SCI
BKS
TC
530
.N45
1983
000000
FLOOD ELEVATIONS FOR THE SOLEDUCK RIVER
AT SOL DUC HOT SPRINGS,
CLALLAM COUNTY, WASHINGTON
--
20
譯
​U.S. GEOLOGICAL SURVEY
Water-Resources Investigations
Report 83-4083
OF
THE 1
DEPARTMENT
March 3, 1849
Prepared in cooperation with
NATIONAL PARK SERVICE
OF
VERSITY
O
MICHIGAN
HIG
HL
1817
<
BRARIES
UNITED STATES
DEPARTMENT OF THE INTERIOR
GEOLOGICAL SURVEY
FLOOD ELEVATIONS FOR THE SOLEDUCK RIVER AT
SOL DUC HOT SPRINGS, CLALLAM COUNTY, WASHINGTON
By Leonard M. Nelson
U.S. GEOLOGICAL SURVEY
WATER-RESOURCES INVESTIGATIONS REPORT 83-4083
Prepared in cooperation with the
NATIONAL PARK SERVICE
Tacoma, Washington
1983
Sc
TC
530
N457
1983
UNITED STATES DEPARTMENT OF THE INTERIOR
JAMES G. WATT, Secretary
GEOLOGICAL SURVEY
Dallas L. Peck, Director
For additional information
write to:
Copies of this report can be
purchased from:
District Chief
U.S. Geological Survey
1201 Pacific Avenue - Suite 600
Tacoma, Washington 98402-4384
O
Open-File Services Section
Western Distribution Branch
U.S. Geological Survey
Box 25425, Federal Center
Lakewood, Colorado 80225
(Telephone: (303) 234-5888)
CONTENTS
Page
Abstract--
Introduction-
Hydrology--
Hydraulics--
References-
1
2
4
5
17
ILLUSTRATIONS
3
6
7
O
FIGURE 1. Map showing location of Sol Duc Hot Springs-
2. Typical cross sections-
3. Map showing flood boundaries along the Soleduck River--
4-7. Flood boundary overlays to National Park Service
drawing No. 149/80018-----
8-9. The 100-year flood profiles of the Soleduck River--
10- 13
14-16
TABLE
TABLE 1.
The 100-year flood elevations and velocities of the
Soleduck River in the vicinity of the Sol Duc Hot
Springs-
8
METRIC CONVERSION FACTORS
Multiply
Ву
To obtain
feet (ft)
miles (mi)---
square miles (mi2)---
cubic feet per second (ft3/s).
0.3048
1.609
2.590
0.02832
meters (m)
kilometers (km)
square kilometers (km2)
cubic meters per second
(m3/s)
National Geodetic Vertical Datum of 1929 (NGVD of 1929): A geodetic datum
derived from a general adjustment of the first-order level nets of both the
United States and Canada, formerly called "mean sea level." NGVD of 1929
is referred to as sea level in this report.
iii
FLOOD ELEVATIONS FOR THE SOLEDUCK RIVER AT
SOL DUC HOT SPRINGS, CLALLAM COUNTY, WASHINGTON
By Leonard M. Nelson
ABSTRACT
Elevations and inundation areas of a 100-year flood of the Soleduck River,
Washington, were determined by the U.S. Geological Survey for the area in the
vicinity of the Sol Duc Hot Springs resort, a public facility in the Olympic
National Park that under Federal law must be located beyond or protected
from damage by a 100-year flood. Results show that most flooding could be
eliminated by raising parts of an existing dike. In general, little flood damage
is expected, except at the southern end of an undeveloped airstrip that could
become inundated and hazardous due to flow from a tributary. The airstrip is
above the 100-year flood of the Soleduck River.
1
INTRODUCTION
Public facilities constructed on Federal lands or with Federal funds are
required by Executive Order 11988 to be located beyond or protected from
damage by a 100-year flood. The National Park Service asked the U.S.
Geological Survey to determine the elevations and inundation areas of a
100-year flood of the Soleduck River in the vicinity of the Sol Duc Hot
Springs resort. The adequacy of dike protection for the developed areas was
also investigated.
