was used to adjust the

storage-stage relationship and storage-discharge relationship.

2. Design Discharge Distribution. The above storage-discharge

relationship for each reach was used in the developed flood routing program

which was also combined with the developed design flood hydrograph from

each subdrainage basin provided by RS&H. The peak discharge was selected

as the design discharge distribution for the backwater computation. The

results of peak discharge and time of peaks are not significantly different

from the results obtained by RS&H for the lower reaches of the creek

(Reaches #7 through #16). However, a slightly higher discharge of about

300 to 500 cfs resulted from the reaches with the channel improvement

(i.e. the channelized portion north of the Turnpike) as compared to the

RS&H results. There is no significant difference in time to peak; with

few exceptions, they generally agree within approximately an hour.

3. Flood Profiles. The maximum water surface elevation was determined

by computing water surface curves using the computed peak discharge in

each reach. This provided a more conservative backwater surface profile.

The peak discharges used in this study are comparably higher than those

used by RS&H. However, the resulting flood profile for the lower reaches

is about the same.

The profile for the design channel portion is comparably much lower

than the natural profile (Phase I Study), particularly in the reach

between Oak Ridge Road and Interstate 4. The profile for the reach

between Orlando Vineland Road and the upper end of the creek is about 1.9

ft. lower than the natural profile. However, there is a two ft. drop of

stage through the bridge crossing at the Orlando Vineland Road. This

backwater resulted from the restriction of an inadequate bridge opening

at this location. Therefore, the assumption of two ft. of excavation

under the existing bridge section may not be a good assumption at this

bridge.

The mean velocity in the main channel is also shown at each station.

The velocity near most bridge sections slightly exceeds 2.5 ft/sec. except

at Station 1231+20 which is 3.69 ft/sec. as compared to 5.7 ft/sec. with

the natural channel. Since the design section was based on a one in ten

year frequency, the velocity under the 100-year frequency exceeded the

permissible velocity for the channel. The velocities in the overbank areas

are much less than 2.5 ft/sec.

4. Delineation of Flood Areas. The outline limit of the flood area

was determined in the same way as described previously. The flooded areas

for the lower reaches are approximately the same as in the Phase I Study.

Generally, for the reaches north of the Florida Turnpike, the outline limit

falls within the encroachment line that resulted from the Phase I Study and

a substantial portion of the floodplain will be outside the floodway limit.

For the reach between Oak Ridge Road and Orlando Vineland Road, the

floodway will be generally confined to within 100 ft. of either side of

the main channel. But the lower land areas of the reach between Orlando

Vineland Road and Section 39 (Station 1445+00) will be flooded due to the

backwater effect that results from the restriction of the Orlando Vineland

Road Bridge. For the rest of the two upper reaches which are already

urbanized, the flood stage will be confined to within the design channel.

However, the depth of flooding is considerably less than that which

resulted under natural channel conditions. The flooded area would be

reduced even further by increasing the flow cross-section under the Orlando

Vineland Bridge.

DISCUSSION OF PHASE I AND II STUDIES

Generally, there are two approaches in floodplain management; one is

through the enactment of floodplain regulations; the other is through the

provision of flood control works. The studies discussed herein were

directed toward both these approaches in an effort to provide in-depth

information on the flood stage and flood hazard areas within the Shingle

Creek Basin and, also, to evaluate the feasibility of flood control works

by considering improvements to the existing Shingle Creek channel north

of the Florida Turnpike. As defined previously, the flood hazard area

is the floodplain along the main channel of Shingle Creek which would be

inundated by the 100-year frequency design storm, assuming existing and

committed land use. This 100-year flood is approximately equal to the

Corps of Engineers Intermediate Regional Flood.

The results of the District studies can be summarized as follows:

1. The flood profiles for the 100-year storm under natural channel

conditions generally agree with the results computed by RS&H. The outline

limits of the flood hazard area also agree very closely with the RS&H

results except for the three locations identified earlier. Taking a

conservative approach, the maximum outer limits of both studies were used

to establish the outline limit of the 100-year flood hazard area.

2. Application of the designated floodway results in a substantial

reduction of the flooded area. The developed areas inside the flood

hazard zone prior to 1970 are mostly located outside of the designated

floodway. However, portions of presently urbanized areas are located

within the encroachment line.

3. The flood hazard area for the Reedy Creek Basin and the area

adjacent to the existing canal from Lake Clear to Shingle Creek can be

delineated by using the flood stage computed in this study and the

discharge developed by RS&H for the appropriate sub-basin; however,

additional cross-sections will be required to define the flooded area.

4. The 100-year flood stage in Lake Tohopekaliga may be slightly

higher than 57.5 ft. It is believed that the effect of the increased

stage would be felt only downstream of the SCL Railroad due to the large

amount of storage available northwest of the SCL Railroad.

5. The designated floodway is very critical. The only types of

land use that can be permitted within the floodway are those which do

not require filling or impede or obstruct flows in any way. Failure to

protect this zone will cause massive flooding upstream and downstream.

