The
Loss of the USS Memphis on 29 August 1916 - Was a Tsunami Responsible?
Analysis
of a Naval Disaster
George Pararas-Carayannis
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 INTRODUCTION
On August 29, 1916,
while anchored off Santo Domingo (Ciudad Trujillo) harbor in
the Dominican Republic, the armored cruiser U.S.S. Memphis was struck
broadside by numerous storm waves and, finally, by an enormous
wave which drove the ship into the rocks on the shore. The damage
to its hull and engines was irreparable. A subsequent
Court of Inquiry and the court-martial of the captain, attributed
the loss of the ship to a tsunami. The following analysis documents
that the loss of the ship was not due to a tsunami as the official
Navy records indicate and that it could have been prevented with
proper planning and vigilance. Human errors and lack of knowledge
of a passing hurricane were primarily responsible for the loss
of the Memphis.
The USS
Memphis
The USS Memphis
was a large 14,500-ton displacement armored cruiser that had
been launched on 3 December 1904 and originally named "Tennessee".
Her armament included four ten-inch guns in twin turrets, sixteen
six-inch guns, and twenty-two three-inch guns. The ship had two
steam powered engines and was capable of reaching a speed of
23 knots.
The USS
Memphis' Mission
In 1916, an unstable
government and political unrest at San Domingo (now the Dominican
Republic) required the dispatch of U.S. Marines to protect U.S.
interests on this Caribbean nation on the island of Hispaniola.
The USS Memphis was ordered to sail to the harbor of Santo
Domingo, the capital, to support the U.S. Marines stationed there.
Captain Edward J. Beach, was the ship's commander. Also,
the Memphis was the flagship of Rear Admiral Charles
F. Pond, the ranking U.S. Navy Commander in the region.or peace-keeping
patrol off the rebellion-torn Dominican Republic arrived at Santo
Domingo harbor in early August 1929.
 The Harbor of Santo
Domingo
In July 1916, the
Memphis got underway for the West Indies, arriving at
San Domingo on 23 July . the ship was anchored at about 55 ft.
depth close to the mouth of Ozama river and near the 1177-ton
U.S. gunboat "Castine". Anchorage on this southern
side of the island was poor, because of its exposure to storms
from the south and the southeast.
Weather
Conditions at Santo Domingo in August 1916 - Ship Preparations
This Caribbean island
of Hispaniola - shared by Haiti and the Dominican Republic -
lies in the middle of the hurricane belt and is subject to severe
storms and hurricanes from June to October. Concerned that it
was hurricane season, Captain Beach proposed to keep four boilers
of the Memphis going at all times to enable the ship to
get out of the harbor quickly if a hurricane approached. However,
because of US. Navy economy measures, Admiral Pond advised Captain
Beach to keep only two of the ship's boilers going for auxiliary
machinery, but to keep the other four boilers ready in case of
emergency.
Around August 22,
the barometric pressure dropped significantly and the weather
begun to deteriorate. Fearing that a storm or a hurricane was
approaching, Captain Beach ordered the other four boilers of
the ship to be fired and all arrangements to be made to get underway.
The feared hurricane did not occur but the preparedness exercise
was useful in demonstrating that the required steam pressure
to power the ship's engines could be raised in about 40 minutes.
Chronology
of Events in the afternoon of 29 August 1916 leading to the Loss
of USS Memphis
 The following chronology of events
summarizes entries from the ship's log, from observations by
the crew and people on the shore, from findings of a Court of
Inquiry, and from testimony at the court martial of the ship's
captain, following the loss of the ship.
Satellite photo of
the Santo Domingo coast where the USS Memphis perished.
29 August 1916 - The few days after 22 August
1916 were uneventful. Both the Memphis and Castine
were riding gently in smooth sea, anchored off Santo Domingo.
No storm warnings
had been received. However, in the early afternoon of
29 August, even though there was no wind, suddenly the
waves became significantly higher. Both the Memphis and
Castine begun to roll considerably at their anchorages.