The resort is located in the Olympic National Park (fig. 1) in northwest
Washington, 20 miles southwest (40 miles by road) of the city of Port Angeles
and 8 miles southeast (14 miles by road) of Fairholm. During the summer a
concessionaire operates a resort at the springs under contract with the
National Park Service. The main resort building, with swimming pools,
cabins, and a maintenance building, is located on the flood plain southwest of
the Soleduck River, and is protected from the floodwaters by a manmade
dike.
A residence, a six-unit motel, the resort trailer campground, and
National Park Service campground are located on the opposite side of the
river and lie above the 100-year flood elevation. An airstrip, located 2,500
feet west of the main resort, also lies above the 100-year flood elevation.
The surrounding area is dense forest. Annual rainfall of the area is
approximately 100 inches. Flooding generally occurs during the winter
months, November through February, when storms originating over the
Pacific Ocean produce intense precipitation.
2
124000
45'
Port Angeles
Study
area
WASHINGTON
STRAIT OF JUAN DE FUCA
T.
Crescent
Bay
Low
Point
31
10'
N.
(112
Joyce
112
T.
30
101
N.
1019
Take crescent
Fairholm
Soleduck
Lake
Sutherland
Valley Road
OLYMPIC
Gaging
T.
Station
2912041500
River
Sole duck
NATIONAL
48
00'
N.
PARK
.F. Soledu
Soleduck
Sol Duc
Hot Springs
River
R. 10 W.
0
R. 9 W.
5
R. 8 W.
10 MILES
0
5
10
15 KILOMETERS
FIGURE 1.--Location of Sol Duc Hot Springs.
3
HYDROLOGY
Several methods of estimating the 100-year flood for the Soleduck River
at the Sol Duc Hot Springs were investigated. The regression equation for the
100-year flood suggested by Moss and Haushild (1978) and the regression
equation used in the Clallam County flood insurance study (U.S. Department of
Housing and Urban Development, 1980) were studied the latter was used.
A gaging station, Soleduck River near Fairholm, is located 7.6 miles
downstream of Sol Duc Hot Springs and has 48 years of streamflow record.
The Soleduck River drains an area of 83.8 mi2 upstream of the gaging
station. The highest discharge during the 48 years was 23,500 ft3/s on
November 26, 1949, and the 100-year flood using the station data is
25,900 ft3/s.
+
The values of the 100-year flood using the Moss and Haushild regression
and the Clallam County regression were compared with those obtained from
the gaging station data. The values obtained from the regressions lie outside
the confidence limits computed from the station data; therefore, frequency
computations based on the station data were used. However, the Clallam
County regression was used as an aid for transferring the 100-year discharge
from the gaging station to Sol Duc Hot Springs: the regression values at the
Hot Springs were increased by the ratio of the station values to the regression
values at the station. The Soleduck River drainage upstream of the Sol Duc
Hot Springs is 22.7 mi2. The 100-year flood was estimated at 7,500 ft3/s
at Sol Duc Hot Springs. This flood has a l-percent chance of occurring in any
one year.
4
HYDRAULICS
Hydraulic analysis was performed to determine water-surface elevations
resulting from passage of the 100-year flood at Sol Duc Hot Springs. The
study reach, shown in figures 8 and 9, extends about 6,500 feet, from just
upstream of the resort area to about a mile downstream of it, and has a total
fall of about 30 feet. The main channel is about 70 feet wide and contains
two islands in the lower half of the reach. A low dike is built along the left
bank in the vicinity of the resort. The flood plain is 500 to 1,000 feet wide.
Seventeen cross sections of the Soleduck River were surveyed during
February 1982 and used in the hydraulic analysis of riverine flooding. Typical
cross sections (J, I, D) are shown in figure 2. The elevation and distance data
for the cross sections were obtained using vertical and horizontal control
from National Park Service drawing No. 149/80,018, a topographic map of
the developed part of the resort. The vertical elevations on this drawing
were obtained from the U.S. Army Corps of Engineers map-control station
RM1 and are referenced to the National Geodetic Vertical Datum of 1929.