6. The delineation of the encroachment line on the floodplain area

by allowing 0.5 ft. rise above 100-year flood profile under the channelized

condition is not included in this report. However, the information is

available in computer output form.

7. Several areas, such as Lake Mann, Turkey Lake, Westside Manor,

etc., did not contribute to the peak flood stages due to a time lag.

Therefore, the flood hazard area has not been delineated. More field

work will be required before the flood hazard area for these areas can

be delineated. Any future improvements to the outfall system of these

lakes may reduce the time lag and cause these areas to contribute to the

flood peak.

8. The results of the improved channel north of Florida Turnpike

can be briefly detailed in the following paragraphs:

a. The peak discharge for the lower reaches (south of the

Florida Turnpike) would not be significantly increased with the improved

flow conditions in the upper reach. This is probably due to the large

amount of storage available in the cypress marsh area immediately down-

stream of Taft Vineland Road.

b. The flood stages and flood hazard areas in the lower reaches

would not be changed as a result of improvement in flow conditions north

of the Florida Turnpike.

c. The flood stages and flooded areas in the channelized reach

would be greatly reduced in depth and area.

d. The flooded areas in the channelized reach would fall within

the encroachment line that results from allowing a 0.5 ft. rise of water

surface elevation above the 100-year natural flood profile.

e. The assumption of 2 ft. of excavation for a design channel

under the Orlando Vineland Bridge is not adequate, since approximately

two ft. of backwater would result north of the bridge crossing due to

restriction of flow by that bridge opening. Therefore, the design channel

section used in this study can be improved, and the flood stages north of

Orlando Vineland Road can be lowered, if the design section under the

existing bridge is improved.

f. In addition to the Orlando Vineland Bridge, improvements to

the following bridges should be investigated in the formation of a flood-

plain management plan:

(1) The present section of State Road 600 is inadequate for

the flow generated by the one in ten year storm proposed in the Corps of

Engineers' "Survey-Review Report on Central and Southern Florida Project -

Shingle Creek Basin". The bridge has adequate length but the substructure

needs investigation.

(2) State Road 531 is an old concrete bridge with a

restricted opening. It may possibly fail if there is a large build-up of

debris during the flood.

(3) The Old Tampa Highway bridge will probably fail as it

did in 1960.

(4) The Conroy Road bridge is a new concrete bridge. The

high velocities can be controlled by use of rip-rap.

(5) There are other bridges that will be submerged under

the 100-year flood. It will be necessary to investigate their structural

stability.

As a result of the discussion of these conclusions with the local

governments concerned, the following suggestions were considered for

inclusion in the management plan:

1. Improvements to the bridges at State Road 600 and State Road 531.

2. Removal or replacement of the Old Tampa Bridge.

3. Excavation to the design bottom elevation of the proposed channel

section improvements at the bridges north of the Florida Turnpike.

4. Construction of a water control structure at approximately

Station 1207+00 in order to prevent over-drainage and control erosion.

A control stage upstream at 86 ft. msl was suggested with the proposed

structure designed to pass the 100-year storm with a 0.5 ft. head loss

above the 100-year flood profile. Since the 100-year flood profile allows

a 0.5 ft. increase of water surface elevation above the natural flood,

the result is a one ft. rise above the natural flood profile.

5. Redesign of the design bottom elevation from 85 ft. msl to 83 ft.

msl in the reach north of Station 1427+00 as an erosion control measure.

Incorporating the improvements suggested above, a new 100-year

flood profile, flood hazard area, and designated floodway, allowing for

a 0.5 ft. increase in flood stage, were computed using the same methods

outlined previously. Generally, the two profiles agreed closely except

in the following reaches:

1. Between State Road 600 and State Road 531 there was no significant

difference in flood stage; however, the velocity was reduced to less than

+ 2.5 ft/sec. instead of the 5.2 and 10.1 ft/sec. velocities that had

existed before the improvements.

2. Between the SCL Railroad and Station 454+00 the new profile

varied from 1 ft. below the old profile at the SCL Railroad to zero

reduction at Station 454+00. The reduction in the width of the floodplain

varied from 300 ft. at the SCL Railroad to zero at Station 454+00 while

the encroachment line showed no significant reduction. To be on the

conservative side, it was suggested that the slight reduction in the

floodplain be ignored in the water management plan.

3. Between Station 1207+00 and Station 1285+10 (Interstate 4) the

profile for the improved condition was up to 1.0 ft. higher than the

previous profile. This was due to the head loss through the proposed

water control structure. However, the floodplain area in this reach did

not increase due to the fact that this reach has been developed and the

ground elevation has been filled to above flood stage. The flood was

mostly confined to the channel except for the reach between Oak Ridge

Road and the proposed water control structure.

4. Between Station 1285+00 (Interstate 4) and Station 1373+85 (McLeod

Road), the profile for the improved condition is much lower (over 2 ft.)

than the previous profile. Thus, the flood flow is confined to the main

channel and a substantial portion of the existing floodplain would be

available for development.

