# Floodplain Delineation of Indiana Streams

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```					Floodplain Delineation of
Indiana Streams

Tom Gormley
Jessica Tempest
Erin Wenger
Problem Statement
Flooding due to
recent development
in rural areas of
Indiana has
heightened public
concerns and
requires the
development of flood
plain mapping in
previously
Objectives
• Create a hydraulic base model
• Delineate areas most prone to
flooding
• Design a flood control
structure to reduce area of
impact
• Recommend the next course of
action
Methods
• Analyze topographic data to determine
representative cross sections
• Determine 100 year flow data from
government resources
• Obtain bridge data from Highway
Department
• Insert data into Hec-Ras
• Based on output, design flood control
structure
Why Use HEC-RAS?

• Hec-Ras, developed by the Army Corps of
Engineers, is the standard model used for
floodplain delineation.

• Performs one dimensional hydraulic analysis

• Energy loss is calculated using Manning’s
Equation.
HEC-RAS
• Inputs                  • Outputs
– Flow Data               – Cross Section
• Drainage area           Plots
• Discharge             – Rating Curves
– Cross Section           – Detailed Tabular
Data                      Output at a
• Manning's “n”           Specific Cross
• Station/Elevation       Section
– Bridge                    • Water Surface
Information                 Elevation
• Height                  • Flow area of
channel
• Restrictions
• Total Discharge
Sensitivity Analysis
• Flow rate, location of bank station, and
Manning’s “n” value for both were
varied to see the results of the change
on velocity, top width, and elevation.

• These values were chosen due to their
variability in Hec-Ras.
Results of Sensitivity Analysis

Sensitivity Analysis for Q
• Velocity and top
width proved to be                    2
the most sensitive                   1.5

Sensitivity
Velocity
for flow rate.
1                                      Top Width
Elevation
• Analyzed inputs                    0.5
have a minimal                        0
impact on elevation.                       0     2000          4000   6000
Q (cfs)
Calibration
• The field data used was a floodway/flood boundary
map for a reach directly above and adjacent to the
model.

• A top width was measured off the flood map and
used to compare to the top width predicted by the
model.

• The model was calibrated coarsely first by varying
the flow rate into the cross section.

• Once the top width was close to the observed value,
an attempt was made to refine the calibration using
Manning’s n value on both the stream channel and
Results of Calibration
Top width measured: 312.5 ft

Run #      Flow   Manning’s Channel   Manning’s Bank   Top Width Predicted

Original   3100         0.04               0.07              284.96

1       3200         0.04               0.07              288.64

2       3300         0.04               0.07              293.89

3       3400         0.04               0.07              297.95

4       3600         0.04               0.07              305.53

5       3700         0.04               0.07               309

6       3800         0.04               0.07              312.28

7       3800         0.038              0.07              313.46

8       3800         0.04               0.06              308.51
Case Studies

Burnett Creek – Tom Gormley
Haw Creek – Jessica Tempest
Indian Creek – Erin Wenger
Jordan Creek
Geographical Data

• 2 mile reach
extending south from
• Township 23 N, Range
5 W, Tippecanoe
County, Indiana
• Model acts as a
southern continuation of
residential development
analysis
Design Considerations

• Model should be able to couple with preexisting HEC-2
data north of SR 26

•    Creek bed experiences a fluctuation in topography
along its path, moving from a narrow V-shape to wide,
low sloping terrain

•    To minimize flooded areas, a levee will be constructed
primarily on the eastern side of the creek, and the creek
bed will be excavated further

•    Reshaping of creek area should not have a negative
impact on the local ecosystem, and alleviation of
flooding in one area should not encourage flooding or
erosion in other areas.
Cross Sectional Analysis and
Design
senior design 2004 jordan creek    Plan: Imported Plan 01         04/13/2004

.07                        .    .07
650                                                    0                             Legend

645
4
EG PF 2
Before:
WS PF 2    Shallow side of creek
Elevation (ft)

will flood during a 100
640                                                                                  EG PF 1
WS PF 1
635
Ground
Year storm.
630                                                                                  Bank Sta

625
0        100         200          300         400           500         600
Station
ALTERED senior design 2004 jordan creek       (ft)Plan: Imported Plan 01    04/14/2004

.07                        .    .07
650                                                    0                             Legend

645
4
EG PF 2
After:
WS PF 2    Construction of a levee combined
Elevation (ft)

with trenching and widening of creek
640                                                                                  EG PF 1
WS PF 1
635
Ground
results in usable land.
630                                                                                  Bank Sta

625
0        100         200          300         400           500         600
Station (ft)
Results
• Flooding area is minimized

• Land previously in danger of flooding
as well as newly constructed levee
may be used to expand local
agricultural practices

• Erosion by flooding is kept to a
minimum
Burnett Creek
Pre Design
• During a 100 year                                   Burnett    Plan: Plan 04     04/13/2004

storm,                                      660
.08                .1        .08
Legend

the waterway splits at                    650
EG PF 1
WS PF 1
640                                                        Ground

the I-65 overpass.

