Fields, Fred K. FLOODS IN THE GUAYANILLA-YAUCO AREA, PUERTO RICO. 1969. GEOLOG;C/41. •
Fields, Fred K.
FLOODS IN THE GUAYANILLA-YAUCO AREA, PUERTO RICO. 1969.
GEOLOG;C/41. •
OF-5
UNITED STATES
DEPARTMENT OF THE INTERIOR
GEOLOGICAL SURVEY
FLOODS IN THE GUAYANILLA-YAUCO AREA,
PUERTO RICO
by Fred K. Fields
Prepared in cooperation with
COMMONWEALTH OF PUERTO RICO
Department of Public Works
Open-file Report
November 1969
(Prior to publication as
Hydrologic Investigations Atlas)
CONTENTS
Page
Rio Guayanilla basin 4
Flood history 6
Flood frequency 9
Flood profiles 13
13Inundated area
Rio Yauco basin 16
Flood history 18
Flood frequency 19
Flood profiles 21
23Inundated area
24High-water mark information
24Water-surface elevations
24Depth of flooding
24Cooperation and acknowledgment
25Additional information
2
ILLUSTRATIONS
Page
Figure 1. Location of Rio Guayanilla and
Rio Yauco drainage basins 5
2. Profile of abandoned railroad
embankment 7
3. Upstream Highway PR-2 bridge spanning
Rio Guayanilla 8
4. Stage-discharge relation of Rio
Guayanilla at upstream Highway PR-2
bridge 10
5. Flood-frequency relation of Rio
Guayanilla at upstream Highway PR-2
bridge 11
6. Flood profiles, Rio Guayanilla 14
7. Area inundated at Guayanilla, 1932 and
1954 floods 15
8. Diagram of flow diversions into and
out of Rio Yauco basin 17
9. Flood stage-discharge relation of Rio
Yauco at Escuela Arturo Lluberas.. 20
10. Flood profiles, Rio Yauco 22
3
FLOODS IN THE GUAYANILLA-YAUCO AREA, PUERTO RICO
by Fred K. Fields
This report is a compilation of data pertaining to
floods in Rios Guayanilla and Yauco, based principally
upon information obtained from residents in the study area.
This information is a useful tool in making land-use and
development decisions.
The Guayanilla and Yauco basins lie in the south-
western part of Puerto Rico. The streams flow southward
from the rugged Cordillera Central and empty into Bahia
de Guayanilla. The lower basins are devoted principally
to the production of sugarcane and are subject to destruc-
tive floods. Details pertaining to basin features, flood
frequency, flood profiles, and inundated areas are discussed
by individual basins. All elevations given are in meters
above mean sea level.
Rio Guayanilla basin
The Rio Guayanilla basin is the easterly basin of
the study area shown in the location sketch, figure 1.
It has a drainage area of 18.5 square miles at the
U.S. Geological Survey gaging station 2.4 kilometers
north of Guayanilla, and 20.8 square miles at the upstream
Highway PR-2 bridge (of three Highway PR-2 bridges across
Rio Guayanilla). The total drainage area of the basin is
about 31 square miles.
OCEANO ATLANTICO
67°15' 67°00' 66°45'
18°301--
Ca
CD
'CI 18°151 4)
cd U)cd 04
Rio Yauco basin
. ,
\ . Rio Guayanilla
basin
Cabo Rojo Yauco• Lajas (
• CrUayanilla
18°00'
MAR CARI•BE
0 5 10 miles 1 t ,tArea of this report
0 10 kilaneters
Portion of Rio Grande de Atiasco basin from which flow.is diverted to Rio Yauco basin
Boundary of drainage basin
Figure 1. Location of Rio Guayanilla and Rio Yauco drainage v4.3ins.
5 6
The lower floodplain is an alluvial fan and most of
the city of Guayanilla is on the floodplain. Four high-
way bridges span Rio Guayanilla in the study area. The
abandoned railroad embankment that crosses the flood plain
downstream from Guayanilla is an important feature that
affects floodwater movement. The embankment profile is
shown in figure 2. Rio Guayanilla is diverted at three
places for irrigation. However, no dams exist that would
reduce the magnitude of floodflow.
Flood history
The earliest floods documented in this basin occurred
in 1876 and 1886. Stages of these floods, cited in highway
damage reports, could not be recovered. The flood of
August 8, 1899, is the greatest known flood. Since the
1899 events, major floods occurred in 1926, 1928, 1932,
and 1954. Small floods, being less destructive and less
spectacular, usually are soon forgotten. However, flood
elevations were recovered for the lesser floods that
occurred in 1955, 1958, 1960, 1963, and 1966. A tabulation
of flood stages and estimated discharges at the upstream
Highway PR-2 bridge is given below. The bridge is shown
in figure 3.