5. Between Station 1373+85 and the northern end of Shingle Creek,

the flood stage ranged from 94.50 ft. msl at McLeod Road to 95.61 ft.

msl at the northern end of the creek. The lands in the reach from Station

1374+60 to Station 1427+00 are low lying, with existing elevation mostly

below 95.00 ft. msl; therefore, some inundation in this reach can be

expected. However, the existing developed area will be excluded from the

floodplain. For the developed area north of Station 1445+00, the flood

will be contained in the main channel.

-16-

PHASE III STUDY

The analyses conducted through early 1977 indicated that flood

stages and flood hazard areas in the lower reaches would not be increased

as a result of the proposed improvements north of the Florida Turnpike.

Although the routings carried out up to that time indicated very limited

flooding problems to existing development, continued local concerns that

future development in Orange County might increase flooding in the downstream

reaches of Shingle Creek in Osceola County necessitated a reexamination of

the potential problem. The basic data and assumptions upon which the

prior analyses were based were reviewed and field reconnaissance investi-

gations, together with topographic surveys, were carried out. For these

purposes, it was assumed that future development of uncommitted lands

would occur in a land use pattern similar to that of existing and committed

land uses.

From the revised routings, which incorporated more accurate and

up-to-date tributary basin areas and conveyance cross-section areas, it

was apparent that a significant flooding problem for existing development

existed in the area downstream of the SCL Railroad bridge.

Initial proposals to eliminate this problem centered on attenuating

upstream flows from Orange County. To this end, a tie-back levee and

weir were envisioned to detail flood flows in the large cypress marsh

immediately north of the Orange-Osceola County line. A proposed low head

weir (0.5 ft.) was located at Station 747+00, immediately north of the

county line. This weir created only very marginal storage increases over

and above the excellent existing detention features of the natural

marsh. A higher head weir (1.0 to 1.3 ft.) was later evaluated in terms

of a length of both 250 ft. and 180 ft. and a crest elevation of 74 ft.

msl. Figures 1 and 2 show the stage-storage curves for each of the

proposed weir lengths, based on the discharge equation for a free fall

rectangular weir where,

Q = CLH 3/2 (1)

and for the submerged flow

Q = Q (1 - Ho 3/2) 0.385 (2)

H

in which Ho is the total head at the tailwater.

Under these conditions the 100-year storm created a peak discharge

of 5440 cfs and flood stages of 78.1 ft. msl and 78.4 ft. msl for the

two weir lengths, respectively. This flood stage is 1.0 ft. to 1.3 ft.

above the 100-year natural flood stage at the location within the

proposed weir.

In evaluating the impacts of this proposed weir, flooding conditions

resulting from the 100, 25 and 10 year frequency storms were determined

for the following cases:

Case 1. Future full development without an on-stream retention

structure and without local runoff restrictions.

Case 2. Future full development with an on-stream retention

structure.

Case 3. Future full development with local runoff restrictions

for Orange County and without an on-stream retention

structure.

Local runoff restrictions refer to a detention storage area,

controlled by structure measures such as a weir, to store the first inch

of storm runoff. The subsequent runoff is allowed to overflow a free

fall rectangular weir designed so that the flow at a 3 ft. head is

equivalent to the peak discharge resulting from a 25-year frequency

storm under existing and committed land use as of September 1974. This

assumption enabled the District to incorporate the local runoff restric-

tion into our flood routing model developed for the basin.

The peak flow rate at the head and foot of each channel reach along

with the time to peak are tabulated in Table 1. Table 2 shows the 100-

year flood discharge along Shingle Creek for all reaches. It can be seen

that there was not a significant difference in discharge between any of

the cases, with the greatest difference being approximately 500 cfs in

the lower reaches. The change in time to peak was also insignificant.

Therefore, it is apparent that the effect of the proposed weir (with 1.0

ft. to 1.3 ft. head above natural profile) on discharge is negligible,

and that the existing detention features of the natural cypress marsh are

excellent. This can be further illustrated by the inflow hydrograph and

outflow hydrographs from the marsh area under the 100, 25, and 10 year

storm frequencies and without the on-stream retention structure (see

Figures 3, 4 and 5). Comparing Cases 1 and 2 to existing conditions, the

increased peak discharge is generally much greater for the reaches above

the marsh area immediately north of the county line, while little difference

is apparent for the reaches below the marsh. Comparing Case 3 to the

existing condition, the peak discharge is slightly less than the existing

condition. Therefore, the substantial effect of local runoff restrictions

in reducing peak discharge is obvious.

The index of flood duration is defined as the duration of flood flow

within 90% of the peak discharge. Flood duration is an important factor

in evaluating flood damage. Table 3 shows the 100-year flood duration

index at the foot of each channel reach along Shingle Creek for the three

cases as well as for existing conditions. In general, future development

in the potentially developable area increases not only the peak discharge

but also the inundation period. The local runoff restrictions not only

reduce the peak rate of flood but also result in no significant increase

in flood duration except in reaches 12 through 14. Those reaches above

the marsh did not show any significant difference.

