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Determination of the 100-Year Flood Plain on Fourmile Branch at the Savannah River Site, South Carolina, 1996
By TIMOTHY H. LANIER
U.S. GEOLOGICAL SURVEY
Water-Resources Investigations Report 96-4271
Prepared in cooperation with the U.S. DEPARTMENT OF ENERGY
Columbia, South Carolina 1997
U.S. DEPARTMENT OF THE INTERIOR BRUCE BABBITT, Secretary
U.S. GEOLOGICAL SURVEY
Gordon P. Eaton, Director
The use of firm, trade, and brand names in this report is for identification purposes only and does not constitute endorsement by the U.S. Government.
For additional information write to:
District Chief U.S. Geological Survey Stephenson Center-Suite 129 720 Gracern Road Columbia, SC 29210-7651
Copies of this report can be purchased from:
U.S. Geological Survey Branch of Information Services Box 25286 Denver, CO 80225-0286
CONTENTS
Abstract.............................................................................................................._^ 1Introduction.......................................................................................................................................................... 1
Purpose and Scope ...................................................................................................................................... 1Description of Study Area........................................................................................................................... 2Acknowledgment........................................................................................................................................ 2
Hydrologic and Hydraulic Data Collection ......................................................................................................... 2Flood Frequency......................................................................................................................... ......................... 5Model Selection and Development...................................................................................................................... 7One-Hundred-Year Flood Plain and Profile......................................................................................................... 9Summary.................................................................................................................................... ......................... 19Selected References ............................................................................................................................................. 19Appendix - List of Elevations Reference Marks.................................................................................................. 21
PLATE
1. Map showing area' extent of the 100-year flood for Fourmile Branch at the Savannah River Site, near Aiken, South Carolina [in pocket]
FIGURES
1. Map showing Savannah River Site with site areas and streams in Aiken, Allendale,and Barnweli Counties, S.C. ............................................................................................................... 3
2. Map showing boundaries, drainage basins, and stream locations at the SavannahRiver Site, S.C..................................................................................................................................... 4
3. Graph showing relation of percentage impervious area and 100-year recurrenceinterval flow for Fourmile Branch at Road A-7, Savannah River Site, S.C........................................ 6
4-7. Graphs showing the flood profile of Fourmile Branch, Savannah River Site, S.C., from:
4. Station 16000 to Station 24000 and Station 24000 to Station 32000.............................................. 10
5. Station 32000 to Station 40000 and Station 40000 to Station 48000.............................................. 11
6. Station 48000 to Station 56000 and Station 56000 to Station 64000.............................................. 12
7. Station 64000 to Station 72000 and Station 72000 to Station 78771.............................................. 13
TABLES
1. Summary of 100-year recurrence-interval flows for Fourmile Branch, Aiken and BarnweliCounties, S.C.............................................................................................................................................. 8
2. Cross-section name, station, location, type, and 100-year flow, flood-plain width, and water-surface elevation for selected cross sections of Fourmile Branch, Aiken and Barnweli Counties, S.C........................................................................................................................ 14
Contents III
CONVERSION FACTORS, VERTICAL DATUM, AND ABBREVIATIONS
Multiply
foot (ft)
foot per mile (ft/mi)
cubic foot per second (ft /s)
square mile (mi 2 )
By
0.3048
0.1894
0.02832
2.590
To obtain
meter
meter per kilometer
cubic meter per second
square kilometer
Sea Level: In this report, "sea level" refers to the National Geodetic Vertical Datum of 1929 a geodetic datum derived from a general adjustment of the first-order level nets of the United States and Canada, formerly called Sea Level Datum of 1929.
Acronyms used in this report:
ERM Elevation reference markNRCS Natural Resources Conservation ServiceSRS Savannah River SiteUSDOE U. S. Department of EnergyUSGS U.S. Geological SurveyUSC&GS U.S. Coastal and Geodetic SurveyWSPRO Computer model for Water Surface Profile Computations
In this report, the station number represents the distance in feet upstream from the mouth of the subject stream. For example, Station 37600 on Fourmile Branch is 37,600 feet upstream from the mouth of Fouimile Branch.
In this report, the words "right" and "left" refer to the directions that would be reported by an observer facing downstream.
IV Contents
Determination of the 100-Year Flood Plain on Fourmile Branch at the Savannah River Site, South Carolina, 1996By Timothy H. Lanier
Abstract
A hydrologic analysis was made to estimate the 100-year recurrence-interval flow for Fourmile Branch. The analysis showed the South Carolina upper Coastal Plain regional rural- and urban-regres sion equations were applicable for the Fourmile Branch drainage basin. This was verified by analysis of the flood-frequency data collected from U.S. Geo logical Survey gaging station 02197342 on Fourmile Branch.
Cross sections were surveyed throughout the reach, and other pertinent data such as flow resistance and land use were collected. The surveyed cross sec tions and computed 100-year recurrence-interval flows were used in a step-backwater model to compute the 100-year flood profile for Fourmile Branch. The pro file was used to delineate the 100-year flood plain on a topographic map. Results are also provided in tabular and graphical formats.
reactor in 1991, all of the remaining reactors have been placed on stand-by since the late 198CTs. Other areas on the SRS include reactor materials (area M), separation (areas F and H), waste man agement (areas E, F, H, S, Y, and Z), heavy-water processing (area D), administration (areas A, B, and CS), the Savannah River Ecology Laboratory, and the Savannah Technology Center (Arnett and others, 1992).
In 1992, the U.S. Geological Survey (USGS), in cooperation with the USDOE, initi ated an investigation to determine the areal extent of the inundation caused by the 100-year recur rence-interval flow (100-year flow) for the Savar- nah River along the SRS boundary and for the major streams and their tributaries on the SRS, with the exception of Lower Three Runs. This report describes the inundation caused by the 10C- year flow on Fourmile Branch.
INTRODUCTION
In 1951, the U.S. Department of Energy (USDOE), formerly the Atomic Energy Commis sion, created the Savannah River Site (SRS) to produce nuclear materials for national defense. The SRS is located in parts of Aiken, Barnwell, and Allendale Counties, South Carolina. The operation of the first nuclear production reactor, in area R, began in 1953 (fig. 1). In addition, there are four other nuclear reactors at the SRS, located in areas C, K, L, and P. Reactors in areas R and P were permanently deactivated in 1964 and 1991, respectively, and except for the restart testing of K
Purpose and Scope
This report documents the approximate boundaries of the 100-year flood plain on the SRS for Fourmile Branch (fig. 2). One-hundred-yeer flows at selected locations, graphical and tabular profiles of the 100-year flood are listed in tables. Descriptions and elevations of benchmarks for Fourmile Branch are listed in the appendix.
