Environment and development
in coastal regions and in small islands
colbartn.gif (4535 octets)

Extract from:

MONTSERRAT BEACH MONITORING
PROGRAMME

BEACH DATA ASSESSMENT
1990 - 1996

October 1997

Abstract
Introduction
Assessment of beach changes in Montserrat between 1989 and 1996
Individual site data
  Sugar Bay
  Sturge Park
  Fox's Bay
  Old Road Bay
  Lime Kiln Bay
  Woodlands Bay
  Bunkum Bay
  Carr's Bay
  Little Bay
  Farm's Bay

Prepared by
Ministry of Agriculture, Trade and Environment, Montserrat.
Physical Planning Unit, Montserrat.
Coast and Beach Stability in the Lesser Antilles Project (COSALC).

 
UNESCO
Coasts & Small Islands
  University of Puerto Rico
Sea Grant College Program

ABSTRACT

This report presents and summarizes the data from Montserrat's beach monitoring programme over the period 1990-1996. Ten beaches have been monitored over the period; a total of fifteen profile sites. The data showed that most of the beaches accreted over the period 1990-1993 as they recovered from Hurricane Hugo which passed directly over the island in 1989. Between 1994 and 1996 there has been an erosion trend. Much of the erosion was due to three tropical systems (Iris, Luis and Marilyn) which passed close to Montserrat in 1995. Little sustained beach recovery was experienced in 1996 since during that year Montserrat was impacted by two further tropical systems (Bertha and Hortense). Hurricanes appear to be the major force shaping Montserrat’s beaches between 1990 and 1996.

A comparison of nine of the beaches showed that six (Sturge Park, Fox's Bay, Lime Kiln Bay, Woodlands Bay, Bunkum Bay, Little Bay) eroded during the period showing a mean reduction in profile area of 21% and a mean profile narrowing of 8 m. Three beaches showed accretion, these were Sugar Bay, Old Road Bay and Carr's Bay. The mean increase in profile area was 66% and the mean profile widening was 7 m. At two of these beaches, Sugar Bay and Old Road Bay, the accretion was at least partly due to sea defences.

At Farm's Bay, the only site monitored on the east coast, there were considerable variations in beach size, these were partly related to beach sand mining. Between 1993 and 1996 this beach was the designated site for sand removal under permit.

With the current volcanic crises, only five of the beach sites lie in the safe area: Lime Kiln Bay, Woodlands Bay, Bunkum Bay, Carr's Bay and Little Bay. Four of these beaches showed serious erosion between 1990 and 1996, only Carr's Bay showed accretion.

 

INTRODUCTION

A beach monitoring programme was started in Montserrat in February 1990, following the serious erosion and damage to the coast caused by Hurricane Hugo in 1989. The monitoring is conducted by the Ministry of Agriculture, Trade and Environment, using standard techniques (Cambers, G., Christopher, W. 1994. Beach Changes in Montserrat 1990-1993. University of Puerto Rico Sea Grant College Program, PRU-T-94 (5), 31 pages). Assistance is provided with the data analysis and interpretation by the Coast and Beach Stability in the Lesser Antilles project (COSALC).

This present document contains a summary of all the data for the period 1990-1996. Overall changes between 1990 and 1996 have been assessed. The document is not , however, a full technical report.

 

ASSESSMENT of the BEACH CHANGES in MONTSERRAT BETWEEN 1990 and 1996

Hurricanes appear to be the major force shaping the beaches of the Caribbean Islands. While winter swells are responsible for many of the seasonal changes observed, hurricanes cause the major, and sometimes permanent, changes. Table 1 shows the major hurricanes that have passed close to Montserrat between 1989 and 1996.

Table 1: Hurricanes passing close to Montserrat between 1989 and 1996

Hurricane name Category Date Distance from Montserrat
Hurricane Hugo 4 17-18/9/89 Centre passed over the island
Tropical Storm Iris N/A 26-27/8/95 50 km
Hurricane Luis 4 4-6/9/95 100km
Hurricane Marilyn 3 15-16/9/95 50km
Hurricane Bertha 1 7-9/7/96 150 km
Hurricane Hortense
(Tropical storm strength
over the Leeward Islands)
1 8-10/9/96 80 km

Hurricane Hugo, a category 4 hurricane, was the most damaging hurricane for Montserrat during the seven year period. Unfortunately the beach monitoring programme was not set up until after this hurricane, so it is impossible to quantify the full impact of this hurricane on the beaches of Montserrat.