The flood stage along Shingle Creek is listed in Table 4 and Figures

6 and 7. It was developed using the Corps of Engineers HEC-2 program and

the same cross-sectional data along Shingle Creek discussed in Phases I and

II. The channelization plan north of the Florida Turnpike and some bridge

improvements were also considered in this study. For those reaches below

the cypress marsh, there were no significant differences in flood stages

for Cases 1 and 2 except for the reach immediately below the on-stream

retention structure. In the upper reaches of Shingle Creek, however, there

were some significant increases in flood stage, such as the reach from

Orlando Vineland Road north to the end of the basin, where increases ranged

from 0.5 ft. up to 1.80 ft. Thus, for the 100-year storm, some areas

would be inundated under future full development conditions.

The small difference between Case 3 and existing conditions indicates

that the effect of local runoff restrictions on the flood stage along

Shingle Creek is very significant, particularly in those reaches north

of the cypress marsh. Flood stages, assuming local runoff restrictions,

would be either the same as existing conditions or slightly lower. Back-

water profiles for the 25 and 10 year frequency storm under assumed future

development are shown in Figures 8, 9 and 10.

Therefore, flooding conditions under future full development in the

upper reaches of Shingle Creek would be relieved were local runoff

restrictions implemented. In addition, due to the excellent existing

detention features of the natural marsh, runoff from Orange County would

not increase the flood hazard in the lower reaches of the Shingle Creek

basin.

Although the previous study had illustrated the effectiveness of

the natural marsh versus the on-stream retention structure, the District

made a more complete topographic survey of the large cypress marsh north

of the Osceola County line during September, 1978 in order to better define

its water storage capabilities. With this information, the effects of a

higher head weir (3 ft.) with a tie-back levee to detain flood flows in

the large cypress marsh was also investigated. The crest elevation for

this higher head weir was 77.0 ft. msl and the proposed length was 200 ft.

Stage-storage curves for this weir are shown in Figures 11 and 12.

The 100-year flood was then routed through this proposed facility

together with the enlarged drainage area for the Reedy Creek swamp.

Figure 13 shows the entire Shingle Creek basin with the Reedy Creek swamp

included. It became apparent that the largest component of the flood

peak passing through the concerned area was a result of the Reedy Creek

swamp runoff rather than the Orange County runoff. Examination of flood

hydrographs from USGS gaging stations at the U.S. 192 and Old Tampa

Highway bridges indicated that a relatively quick runoff hydrograph (time

of concentration less than 10 hours) is generated between the two stations

before the Orange County flows arrive. This can be seen on the hydrographs

shown on Figure 14 which are the result of hydrologic routings for reaches

14 and 15. The high weir resulted in a reduction of peak flows at

State Road 531 from approximately 8000 to 6800 cfs which was not enough

to prevent most of the damages. In fact, total retainage of the flow from

Orange County will not reduce this flow peak further. Therefore, it can

be concluded that:

1. The existing marsh behaves as an efficient buffer between the

counties,

2. Although Orange County runoff will extend the period of

inundation of flooding in Osceola County, the peak flow and stage is

largely generated locally.

To reduce the flood stage in the area below the SCL Railroad to below

damage levels, there are two alternatives which may be considered. The

first would be to reduce the amount of flow while the second would be to

increase the floodway conveyance. To accomplish the first would require

detention of runoff in the Reedy Creek Swamp drainage area, which is now

primarily pasture with a developed secondary drainage system. If a

significant portion of this were detained, it would then have to be

released at a later time where it would combine with upstream flows

resulting in the same flooding problem which currently exists, but at a

later time. Therefore, in order to resolve the current problem, it

appears that the remaining alternative of increased conveyance must be

considered.

The reach considered for this conveyance improvement is between U.S.

17-92 and the Old Tampa Highway. Two separate schemes have been considered.

First, the conventional approach, which would widen the existing natural

creek. Second, because of obvious esthetic and potential environmental

problems with the first approach, a floodway bypass was considered which

would only carry water during periods of flood conditions, leaving the

natural creek essentially unchanged.

As noted previously in the discussion of the Phase I and II studies,

the 100-year stage on Lake Tohopekaliga could be higher than 57.5 ft.

msl. Therefore, an initial stage of 58.5 ft. msl was used, and several

backwater profiles were computed by using HEC-2 program. The results are

shown on Tables 5 through 9 and Figure 15. The backwater profiles for

the initial stages of 57.5 and 58.5 ft. in Lake Tohopekaliga did not show

a significant difference for the reach above State Road 531 and were about

0.15 ft. higher for the reach between U.S. 17-92 and State Road 531.

However, the 100-year flood profile elevation in the concerned reach is

over 63.0 ft. msl with the inclusion of inflow from the Reedy Creek

swamp area. To evaluate actual damage levels, a District survey crew

was sent to the area in December, 1975 and finished floor elevations of

numerous apartments and homes in the area were determined. In the

Aldersgate community, the floor elevation for 198 apartments ranged from

61.9 ft. to 62.2 ft. msl. Therefore, it is necessary to lower the profile

to about 61.0 ft. msl elevation in this area in order to prevent flooding

during the 100-year storm.