Long period waves could be seen coming into the harbor from the
east and breaking on the rocks.
15.30 - Concerned about the increasing
wave activity, an order was issued to the engine room of the
Memphis to raise steam pressure. However, major difficulties
were reported from the engine and boiler rooms. Water spray was
entering through the ventilators on the ship's deck which had
not been properly secured. Some of the ventilators on the
deck were subsequently shut off, but a lot of water had already
entered the engine rooms, creating problems in raising steam
pressure. The engine room reported to the bridge that there would
be adequate steam pressure from the four boilers to power the
engines by 16.35.
15.35 - 15.40 - In the next few minutes the swells
in the harbor increased considerably. The Memphis was
rolling very heavily and seas were now covering her decks. Spray
continued to come down the ventilator funnels. According
to officers on the bridge, the waves were so enormous that the
ship's keel bumped the seabed once or twice. Given the fact that
the ship was presumably anchored in 55 feet of water, this
meant that the waves must have been about 40 feet in height.
16.00 - Huge breakers capsized a motor
launch returning to the Memphis. There was nothing that
could be done to help the crew and passengers struggling in the
water. By that time, the gunboat Castine had managed
to increase steam pressure, start its engines and raise her anchor.
In an effort to rescue those in the water, the gunboat came into
the surf. However, the seas were too rough to lower a boat
and the Castine got dangerously close to the rocks. Fearing
that Castine may end up on the rocks, the rescue effort
was abandoned but life jackets were thrown in the water. Castine's
commander ordered to head out. The battered gunboat struggled
past the Memphis, but managed to get safely out to deeper
water.
 16.30 - By that time the swell was even greater. The
Memphis kept on rolling 60 and perhaps as much as 70 degrees.
Her decks were being washed over by the waves and repeatedly
she was battered into the harbor bottom.
With each wave, the
ship appeared to be lifting and dragging towards the rocks on
the shore. Captain Beach ordered the drop of a second anchor,
but the order was canceled when the engine room informed him
that steam pressure would be adequate in five minutes to start
the engines. With the ship rolling that much and the seas washing
over the decks, attempting to drop the second anchor was impossible.
16.35 - An immense wave estimated to
be about 70 feet in height was seen approaching the harbor.
16.38 - The engine room could not
generate sufficient steam pressure for the engines. The ship's
anchor cable was straining and appeared that it would break.
With only 90 lb. of steam pressure, Captain Beach had no choice
and could not wait for more steam. In an effort to at least turn
the ship's bow into the approaching huge wave, he ordered the
starboard engine full astern and the port engine full ahead.
It was a futile effort. There was simply not sufficient steam
pressure to turn the ship ninety degrees and complete the maneuver.
16.40 - The enormous wave was quickly
approaching the Memphis. It could be seen churning sediments
of sand and mud from the sea bottom. It appeared that it would
hit the ship broadside - the most vulnerable position. The shallower
water depth had slowed the wave down a bit but its height had
increased. In front of it, a 300 ft long trough had formed. As
the wave got closer to the Memphis, its peak begun to break.
The top of the breaking crest was now about 30-40 feet above
on the ship's bridge. The wave form appeared to consist of three
distinct steps, each separated by a large plateau.
The huge wave broke
thunderously upon the Memphis, completely engulfing it.
Two seamen trying to release the second anchor were washed overboard.
The wave's impact injured members of the crew. Other crew members
were injured or killed by steam or by steam inhalation when the
ship boilers exploded. The ship did not capsize but recovered
to an upright position but hit bottom hard, which normally would
be about twenty-five feet below her keel. The battering caused
great damage on her hull.
16.45 - Slowly, dragging her anchor,
the Memphis struck the first rocks at about 16.45. As each succeeding
wave pounded her, she was forced a little further ashore until
her port side crushed against the rocks, which pierced this side
repeatedly. The Memphis was still rolling from side to side,
although now firmly aground.