The horizontal positions and distances are based upon the assumed coordinate
system used for the drawing.
were
on
The U.S. Geological Survey step-backwater computer program
(Shearman, 1976) was used to determine elevations at each of 13 cross
sections (table 1) for a peak flood discharge of 7,500 ft3/s. Cross-section
locations are shown in figure 3 and the Thalweg and water surface profiles
are shown in figure 9. The most downstream point of interest in this study is
at section A. In order to have a defined starting elevation at section A,
water-surface profiles
computed through four cross sections
downstream from section A. The hydraulic analysis
analysis was based
unobstructed flow. Backwater from debris pileup may cause the flood
elevations to be higher in some areas. Channel roughness factors (Manning's
n) used in the hydraulic computations were chosen on the basis of field
observations. The main channel bed and banks are composed of sand, gravel,
and cobbles. The overbank areas are covered with heavy brush, trees, and
many fallen trees. Roughness value of 0.035 was used for the main channel,
and 0.050 to 0.100 was used for the flood plains. Average water velocities
were found to range from 4.3 ft/s at section M to 12.8 ft/s at section H (table
1).
5
UT
1650
Left bank
1645
100-year flood elevation
1640
1635
Cross section J
1630
1650
Left bank
100-year
flood elevation
1645
1640
1635
ELEVATION ABOVE NATIONAL GEODETIC VERTICAL DATUM OF 1929, IN FEET
1630
سعر ون اور راه استا الست ، به س نا و
Cross section I
1625
1635
Left bank
Airstrip
1630
1625
100-year flood elevation
1620
hu
1615
Cross section D
1610
100
200
300
400
500
600
700
800
900
DISTANCE, IN FEET
FIGURE 2.--Typical cross sections.
6
island.
laland
Cross section A
100_year
flood boundary.
Island
cross section
Island
Sol Duc
Hot Springs
Road
Manden
solodack
-100-year flood boundary--
Cross section
Crows section D
7
Croot
River
Cross section E
100-year flood boundary
Culvert
Island
I
laland
Air strip
Cross section
100-year flood boundary
Crow reotion
Maintenanco
building
Shallow
flooding
Road to air strip
Kitchenettes
Draina
+N 80.000
SO-1
J
+00003
Croesestion
Cabine
Motel
Concreto
-bridoo
к
Cabino
Cros section
SOL DUC
HOT SPANGS
Cabine
Lodoo
Soleduck
Cross section L
200
0
200
400
600 FEET
:
+8
Pool
80
0
120
180 METERS
+ N 40,200
E 4.700+
Blvor
Crowsection
FIGURE 3.--Flood boundaries along the Soleduck River in the vicinity
of Sol Duc Hot Springs (in T. 29 N., R. 9 W., Willamette meridian)
Horizontal and vertical control taken from National Park Service
control markers SD-1 and SD-2. Area between cross sections H and M
shown in more detail in figures 4-7.
TABLE 1.--The 100-year flood elevations and velocities of the
Soleduck River in the vicinity of the Sol Duc Hot
Springs
Mura..
Cross section
(location shown
in fig. 3)
100-year flood
elevation, in
feet above sea
level
Average
velocity
(ft/s)
A
В
с
D
E
BFGHIOT (0Bobo
1,606.6
1,612.8
1,617.8
1,624.1
1,627.7
1,631.8
1,634.1
1,636.9
1,640.0
1,641.5
1,642.7
1,643.8
1,646.5
5.5
9.7
4.8
5.6
4.6
7.2
7.6
12.8
10.4
10.2
9.4
8.8
4.3
Н
J
K
L
M
8
The 100-year flood boundaries are shown on a flood-boundary map (fig. 3)
and on overlays to drawing 149/80,018 (figs. 4-7). The flood profile is shown in
figure 8. The profile and the flood boundaries between cross sections are
interpolated from those at the cross sections. The contours shown on drawing
149/80,018 were used as an aid in defining the flood boundaries between cross
sections G through M, and a few surveyed ground points were used as an aid
elsewhere.