For the conventional approach the creek would need to be widened to

a bottom width of 150 ft. which would yield a total top width of about

235 ft. This assumes that the natural bottom elevation of 45 ft. msl

would be maintained. As the creek varies from about 40 to 70 ft. in width,

this widening would require about 175 ft. of bank removal. The existing

State Road 531 bridge is a source of a large energy loss and would thus

require rebuilding to an accomodating width of 300 ft. This alternative

would eliminate at least half of the existing shoreline vegetation,

notably large overhanging oak and cypress trees. It is estimated to

cost $1,317,000 at a minimum.

The second approach would be to clear a floodway bypass around to

the north of the creek through existing pasture lands (see Figure 16).

Though this would be 500 ft. wide, the depth would be shallow with a

bottom elevation of 55.5 ft. msl. Very gradual (10 horizontal to one

vertical) side slopes to existing land would insure continued utility

of the land. A bridge crossing State Road 531 would also have to be

built for this scheme. With a bottom elevation of 55.5 ft. (Lake

Tohopekaliga is regulated to a maximum 55.5 ft.), flow in the bypass

could only begin to occur when flow in the natural creek exceeded

about 500 cfs. It would, therefore, be dry except during brief storm

periods of less than annual expectation. At the 100-year flood peak,

the flow would be divided with approximately 6000 cfs discharging through

the bypass and 2000 cfs remaining in the existing channel. These flows

would join again on the upstream side of the U.S. 17-92 crossing. The

results of this approach are shown on Figure 17. Estimated costs for the

floodway bypass are $1,062,500.

Based on a comparative analysis of the preliminary costs and the

environmental impacts associated with each of the alternatives, the

floodway bypass was recommended.

DISCUSSION OF PHASE III STUDIES

Due to the long and narrow shape of the drainage basin, the flood

flow in the main stream is compounded by local runoff inflows. Whether

the peak flow responds to local runoff or to the flow in the main

stream is generally determined by the relative size of the immediate

sub-basins. Although there is a great difference in local hydrographs

resulting from various conditions, they are generally attenuated by the

Shingle Creek floodplain.

The results of the Phase III studies can be briefly stated as

follows:

1. Assuming no local runoff restrictions, future development in

potentially developable areas will increase the flood stage along the

main channel to a certain degree depending upon the amount of urbaniza-

tion. For reaches near the northern end of Shingle Creek, with the

proposed channelization plan, the flood stage may increase up to 1.8 ft.

above 100-year flood profile.

2. The creation of local runoff restrictions in potentially

developable areas can reduce the flood stage which would result from

such development.

3. The on-stream retention structure proposed for the outlet to

the large cypress marsh north of Orange-Osceola County line is ineffective

in reducing flood stages downstream.

4. The existing large cypress marsh behaves as an efficient buffer

between the two counties as far as flood flows from Orange County are

concerned.

5. Although Orange County runoff will extend the period of inunda-

tion of flooding in Osceola County, the peak flow and stage is largely

generated locally (along the reaches in Osceola County).

6. The 100-year flood stage in Lake Tohopekaliga has a very limited

effect on the backwater except at the lowest reach near the lake.

7. The creation of a bypass floodway at the reach of Shingle Creek

between U.S. 17-92 and Old Tampa Highway will be the most effective way

to relieve the existing flooding problem at Aldersgate community due to

existing development in the flood hazard area of Shingle Creek itself.

REFERENCES

1. "Inventory of Existing Flooding Conditions (Floodplain Information)Shingle Creek", Reynolds, Smith and Hills, Preliminary EngineeringReport, September 1974.

2. Lin, S. T. and Lane, J. "Shingle Creek Floodplain Study", Centraland Southern Florida Flood Control District, June, 1975. UnpublishedReport.

3. "Shingle Creek Flood Analysis", South Florida Water ManagementDistrict, Technical Review Division, Resource Control Department,March 1977. Unpublished Report.

4. "SCS National Engineering Handbooks", Section 4, Hydrology, SoilConservation Service, Washington, D.C. 1972.

5. Miller, C. R. and Veissman, W. Jr., "Runoff Volumes for Small UrbanWatersheds", Water Resources Research, Vol. 2 No. 2, April 1972.

6. "The Effects of Urbanization on Unit Hydrographs for Small Watersheds,Houston, Texas, 1964-67", Tracor, 6500 Tracor Lane, Austin, Texas,September 1968.

7. "Survey-Review Report on Central and Southern Florida Project -Shingle Creek Basin" U.S. Army Corps of Engineers, Jacksonville,Florida District, August 9, 1961.