Less-than-detailed methods, which require less cross-sectional definition, were used to com pute the 100-year flood-plain boundaries. In par ticular, cross sections were surveyed primarily at road crossings or other easily accessible locations.
Introduction 1
Intermediate cross sections were interpolated using these surveyed cross sections and 7.5-minute topographic maps (U.S. Geological Survey, 1963-65b). This method was requested by the USDOE, because greater accuracy was not warranted.
Description of Study Area
The SRS occupies more than 300 mi along the Georgia-South Carolina border in parts of Aiken, Bamwell, and Allendale Counties, South Carolina. The southwestern boundary of the SRS is formed by the Savannah River. The five major streams that drain into the Savannah River from the SRS are Upper Three Runs, Fourmile Branch, Pen Branch, Steel Creek, and Lower Three Runs (fig. 2). The SRS is located in the upper Coastal Plain of South Carolina, which encompasses about 20 percent of the State (fig. 1). The general topography of the upper Coastal Plain consists of rounded hills with gradual slopes; however, some areas of highly irregular terrain exist in the prov ince, and some elevations exceed 700 ft above sea level. The highest elevation on the SRS is approx imately 420 ft above sea level, near Tims Branch and the northwest boundary of SRS (fig. 2). The land-surface elevation at the boundary of the upper and lower Coastal Plains, located southeast of the SRS, is usually less than 200 ft above sea level. Upper Coastal Plain stream slopes range from 5 to 20 ft/mi, and many of the streams are bordered by swamps with wide flood plains rela tive to the size of the stream (Zalants, 1990).
The study area is the Fourmile Branch Basin (pi. 1). Fourmile Branch begins just upstream from Road F (fig. 1; pi. 1), and flows into the Savannah River south of Augusta, Ga., at river mile 150.7 (pi. 1). Fourmile Branch enters the Savannah River Swamp approximately 11,400 ft upstream from its confluence with the Savannah River; downstream from this point, Fourmile Branch becomes braided and mixes with flow from the Savannah River. The down stream study limit is the confluence of Fourmile
Branch and the Savannah River; however, 100- year flood-plain and profile computations begin upstream from where Fourmile Branch enters the Savannah River Swamp because of the effect of backwater from the Savannah River (pi. 1). The drainage area of Fourmile Branch before it enters the Savannah River Swamp is 23.0 mi".
The upstream study limit is located at Road F; this point was selected because the drainage area upstream of Road F is less th?n 1.0 mi2 , and there is no urbanization or road crossings upstream of this point. All of the Fciirmile Branch drainage basin lies within the SRS, and contains significant industrialization, which includes areas C, CS, E, F, and H (fig. 1).
Acknowledgment
The author is grateful to Lee Davis, USDOE, for his logistical and administrative sup port of this project.
HYDROLOGIC AND HYDRAULIC DATA COLLECTION
Hydrologic data, which includes drainage area, soil type, impervious area, and peak-flow records at USGS gaging stations, were used to estimate the 100-year flow for Fourmile Branch. The drainage area for the basin was delineated using 7.5-minute series topographic maps (U.S. Geological Survey, 1963-65b) at selected loca tions along the reach. These locations were selected based on major tributary confluences, changes in drainage-area shape, and changes of imperviousness within the drainage basin. Soil types were determined from the Natural Resources Conservation Service (NRCS) [for merly the Soil Conservation Service] soil reports of Aiken and Bamwell Counties and the Savan nah River Plant Area (Rogers, 1977; 1985; 1990). Urbanized areas in the drainage basin were deter mined from aerial photographs, 7.5-minute series
Determination of the 100-Year Flood Plain on Fourmile Branch at the Savannah River Site, South Carolina, 1996
81°50' 81°40' 81°30'
Site BoundarySouth Caro
Savannah River Site
Savannah Technology Center
Savannah River Ecology Laboratory
Upstream x Study Limit)
DownstreamStudy Limit - -
EXPLANATION
UNITED STATES ROUTE
SOUTH CAROLINA ROUTE
SAVANNAH RIVER SITE ROUTE
USGS GAGING STATION AND NUMBER
012345 KILOMETERS
Figure 1. Savannah River Site with site areas and streams in Aiken, Allendale, and Barnwell Counties, S.C.oQ.0)5T oo
9
I§a o 575' o
5"
CD
io
(D
a?
CO
ff
isoOJ
3
81°50' 81°40' 81°30'
33°20'
33°10'
Site Boundary
EXPLANATION
FOURMILE BRANCH BASIN BOUNDARY
BASIN BOUNDARY
HIGHEST LAND SURFACE ELEVATION OF THE SAVANNAH RIVER SITE , IN FEET ABOVE SEA LEVEL
Figure 2. Boundaries, drainage basins, and stream locations at the Savannah River Site, S.C.
topographic maps (U.S. Geological Survey, 1963-655), the SRS Atlas (Savannah River Site, 1994), and field inspections. Only urbanization in and around the industrial areas of the basin, which include areas C, CS, E, F, and H, were considered. Paved roads outside of these areas were not included. Percent-imperviousness data associated with urbanized areas were obtained from Cron- shey and others (1986). Peak-flow data were obtained from USGS gaging station 02197342, Fourmile Branch at Road A-7 (fig. 1). These peak-flow data were used to verify the methods of regionalization of selected recurrence-interval flows described by Guimaraes and Bohman (1992) and Bohman (1992).
Cross sections for the step-backwater analy sis of Fourmile Branch were taken upstream and (or) downstream from bridge and culvert cross ings, along road grades at these crossings, and at selected locations along the streams, such as natu ral or man-made expansions or contractions and powerline right-of-ways. In addition, elevation data and structural geometry for all bridges and culverts were determined. Synthesized cross sec tions were developed using surveyed cross-sec tional data and 7.5-minute series topographic maps (U.S. Geological Survey, 1963-65b).
Cross-section elevations were referenced to sea level. In areas where no elevation reference marks (ERM) were located, a global positioning system was used to establish temporary ERM's. Standard surveying levels were used to reference the temporary ERM's to more per manent structures.
Manning's roughness coefficients used in the hydraulic computations were estimated for the channels and flood plains using engineering judgement. Coefficient estimates were based on field notes, photographs, and methods docu mented by Arcement and Schneider (1984) and Barnes(1967).