The flows over the flood plain are generally less than 3 feet deep and have
velocities (estimated) of less than 3 feet per second. The areas covered by
these flows are shown on the overlays to drawing 149/80,018 (figs. 4-7).
However, because the ground elevations are not described in the necessary
detail except at cross sections, there may be a few places where floodwater
may be slightly greater than 3 feet deep. Slightly higher flood elevations
probably will occur where small streams are flowing onto the flood plain.
The 100-year flood would cause shallow overflow along the northeast bank
upstream of the concrete bridge (cross section "J"). The overflow would not
reach any existing building, but could cover some utilities. Little flood
damage would be expected because the depths would be shallow and the
velocities low. Because it would increase velocities in the main channel and
retard local drainage, diking along the northeast bank upstream of the
concrete bridge probably would cause accelerated erosion of the banks and
ponding of the floodwater.
The dike on the southwest bank protects the resort from most flooding. A
small amount of water from a 100-year flood would flow over the dike
between cross sections I and J, causing shallow flooding. Very little water
would flow through the low spot in the dike near section J. Thus, no shallow
flooding from this breach is shown in figure 3. Flooding between sections I and
J could be eliminated by raising the dike in two places by approximately 2 feet
to match the existing dike line (fig. 8). Because the overflow through the dike
breaches is negligible with respect to the total flow, flood elevations would
not be increased by containing the flow in the channel at cross sections I and J.
9
B.M. No. 7
Match line to figure 6
100-year flood
bound
N40,200
£60,000+
Flooding less than 3 feet deop.
low velocities.
tuto ILA
SOLEDUCK
3-foot depth line:
+
N40,000
+
N40,000 1
RIVER
100-year Flood boundary
E80,400
E60,000
M
100-year flood elevation =
1648.5-foot elevation at cross section M.
Cross section
40
0
40
80
120 FEET
:
10
0
10
20
30 METERS
FIGURE 4.--Overlay to National Park Service drawing No. 149/80018
showing flood boundaries for the Soleduck River.
10
Residence
100-year flood elovation -
1642.7-foot alevation at cross section K
Cross section K
+
N40,000
Match lino to figure o
E60,200
Mon. 80-3
A
Flooding less than 3 foot
deep, low velocities.
SOLEDUCK
100-year flood elevation =
1843.8-foot elevation at cross section L
Jepunog pooli nook-001
oundary
S. 2001
000'ora
dopth line
700-your liood boundary
+ €60.200
+
N40,400
N40,400
Cross section L
Pool
RIVER
Match line to figure 4
40
80
40
1
120 FEET
.
Oto
10
10
20
30 METERS
FIGURE 5.--Overlay to National Park Service drawing No. 149/80018
showing flood boundaries for the Soleduck River.
11
A
Mon. 80-.
100- your flood boundary
Match Uno to figure 7
Rjepunog poolt hok-001
Mon. SD-5
SOLEDUCK
Shallow flooding less
than 1 foot doop.
Cross section 1
Flooding less than 3 feet
deep, low velocities.
ه ا نقدنا امده له ما هذا الا ان عدد بالا که با نام | و در قل ۹۹
+
N60,000
N80,000
100-year Hood
Mon. SD-1
000'03
900
100-year flood olovation •
1640.0-foot elevation at cross section 1
ispunog pool
RIVER
I lood
boundary
100-year
Flooding less than 3 feet
deep, low velocities
Concrete bridge
3-
N40.800
E40.000-
groot depth Ting
Mon. SD-2
100-
avear I lood boundary
Match line to figure 5
Cross section
100-year flood elevation -
1641.6-foot elevation at cross soction J
Mon. SD-4
40
O
80
120 FEET
oto
10
o
10
20
T
30 METERS
FIGURE 6.--Overlay to National Park Service drawing No. 149/80018
showing flood boundaries for the Soleduck River.