17.00 - At about 17.00 the battered
ship was given one final push by the waves, thus moving her hard
aground on Santo Domingo's rocky coast in water depth ranging
from 12-19 feet and only 40 feet from the cliffy shoreline. Large
holes in the ship's hull could be seen by observers on the shore.
 Securing the Wreck
of the Memphis
Actions that followed
the grounding of the Memphis are not of direct relevance to the
evaluation of causes that caused this disaster and details are
omitted since they have been adequately documented in U.S. Navy
archives and the literature. It will suffice to say only that,
as soon as the Memphis had gone firmly aground, Captain Beach
ordered the crew to fully secure the ship with ropes to the shore.
This was accomplished with the assistance of U.S. Marines and
hundreds of Dominicans on the cliffy shore of the harbor. Then
the captain ordered the evacuation of the injured, followed by
the evacuation of 850 others. This was done in an orderly and
safe fashion, using hawsers on land and ropes.
Death Toll
and Injuries - Damage to the Ship
What had started as
a normal routine afternoon on board the USS Memphis on
29 August 1916, in a matter of about one hour, turned into a
disaster of major proportions. Forty three people lost their
lives that fateful afternoon. Twenty five crew members died when
the ship's motor launch capsized in huge breakers at about 14.00,
as it was attempting to return to the ship. Another eight members
of the crew were lost when three boats sent to sea sank or were
wrecked attempting to reach shore after dark. Ten more died either
by being washed overboard or from burns and steam inhalation
when the ship's boilers exploded. The total casualties,numbered
43 dead and 204 injured.
The ship itself sustained
irreparable damage. Though she appeared to be nearly normal in
appearance above the water, the USS Memphis was a total
loss. Her bottom was driven in, her hull structure was badly
distorted and her boilers had exploded. Her 23,000 horsepower
steam power plant had been destroyed. The Memphis, would never
sail again. Although her guns and other components were eventually
salvaged, her punctured and twisted hull remained an abandoned
wreck on the cliffs of Santo Domingo for 21 years - before being
dismantled by ship breakers.
Conclusions
of the Court of Inquiry as to What Caused the Loss of the Memphis
The loss of the Memphis
was followed by a Court of Inquiry and the court martial of Captain
Edward J. Beach, the ship's commander. The court
concluded that conditions had deteriorated very rapidly to save
the Memphis. Also, that the heavy rolling of the ship and
the flooding from the ventilator funnels was the reason that
steam pressure could not be raised in time to fire the engines
and head out to sea, as the gunboat Castine had barely
managed to do. Complications in the engine room were blamed for
the failure. The Court found that Captain Beach was guilty of
not keeping up sufficient steam to get underway at short notice
and of not properly securing the ship for heavy weather.
The huge waves that
engulfed and wrecked the Memphis and drowned the sailors were
attributed to a "tropical disturbance", a "seismic
storm", but also to a "tsunami" that originated
from a seismic event somewhere in the depths of the Atlantic
Ocean or Caribbean Sea.
Photographs
of the USS Memphis Wreck taken in 1917 and Later
(U.S. Naval
Historical Center Photographs)
Analysis
of the Naval Disaster
 A Tsunami in the Caribbean
Sea was not Responsible for the Loss of USS Memphis
The Navy's conclusion
that the loss of the Memphis was due to a 'seismic storm' or
a tsunami was erroneous. There is no such thing as a "seismic
storm". Furthermore, no tsunami occurred in late August
1916 in the Caribbean Sea or the Atlantic Ocean. The characteristics
of the waves observed breaking on the coastline of Santo Domingo
in the afternoon of 29 August 1916 were not those of a tsunami.
The Hurricanes of
1916 -Tracks of Hurricanes in 1916 in the Caribbean Sea and the
Western Atlantic Ocean
Tsunami waves were
not responsible for the loss of the Memphis. Most of the
historical tsunamis in the Caribbean region have been generated
by tectonic earthquakes. A review of historical catalogs of tsunamis
does not show an event specifically occurring on August 29, 1916.