FLOOD FREQUENCY
The regionalized rural- and urban-regres sion equations developed by Guimaraes and Bohman (1992) and Bohman (1992) were used to compute the 100-year flow for Fourmile Branch. The use of these equations was verified by a hydrologic analysis of peak-flow data from gag ing station 02197342, Fourmile Branch at Road A-7 (fig. 1). In the hydrologic analysis, the 100- year flow was computed using the log-Pearson method and 23 years of peak-flow data; this 100- year flow was compared to the 100-year flow computed using the regional rural- and urban- regression equations. This comparison showed that the regional rural- and urban-regression equa tions reasonably describe the 100-year flows of Fourmile Branch.
By using the peak-flow data of gaging sta tion 02197342, a 100-year flow of 1,080 ft3 /s was computed using the log-Pearson method. How ever, the 100-year flow computed with the regional rural-regression equation was 661 ft /s. This large difference in computed flows is proba bly the result of the 5.0-percent imperviousness of the basin. However, the lower limit of impervi ousness used to develop the regional urban- regression equations presented by Bohman (1992) is 10 percent. Therefore, a relation of impervious area to flow was established for the drainage area of station 02197342, using the rural flows which assume no significant imperviousness and the urban-regional flows using 10- to 50-percent imperviousness (fig. 3). The relation and an impervious area of 5.0 percent were used to obtain a 100-year flow of 1,170 ft3/s. This flow was adjusted using methods described in Guima raes and Bohman (1992) for determining flood frequency at or near a gaged site on the same stream. A 100-year flow of 1,110 ft3/s was obtained, compared to 1,080 ft3/s computed by log-Pearson methods. The flows are well within the 95-percent confidence limits of both methods. Therefore, the regionalized rural and urban- regression equations were used to compute the 100-year flows on Fourmile Branch.
Flood Frequency
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The equations are:
for rural Upper Coastal Plain watersheds (Guima- raes and Bohman, 1992),
RQ inn = 116 (A)0.69
(1)
and for urban watersheds (Bohman, 1992),
TT^ m At AA°- 506 /^T A\°-932 /r>^ s 0.280 ...UQ loo = 10.4(A) (TIA) (RQ 100 ) , (2)
typically less than 10 percent. Therefore, the pre viously described method to adjust flows for urbanization at Station 02197342 was used to compute flows for the subbasins which had an imperviousness of less than 10 percent.
The 100-year flow was computed at 15 loca tions on Fourmile Branch. The drainage area of nine of these sites was within 50 percent of the drainage area of the Station 02197342, therefore the flows were adjusted using the methods described in Guimaraes and Bohman (1992). The results of the hydrologic analysis on Fourmile Branch are presented in table 1.
whereRQioo is me 100-year recurrence-inter
val flow for rural drainage basins, in cubic feet per second;
A is the drainage area, in square miles;
UQjoo is the 100-year recurrence-inter val flow for urban drainage basins, in cubic feet per second; and
TIA is the total impervious area, in per cent of total drainage area.
Equation 1 requires that the drainage areas be greater than 4.4 mi2 and less than 1,720 mi2 . However, the relation was extended downward to 1.04 mi2 , because no other regional-regression equations specific to South Carolina were avail able. This extrapolation seems to be viable, because the logarithmic regional relation is linear. In addition, the relations for other physiographic provinces are generally linear throughout the range of data, and therefore, it is expected that the relation for the upper Coastal Plain could be extrapolated below a drainage area of 4.4 mi2 .
Equation 2 requires that the impervious area be greater than 10 percent, and the drainage area be greater than 0.18 mi2 and less than 41.0 mi2 . The subbasins of Fourmile Branch meet the drain age area requirement for urbanized basins; how ever, the impervious area of the subbasins is
MODEL SELECTION AND DEVELOPMENT
Water-surface elevations for the 100-year flows were computed for Fourmile Branch by using either the USGS/Federal Highways Admin istration step-backwater water-surface profile computer model (WSPRO) (Shearman and others, 1986; Shearman, 1990), or where flow is affected by backwater from the Savannah River, data from Lanier (1996) were used. The WSPRO model can compute backwater caused by bridges without subdividing the reach; however, the reach must be subdivided at culverts and a separate culvert-flow computation must be made to determine the back water caused by the culvert. The culvert backwa ter was calculated using the USGS A-526 culvert- flow model (Bodhaine, 1968). The computed water-surface elevation at the approach to the cul vert was used as the initial water-surface elevation for the WSPRO analysis of the next upstream reach.
The downstream limit of the Fourmile Branch study area was located at the confluence of the Savannah River. Because the drainage area of the Savannah River is much larger than the drainage area of Fourmile Branch, it is assumed that at the time of the 100-year flood, the flow in Fourmile Branch would have peaked and receded before peak flow occurred on the Savannah River.
Model Selection and Development
Table 1.--Summary of 100-year recurrence-interval flows for Fourmile Branch, Aiken and Barnwell Counties, S.C.
[mi~, square miles; ft /s, cubic feet per second; ft, feet; --, cross section not surveyed; *, impervious area les? than 1 percent.]
Location (plate 1)
Station 2 1707; Road A- 12. 2
Station 32057; at Road A
Station 38000; 5,943 ft upstream from Road A and 3,650 ft downstream from Road 3
Station 39950; upstream from the confluence with an unnamed tributary; 1 ,700 ft below Road 3
Station 44888; Road A-7
Station 49750; 4,862 ft upstream from Road A-7 and 5,372 ft downstream from Road C-4
Station 52500; 2,622 ft downstream fromRoad C-4
Station 55350; 228 ft upstream from Road C-4
Station 59623; 3 15 ft upstream from Road C
Station 63813; 340 ft downstream from Road 4
Station 65238; 1,085 ft upstream from Road 4
Station 71750; 3,918 ft upstream from Road E-l
Station 73400; 5,568 ft upstream from Road E-l and 5,320 ft downstream from Road F
Station 76750; 1,970 ft downstream from Road F
Station 78720; at Road F
Drainage area (mi2)
21.9
18.7
17.1
13.3
12.5
11.4
10.7
8.15
6.96
6.08
4.50
3.66
1.91
1.29
1.04
Percentage of
impervious area
3
4
4
5
5
5.5
5.5
5
2
3
*
*
*
*
*
One- hund red- year flow
(tt3/s)
'1,380
1 1 ,400
'1,320
'1,170
'1,110
1 1 ,060
'1,030
'823
'590
570
327
284
181
138
119
Cross- section name
BR30
BR70
S97.5
EMB
SE240
'Flow adjusted using data from gaging station 02197342.