-26-

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TABLE 2 100 YEAR FLOOD PEAK DISCHARGE ALONG SHINGLE CREEK(AT FOOT OF THE REACH)

Reach No. Existing Condition1

Case 1 Case 2 Case 3

1 450 510 510 3502A 2,230 2,440 2,440 2,2602B 1,910 3,480 3,480 2,3603 2,340 3,610 3,610 2,6504 2,550 3,730 3,730 2,7605A 3,710 4,710 4,710 3,4305B 3,720 4,710 4,710 3,5306A 5,200 5,930 5,930 4,7106B 5,340 5,960 5,960 4,8807 5,490 5,700 5,700 4,9308A 6,180 5,900 5,900 5,3308B 6,390 6,110 6,110 5,5709 7,630 7,030 7,030 6,39010A 8,700 7,910 7,910 6,87010B 5,950 5,540 5,540 4,98011A 5,590 5,520 5,44011B 5,590 5,520 5,430 (5360)2 4,87012 5,630 6,020 5,630 (5420) 4,880

13 5,580 6,080 5,690 (5380) 4,88014 5,420 5,890 5,570 (5350) 4,88015 7,420 8,170 7,720 (7580) 7,08016 7,530 8,170 7,760 (7640) 7,140

Note: IRefers to existing and committed land use as of Sept. 1974.

2Peak discharge with 180 ft. long rectangular weir.

Case 1: Future full development without on-stream retention structure.Case 2: Future full development with on-stream retention structure

(weir length =

250 ft.).Case 3: Future full development with local runoff restrictions for

Orange County and without on-stream retention structure.

TABLE 3 100 YEAR FLOOD INDEX FLOODING DURATION* ALONG SHINGLE CREEK(AT FOOT OF THE REACH)

Reach No.

12A2B345A5B6A6B78A8B910A10B11A11B1213141516

Existing Condition

2.54.05.58.56.03.03.03.54.05.55.56.06.56.58.5

10.011.512.013.59.0

13.5

Case 1

2.54.06.58.09.03.04.54.05.07.57.59.010.06.0

15.5

16.518.517.019.011.012.5

Case 2

2.54.06.08.09.03.04.54.05.07.07.59.09.56.0

15.517.017.022.522.022.512.514.0

Case i: Future FullStructure

Development Without On-Stream Retention

Case 2: Future Full Development With On-Stream RetentionStructure

Case 3: Future Full Development With Local Runoff Restrictionsfor Orange County and Without On-Stream Retention Structure.

* Index of flooding duration is defined as the duration of flood flow

within 90% of the peak discharge in hours.

Case 3

3.54.06.08.5

10.05.55.54.05.56.56.57.07.07.5

15.0

15.527.026.527.013.014.5

TABLE 4 SHINGLE CREEK 100 YEAR FLOOD STAGESTAGE, FT. ABOVE MSL

Existing1

Station Identification Condition Case 1 Case 2 Case 3

293+00 Lake Toho. 57.50 57.50 57.50 57.50

310+50 U.S. 17, S.R. 600 59.42 60.02 59.75 59.35

345+20 S.R. 531 59.89 60.16 60.02 59.85

388+00 Old Tampa Hwy. 62.75 63.32 63.15 62.92

389+30 SCL R.R. 64.28 65.09 64.74 64.32

537+17 U.S. 192, S.R. 530 71.04 71.23 71.08 70.76

817+70 Power Line Road 79.09 79.11 79.32 78.82

903+15 Rd. "E" Bridge B-2 82.57 81.95 81.93 81.60

956+19 Taft Vine Lane Rd. 83.02 82.47 82.46 82.20

975+58 Rd. "D", Bridge B-3 83.13 82.56 82.55 82.25

999+29 Beeline Connector 83.27 82.69 82.68 82.41

1113+55 Sand Lake Road 87.81 88.12 88.12 87.76

1159+35 Florida's Turnpike 88.02 88.35 88.35 87.94

1214+30 Oak Ridge Road 90.18 90.62 90.62 89.95

1269+00 Tropical Drive 91.45 92.49 92.49 91.26

1285+80 1-4, S.R. 400 92.30 93.75 93.75 92.22

1293+50 Orlando, Vineland Rd. 92.33 94.11 94.11 92.33

1326+25 Conroy Road 92.65 94.36 94.36 92.62

1373+85 Mcleod Dr., SR. 446 93.50 96.22 96.22 94.00

1395+30 Abilene Trail 94.60 96.43 96.43 94.00

1485+30 Northern End 95.61 96.90 96.90 94.97

Note: 1Refers to existing and committed land use as of September 1974.

Case 1: Future Development Without On-Stream Retention Structure.

Case 2: Future Full Development With On-Stream Retention Structure.

Case 3: Future Full Development With Local Runoff-Restrictions forOrange County and Without On-Stream Retention Structure.

-30-

TABLE 5 100 YEAR FLOOD PROFILE WITH EXISTING LAND USE - NO IMPROVEMENT INBRIDGE SECTION - WITH ON-STREAM RETENTION (HIGHER HEAD WEIR) INSHINGLE CREEK - INITIAL STAGE - 58.50 FT. MSL.