12
100-year flood boundary
ti
NGO, 400
SOLEDUCK
+000ʻora
RIVER
Cross section G
100-year flood elevation =
1638.0-foot olevation at cross section H
100-year flood boundary
.
depth
100-your flood olevation -
1634.1-foot olevation at cross section G
3-10
+
N60.200
+
NO.200
Cross section H
€40.000
cron
Maintenanco
building
Flooding 10 than 3 feet doop.
low velocities.
1
100-your flood boundary
Match line to figure 6
40
0
40
120 FEET
80
1
10
U
10
O
20
30 METERS
FIGURE 7.--Overlay to National Park Service drawing No. 149/80018
showing flood boundaries for the Soleduck River.
13
1650
Concrete Bridge
Southwest dike
Bank
1645
Dike
-100-Year Flood_Profile
Raise dike to
prevent flooding
Dike
1640
ELEVATION ABOVE NGVD OF 1929, IN FEET
Overflow to
shallow flooding
M
100-Year Flood Profile
Thalweg
1635
Thalweg
1630
Thalweg
Cross sections (horizontal location
shown in figures 4-7)
اید ، با اها ايه ال که ه|
11
1625
4500
1
4700
1
5100
4900
5300
5500
5700
5900
6100
6300 6400
DISTANCE UPSTREAM FROM SECTION A, IN FEET
.
FIGURE 8.--The 100-year flood profile of the Soleduck River
along the dike protecting the Sol Duc Hot Springs.
14
Shallow flooding has been reported at the maintenance building located
between cross sections I and H. This flooding probably was caused by a
combination of local drainage and slack water from the river. The dike
appears to have been built another 200 feet downstream at one time and has
been removed in several spots to provide release for local drainage. Replacing
this part of the dike could reduce flood elevations from river water on the
landward side of the dike. In fact, a dike could encircle all of the developed
southwest area if a floodgate were used to release local drainage. Because the
extension of the dike downstream would contain the floodwater in the main
channel, the elevation of the slack water in the resort area would be lower.
The amount of this reduction could be obtained from the profile shown in
figure 9 by comparing the elevations at the end of the present dike to that of
the extended dike.
The undeveloped airstrip lying between cross sections B and E lies outside
the 100-year flood boundary. The area between the airstrip and the river,
which is crossed by several small drainages and channels, shows evidence of
past flooding. A few areas adjoining and toward the upstream end of the
airstrip should be safe for construction of buildings. Manden Creek crosses the
valley from the south to join the river near the western end of the airstrip.
The overflow from this creek will likely join with local drainage to inundate
the western part of the airstrip at times.
or
An area along the Soleduck River between cross sections C and E that has
had previous development may be recommended for trailer camping
overflow parking in the future (Jeff Swan, National Park Service, written
commun., 1982). Part of the area is subject to the 100-year flood. However,
it could be used for these purposes without heavy flood damage, except during
large floods.
15
1650
1640
M
L
1630
K
H
Flood / Profile
Concrete bridge
at cross section "J"
Thalweg
G
ELEVATION ABOVE NGVD OF 1929, IN FEET
1620
100-Year
F
E
.
Thalweg
1610
с
Cross sections (horizontal
location shown in figure 3)
B
1600
A
1590
0
II
4000
1000
2000
3000
5000
6000
7000
DISTANCE UPSTREAM FROM SECTION A, IN FEET
FIGURE 9.--The 100-year flood profile of the Soleduck River
in the study area.
16
REFERENCES
>
Moss, M. E., and Haushild, W, L., 1978, Evaluation and design of a
streamflow-data network in Washington: U.S. Geological Survey
Open-File Report 78-167, 43 p.
Shearman, J. 0., 1976, Computer applications for step-backwater and
floodway analysis, Users manual: U.S. Geological Survey Open-
File Report 76-499, 103 p.
U.S. Department of Housing and Urban Development, 1980, Flood insur-
ance study, Clallam County, Washington: Federal Insurance Admin-
:
istration, 45 p., 75 pl,
17
UNIVERSITY OF MICHIGAN
3 9015 06244 1848


BAT.am
SLIMMELEN
Sun