8 Determination of the 100-Year Flood Plain on Fourmile Branch at the Savannah River Site, South Carolina, 1996
The elevation of the 100-year flood on the Savan nah River at the mouth of Fourmile Branch is 106.0 ft, which intersects Fourmile Branch at Sta tion 22625. Therefore, due to the backwater of the Savannah River, the initial Fourmile Branch water-surface elevation was computed by slope conveyance at cross section SEC 10, which is located 18,287 ft upstieam of the confluence of Fourmile Branch and the Savannah River (pi. 1). The 100-year flood elevation on the Savannah River of 106.0 ft intersects the 100-year flood ele vation on Fourmile Branch at Station 19846.
the CSX Railway Bridge. The old road embank ment just upstream of Road 4 causes 1.9 ft of backwater. In addition, Roads A-7, C-4, and E-l are overtopped by a depth of 2.7 ft, 1.2 ft, and 1.0 ft, respectively. Graphical and tabular profiles of Fourmile Branch are shown in figures 4 through 7 and listed in table 2, respectively. The areal extent of the inundation caused by the 100- year flood on Fourmile Branch is shown in plate 1.
ONE-HUNDRED-YEAR FLOOD PLAIN AND PROFILE
Fourmile Branch was analyzed from its con fluence with the Savannah River to Road F (pi. 1). Station 0 is located at the confluence of Fourmile Branch and Savannah River. The 78,800-ft long study segment consists of 49-surveyed and 132-synthetic cross sections. Within the study area, there are 4 highway bridges, 1 railway bridge, 5 culvert crossings, and 10 breached dams or old road beds that cross Fourmile Branch. The highway bridges are located on Roads A-12.2, A, C,"and 4 at Stations 21707, 32057, 59308, and 64153, respectively (pi. 1). The CSX railway bridge crosses Fourmile Branch at Station 25806 (pi. 1). The culverts are located at Roads 3, A-7, C-4, E-l, and F at Stations 41650, 44888, 55122, 67832, and 78720, respectively (pi. 1). The breached dams/road beds are located at Stations 18457, 21885, 24807, 27132, 35870, 36307, 39930, 49654, 59391, and 64218 (pl.l). Roads 6-1, 6-2, 6-3, and A-6 are located at Stations 32650, 33250, 34020, and 46475, respectively, but do not cross Fourmile Branch. In the area of Fourmile Branch affected by backwater from the Savannah River, the 100-year flood-plain widths range from 1,150 ft at Station 15850 to 350 ft at Station 20500 (pi. 1). Outside of this area, the 100-year flood-plain widths range from 900 ft at Station 58025 to 120 ft at Station 68250 (pi. 1). Backwater caused by the road and railway bridges ranges from less than 0.1 ft at Road C to 2.0 ft at
One-hundred-Year Flood Plain and Profile
150
140
- 130
120
OCD
110<
100
9016,000
I100-YEAR WATER-SURFACE ELEVATION
BED ELEVATION
TOP OF ROAD
LOW STEEL OF DRAINAGE STRUCTURE
SURVEYED CROSS SECTION AND IDENTIFIER
(SECIO&DAMIS)
.I,,,,
18,000 20,000 22,000 24,000
DISTANCE UPSTREAM FROM THE CONFLUENCE WITH SAVANNAH RIVER, IN FEET
160
OCD
150-
140
130
8' 120 <
110
100
DC 0)
100-YEAR WATER-SURFACE ELEVATION
BED ELEVATION
TOP OF ROAD
LOW STEEL OF DRAINAGE STRUCTURE
(RDeoa'sEcei) SURVEYED CROSS SECTION AND IDENTIFIER j
(DAM38 & SEC39)
24,000 26,000 28,000 30,000 32,000
DISTANCE UPSTREAM FROM THE CONFLUENCE WITH SAVANNAH RIVER, IN FEET
Figure 4. Flood profile of Fourmile Branch, Savannah River Site, S.C., from (a) Station 16000 to Station 24000 and (b) Station 24000 to Station 32000.
10 Determination of the 100-Year Flood Plain on Fourmile Branch at the Savannah River Site, South Carolina, 1996
170
160
- 150
140
130 <
120 -
I
100-YEAR WATER-SURFACE ELEVATION
BED ELEVATION
TOP OF ROAD
LOW STEEL OF DRAINAGE STRUCTURE
SURVEYED CROSS SECTION AND IDENTIFIER
(JRD90 & SEC92)
^EX69, BR70, & APP7g)
no32,000 34,000 36,000 38,000
DISTANCE UPSTREAM FROM THE CONFLUENCE WITH SAVANNAH RIVER, IN FEET
40,000
180
170
160
150
140-
130-
(SEC99& SE100)
I
100-YEAR WATER-SURFACE ELEVATION
BED ELEVATION
TOP OF ROAD
LOW STEEL OF DRAINAGE STRUCTURE
SURVEYED CROSS SECTION AND IDENTIFIER
LOW POINT OF ROAD, 160 FEET TO THE RIGHT OF THE CULVERT AT ROAD A-7
12040,000 42,000 44,000 46,000
DISTANCE UPSTREAM FROM THE CONFLUENCE WITH SAVANNAH RIVER, IN FEET
48,000
Figure 5. Flood profile of Fourmile Branch, Savannah River Site, S.C., from (a) Station 32000 to Station 40000 and (b) Station 40000 to Station 48000.
Figures 11
210
200
- 190
180
170 <
160
150
y -L
1 00-YEAR WATER-SURFACE ELEVATION
BED ELEVATION
TOP OF ROAD
LOW STEEL OF DRAINAGE STRUCTURE
SURVEYED CROSS SECTION AND IDENTIFIER
I
(DM130. SW131, SE1J2. & SE133)
48,000 50,000 52,000 54,000 56,000
DISTANCE UPSTREAM FROM THE CONFLUENCE WITH SAVANNAH RIVER, IN FEET
230
OCQ <
z O
220 -
210
200 -
190
180
I
100-YEAR WATER-SURFACE ELEVATION
BED ELEVATION
TOP OF ROAD
LOW STEEL OF DRAINAGE STRUCTURE
SURVEYED CROSS SECTION AND IDENTIFIER
(SE160 BR170. & AP18(Q
17056,000 58,000 60,000 62,000 64,000
DISTANCE UPSTREAM FROM THE CONFLUENCE WITH SAVANNAH RIVER, IN FEET
Figure 6. Flood profile of Fourmile Branch, Savannah River Site, S.C., from (a) Station 48000 to Station 56000 and (b) Station 56000 to Station 64000.