14
cr) •-4 12 Railroad embankment
10 Water surface, flood of l>a / September 13, 19288 d coi.c• cn Guayanilla cqct,
6 bo boi c4
Ground surface-1 2
0 2 4 6 8 12 16 20 24 STATIONING, IN HUNDREDS OF METERS
Figure 2.--Profile of abandoned railroad embankment between Highways PR-335 and PR-336.
7
Figure 3.--Upstream HighwAy 2a-2 spanning Rio Guayanilla. The 1(.:S=1 L..600d reached the low bean of this bridge. The top of the bridge railing is about the same elevation as the crest of the 1899 flood.
8
Elevation above Peak discharge, mean sea level, in cubic feet
Date in meters per second
August 8, 1899 22.0 39,000
September 13, 1928 20.9 23,000
September 21, 1932 21.3 28,000
October 13, 1954 20.5 18,000
May 6, 1958 19.4 6,400
September 14, 1961 18.5 2,800
The 1926 flood stage was not established at the
upstream Highway PR-2 bridge. Flood elevations. farther
downstream indicate the magnitude of the flood was
slightly less than that of the 1928 flood. Stage and
corresponding discharge at this site permit the develop-
ment of the stage-discharge relation shown in figure 4.
Flood frequency
Historical floodmark elevations were used in
conjunction with discharge records collected at the Rio
Guayanilla near Guayanilla gaging station, unadjusted for
the intervening 2.3 square miles of drainage area, to
establish a flood-frequency relation at the upstream
Highway PR-2 bridge. The general relation of recurrence
interval to river stage and discharge is shown in figure 5.
Stage and discharge for selected recurrence intervals are
tabulated below.
9
22 August 18, 1899
'September 21, 1932
September 13, 1928 October 13, 1954
20 -
May 6, 1958-4w 19n8
September 14, 1961
L_ L-118 4 7 10 20 40
DISCHARGE, IN THOUSANDS OF CUBIC FEE PER 32COND
Figure 4.--Flood stage-discharge relation of Rio Guayanilla at upstream Highway PR-2 bridge.
10
50 r .1 1 I 1
F;3
f% 40 a, August 8, 1899 E-4
C.)
VI 30
September 21, 1932
0
cf) September 13, 19282 .444 October 13, 19540 20 B September 14,1961* E-4 November 12, 1965* H
May 6, 1958 z
August 3, 1963*
* Fran gaging station records- ] 0 1 1 1 1 1 1 1 1 1 1 1 2 4 7 10 20 40 70 100
RECURRENCE INTERVAL, IN YEARS
Figure 5.--Flood -frequency relation of Rio Guayani] at upstream Highway PR-2 bridge.
11
Recurrence Elevation above Peak discharge,
interval, mean sea level, in cubic feet in years in meters per second
5 19.0 4,500
10 20.0 13,000
20 20.7 21,000
30 21.2 27,000
50 21.7 34,000
There is no means of predicting the date a flood of
a given magnitude will occur. If a long-enough record
of floods is available, however, the average recurrence
interval of such a flood and the probability of its
occurrence in any year can be computed. The recurrence
interval, or frequency, of a flood of specific magnitude
is the average length of time during which that flood has
been equaled or exceeded. For floods greater than the
10-year flood, the reciprocal of the recurrence interval
is virtually the probability of occurrence in a year;
thus a 20-year flood will have a 5-percent chance of
occurring in a year, and a 50-year flood will have a
2-percent chance.
At the upstream bridge on Highway PR-2, a flood
elevation of 20.0 meters has an indicated 10-year recur-
rence interval. However, the 20.0 meter elevation was
exceeded 3 times during the 7-year period 1926-32. It
12
thus is emphasized that recurrence intervals are average
figures--the average number of years in which floods of
a specific magnitude have been equaled or exceeded.
Flood profiles
Flood elevations referenced to the arbitrary base
line shown on the topographic map are shown in figure 6.
The 1932 and 1954 flood profiles are well defined above
an elevation of 8 meters. The 1928 flood profile is
poorly defined and has been drawn on the basis of the
shape of the other flood profiles. The 1928 and 1954
profiles are estimated in the reach from 0.4 to 1.8 kilo-
meters above the stream mouth.
Inundated area
The area inundated by the 1928 flood has been
delineated on the large topographic map. The area
inundated by the 1932 and 1954 floods at Guayanilla
is shown in figure 7. The 1928 flood was selected to
be shown on the large map because it is known to have
intermingled with Rio Yauco and to have been consistent
with the Rio Yauco inundation area of 1928. The inundated
area in the vicinity of El Faro and along Rio Macana is
undefined and has been estimated. The effect of the
abandoned railroad embankment upon the height of the
water could not be defined from the available floodmarks.