The only earthquake and tsunami in the vicinity which could have
affected Santo Domingo occurred on April 24, 1916 north of Puerto
Rico, probably in the Mona Passage. Another earthquake/tsunami
occurred in the vicinity of Guatemala/Nicaragua on January 31,
1916. This event could not generate a tsunami at Santo Domingo.
A tsunami was generated on the Pacific side of Central America.
The waves that resulted in the loss of the USS Memphis
were not caused by a tsunami. There were no earthquakes of significance
in the region during the latter part of August 1916. Similarly
, there were no volcanic eruptions or major underwater landslides.
The Navy officers
who participated in the Court of Inquiry and the court martial
of the ship's captain did not appear to have much technical experience
or training about storm-generated waves or tsunamis. In 1916,
Oceanography and Meteorology had not developed sufficiently as
fields of science. Very little was known about tsunamis or the
modes of their generation. Also, it appears that very little
was known about tropical storms or hurricanes. There was no effective
way of tracking hurricanes or reporting vital weather data to
the Navy Command. Weather forecasting was at a rudimentary state
and there was no effective monitoring system or synoptic observations
which could be shared in real time. Finally, communications were
not very good in those days. Thus, it appears that the Navy Command
did not even have information on the three hurricanes that had
passed close to Santo Domingo in the month of August 1916. In
fact, on 18 August, one of these hurricanes had made landfall
at Corpus Christi, Texas, and had been responsible for widespread
destruction. Even if this information was known, it appears that
it was not conveyed to the captains of the Memphis or
the Castine at Santo Domingo.
The USS
Memphis was wrecked by storm waves generated by a passing hurricane
The location at Santo
Domingo where the Memphis and the Castine were anchored
was very vulnerable to approaching storm waves from the east
and southeast. The water depth of 55 feet where the Memphis had
dropped anchor was too shallow and within the breaking depth
zone of potential significant waves of longer period and wavelength,
generated by hurricanes.
As it will be demonstrated,
the series of huge breakers and the enormous wave that wrecked
the ship on the afternoon of 29 August 1916 were generated by
an approaching hurricane.
The most significant
of the waves that wrecked the Memphis were generated within this
hurricane's zone of maximum winds. Once outside the fetch region
of generation, these storm waves had outrun the slower moving
hurricane system and raced as swells across the Caribbean and
towards the harbor of Santo Domingo.
The following is an
account of the hurricanes that passed near the Dominican Republic
in August 1916 and an analysis of the storm waves of the particular
hurricane that caused the loss of the ship.
 The Hurricanes of 1916
This region of the
Caribbean is in the middle of the hurricane belt and is subject
to severe tropical storms and hurricanes from June to October.
As shown by the hurricane tracking diagram, there were numerous
hurricanes that traversed the region in 1916. Most of them developed
in the Atlantic Ocean as tropical storms but when they reached
winds of more than 75 miles per hour, they were classified as
hurricanes. Three of these storm systems became hurricanes in
August 1916. Two of them crossed the Central Caribbean Sea, south
of Santo Domingo, and one headed north.
Track of the unnamed
1916 hurricane that struck Corpus Christi, Texas in 1916
The first of the unnamed
hurricanes in August 1916 (8/12 - 8/19) reached Category 3 and
made landfall at Corpus Christi, Texas - causing extensive destruction
there. The second unnamed hurricane (8/21 - 8/25) reached briefly
a Category 2 status as it passed near the island of Hispaniola,
but quickly degenerated into a tropical storm. Finally, the third
unnamed hurricane in late August (8/27 - 9/2) reached a Category
2 status with sustained winds of over 100 miles per hour. It
passed south of Santo Domingo on August 29. It is believed that
it was this hurricane that generated the huge waves at Santo
Domingo. Because its waves wrecked the USS Memphis, we
shall refer to it as "Hurricane Memphis".
