Development of a Stage-Discharge Rating Curve: Beaver Creek, Springfield, Ohio

James Blumenschein, John Ritter Ph.D.

Wittenberg University, Department of Geology, Springfield, Ohio 45501

In this study, a stage-discharge rating curve was developed for Beaver Creek, a major

tributary of Buck Creek, Springfield Ohio, USA. The selected site was chosen for its

stable channel and bed form. The cross-section where discharge data were collected is

approximately 65 feet wide and exhibits stable channel conditions. Two methods were

used to collect field discharge measurements, the 6/10 Method (which measures flow

velocity at 6/10 of the flow depth from the surface, which approximates the mean velocity

of the water column) coupled with the Area-Velocity Method (which measures discharge

in a cross-stream section). Twelve field discharge measurements were made from June

through November, 2011. For a full characterization of a stage-discharge rating curve,

there was a need to create a synthetic curve to estimate discharges at higher flow stages

that would otherwise be too dangerous to measure by wading. Using the Step-backwater

Method in conjunction with survey and discharge data of the study reach, a stage-

discharge rating curve was developed for discharges up to 5000 cubic feet per second. In

addition, along-stream water surface profiles and along-stream bed profiles for each stage,

at its corresponding discharge, were produced. With a stage-discharge rating curve

developed for Beaver Creek, future changes in both land use and climate can be modeled

with increased resolution and accuracy.

Figure 1 - Map of the Beaver Creek Watershed (shaded

green).

The study reach is located east of Pumphouse Road and includes the cross section where

discharge measurements were recorded (Figure 2). The cross-section is

approximately 65 feet in width and exhibits stable channel conditions. The site is

upstream of a low head dam and immediately downstream of a water quality sonde that

records stage, turbidity, pH, and temperature at fifteen-minute intervals (Figure 3).

Study Area

Beaver Creek, whose drainage area comprises 39 square miles, is a major tributary river to

Buck Creek and makes up 28% of the Buck Creek Watershed (Figure 1). Beaver Creek’s

watershed is generally agricultural in land-use and B and C hydrological soil groups

(Table 1). It is moderately vegetated with forestry, heavily in some areas, row crops, and

pasture land.

Table 1 - Landuse within the Beaver Creek Watershed.

Figure 4 (above) - The study reach looking

upstream from Pumphouse Road.

Figure 5 (Left) - The water quality sonde along

Beaver Creek’s right bank, immediately upstream

of the study cross-section.

Abstract Methodology Field Discharge Measurements 6/10 Method

Velocity measurements taken 6/10 of the flow depth from the water surface

Approximates the mean velocity of the profile

Measurements are free from heavy frictional influence

Area Velocity Method

Coupled with the 6/10 Method

Measures discharge in a cross-stream section

Measurements are taken in smaller sections throughout the cross-section

Discharge is calculated using average velocity throughout the section

Measurements taken using a Sontek Flowtracker (Figure 6)

Handheld Acoustic Doppler Velocimeter

Used with a 4-foot, top setting wading rod

Features: Automatic discharge computation

Quality control that checks for irregularities with the data and

internal workings of the unit (Figure 7)

Figure 6 - A brochure of the Sontek Flowtracker

Figure 7 - Example quality control test on the acoustic beams if the Sontek Flowtracker

Stage-Discharge Rating Curve Development

Step-backwater Method

Uses water surface profiles, channel geometry and discharge data to extrapolate

a stage-discharge rating curve

Optimally used when controls other than channel geometry are present

including: in-line weirs, waterway structures, and dams

Used in conjunction with survey and discharge data of the study reach

Figure 8 - HEC-RAS home screen

Results

Date Start Time End Time Duration Mean Depth (ft) Discharge (cfs) Sonde Stage (ft)

6/27/11 12:30 13:10 0:40 1.629 31.6325 0.665

6/30/11 14:50 15:25 0:35 1.606 26.9736 0.640

7/7/11 12:10 12:37 0:27 1.533 21.4750 0.611

7/8/11 15:22 15:49 0:27 1.545 22.6575 0.612

7/18/11 12:03 12:27 0:24 1.530 17.0275 0.582

7/19/11 16:14 16:39 0:25 1.735 71.0178 0.878

8/3/11 14:21 14:46 0:25 1.653 43.5302 0.709

8/9/11 14:10 14:33 0:23 1.616 36.1130 0.685

8/25/11 16:19 16:51 0:32 1.503 14.9154 0.548

9/27/11 11:18 11:48 0:30 1.726 58.6875 0.784

11/14/11 15:19 15:51 0:32 1.830 82.9664 0.904

11/16/11 12:01 12:29 0:28 1.856 93.8992 0.925

Table 2 - table of the 12 field discharge measurements taken from June through November, 2011.

0

1

2

3

4

06/26/2011 0:0008/05/2011 0:0009/14/2011 0:0010/24/2011 0:00

Wa

ter

Su

rfa

ce E

lev

ati

on

(F

t)

Date & Time

Flow Hydrograph

Figure 3 - Study reach looking downstream

Stage-Discharge Rating Curve

A stage-discharge rating curve was developed for discharges up to 5000 cfs (above)

Along-stream water surface (below, right) and channel velocity (below, left) profiles were

also produced

A

B

C

D

E

F

Figure 11 - XYZ perspective plot of cross-sections with water

surface represented.

Figure 12 - Flow hydrograph of Beaver Creek from June 26

through November 16, 2011.

Further Study The Stage-discharge rating curve is no yet complete

Several items must be worked out:

Gauge Height of Zero Flow (GZF)

The GZF is the point where discharge is immeasurable

It can be measured by taking soundings along the longitudinal thread of

Beaver Creek near the control

In this study, the low-head dam downstream of the study cross-section is

the control

A control is a section (usually channel morphology) that controls the

relation between discharge and stage

The minimum sounding is subtracted from the gauge height

Channel conditions of the reach and the permanent nature of the control

allows for effective measurements of the GZF

Further Measurements

The top part of the curve, beyond the maximum measured discharge, is an

extension extrapolated by the program.

Accuracy of the extrapolation is as clear as the highest measurement.

Measurements at higher discharges will increase the accuracy of the

extension

Acknowledgments I would like the thank Dr. John Ritter for all of his help and support throughout the

duration of this study. I would also like to thank Dr. Mike Zaleha and Dr. Sarah

Fortner for their helpful insights towards the development of this thesis.

Figure 2 - Arial view of the study reach. Note the position of

study cross-section and water quality sonde are approximated.

Fig

ures A

- F - C

ross-sectio

n o

f station

s 14

(A), 1

2 (B

), 11

(C), 1

0 (D

), 08

(E), an

d 0

6 (F

). No

te that statio

n 1

1 (F

) is the lo

w-h

ead d

am.

Figure 9 - Flowtracker program data

output in a printable, report layout.