5
Conclusions
The wind-generated wave characteristics and the
related wind setup and wave runup on a sloping
embankment within a reservoir must be considered for
the purposes of designing embankments and
embankment slope protection. Slope protection for
the embankment must also be considered and a
procedure for the design of riprap slope protection is
described in the following article titled, “Design of
Riprap for Slope Protection against Wave Action.”
Local Climatological Data:
http://www.ncdc.noaa.gov/IPS/lcd/lcd.html
Climate Maps of the United States:
http://cdo.ncdc.noaa.gov/cgi-bin/climaps/climaps.pl
NOAA Climate Data Online:
http://www.ncdc.noaa.gov/cdo-web/
 USDA (1983), Technical Release No. 69: “Riprap for Slope Protection
against Wave Action.”
 Reclamation (1992), ACER Technical Memorandum No. 2: “Freeboard
Criteria and Guidelines for Computing Freeboard Allowances for
Storage Dams.”
 Reclamation (1987), Design of Small Dams, Third Edition.
 USACE (1976), Engineering Technical Letter No. 1110-2-221: “Wave
Runup and Wind Setup on Reservoir Embankments.”
 Saville, Thorndike J. (1954), “The Effect of Fetch Width on Wave
Generation,” Technical Memorandum No. 70, Beach Erosion Board,
USACE.
Example #1:
Find the wind setup, the wave height and the wave
runup of a reservoir as shown on Figure 1. The
observed fastest mile wind speed is 75 mph for this
site. The average depth of the reservoir is 10 feet, and
the riprap protected embankment has a 3H:1V or 18°
slope.
Calculations:
1. To measure the lengths of the central (longest)
and radial lines as shown in Figure 1, compute the
effective fetch using Equation 1. The computation
is shown in Table 2.

Table 2: Procedure to determine the effective fetch
No.
(mi), Xi
α
(Degree) cos α Xi·cos2 α
1 1.7 42 0.74 0.96
2 1.8 36 0.81 1.20
3 1.9 30 0.87 1.45
4 2.0 24 0.91 1.70
5 2.2 18 0.95 2.02
6 2.3 12 0.98 2.23
7 2.4 6 0.99 2.41
8 2.6 0 1.00 2.63
9 2.5 6 0.99 2.51
10 2.4 12 0.98 2.33
11 2.3 18 0.95 2.11
12 2.1 24 0.91 1.78
13 2.0 30 0.87 1.53
14 1.8 36 0.81 1.20
15 1.7 42 0.74 0.96
Sum= 13.51 27.02
∑( )
∑( )

miles
This effective fetch of 2.0 miles or 10,560 feet
from the given reservoir with a longest fetch of
2.6 miles is estimated.
2. Refer to Figure 5 of TR-69 or Table 1 in this article,
the generalized maximum wind speed-duration
relationship is plotted as the red line on Figure 5.
This is computed by using the observed fastest
mile wind speed, 75 mph, interpolating the ratio
of land wind speed to the fastest mile wind for
each of the durations shown and then multiplying
this ratio by the observed fastest wind speed. The
results of these computations are shown in Table
2.
Table 2: Maximum Wind Speed-Duration Relationship
for a Fastest Mile Wind of 75 mph
1 min 30 min 60 min 100 min
Interpolated Ratio
from Table 1 100% 59% 53% 49%
Corresponding Max.
Wind Speed (mph) 75 44 40 37
3. By using Equation 2 and the effective fetch, 2.0
miles, the relationship of overland wind speed-
duration for the selected fetch is determined for a
range of selected speeds (in this case, UL= 90
mph, 60 mph, and 35 mph). Remember to first
convert UL to ft/sec and fetch length to feet. T is
calculated in seconds with Equation 2 and then
converted to minutes for the plot. The results are
shown as the blue curve in Figure 5.