1995, the second most active year on record for Atlantic hurricanes, produced three storms that affected the island. Hurricane Luis was the largest system and caused the most damage. However, it is impossible to separate the individual effect of the three storms, Iris, Luis and Marilyn, all of which passed close to Montserrat within a three week period.

In 1996 Hurricane Bertha passed to the north of Montserrat in July. This was followed by Tropical Storm Hortense, which later became a hurricane, and passed south of Montserrat in September. This system then stalled for a couple of days before moving over Puerto Rico. During that period high waves were generated along the west coasts of the Leeward Islands, including Montserrat.

In order to determine the overall changes taking place on Montserrat's beaches, the following analysis was undertaken. For each site the change in profile area was calculated by comparing the average profile area with that of the previous year. Then for each year the changes at the individual sites were averaged. The number of sites which eroded or accreted in a particular year was calculated as well as the average change. The same procedure was repeated for profile width, see Tables 2 and 3.

Table 2: Average Change in Beach Profile Area

Year Average change in
Profile Area (%)
Number of Sites
Eroding
Number of Sites
Accreting
Total number
of sites
1990- 1991 +12.8 2 7 9
1991-1992 +10.5 3 6 9
1992-1993 +7.8 2 8 10
1993-1994 -7.9 8 2 10
1994-1995 -11.4 8 2 10
1995-1996 -1.0 8 6 14

Table 3: Average Change in Beach Profile Width

Year Average Change in Profile Width (m) Number of Sites Eroding Number of Sites Accreting Total Number of Sites
1990-1991 +3.9 0 9 9
1991-1992 +0.6 3 6 9
1992-1993 +4.6 3 7 10
1993-1994 -5.5 10 0 10
1994-1995 -2.9 8 2 10
1995-1996 -1.6 8 6 14

The two tables show the same trends, although there are some differences. Beach profile area includes profile width as well as slope and is the more accurate parameter. However, in order to compare sites, profile area is usually calculated as a percentage change, because of the width variations in beach shape and size. Profile width has been left as an absolute value, however, it is less indicative of overall beach change than the profile area parameter.

The table for profile area (Table 2) shows that for the first three years after Hurricane Hugo, beaches in Montserrat accreted, with most of the accretion occurring in the first year. However, this trend was reversed in 1994, when most of the beaches eroded at a fairly significant rate. It is not clear at the present time why this change took place. There was no significant hurricane activity in the Caribbean in 1994. Possibly there were a higher than usual number of winter swells in 1994, but no data exists to substantiate this hypothesis. The erosion trend continued, at an increased rate in 1995. This was to be expected in view of the active hurricane season in that year. The erosion continued in 1996 and there was no significant recovery from the 1995 hurricanes. Again this can be explained by the fact that two less severe hurricanes did impact Montserrat's beaches in 1996, thereby reducing the likelihood of beach recovery.

In order to assess the individual site data, a very simple comparison can be made of the values for profile area and width at each site in 1990 with those in 1996, see Table 4. This comparison can only be done for nine beach sites where the same reference point is still in use. Table 4 shows that in 1996, six sites had eroded and three had accreted as compared with the 1990 baseline conditions. Of the three sites which showed accretion, sea defences were at least partly responsible for the accretion at Sugar Bay and Old Road Bay. Sea defences cannot, however, explain the very significant accretion at Carr's Bay.

Table 4: Comparison of the Beach Profile Data for 1990 and 1996

Site Change in Profile Area (%) Change in Profile Width (m)
Sugar Bay +11.3 +5.0
Sturge Park North* -49.0 -14.3
Fox's Bay North -13.8 -13.6
Old Road Bay +87.9 +9.6
Lime Kiln Bay -5.3 -0.4
Woodlands Bay -16.3 -6.3
Bunkum Bay -22.3 -6.3
Carr's Bay +100.0 +5.2
Little Bay -16.0 -6.3

* Comparison between 1991 and 1996 datasets

The results from this 1990/1996 comparison are summarized below:

With the current volcanic crisis in Montserrat, only five of the beach sites lie in the safe area: Lime Kiln Bay, Woodlands Bay, Bunkum Bay, Carr's Bay and Little Bay. Four of these beaches showed serious erosion between 1990 and 1996, only Carr's Bay (southern end) has accreted.