12 Determination of the 100-Year Flood Plain on Fourmile Branch at the Savannah River Site, South Carolina, 1996
250
240 -
230-
Om
Q<
_ _ _ _ 100-YEAR WATER-SURFACE ELEVATION
BED ELEVATION
TOP OF ROAD
LOW STEEL OF DRAINAGE STRUCTURE
iiTSD SURVEYED CROSS SECTION AND IDENTIFIER
(FV209. SE210, & AP220)
XSE190. BR' 90. & AP200)
220 -
64,000 66,000 68,000 70,000
DISTANCE UPSTREAM FROM THE CONFLUENCE WITH SAVANNAH RIVER, IN FEET
72,000
~7 270 L
Om
Q - - - - 100-YEAR WATER-SURFACE ELEVATION
BED ELEVATION
T TOP OF ROAD
-1 LOW STEEL OF DRAINAGE STRUCTURE
SURVEYED CROSS SECTION AND IDENTIFIER
260-
250-
240-
23072,000 74,000 76,000 78,000
DISTANCE UPSTREAM FROM THE CONFLUENCE WITH SAVANNAH RIVER, IN FEET
80,000
Figure 7. Flood profile of Fourmile Branch, Savannah River Site, S.C., from (a) Station 64000 to Station 72000 and (b) Station 72000 to Station 78771.
Selected References 13
o <DTa
ble
2.--
Cro
ss-s
ectio
n na
me,
sta
tion,
loc
atio
n, t
ype,
and
100
-yea
r flo
w,
flood
-pla
in w
idth
, an
d w
ater
-sur
face
ele
vatio
n fo
r se
lect
ed c
ross
sec
tions
of
Four
mile
Bra
nch,
Aik
en a
nd B
arnw
ell C
ount
ies,
S.C
.
ion
of
the
100-
Year -n 0 o Q. o CO 3'
0 -n
o c <D Branch
at tl .j o w CO CO 3 CO 2 0 w p V) o c O m o_ 5' 0) _L tO J)
[11
/t
>,
CU
U1C
ltd
JJC
1
:
Cro
ss-s
ecti
on
nam
e
SEC
10
DA
M 1
5
S17.
3
SYN
19
SEC
20
SYN
21
EX
29
BR
30
S3 1
.5
SEC
32
SYN
37
DA
M38
SEC
39
EX
40
>C
CU
11
VJ,
1
1,
It-S
/lJ
Cro
ss-s
ectio
n st
atio
n
1828
7
1845
7
1900
0
2028
3
2034
0
2039
0
2160
2
2170
7
2188
5
2195
5
2479
0
2480
7
2484
7
2568
0
Cro
ss-s
ectio
n lo
catio
n
170
ft do
wns
trea
m f
rom
a b
reac
hed
dam
Bre
ache
d da
m, 3
,250
ft d
owns
trea
m f
rom
Roa
dA
-12.
2
543
ft up
stre
am f
rom
a b
reac
hed
dam
57 f
t do
wns
trea
m f
rom
an
unna
med
pow
erlin
e
Unn
amed
pow
erlin
e, 1
,367
ft d
owns
trea
m f
rom
R
oad
A- 1
2.2
50 f
t ups
trea
m f
rom
an
unna
med
pow
erlin
e
105
ft do
wns
trea
m f
rom
Roa
d A
-12.
2
Bri
dge
at R
oad
A-1
2.2
Bre
ache
d da
m,
1 78
ft up
stre
am f
rom
Roa
dA
-12.
2
248
ft up
stre
am f
rom
Roa
d A
-l 2
.2
1 7 f
t do
wns
trea
m f
rom
a b
reac
hed
dam
Bre
ache
d da
m.
3,10
0 ft
upst
ream
fro
m R
oad
A-1
2.2
40 f
t up
stre
am f
rom
a b
reac
hed
dam
126
ft do
wns
trea
m f
rom
CSX
rai
lway
bri
dge
Type
of
cros
s se
ctio
n1
surv
eyed
surv
eyed
synt
hetic
synt
hetic
surv
eyed
synt
hetic
synt
hetic
surv
eyed
surv
eyed
surv
eyed
synt
hetic
surv
eyed
surv
eyed
surv
eyed
1 00-
year
flo
w
(ft3/
s)
1,38
0
1,38
0
1,38
0
1,38
0
1,38
0
1,38
0
1,38
0
1,38
0
1,38
0
1,38
0
1,38
0
1,38
0
1,38
0
1,38
0
1 00-
year
fl
ood-
plai
n w
idth
(«)
636 73 541
318
320
318
523 85 108
548
521
483
526
375
100-
year
w
ater
-sur
face
el
evat
ion
(ft, a
bove
sea
leve
l)
2 1 0
6.0
2 1 0
6.0
2l06
.0
106.
64
106.
74
106.
81
110.
06
31 1
0.09
1 1 1
.25
111.
75
117,
86
117,
85
118.
09
120.
20
Tabl
e 2.
--C
ross
-sec
tion
nam
e, s
tatio
n, l
ocat
ion,
typ
e, a
nd 1
00-y
ear
flow
, flo
od-p
lain
wid
th,
and
wat
er-s
urfa
ce e
leva
tion
for
sele
cted
cro
ss s
ectio
ns o
f Fo
urm
ile B
ranc
h, A
iken
and
Bar
nwel
l Cou
ntie
s, S
.C.--
Con
tinue
d
[ft3
/s, c
ubic
fee
t per
sec
ond;
ft,
feet
]
Cro
ss-s
ectio
n na
me
RB
R50
APP
55
SYN
59
RD
60
SEC
61
EX
69
BR
70
APP
72
SEC
80
S80.
5
SYN
81
SEC
84
DA
M85
SY85
B
SYN
89
BR
D90
SEC
92
Cro
ss-s
ectio
n st
atio
n
2580
6
2593
3
2711
2
2713
2
2715
2
3199
5
3205
7
3211
9
3265
0
3325
0
3402
0
3584
5
3587
0
3589
0
3629
5
3630
7
3631
9
Cro
ss-s
ectio
n lo
catio
n
CSX
rai
lway
brid
ge
1 27
ft up
stre
am f
rom
CSX
rai
lway
bri
dge
20 f
t dow
nstr
eam
fro
m a
n un
nam
ed p
ower
line
Unn
amed
pow
erlin
e ro
ad,
1 ,32
6 ft
upst
ream
fr
om th
e C
SX r
ailw
ay b
ridg
e
20 ft
ups
trea
m fr
om a
n un
nam
ed p
ower
line
62 f
t dow
nstr
eam
fro
m R
oad
A
Bri
dge
at R
oad
A, (
Rou
te S
.C.