The unnamed
Hurricane of August 12 - August 19, 1916
As the tracking indicates,
this hurricane reached Category 3 status passing south of Santo
Domingo on 14-15 of August. It continued in a northwest direction,
making landfall at Corpus Christi, Texas on August 18.
 There is no information on any
unusual wave activity at Santo Domingo around August 14-15 when
this hurricane passed about 275 nautical miles to the south.
It appears that the directionality of the hurricane's path was
the reason that no significant waves struck the coast of Santo
Domingo.
However, this hurricane
was very destructive in the Corpus Christi, Texas region. In
fact it was the strongest storm since the Great Galveston storm
of 1900 had struck the area south of Corpus Christi
Although this hurricane
caused some damage, it moved very fast over the Texas coastal
area, thus resulting in low loss of life. Only 15 people died.
However, property damage was significant and was estimated at
$1,600,000 (1916 dollars). Most affected were the cities of Bishop,
Kingsville and Corpus Christi. In Corpus Christi, all the wharves
and most of the waterfront buildings were destroyed. There was
hardly any property that was not damaged. Most of the damage
resulted from the hurricane surge flooding and the superimposed
storm waves.
Evaluation
of Hurricane "Memphis" of 8/27 - 9/02, 1916
As the tracking diagram
indicates this particular system developed from a tropical storm
on 27 August to a Category 2 hurricane on 29 August. It reached
sustained winds of over 100 miles an hour and maximum probable
wind speeds and gusts of 125 miles per hour.
This was a dynamic
storm system which advanced into the Caribbean Basin rapidly.
The hurricane's speed of translation eastward is estimated at
about 15- 20 nautical miles per hour, since it traversed approximately
400 nautical miles on 29 August. At its closest point, the hurricane
center was about 250 nautical miles south of Santo Domingo.
The following is tracking
information for hurricane Memphis, followed by an analysis of
the storm waves it generated.
 Tracking information
for Unnamed Hurricane (Hurricane Memphis) Passing South of Santo
Domingo on 29 August 1916
Time Lat
Lon Wind(mph) Pressure Storm type
------------------------------------------------------------------
6 GMT 8/27/16 14.0N
46.3W 70 -999 Tropical Storm
12 GMT 8/27/16 14.0N 48.5W 70 -999 Tropical Storm
18 GMT 8/27/16 14.3N 51.2W 75 -999 Category 1 Hurricane
0 GMT 8/28/16 14.7N 53.5W 75 -999 Category 1 Hurricane
6 GMT 8/28/16 15.1N 56.0W 80 -999 Category 1 Hurricane
12 GMT 8/28/16 15.3N 58.5W 85 -999 Category 1 Hurricane
18 GMT 8/28/16 15.4N 60.5W 85 -999 Category 1 Hurricane
0 GMT 8/29/16 15.5N
62.8W 90 989 Category 1 Hurricane
6 GMT 8/29/16 15.6N 65.1W 100 -999 Category 2 Hurricane
12 GMT 8/29/16 15.6N 67.6W 100 -999 Category 2 Hurricane
18 GMT 8/29/16 15.7N 69.2W 100 -999 Category 2 Hurricane
0 GMT 8/30/16 15.9N 71.3W 100 -999 Category 2 Hurricane
6 GMT 8/30/16 16.0N 73.1W 100 -999 Category 2 Hurricane
12 GMT 8/30/16 16.2N 75.1W 100 -999 Category 2 Hurricane
18 GMT 8/30/16 16.6N 76.7W 100 -999 Category 2 Hurricane
0 GMT 8/31/16 16.8N 78.2W 100 -999 Category 2 Hurricane
6 GMT 8/31/16 17.0N 79.6W 100 -999 Category 2 Hurricane
12 GMT 8/31/16 17.4N 81.0W 90 -999 Category 1 Hurricane
18 GMT 8/31/16 17.7N 82.0W 90 -999 Category 1 Hurricane
0 GMT 9/ 1/16 18.0N 83.2W 85 -999 Category 1 Hurricane
6 GMT 9/ 1/16 18.1N 84.1W 85 -999 Category 1 Hurricane
12 GMT 9/ 1/16 18.2N 85.3W 80 -999 Category 1 Hurricane
18 GMT 9/ 1/16 18.2N 86.4W 80 -999 Category 1 Hurricane
0 GMT 9/ 2/16 18.1N 87.6W 75 -999 Category 1 Hurricane
6 GMT 9/ 2/16 17.9N 89.3W 65 -999 Tropical Storm
12 GMT 9/ 2/16 17.0N 91.0W 35 -999 Tropical Depression
Hurricane
"Memphis" Wind Field - Directionality of Hurricane
Fetches, Duration and Significant Storm Waves and Swells
The hurricane's winds
blew in a counterclocwise pattern. Soon after the hurricane crossed
the Lesser Antilles islands arc, significant storm waves of longer
period begun developing within the radius of maximum winds, within
fetches of 10 to 20 nautical miles and over a durations of 1
to 2 hours.
