Stream-Profile Analyses Using a Step-Backwater Model for ... - USGS

6 Stream-Profile Analyses Using a Step-Backwater Model for Selected Reaches in the Chippewa Creek Basin in Ohio
Table 1. Original design characteristics of the Soil Conservation Service flood-retention structures.
[From U.S. Department of Agriculture, 1956]
Flood-retention
structure
Tributary to
Chippewa Creek
Storm recurrence
interval for
flood-retention
structure
(years)
Year
of dam
completion
Drainage area
above dam
(square miles)
Conservation
pool
storage capacity
(acre-feet)
Flood storage
capacity up to the
emergency crest
(acre-feet)
II–A Buck Creek 25 1969 2.95 77 278
III–A Hubbard Creek 50 1980 5.88 124 676
IV–A Fall Creek 25 1973 1.51 16 120
V–C East Branch Steele Ditch 1 25 1971 3.73 None 432
V–D West Branch Steele Ditch 1 25 1971 1.75 30 156
VII–C Little Chippewa Creek 50 1974 14.42 None 2,225
VIII–C River Styx 2 5.7 inches 1976 3.86 None 673
VIII–D Holmes Brook 3 50 1976 2.02 None 427
Totals 36.12 247 4,987
1 East and West Branch Steele Ditch form Steele Ditch, a tributary to Chippewa Creek.
2 This dam designed to control a storm runoff of 5.7 inches in 6 hours.
3 Holmes Brook is a tributary to River Styx.
Table 2. Hydraulic model limits for selected streams in the Chippewa Creek basin, Medina, Wayne, and Summit Counties, Ohio.
Stream Upstream limit Downstream limit
The Inlet 1 About 1,200 feet above
Wedgewood Road /State Route 162
About 750 feet below
Chippewa Road
Reach length
(miles)
Chippewa Creek 2 Chippewa Lake Mouth 19.1
Little Chippewa Creek Steiner Road Mouth 3.2
River Styx Flood Control Structure VII–C Mouth 7.9
1 The Inlet is the head of Chippewa Creek.
2 Westfield Ditch was modeled as an overflow channel to Chippewa Creek.
Study Methods
Data Collection
Field visits were made to the Chippewa Creek basin to
determine applicable stream-channel roughness coefficients
(Manning’s n), cross-section elevations, and geometries of
hydraulic structures. Cross sections and geometries were surveyed
at all structures in each reach. If the distance between
structures was more than 1 mi, an open-channel cross section
was surveyed by the USGS at a convenient location near the
halfway point. By use of a Geographic Information System,
a Triangular Irregular Network (TIN) was developed from
digital 2-ft contour interval mapping provided by Medina,
Wayne, Stark, and Summit Counties to supplement surveyed
cross-sectional data. In-channel bottom elevation data for
TIN-derived cross sections were estimated by interpolating
values between surveyed cross sections. The in-channel
bottom width for each TIN-derived cross section was estimated
from the “AS-BUILT” plans provided by the MWCD
(U.S. Department of Agriculture, 1980) for each stream. The
combination of TIN-derived cross sections with interpolated
in-channel elevations will be referred to as “synthetic” sections
in this report. For this investigation, 246 cross sections
were surveyed in the field (table 3) and 484 synthetic sections
were developed. Geometries of 56 culverts and bridges and
4 low head dams also were obtained from field surveys.
The initial starting water-surface elevation for each
model was determined from a normal-depth calculation in the
HEC-RAS model. The initial slope was determined from the
minimum channel elevations of surveyed cross sections near
the mouth of each stream studied. All models were assumed to
be independent of the downstream water-surface conditions.
Backwater from the receiving stream was not considered in
the beginning of each model. Therefore, the water surface of
each model will most likely be lower than the actual water sur-
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