125)
62 f
t ups
trea
m f
rom
Roa
d A
Roa
d 6-
1
Roa
d 6-
2
Roa
d 6-
3
25 f
t dow
nstr
eam
fro
m a
bre
ache
d da
m
Bre
ache
d da
m, 3
,813
ft u
pstr
eam
fro
m R
oad
A
20 f
t ups
trea
m f
rom
a b
reac
hed
dam
12 f
t dow
nstr
eam
fro
m a
bre
ache
d ro
ad
Bre
ache
d ro
ad, 4
,250
ft u
pstr
eam
fro
m R
oad
A
1 2 f
t ups
trea
m f
rom
a b
reac
hed
road
Type
of
cros
s se
ctio
n1
surv
eyed
synt
hetic
synt
hetic
surv
eyed
surv
eyed
surv
eyed
surv
eyed
surv
eyed
surv
eyed
synt
hetic
synt
hetic
surv
eyed
surv
eyed
synt
hetic
synt
hetic
surv
eyed
surv
eyed
100-
year
flo
w
(ft3/
s)
1,38
0
1,38
0
1,38
0
1,38
0
1,38
0
1,40
0
1,40
0
1,40
0
1,40
0
1,40
0
1,40
0
1,40
0
1,40
0
1,40
0
1,32
0
1,32
0
1,32
0
100-
year
flo
od-p
lain
w
idth
(ft
) 38 474
432
167
443
354 38 374
278
244
221
434 99 436
414
277
414
100-
year
w
ater
-sur
face
el
evat
ion
(ft, a
bove
se
a le
vel)
3120
.50
122.
62
123.
31
5123
.38
123.
66
134.
89
3134
.89
136.
11
5136
.68
5137
.58
5139
.23
143.
56
143.
59
143.
76
144.
42
5 144
.43
144.
46
Tabl
e 2.
-Cro
ss-s
ectio
n na
me,
sta
tion,
loc
atio
n, t
ype,
and
100
-yea
r flo
w, f
lood
-pla
in w
idth
, an
d w
ater
-sur
face
ele
vatio
n fo
r se
lect
ed c
ross
sec
tions
of
Four
mile
Bra
nch,
Aik
en a
nd B
arnw
ell C
ount
ies,
S.C
.-C
ontin
ued
[ft
/s, c
ubic
fee
t per
sec
ond;
ft,
feet
]S srmination
of
tl j (D 0
O (D 0) n o a T
J0) 3' O ^n :ourmi (D 7 3
O 3-
0) (D (/> 0) 0) 3
3
0) 3-
3) i 1 o c o 0) o. 5' 0)
L
7
i
Cro
ss-s
ecti
on
nam
e
S96.
5
DA
M97
S97.
5
SEC
99
SE10
0
APP
99
SE10
9
EM
B
APP
R1
RW
119
RD
120
RW
121
API
22
DM
130
swm
Cro
ss-s
ectio
n st
atio
n
3991
0
3993
0
3995
0
4149
5
4165
0
4171
6
4467
2
4488
8
4492
7
4643
9
4647
5
4651
1
4673
5
4965
4
4Q66
Q
Cro
ss-s
ectio
n lo
catio
n
20 ft
dow
nstr
eam
fro
m a
bre
ache
d da
m
Bre
ache
d da
m,
1 ,72
0 ft
dow
nstr
eam
fro
mR
oad
3
20 f
t ups
trea
m f
rom
a b
reac
hed
dam
1 55
ft do
wns
trea
m f
rom
Roa
d 3
Roa
d 3
66 f
t ups
trea
m f
rom
Roa
d 3
216
ft do
wns
trea
m f
rom
Roa
d A
-7
Roa
d A
-7
39 f
t ups
trea
m f
rom
Roa
d A
-7
36 f
t dow
nstr
eam
fro
m R
oad
A-6
Roa
d A
-6
36 f
t ups
trea
m f
rom
Roa
d A
-6
260
ft up
stre
am f
rom
Roa
d A
-6
Bre
ache
d da
m, 6
6 ft
dow
nstr
eam
fro
m th
edo
wns
trea
m e
dge
of a
n un
nam
ed p
ower
line
5 1
ft d
ow
nst
ream
frr
mi
the d
ow
nst
ream
edoe n
f
Type
of
cros
s se
ctio
n1
synt
hetic
surv
eyed
surv
eyed
surv
eyed
surv
eyed
synt
hetic
surv
eyed
surv
eyed
surv
eyed
synt
hetic
surv
eyed
surv
eyed
surv
eyed
surv
eyed
surv
ived
100-
year
flo
w
(ft3/
s)
1,32
0
1,32
0
1,32
0
1,17
0
1,17
0
1,17
0
1,11
0
1,11
0
1,11
0
1,06
0
1,06
0
1,06
0
1,06
0
1,06
0
i n^
n
1 00-
year
fl
ood-
plai
n w
idth
/£A
\(f
t)
514
4148 514
369
324
389
404
132
327
281
250
279
422
245
TO
8
100-
year
w
ater
-sur
face
el
evat
ion
(ft, a
bove
sea
leve
l)
151.
16
151.
18
151.
29
155.
08
157.
72
157.
72
161.
05
6163
.37
163.
80
165.
16
5165
.21
165.
28
165.
78
171.
11
171
91
an u
nnam
ed p
ower
line
0> IN)
Tab
le 2
.--C
ross
-sec
tion
nam
e, s
tatio
n, l
ocat
ion,
typ
e, a
nd 1
00-y
ear
flow
, flo
od-p
lain
wid
th,
and
wate
r-su
rface
ele
vatio
n fo
r se
lect
ed c
ross
sec
tions
of
Fou
rmile
Bra
nch,
Aik
en a
nd B
arnw
ell
Cou
ntie
s, S
.C.-
-Con
tinue
d
| IV
/s,
cubi
c fe
el p
er s
econ
d; l
l, fe
el)
Cro
ss-s
ectio
n na
me
Cro
ss-s
ectio
n ^
. .
. ..