As the hurricane progressed
westward in the Caribbean in the early morning hours of 29 August,
the fetches of maximum winds kept on changing direction in the
same counterclockwise pattern. Initially the winds generated
huge storm waves from an easterly direction. At the time, the
wave field in front and on either side of the hurricane center
consisted of locally generated seas and traveling swells from
other regions of the storm system. However, in the next few hours,
as the hurricane was approaching the longitude of Santo Domingo,
additional huge storm waves were generated, not only along the
east-west fetches of maximum winds, but along fetches with a
southeast - northwest orientation.
The longer period
storm waves begun to outrun the moving storm system and sorted
out as distinct wave trains traveling as swells towards the southern
coasts of the Dominican Republic. Because of the hurricane's
eastward movement and orientation of the fetches of maximum winds,
the waves that were generated became very directional towards
Santo Domingo. The direction of approach of converging swells
was from the east, from the east south-east, and from the south
east.
Estimate
of the Height and Period of the Most Significant Deep Water Storm
Wave Generated by Hurricane "Memphis" - The Killer
Wave
Based on limited data
for this historical hurricane but on certain known parameters
of other more recent hurricanes, mathematical modeling can be
applied to simulate the near sea surface wind field and to estimate
the upper limit of the long period waves generated by this storm
system. However, such modeling is a very involved process. For
the purpose of the present analysis, an empirical approach is
sufficient to roughly evaluate the Rayleigh wave distribution
function, and the upper limit of storm wave height variability,
as well as the maximum period, wavelength, and deep water height
of the most significant of the storm waves.
Based on this
analysis it can be concluded that it was this significan wave
or a very similar long period wave, which combined in resonance
with other storm waves, and resulted in the huge breaker that
engulfed the USS Memphis at 1640 on 29 August 1916 - wrecking
it on the rocks of Santo Domingo.
The significant height (Ho) and period
(To) of the most
significant wave generated in deep water at a point on the radius (R) of maximum wind of a hurricane can be calculated
mathematically, provided that the hurricane's pressure differential from the normal (Dp) is known, as well as the hurricane's
forward speed, its maximum gradient wind speed near the water
surface (30 feet above), and the Coriolis parameter (f) at that latitude. The mathematical equations
for this calculation are ommitted here but the results are presented.
Based on the limited
data available for this August 1916 hurricane ("Memphis"
- Category 2 hurricane), and assuming that its radius of maximum
winds was about 35 nautical miles away from the storm center
(a reasonable approximation for a hurricane of this type), the
forward speed was 20 knots, and the barometric pressure differential
of about 2.3 inches of mercury, the most significant deep water height (Ho) is calculated
to be about 58.9 feet.
The deep water period of this significant wave is
calculated to be about 16.1
seconds - indeed
a long period. Once outside the hurricane region this significant
wave maintained its wavelength and period, but attenuated somewhat
in height during its travel towards Santo Domingo.