Station Q Water Elev.ft. cfs ft. msl.

293+00309+84310+50310+51310+65310+80320+30341+00344+58345+08345+20345+72361+00388+00388+50388+51388+70389+00389+30389+90390+40402+70454+00507+00536+67537+50538+00539+50580+00603+00675+50708+50747+00

58.5058.5959.0259.2859.3959.7959.8361.0961.2261.2361.2461.2561.9262.7762.6362.3663.1063.9664.0864.1964.3164.4664.7169.0669.8369.8469.8470.0472.8973.0673.8374.4174.95

TABLE 6 100 YEAR FLOOD PROFILE WITH EXISTING LAND USE AND NO IMPROVEMENTIN BRIDGE SECTIONS. REEDY CREEK SWAMP INFLOW INCLUDED WITH

INITIAL STAGE OF 57.50 FT. MSL AT LAKE TOHOPEKALIGA.

Station Q Water Elev.

ft. cfs ft. msl.

293+00309+84310+50310+65310+80320+30341+00344+58345+08345+20345+72361+00388+00388+50388+70389+00389+30389+90390+40402+70454+00507+00536+67537+50538+00539+50580+00603+00675+50708+50747+00781+00817+70831+05858+40885+52888+00902+65903+15903+55904+10912+60918+60955+70956+20

807080708070807080708070807080708070807080708030803080308030803080308030601060106010611061106110611061106110627062705590559055907880793079307930793079307460746074607460746074607460

57.5057.8659.0259.2959.9259.9661.3761.5061.5262.4762.4862.8963.5663.3864.3965.1865.1865.2365.3765.4766.0070.4071.2171.2371.2371.4774.4474.6675.4476.1277.1178.7599.2079.3479.5780.1080.4281.5881.5881.5981.5981.6881.8782.7582.75

TABLE 6 (Continued)

956+50956+80975+09975+59975+70976+00998+80999+301000+701001+701028+001056+451063+001081+401113+001113+551113+901115+501157+851158+351159+351159+85

82.8082.8082.8382.8382.8582.8682.9682.9382.9483.0884.3985.7186.3287.3587.6687.7387.7987.7987.9187.8387.9288.12

TABLE 7 100 YEAR FLOOD PROFILE WITH EXISTING LAND USE AND IMPROVEMENT IN

BRIDGE SECTIONS. REEDY CREEK SWAMP INFLOW INCLUDED WITH INITIAL

STAGE OF 57.50 FT. MSL AT LAKE TOHOPEKALIGA.

Station Q Water Elev.

ft. cfs ft. msl.

293+00309+84310+50310+65310+80320+30341+00344+58345+08345+20345+72361+00388+00388+50388+70389+00389+30389+90390+40402+70454+00507+00536+67537+50538+00539+50580+00603+00675+50708+50747+00781+00817+70831+05858+40885+52888+00902+65903+15903+55904+10912+60918+60955+70956+20

807080708070807080708070807080708070807080708030803080308030803080308030601060106010611061106110611061106110627062705590559055907880793079307930793079307460746074607460746074607460

57.5057.8659.0259.3059.8459.8961.3461.4761.4962.4662.4762.8863.5663.3764.3965.1765.1865.2265.3465.4766.0070.4071.2171.2371.2371.4774.4474.6675.4476.1277.1178.7579.2079.3479.5780.1080.4281.5881.5881.5981.5981.6881.8782.7582.75

-34-

TABLE 7 (Continued)

956+50956+80975+09975+59975+70976+00998+80999+30

1000+701001+701028+001056+451063+001081+401113+001113+551113+901115+501157+851158+351159+351159+85

82.8082.8082.8382.8382.8582.8682.9682.9382.9483.0884.3985.7186.3287.3587.6687.7387.7987.7987.9187.8387.9288.12

TABLE 8 100 YEAR FLOOD PROFILE WITH EXISTING LAND USE AND NO IMPROVEMENTIN BRIDGE SECTION - REEDY CREEK SWAMP INFLOW INCLUDED WITHINITIAL STAGE OF 58.50 FT. MSL AT LAKE TOHOPEKALIGA.

Station Q Water Elev.ft. cfs ft. msl.

293+00309+84310+50310+65310+80320+30341+00344+58345+08345+20345+72361+00388+00388+50388+70389+00389+30389+90390+40402+70454+00507+00536+67537+50538+00539+50580+00603+00675+50708+50747+00781+00817+70831+05858+40885+52888+00902+65903+15903+55904+10912+60918+60955+70956+20945+50956+80975+09975+59

8070807080708070807080708070807080708070807080308030803080308030803080306010601060106110611061106110611061106270627055905590559078807930793079307930793074607460746074607460746074607460618061806180

58.5058.6259.0259.7460.3060.3261.5361.6561.6662.5262.5362.9363.5863.4064.4165.1965.2065.2465.3965.4866.0170.4071.2171.2371.2371.4774.4474.6675.4476.1277.1178.7579.2079.3479.5780.1080.4281.5881.5881.5981.5981.6881.8782.7582.7582.8082.8082.8082.83

TABLE 9 100 YEAR FLOOD PROFILE WITH BRIDGE IMPROVEMENT AND BY-PASSCHANNEL - INITIAL STAGE OF 58.50 FT. MSL.