13
24 T
22
T Deck elevation 20- Bridge-
Low bean elevation 1-1 18 _
/.••• •
z 16 }), . • 0.•
14 .
September 27,1932 •• •-• •
12 U) ?=-ti 10 Central Rufinal Highway PR-2 bridges
/A 8 September 13, 1928
H " Ab: ' 12d railroad crossing „ • • •••60
E-4 g 4 October 13, 1)54
---,--- - I 2- o Q.
LRailroad bridge I _I L I__ :_l_ J _1 _1 __I__ L i 1 f _ 1 - L___ -4._ ____ o 1 ____1 __I_ _1
0 1 2 3 4 DISTANCE UPSTREAM FRai MOUTH, IN KILOMETERS
Figure 6.--Flood profiles, Rio Guayanilla.
, .
Septembtrz7193Z" Otob-er 13;1954'' 0 B AN. D 0
0N
%CI-171r( \\
c)
11
Figure 7.-- Area inundated in the vicinity of Guayanilla by the floods of September 27, 1932, and October 13, 1954.
15
The flood boundaries delineated on the topographic
maps provide a record of historic facts that reflect
channel and flood-plain conditions existing at the time
of each flood. No attempt was made to appraise the effect
of later changes in the channel or flood plain. The Rio
Guayanilla channel was dredged in 1948, 1952, and 1965,
and increasing urbanization may have changed runoff
characteristics.
Highway PR-2 will be relocated upstream from the
present (1968) upstream bridge. The inundation pattern
of future flood may be affected by this relocation, by
the possible relocation and improvement of the stream
channel, by the removal of the railroad embankment, and
by other cultural changes.
Rio Yauco basin
The Rio Yauco basin is the westerly basin shown in
the location sketch, figure 1. The drainage area of the
basin at Escuela Arturo Lluberas, 1.3 kilometers northwest
of Central San Francisco, is 45.5 square miles. The total
drainage area of the basin is about 48 square miles. These
areas include that part of the basin upstream from Antonio
Lucchetti Dam.
Reservoirs partly regulate streamfiow within this
basin. A schematic diagram of the interconnected reservoir
system is shown in figure 8. Lagos Yahuecas, Guayo, Toro,
6C0 Dam spillway crest _
Tam. - - _ Connecting tunnel 1
Diversion from Rio I IN 400,_ Grande de Afiasco\ Yahuecas Dambasin to Rio Yauco\
4 c, Guayo Dam1_ :e 303, basin Prieto Dam
o Power plants H 2 -E-4 _„-Antonio Lucchetti Dam
Lx1
100 N-- Diversion to Rio Loco basin w ''---Loco Dam
Figure 8.--Schematic diagram of streamflow diverted into and out of Rio Yauco basin.
17
and Prieto, the four reservoirs in the headwaters of
Rio Grande de Afiasco, have a combined storage capacity
of about 20,000 acre-feet. These reservoirs, constructed
during 1955 and 1956, divert flow from 39 square miles of
the Rio Grande de Afiasco basin to Lago Yauco (above
Antonio Lucchetti Dam) on Rio Yauco. Lago Yauco also
collects flow from 17.3 square miles of the Rio Yauco
basin, and it has a storage capacity of 16,500 acre-feet.
Water from Lago Yauco then is conveyed to Lago Loco for
power generation and for distribution to Valle de Lajas
for irrigation.
One major flood, in 1960, has been experienced at
Yauco since the construction of Antonio Lucchetti Dam in
1953. The numerous irrigation diversions on Rio Yauco
from Yauco to Escuela Arturo Lluberas have minor influence
on flood discharge. Six highway bridges and one foot
bridge span Rio Yauco in the study area.
Flood history
The earliest flood known on Rio Yauco was in 1867
during Hurricane San Narciso, when the highway bridge at
Yauco was destroyed. No data were recovered to indicate
the magnitude of this flood. The greatest known flood
to occur in the basin was on August 1899. Other major
floods occurred in 1926, 1928, and 1960. A tabulation
of stage and approximate discharge of historical floods
at Escuela Arturo Lluberas is shown below.
18
Elevation above Peak discharge, mean sea level, in cubic feet
Date in meters per second
August 8, 1899 10.9 42,000
September 13, 1928 9.9 18,000
September 18, 1960 9.5 10,000
November 11, 1961 8.8 2,900
April 28, 1962 8.4 1,800
September 27, 1963 8.9 3,300
July 21, 1968 8.6 2,200
Flood stages after 1926 were collected at the Highway
PR-335 bridge about 50 meters east of the school. These
elevations have been transferred upstream to the school
as a common point on the basis of the indicated water-
surface slope,
Flood stage and discharge define the relation shown
in figure 9.
Flood frequency
Sufficient data are not available to define a flood-
frequency relation for Rio Yauco. The 1899 flood is
estimated to have a recurrence interval of about 70 years
and the 1928 flood a recurrence interval of about 35 years.