Wave Transformation
in Shallow Water - Effects of Near Shore Refraction and Resonance
In the meantime, the
first of the longer period storm waves - which outrun the hurricane
system's eastward progression - begun arriving as swells at Santo
Domingo at about 1500 on August 29. Up to that time the sea had
been smooth and there were no reports of winds or a drop in barometric
pressure. At that time, the hurricane's center was fairly far
away at about 15.6 N and 67.6 W, approximately 300 nautical miles
southeast of Santo Domingo. However, these initial waves that
begun arriving at 1500 had been generated much earlier, mainly
from east-west fetches when the hurricane was as far as 600 nautical
miles away. The swells had traveled almost twice as fast as the
overall storm.
In the next hour,
additional storm waves generated closer to Santo Domingo - but
coming from a changing east-southeast direction - begun to outrun
the moving hurricane and interfere with swells arriving from
the east. The direction of the waves approaching Santo Domingo
kept on changing, but when the swells reached shallower water,
the bottom effects begun to be felt. Near-shore refraction unified
the waves' directional approach towards the harbor of Santo Domingo
and the location where the Memphis and the Castine were anchored.
Some of the waves that had similar periods and wavelengths arrived
in resonance, and begun to superimpose on each other - thus augmenting
their heights. The longer period waves begun to break in water
deeper than the 55 feet where presumably the Memphis was anchored.
These breaking waves, some striking broadside, washed over the
decks of the Memphis, and thus water went into the ventilator
shafts. This in turn caused the problems in raising steam for
the engines of the ship. The anchor was still holding, but probably
slightly dragging on the sea floor. Apparently not enough scope
had been let out on the anchor's chain. Dropping a second anchor
would not have helped the Memphis since not enough scope could
be released for the anchor to grab and be effective.
The Most Significant
of the Waves - According
to the crew on the Memphis, a huge wave appeared in the horizon
and its height was estimated to have been about 70 feet. This
must have been the most significant of the waves generated by
the hurricane which was estimated earlier to have a maximum deep
water height of 58.9 feet and a period of 16.1 seconds when it
left the fetch in the hurricane's region of maximum winds (estimated
to have been 125 knots/hour).
As this huge wave
got close to the Memphis, crew members observed that it had three
distinct steps and two plateaus on its forward face. Also, they
reported that its crest was preceded by a trough which was estimated
to be 300 ft. long. These observations suggest that this wave's
overall wavelength was about 600 feet and that two other waves
had superimposed on it when refraction begun to take place in
the shallows off Santo Domingo. Since the period of this extreme
wave was calculated to be 16.1 seconds in deep water (unchanged
by refraction), the deep water wave celerity (speed) can be estimated
- based on Airy and Cnoidal wave theories - to have been: C=L/T =600/16.1= 37.27 ft/sec (independent of depth). However
in water shallower than one half the wavelength (in this case
less than 300 feet) refraction by bathymetry and effects of resonance
begun to take place - thus combining this huge wave with two
other significant, long period waves approaching from different
sources and directions. This explains the three steps and plateaus
that were observed on the face of the huge wave.
The transformation
of the huge wave had begun about two minutes earlier. When the
wave reached water depths ranging much less than 1/2 its wavelength
(much less than 300 feet), the refraction effects became more
significant. Its speed was reduced considerably. The wave speed
was now dependent on the depth of the water and was governed
by the shallow water wave equation, which can be simplified as:
C = Square Root of
gxd - where d=depth of the water, and g= gravitational acceleration for that particular latitude. Based on solitary
wave theory, and without knowing the slope profile off Santo
Domingo harbor, an estimate of the breaker height can be made
based on the relationship between the breaker height (Hb) to the breaking
depth (Db). At the
breaker depth, all of the wave's potential energy became forward
kinetic energy - much to the detriment of Memphis. The relationship
from which the depth of the water where the wave will begin to
break can be obtained from Hb=Db/1.28. Since the observation was made
by members of the crew that the huge wave was about 30 to 40
feet above the bridge of the Memphis - and assuming that the
bridge was about 30 feet above sea level, the height of the wave
at breaking, Hb, must have been 70 feet. Thus
the huge wave must have begun breaking when it reached a depth
of 89.6 feet. Had the Memphis been anchored
in deeper water, like 120 feet instead of 55 feet, the entire
disaster would have been prevented. The ship would not have sustained
the earlier flooding of the engine room through the ventilators
by the earlier waves and it would have been able to raise steam
and sail to deeper water in a timely fashion. Alternatively,
if the Memphis had been anchored in 100 or better 120 feet of
water - instead of 55 feet - it would have been able to ride
all the swells, including the huge 70 foot wave, without a problem.