Elevation (ft)
Bank Sta
630

• By reshaping the channel                   620

where the waterway splits,                 610

600

the floodplain will be greatly                   0      500          1000
Station (f t)
1500       2000

reduced.
Channel Split                          Main Channel
Post Design
•Soil will be taken from                                 BurnettDesign    Plan: Plan 04   04/13/2004

various locations and used                    660
.08                .1       .08
Legend

EG PF 1

in the reshaping of the land.
650
WS PF 1
640                                                            Ground

Elevation (ft)
Bank Sta
630

•The dig areas will:                           620

reduce erosion                               610

decrease water elevation.
600
0         500          1000          1500         2000
Station (f t)

•All soil will be excavated from                             New Channel
this location.
Recap of River Station 3508
Before Design                                                                               After Design

Burnett    Plan: Plan 04     04/13/2004                                               BurnettDesign    Plan: Plan 04   04/13/2004

.08                .1        .08                                                         .08                .1       .08
660                                                        Legend                     660                                                            Legend

EG PF 1                                                                                   EG PF 1
650                                                                                   650
WS PF 1                                                                                   WS PF 1
640                                                        Ground                     640                                                            Ground
Elevation (ft)

Elevation (ft)
Bank Sta                                                                                  Bank Sta
630                                                                                   630

620                                                                                   620

610                                                                                   610

600                                                                                   600
0      500          1000           1500       2000                                    0         500          1000          1500         2000
Station (f t)                                                                            Station (f t)

Excess                    Main Channel                                                                            New Channel
Floodplain Map

Note: Original Floodplain is based on Tippecanoe’s floodplain estimate
found in Arcmap.
Final Results
• All flow is contained within the
channel.

• The total land eliminated from the
floodplain is estimated at 977.3
hectare. (2415 acres)

• The land can now be used for
development.
Haw Creek
Site Characteristics

• Approximately a 5 mile
reach between
Columbus and Hope,
Indiana

• Located in Township
10 N, Range 6 E,
Bartholomew County

• Connects Columbus FIS
and Hope FIS models
Design Criteria
• Significant flooding in the area between the 450
has caused loss in farmland.

• To reduce flooding in this area, a levee will be
constructed and the channel will be excavated to
contain the flow in the channel in this area.

• The effects of this design must not increase
flooding at other locations along the stream.

• Several cross section dimensions were modified to
achieve the desired results.
Example of Modified Cross
Section
Before                                                                                    After
Haw Creek     Plan: Plan 01 04/05/2004                                                  Modified Design       Plan: Plan 01 04/08/2004

.07        .055             .07                                                     .07              .055                 .07
670                                                       Legend                        670                                                         Legend

665                                                   EG 100 year                       665                                                       EG 100 year
WS 100 year                                                                                 WS 100 y ear

Elevat ion (f t)
Elevation (ft)

660                                                       Ground                        660                                                         Ground

Bank Sta                                                                                 Bank Sta
655                                                                                     655

650                                                                                     650

645                                                                                     645
1000     1100      1200       1300        1400   1500                                   1000       1100     1200           1300   1400    1500

Station (ft)                                                                                Station (f t)
Floodplain Delineation

Note: Delineation is based on 10 foot contour mapping.
Results
• The flow was contained in the channel in the
area of concern.

• The velocity of the channel decreased in the
area of modification due to an increase in
volume that the new channel holds therefore
erosion is not a concern.

• The land previously in the floodplain can
now be used for development purposes
without the risk of flooding based on a 100
year storm.
Indian Creek
Area of Study

• Extends upstream
5.75 miles from the
convergence with
the Wabash River to
join an existing DNR
study
• Township 23 N,
Range 5 W,
Tippecanoe County,
IN
Current Situation
• A residential area with bridge is
threatened

• Design must not interfere with housing
or local bridge

• Due to steep topography and high
velocities in the channel, erosion is a
concern
Recommendation

• Selective stream bed modifications in
the surrounding area can alleviate the
flooding problems without interfering
with the bridge.

• The addition of vegetation and riprap
will help decrease erosion.
Before and After
Indian Creek to Wabash      Plan: plan_new     4/24/2004
13
.07                    .04     .07
610                                                                         Legend

600                                                                        EG 100y r
WS 100y r

Elevation (ft)
590                                                                         Ground

Bank Sta
580

570

560
0     100      200      300          400   500        600      700
Station (f t)

Indian Creek to Wabash    Plan: plan_design    4/24/2004
13
.07                    .04     .07
610                                                                         Legend

600                                                                        EG 100y r
WS 100y r
Elevation (ft)

590                                                                        Crit 100y r

Ground
580
Bank Sta

570

560
0     100      200      300          400   500        600      700
Station (f t)
Ind ian Creek to Wabas h              Plan: plan_new

. 07                   .          . 07
610                                            0                                Legend
4

600                                                                             EG 100y r
W S 100y r
Elevation (ft)

590                                                                            Crit 100y r

Ground
580
Bank St a

570

560
0      100      200     300          400       500       600     700
St ation (f t )

Indian Creek to Wabash      Plan: plan_design        4/24/2004

. 07                   . 04         . 07
610                                                                                   Legend

600                                                                                  EG 100y r
WS 100y r
Elevation (ft)

590                                                                                  Crit 100y r

Ground
580
Bank St a

570

560
0         100      200      300           400       500        600       700
St ation (f t )
Results

• Local houses and pasture land are no
longer in the flood plain

• Bridge is not at full capacity

• Erosion is keep to a minimum
Conclusion

As seen in each of the four case
studies, improvements in channel
construction can help contain
floods, reduce erosion, and
optimize usable land.
Any Questions?

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 views: 18 posted: 3/10/2012 language: pages: 34