Cro
ss-s
ectio
n lo
catio
n st
atio
n
Type
of
cros
s se
ctio
n1
100-
year
flo
w
(ft3
/s)
100-
year
flo
od-p
lain
w
idth
(f
t)
100-
year
w
ater
-sur
face
el
evat
ion
(ft,
abov
e se
a le
vel)
SE13
2
SE13
3
SW13
3
4973
5
4980
4
4981
0
SE13
9
EX 140
RDC4
AP150
SE16
0
BR170
API 80
SE190
BR190
AP20
0
FV209
SE210
AP220
54827
55056
55122
55149
58916
59308
59391
63910
6415
3
64218
6781
3
67832
67868
15 f
t ups
trea
m f
rom
the
dow
nstr
eam
edg
e of
an
unna
med
pow
erlin
e
26 f
t dow
nstr
eam
fro
m t
he u
pstr
eam
edg
e of
an
unna
med
pow
erlin
e
20 f
t dow
nstr
eam
fro
m th
e up
stre
am e
dge
of a
n un
nam
ed p
ower
line
295
ft do
wns
trea
m f
rom
Roa
d C
-4
66 f
t dow
nstr
eam
fro
m R
oad
C-4
Roa
d C
-4
27 f
t ups
trea
m f
rom
Roa
d C
-4
392
ft do
wns
trea
m f
rom
Roa
d C
Bri
dge
at R
oad
C
Old
Roa
d be
d, 8
3 ft
upst
ream
fro
m R
oad
C
243
ft do
wns
trea
m f
rom
Roa
d 4
Bri
dge
at R
oad
4
Old
roa
d be
d, 6
5 ft
upst
ream
fro
m R
oad
4
19 f
t dow
nstr
eam
fro
m R
oad
E-l
Roa
dE-1
36 f
t ups
trea
m f
rom
Roa
d E
-l
surv
eyed
surv
eyed
synt
hetic
1,06
0
1,06
0
1,06
0
391
406
405
171.
31
171.
37
171.
37
surv
eyed
surv
eyed
surv
eyed
surv
eyed
surv
eyed
surv
eyed
surv
eyed
surv
eyed
surv
eyed
surv
eyed
surv
eyed
surv
eyed
surv
eyed
1,03
0
1,03
0
1,03
0
1,03
0
590
590
590
570
570
570
327
327
327
326
752
315
378
571 60 37 322 45 54 266 93 315
181.
38
183.
01
6186
.75
186.
98
191.
67
3 192
.70
192.
95
202.
37
3203
.22
203.
61
216.
61
6219
.59
219.
80
Tabl
e 2.
--C
ross
-sec
tion
nam
e, s
tatio
n, lo
catio
n, ty
pe, a
nd 1
00-y
ear f
low
, flo
od-p
lain
wid
th,
and
wat
er-s
urfa
ce e
leva
tion
for
sele
cted
cro
ss s
ectio
ns o
f Fo
urm
ile B
ranc
h, A
iken
and
Bar
nwel
l Cou
ntie
s, S
.C.-C
ontin
ued
3 21
o" 3 a CD _L O -n o 0 ex
o £.3* O
3 51 5"
co i o 3" O 0) 0> 3
" 31 1 O c 5
O 1 j>
Cro
ss-s
ectio
n C
ross
-sec
tion
nam
e st
atio
n
EX
230
7865
9
SE24
0 78
720
APP
F 78
771
Cro
ss-s
ectio
n lo
catio
n
61 f
t dow
nstr
eam
fro
m R
oad
F
Roa
dF
5 1
ft up
stre
am f
rom
Roa
d F
Type
of
100-
year
cr
oss
flow
se
ctio
n1
(ft3/
s)
surv
eyed
1 1
9
surv
eyed
1 1
9
synt
hetic
1 1
9
100-
year
^J
floo
d-pl
ain
wat
er-s
urfa
cew
idth
f'
evaKt
l0n
,m
(ft, a
bove
v ;
sea
leve
l)
176
276.
88
10
3277
.82
183
277.
82
*A11
sur
veye
d cr
oss
sect
ions
are
sho
wn
on p
late
1;
synt
hetic
cro
ss s
ectio
ns a
re n
ot s
how
n on
pla
te 1
. 2B
ackw
ater
fro
m th
e Sa
vann
ah R
iver
. 3R
oad
or r
ailw
ay is
not
ove
rtop
ped.
4D
ue to
mor
e th
an o
ne b
reac
h in
the
dam
, the
flo
od-p
lain
wid
th m
ay n
ot m
atch
pla
te 1
. 5R
oad
does
not
cro
ss F
ourm
ile B
ranc
h.
6Roa
d is
ove
rtop
ped.
7D
ue to
roa
d ov
erfl
ow, t
his
floo
d-pl
ain
wid
th i
s in
crea
sed
to th
e sa
me
floo
d-pl
ain
wid
th a
s cr
oss
sect
ion
RD
C4.
SUMMARY SELECTED REFERENCES
In 1951, the U.S. Department of Energy, formerly the Atomic Energy Commission, created the Savannah River Site to produce nuclear mate rials for national defense. The Savannah River Site occupies approximately 300 square miles along the Georgia-South Carolina border in parts of Aiken, Barnwell, and Allendale Counties, South Carolina. In 1992, the U.S. Geological Sur vey, U.S. Department of the Interior, in coopera tion with the U.S. Department of Energy, initiated an investigation to determine the areal and verti cal extent of inundation caused by the 100-year recurrence-interval flood for the Savannah River along the Savannah River Site southwestern boundary, and for the major streams and their trib utaries on the Savannah River Site, with the exception of Lower Three Runs.
This report includes a map of the 100-year flood plain and flood profile on Fourmile Branch. The results also are provided in tabular format. The 100-year flood-plain map and flood profile provide water-resource managers with a technical basis for making flood-plain management deci sions that could minimize future flood problems and provide a basis for designing and constructing drainage structures along roadways.
A hydrologic analysis was made to estimate the 100-year recurrence-interval flow for Four- mile Branch and its tributaries. This analysis showed the U.S. Geological Survey regional rural- and urban-regression equations for South Carolina reasonably describe the 100-year flows of Fourmile Branch.
Throughout the reach, cross sections were surveyed and other pertinent data such as flow resistance and land-use data were collected. The computed 100-year flows and surveyed cross sec tions were used in a step-backwater model to compute the 100-year flood plain for Fourmile Branch. The profiles computed by the step-back water model were used to delineate the 100-year flood plain on topographic maps.
Arcement, G.J., Jr., and Schneider, V.R.. 1984, Guide for selecting Manning's roughness coefficients for natural channels and flood plains: Federal Highway Administration Pub lication FHWA-TS-84-204, 62 n.
1989, Guide for selecting Manning's roughness coefficients for natural channels and flood plains: U.S. Geological Survey Water-Supply Paper 2339, 38 p.
Arnett, M.W., Karapatakis, L.K., Mamatey, A.R., and Todd, J.L., 1992, Savannah River Site environmental report for 1991: Westinghouse Savannah River Company Publication WSRC-TR-92-186, 562 p.