Unfortunately the
Memphis was anchored in too shallow and unsafe water depth. When
the huge wave had reached a depth of about 90 feet, its crest
peaked and the water particle velocity exceeded the wave's forward
velocity (celerity). At that breaking depth, all of the wave's
energy became kinetic and a huge volume of water begun to move
forward at a speed of 25-30 miles per hour. When this huge breaker
struck the Memphis broadside, it engulfed its decks and smokestacks
and pushed it onshore with tremendous force. At that point in
time, the Memphis was forever doomed. The anchor was of no use.
The engines, even if they had more than the 90 lbs of steam pressure,
would have not saved the ship. Even if the maneuver of turning
the ship's bow into the face of the wave had been completed,
it would have been futile within the breaking zone of this huge
wave. Neither the engine nor the anchor could have opposed the
huge wave force.
Human Errors
Contributed to the Loss of the USS Memphis
Human errors were
inadequately addressed by the Navy's Court of Inquiry into the
disaster and by the court martial of the ship's captain.
Complications in the engine room were blamed for the failure.
The Court found that the only human errors responsible for the
ship's loss was the captain's failure to keep sufficient steam
pressure to get underway at short notice and of not properly
securing the ship for heavy weather.
However, the Navy's
economy measures were the main reason that the boilers of the
Memphis were not fired at all times to keep steam pressure up
for the engines.
The huge waves that
wrecked the Memphis at the harbor of Santo Domingo in the afternoon
of 29 August 1916 were inacurrately attributed by the Court of
Inquiry to a "tropical disturbance", a "seismic
storm", but also to a "tsunami". The offiicial
Navy records still show that the loss of the Memphis was caused
by a tsunami or a tropical disturbance - but without further
explanation. As explained above, the waves that wrecked the Mempis
were not those of a tsunami but were generated by a hurricane
that passed south of Santo Domingo. What is perplexing is that
no one made a connection between this hurricane and the huge
waves it generated. It is apparent that storms were not properly
monitored in 1916 and that communications on weather information
were poor.
The loss of the Memphis
was a considerable disaster but, in fact, it was one that could
have been prevented with some rudimentary knowledge of storms,
storm waves, and with some additional preparation. The most serious
of the human errors that resulted in the loss of the ship was
the decision to drop anchor in only 55 feet of water. It was
an error in judgment, knowing very well that it was hurricqane
season. Anchoring in deeper water would have averted the disaster.
From the court martial proceedings, it appears that none of the
officers in charge had any training or conception of the speed
by which a storm would move, or that significant waves of greater
heights, wavelengths and periods could be generated by a distant
storm, or that the waves could outrun the storm and be immense
at distant locations. No one at that time recognized the potential
severity of such waves in shallow water, or realized that such
waves transform their potential energy into kinetic forward moving
energy once a certain depth is reached. Everyone was aware
that it was hurricane season, that the barometric pressure had
dropped previously and that there was a possibility of an approaching
hurricane and possible waves. They made preparations by
firing the engines on August 22nd and preparing for such an eventuality.
However, none considered the most simple and inexpensive solution
to this potential problem by simply anchoring the ship at 100-120
feet depth and out of harm's way. Lack of proper training on
weather and wave phenomena was the most important human error
in the loss of the USS Memphis.
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