Station Q Water Elev.ft. cfs ft. msl.

58.5058.6259.0259.9959.9959.9960.4560.9660.9961.0061.0061.0361.3160.9962.5163.9064.0764.2364.4164.59

293+00309+84310+50310+51310+65310+80320+30341+00344+58345+08345+20345+72361+00388+50388+70389+00389+30389+90390+40402+70

-37-

STAGE IN FEET ABOVE MEAN SEA LEVEL

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SECTION 5STA 454+00

SECTION 6

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US. 192 S.R.530STA. 53775

- SECTION 7

SSTA. 539+50

SECTION 8

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- sECTIUNSTA 293+00

US. /7-92 SR. 600STA. 310+50

SECTION 2- SA. 341+00

SR. 53/1STA 345+20

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1340400- i E SECTION 35/ 0- STA 1343+00

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1370+00- srTA. 37s+s/ 4 - -- SECTION 36

140 00

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/4 +00--

/440+00 - -SECTION 37

STA. 1440+00/450+00- I

14000-- SECTION 40

/460+00 - - - -- - - - STA. 1462 +00

1470+00-

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/ 5 0 -_ _ _ SEC ,O / 2 o

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1230+00---- - -- _-- STA /23/+20

/240+00 '

/250+00 __ SECTION 30

/26o+00 ', TROPICAL ORIVE

/270+00 ______-_ 0 SECT/ON 3/0 STA. 127070

120 00 400

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2 9 SECTION 2- STA. 341+00

S R. 531STA 345+20

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SECTION /2STA 747+00

SECTION /3STA.78I.00

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SECTION /5- STA 888+00

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-- SECTION 28/220+0O SrA 1et6/ioo- o STA /2/610

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1 0 ORLANDO VINELA( _- - - STA 1293+50

1300+00I b b SECT/ON33

1320+00 y a SECTION 34/ _0 .STA /322+00

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1350+00 -

1360+00-

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SEC TION 28STA 12/6+10

SECTION 29STA 1231+20

SECTION 30STA /25400

TROPICAL DRIVESTA 1/26960SECTION 3/STA. 1270 +70

1-4 S.R. 400STA 1285 +0SECTION 32STA. 128730ORLANDO VINELAND RDSTA. 1293+50SECTION 33STA /2296-00

SECTION 34S TA. 1322+00CONROY RDSTA. 1327+00

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- SECTION 36STA 1374+60

0

ABILENE TRAILSTA. 139565SECTION 37STA. 1400+O

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SECT/ON 38STA. 1427+00

SECTION 39

STA. 1445+00

N SECTION 40STA 1462+00

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SECTION 13

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- SECTION 14

S TA. 810

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US /7/-92 SR600

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STA,345+20

SECTION 3STA 36/+00

2 (OLD TAMPA NWY,STA. 36870

S.L. R.R.

SECTION 4

STA. 402+70

SECTION 5

STA. 454 +00

SECTION 6

STA. 507-DO

U.S /92 SR 530STA. 537 +75

SECTION 7STA. 53+50

SECTION 8STA 580+00

| o 1 1I29000-

300+00-

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360+00-

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SECTION 16STA.9/2+60

TAFT VINELAND RD.STA.956+35

SECTION 17STA 95608O

RD "D"BRIOGEB-3STA 975 +85

SECTION 18STA. 976+0

BEELINE CONNECTORSTA. 000+00

SECTION 19

n STA. OO/+70

SECTION 20STA.1028

SECTION 2/STA. /1056+45

SECTION 22STA.I063+00

SEC TION 23STA 1081+40

SAND LAKE RD.S. R. 528-ASTA. 1113+ 75

SECTION 24rA.1115i+50

FLA. TURNPIKESTA. 1158 +85

S ETTION 25STA. 161/+90

SECTION 2oSTA. 1181/400

,,,

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SHINGLE CREEK BASIN

Figure 13 SHINGLE CREEK BASIN

-65-

_IL

FLOW (c.f.s.)

N~

ELEVATION IN FEET ABOVE MEAN SEA LEVEL

SOI U

-

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290+00 -

300+00 -

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SECTION I

STA1393+00

_U I7-92 R600

STA.3I0+55

2

a SECTION 2-STA.341+00

STA.394520

SECTION 3STA. 36+00

SOL TAMPA IW'_.STA 388+70

SCL R.Rn5TA.389+40

SECTION 4STA. 402+70

SECT/ON 5

STA. 454+00

SEC TION 6STA 507+00

N U.S./02 SR55309 STA. 537+75

WSECTION 7STA 539+50

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ELEVATION IN FEET ABOVE MEAN SEA LEVEL

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ELEVATION IN FEET ABOVE MEAN SEA LEVEL

0 N b b b b