Barnes, H.H., Jr., 1967, Roughness characteristics of natural channels: U.S Geological Survey Water-Supply Paper 1849, 213 p.
Bodhaine, G.L., 1968, Measurement of peak dis charge at culverts by indirect methods: U.S. Geological Survey Techniques of Water- Resources Investigations, book 3, chap. A3, 60 p.
Bohman, L.R., 1992, Determination of flood hydrographs for streams in South Carolina: Volume 2. Estimation of peak-discharge fre quency, runoff volumes, and flood hydro- graphs for urban watersheds: U.S Geological Survey Water-Resources Investigations Report 92-4040, 79 p.
Chow, V.T., 1959, Open-Channel Hydraulics: New York, MacMillan Publishing Co., Inc., 522 p.
Cronshey, Roger; McCuen, R.H.; Miller, Norman; Rawls, Walter; Robbins, Sam; and Wood ward, Don, 1986, Urban hydrology for small watersheds: Soil Conservation Service, Tech nical Release 55, Washington D.C., 94 p.
Guimaraes, W.B., and Bohman, L.R., 1992, Tech niques for estimating magnitude and fre quency of floods in South Carolina, 1988: U.S. Geological Survey Water-Resources Investigations Report 91-4157, 174 p.
Hulsing, Harry, 1967, Measurement of peak dis charge at dams by indirect methods: U.S.
Summary 19
Geological Survey Techniques of Water- Resources Investigations, book 3, chap. A5, 29 p.
Lanier, T.H., 1996, Determination of the 100-year flood plain on Upper Three Runs and selected tributaries, and the Savannah River at the Savannah River Site, South Carolina, 1995: U.S. Geological Survey Water-Resources Investigations Report 96-4014.
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Savannah River Site, 1994, Savannah River Site atlas including off-site locations and index, OSR3-158,40p.
Shearman, J.O., 1990, User's manual for WSPRO a computer model for water surface profile computations: Federal Highway Administration Publication FHWA-IP-89- 027,187 p.
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U.S. Geological Survey, 1963, New Ellenton SE, S.C., quadrangle: 7.5-minute series topo graphic map, scale 1:24,000.
1964, Girard NW, S.C., quadrangle: 7.5-minute series topographic map, scale 1:24,000.
1965a, New Ellenton SW, S.C., quadran gle: 7.5-minute series topographic map, scale 1:24,000.
1965b, Shell Bluff Landing, Ga.-S.C..quadrangle: 7.5-minute series topographic map, scale 1:24,000.
Zalants, M.G., 1990, Low-flow characteristics of natural streams in the Blue Ridge. Piedmont, and upper Coastal Plain physiographic prov inces of South Carolina: U.S. Geological Sur vey Water-Resources Investigations Report 90-4188, 92 p.
20 Determination of the 100-Year Flood Plain on Fourmile Branch at the Savannah River Site, South Carolina, 19
APPENDIX
List of Elevation Reference Marks
Appendix 21
APPENDIX-List of Elevation Reference Marks
[ft, feet; USGS, U.S. Geological Survey; mi. mile; USC&GS, U.S. Coastal and Geodetic Survey] (In this report, the words "right" and "left" refer to directions that would be reported by an
observer facing downstream.)
Benchmark LocationElevation atove sea
level(ft)
FMB30 Chiseled square in the downstream left end of the Road A-12.2bridge crossing Fourmile Branch; 10,326 ft downstream from Road A. Established by the USGS.
112.49
FMB50 Chiseled square in the downstream left abutment headwall of the CSX Railway bridge crossing Fourmile Branch, 6,257 ft down stream from Road A. Established by the USGS.
146.67
FMB70 Chiseled square in the upstream left abutment headwall of theRoad A bridge crossing Fourmile Branch. Established by the USGS.
146.02
FMB170 Chiseled square on the downstream left abutment headwall of theRoad C bridge crossing Fourmile Branch. Established by the USGS.
202.68
R102 Brass tablet located 3.15 mi southwest of the junction of Road C and Road 3, about 0.4 mi northeast of four 6-ft diameter concrete pipes over Fourmile Branch, at the junction of the woods road leading north, 59 ft north of the center line of Road 3, 37 ft west of the center line of the woods road, 2 ft east of the metal witness post, 1.5 ft below the level of the highway. Established by the USC&GS.
200.154
U102 Brass tablet located at the junction of Roads C and 5, set in the junc tion Y of Road 5, 80.5 ft southwest of the centerline of the southwest two of four lanes of Road C north, 77 ft southeast of the center line of Road 5, 71 ft northwest of the centerline of the southeast leg of the junction. Established by the USC&GS.
301.213
22 Determination of the 100-Year Flood Plain on Fourmile Branch at the Savannah River Site, South Carolina, 199f
APPENDIX-List of Elevation Reference Marks-Continued
[ft, feet; USGS, U.S. Geological Survey; mi, mile; USC&GS, U.S. Coastal and Geodetic Survey] (In this report, the words "right" and "left" refer to directions that would be reported by an
observer facing downstream.)
Benchmark LocationElevation above sea
level(ft)
M101 Brass tablet located at crossing of CSX Railway and Road 3, 259 degrees north and across the track from mile post Number 438, 33 ft northeast of northeast rail, 49.5 ft southeast of the centerline of the road, 60.5 ft east of the center of the crossing. Established by the USC&GS.
153.372
L101 Brass tablet located 0.6 mi southeast along the CSX railway from the Road 3 crossing, thence 0.15 mi south on a spur track to Area D, at the crossing of Road A-12 (a black top road), the road passes between the main line track and the Area D, 114 ft southeast of the southeast rail of the spur track, in the top of a concrete block 18 ft wide by 27 ft long by 1 ft high, 188 ft northeast of the center line of the road. Established by USC&GS.
152.218
H101 Brass tablet located 4.75 miles northwest along CSX railway from the railway station at Robbins, at the crossing of Road A-13 and CSX Railway, 24 ft northeast of the northeast rail, 27 ft southwest of the center line of the road, 69 ft north of the center of the crossing, and 1 ft southeast of a metal witness post. Established by the USC&GS.
150.193
X102 Brass tablet located 1.35 mi north on Road 4 from junction of Road C and Road 4, thence 0.9 mi northwest on M Line U.S. Government Railway track, about 0.1 mi northwest of milepost No. 12, 85 ft southwest from the southwest rail of track, 2 ft southeast of the metal witness post, 1 ft above the level of the track. Established by the USC&GS.
249.350
Appendix