Floodplain Delineation of Indiana Streams

Allison CraddockTom Gormley

Jessica TempestErin 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 unmapped areas.

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

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

• Performs one dimensional hydraulic analysis for steady and unsteady river systems.

• Energy loss is calculated using Manning’s Equation.

Why Use HEC-RAS?

HEC-RAS

• Inputs– Flow Data

• Drainage area• Discharge

– Cross Section Data• Manning's “n”• Station/Elevation

– Bridge Information• Height• Restrictions

• Outputs– Cross Section Plots– Rating Curves– Detailed Tabular

Output at a Specific Cross Section• Water Surface

Elevation• Flow area of

channel• 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.

Sensitivity Analysis for Q

0

0.5

1

1.5

2

0 2000 4000 6000

Q (cfs)

Sens

itivi

ty

Velocity

Top Width

Elevation

• Velocity and top width proved to be the most sensitive for flow rate.

• Analyzed inputs have a minimal impact on elevation.

Results of Sensitivity Analysis

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 the banks.

Results of Calibration

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

Top width measured: 312.5 ft

Case Studies

Jordan Creek – Allison CraddockBurnett Creek – Tom GormleyHaw Creek – Jessica TempestIndian Creek – Erin Wenger

Jordan Creek

Geographical Data

• 2 mile reach extending south from State Road 26• Township 23 N, Range 5 W, Tippecanoe County, Indiana• Model acts as a southern continuation of Green Meadows 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

0 100 200 300 400 500 600625

630

635

640

645

650

ALTERED senior design 2004 jordan creek Plan: Imported Plan 01 04/14/2004

Station (ft)

Ele

vatio

n (f

t)

Legend

EG PF 2

WS PF 2

EG PF 1

WS PF 1

Ground

Bank Sta

.07 .04

.07

0 100 200 300 400 500 600625

630

635

640

645

650

senior design 2004 jordan creek Plan: Imported Plan 01 04/13/2004

Station (ft)

Ele

vatio

n (f

t)

Legend

EG PF 2

WS PF 2

EG PF 1

WS PF 1

Ground

Bank Sta

.07 .04

.07

Before:Shallow side of creek will flood during a 100 Year storm.

After:Construction of a levee combined with trenching and widening of creek results in usable land.

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

0 500 1000 1500 2000600

610

620

630

640

650

660

Burnett Plan: Plan 04 04/13/2004

Station (ft)E

leva

tion

(ft)

Legend

EG PF 1

WS PF 1

Ground

Bank Sta

.08 .1 .08

• During a 100 year storm, the waterway splits at the I-65 overpass. • By reshaping the channel

where the waterway splits, the floodplain will be greatly reduced.

Channel Split Main Channel

Post Design

0 500 1000 1500 2000600

610

620

630

640

650

660

BurnettDesign Plan: Plan 04 04/13/2004

Station (ft)E

leva

tion

(ft)

Legend

EG PF 1

WS PF 1

Ground

Bank Sta

.08 .1 .08

•Soil will be taken from various locations and used in the reshaping of the land.

•All soil will be excavated from this location.

•The dig areas will: reduce erosion decrease water elevation.

New Channel

Recap of River Station 3508

0 500 1000 1500 2000600

610

620

630

640

650

660

Burnett Plan: Plan 04 04/13/2004

Station (ft)

Ele

vatio

n (f

t)

Legend

EG PF 1

WS PF 1

Ground

Bank Sta

.08 .1 .08

0 500 1000 1500 2000600

610

620

630

640

650

660

BurnettDesign Plan: Plan 04 04/13/2004

Station (ft)

Ele

vatio

n (f

t)

Legend

EG PF 1

WS PF 1

Ground

Bank Sta

.08 .1 .08

Excess Main Channel New Channel

Before Design

After Design

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 North Road Bridge and the 550 North Road bridge 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

1000 1100 1200 1300 1400 1500645

650

655

660

665

670

Haw Creek Plan: Plan 01 04/05/2004

Station (ft)

Elev

atio

n (ft

)

Legend

EG 100 year

WS 100 year

Ground

Bank Sta

.07 .055 .07

1000 1100 1200 1300 1400 1500645

650

655

660

665

670

Modified Design Plan: Plan 01 04/08/2004

Station (ft)

Elev

ation

(ft)

Legend

EG 100 year

WS 100 year

Ground

Bank Sta

.07 .055 .07

Before After

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

0 100 200 300 400 500 600 700560

570

580

590

600

610

Indian Creek to Wabash Plan: plan_new 4/24/2004 13

Station (ft)

Ele

vatio

n (

ft)

Legend

EG 100yr

WS 100yr

Ground

Bank Sta

.07 .04 .07

0 100 200 300 400 500 600 700560

570

580

590

600

610

Indian Creek to Wabash Plan: plan_design 4/24/2004 13

Station (ft)

Ele

vatio

n (f

t)

Legend

EG 100yr

WS 100yr

Crit 100yr

Ground

Bank Sta

.07 .04 .07

0 100 200 300 400 500 600 700560

570

580

590

600

610

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

Station (ft)

Ele

vation (

ft)

Legend

EG 100yr

WS 100yr

Crit 100yr

Ground

Bank Sta

.07 .04 .07

0 100 200 300 400 500 600 700560

570

580

590

600

610

Indian Creek to Wabash Plan: plan_new

Station (ft)

Ele

vation (

ft) Legend

EG 100yr

WS 100yr

Crit 100yr

Ground

Bank Sta

.07 .04

.07

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?