The scattered flood discharge information relating to
floods after the construction of Antonio Lucehetti Dam is
19
E-4
T-T-1 I12.0 J cr, 11.0 August 8, 1899
10.0r- September 13, 1928 J September 18, 1960
cs) 9.0 September 27, 1963* November 11, 1961*
0 fill 8 • 7 July 21, 1968*
8.4 1- c,-April 28, 1962k
*Elev. transferred to Escuela A. Llub_ras J- I .Al L-8.2--
1 2 4. 7 10 20 40 70 100 DISCHARGE, IN THOUSANDS OF CUBIC FEET PER SECOND
Figure 9 .--Flood stage-discharge relation of Rio Yauco at Escuela Arturo Lluberas.
20
not sufficient to define the present (1967) flood-
frequency relation.
Flood profiles
The 1928 and 1968 flood elevations, referenced
to the arbitrary base line on the topographic map, are
shown in figure 10. The 1928 water-surface profile
between the elevation range of 13 to 26 meters is not
defined by floodmarks, but it has been estimated. An
average value of high-water marks was used near the
elevation of 28 meters. Although several residents
along the reach from 5 to 9 kilometers upstream from
the mouth recalled the 1928 flood, the west edge of the
valley has been changed, mainly by road construction,
and old landmarks have been erased. One resident
recalled that the flood reached Escuela Segunda Unidad
de Barinas, but could point out no definite elevation of
the flood. The profile has a probable accuracy of +0.5
meter at elevations above 12 meters.
The flood of July 21, 1968, was not a major event,
but its profile provides a basis for estimating the
1928 flood profile. Rio Yauco is confined at low
discharge by small levees downstream from about kilometer
2.5. The 1968 profile below this point is not applicable
for comparison with the 1928 flood and is not shown.
_1
I N M
E TE
RS
AB
OV
EM
EAN
SEA
LEV
EL
'RT, R
VA
TIO
N,
Highway PR-23o
28
0c, 26 .0_
September 13, 1928
24
22
20 -
18 z
16 Escuela Arturo Lluberasi
14 Highway PR-335 July 21, 1968 12
10
Service road 8
6 I
4 Deck elevation - Low beam elevation 2
1 1 L _I 1 t i 1 0 1 2 3 4 5 6 . 7 8 9 10
DISTANCE UPSTRELn FR MOUTH, IN KILOMETERS
Figure 10.--Flood profiles, Rio 1:11,x
Inundated area
The area inundated by Rio Yauco during the 1928
flood is shown on the topographic map. The delineated
boundary reflects the channel and flood-plain con-
ditions at the time of the 1928 flood. No attempt was
made to ascertain the effect of later changes in the
channel and flood plain, or in runoff characteristics.
Apparently only the buildings along Rio Yauco in
the vicinity of Highway PR-2 and at the southeastern
tip of the city were affected by the flood. Water may
have backed up some distance in Quebrada Berrenchin
along the west and south edge of Yauco, but the extent
could not be determined.
Housing has been expanding onto the flood plain of
Rio Yauco on the basis of unproven confidence that Lago
Yauco has eliminated major floods. Lago Yauco may
reduce the frequency of flooding, but it will not
eliminate floods, particularly at times when it may be
at full capacity. A service road recently has been
constructed across the lower flood plain of Rio Yauco,
which crosses Rio Yauco at baseline station 2.05 and
extends to Punta Verraco. This and other changes along
the channel and in the flood plain may well affect the
inundation pattern of future floods.
23
High-water mark information
The inundated areas have been delineated on the
basis of flood-stage information furnished by residents.
Field surveys were conducted to determine the elevation
of the flood stages.
Water-surface elevations
The estimated water-surface contours of the
September 13, 1928, flood for both basins and of the
1932 and 1954 floods at Guayanilla are shown on the
topographic maps.
Depth of flooding
Depth of flooding at any point may be estimated by
subtracting the ground elevation from the water-surface
elevation. Each is shown by contours on the map. In-
termediate estimates of depth may be determined by
interpolation.
Cooperation and acknowledgment
This report was prepared as part of the floods
investigation authorized by a cooperative agreement
between the Department of Public Works, Commonwealth
of Puerto Rico, and the United States Geological Survey.
Many of the flood data were provided by the Department
of Public Works. Historical flood information was made
available by the general archives of the Instituto de
Cultura Puertorriqueha and by many residents of the
study area.
Additional information
Additional information relating to floods on Rio
Guayanilla and Rio Yauco can be obtained from the
U.S. Geological Survey, San Juan, Puerto Rico, or from
the Area of Flood Control and Maintenance of Beaches
and Rivers, Departamento de Obras P5blicas, Santurce,
Puerto Rico.
25
•
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