INDIVIDUAL SITE DATA

File Summary Master Sheet

Site Name Standard Vertical Drop (m) Dates
Sugar Bay 2.970 2/90 -
Sturge Park Cemetery 5.266 7/95 -
Sturge Park North (Hotel) 2.750 7/91 -
Fox's Bay South 2.990 7/95 -
Fox's Bay North 2.715 2/90 -
Old Road Bay 2.213 2/90 -
Lime Kiln Bay 5.001 2/90 -
Woodlands Bay 3.462 2/90 -
Bunkum Bay 2.530 2/90 -
Carr's Bay South 4.378 2/90 -
Carr's Bay North 3.802 7/95 - 1/96
Little Bay South 4.467 2/90 -
Little Bay North 4.210 7/95 -
Farm's Bay South 4.605
2.248
2/90 - 12/91
9/92 -
Farm's Bay North 4.598 7/95 -

SUGAR BAY

Sugar Bay lies south of the Plymouth Port reclamation. This site is located in front of the Yacht Club and south of a groyne. The groyne helps to promote accretion at this beach when the wave direction is from the southwest, which is generally during the summer months.

Between 1990 and 1993, this site showed an accretion trend as the beach recovered after Hurricane Hugo. There was a reduction of the profile area in 1994. In 1995, after Hurricane Luis, the profile area decreased by 50% and the beach width narrowed by 15m.

In 1996, there was significant beach recovery, although not to the 1993 levels.

STURGE PARK

A site was established near the Sturge Park Cemetery in July 1995. There was significant erosion after Hurricane Luis in September, 1995, the profile area decreased by 24% and the profile width decreased by nine metres. There had been significant recovery to pre-hurricane levels by the summer of 1996. However, Hurricane Hortense in September 1996, caused further erosion at this site.

A site was established at the north end of the beach, near the Montserrat Springs Hotel in 1991. Between 1991 and 1993, the beach was stable, there was slight accretion. Significant erosion started in 1994. After the hurricanes of 1995, this profile was very severely eroded. A comparison of the profile area before and after Hurricane Luis showed the profile area decreased by 89% and the profile width decreased by thirty metres. This was the most severely impacted site in Montserrat. Some recovery did take place in 1996, but the beach had not returned to its pre-hurricane level.

FOX'S BAY

One profile site was established at the north end of the bay in February 1990. During the period 1990 to 1992 this site showed steady accretion as the beach recovered after Hurricane Hugo in 1989. During 1993 and 1994 there was erosion and in 1995 there was very dramatic erosion as a result of the hurricanes that year. A comparison of the data before and after the hurricanes showed the profile area decreased by 62% and the profile width narrowed by twenty five metres. There has been some recovery since 1995, although the beach has not returned to its pre-hurricane level.

A second profile site was established at the south end of the beach in July 1995. This site showed slight accretion after Hurricane Luis, the profile area increased by 9% although the profile narrowed by three metres. However, when comparing average annual figures, the site showed slight erosion between 1995 and 1996.

Examination of the data tables shows that as one site erodes the other accretes, indicating sand is moving from one end of the bay to the other. However, examination of the area graph for Fox's Bay North shows that beach levels in 1996 were lower than in 1990 after Hurricane Hugo, indicating some sand may have been lost from the bay system.

OLD ROAD BAY

One site was established at the northern end of the bay in February 1990. This site was south of the jetty. In February 1994 the jetty was lengthened and made into an 'L' shape with a twenty metre extension. The profile at this site has accreted steadily between 1990 and 1996. The jetty provided shelter to this profile site even during the 1995 hurricanes. There was very little change at this profile site after the 1995 hurricanes.

LIME KILN BAY

Like many other west coast sites, this beach accreted between 1990 and 1993. However, an erosion trend set in between 1994 and 1996. There was only slight erosion at this beach following the 1995 hurricanes, profile area decreased by 4% and profile width increased by four metres. The erosion trend continued through 1996.

WOODLANDS BAY

There is one site at this beach, near the centre of the bay. Like at Lime Kiln Bay, there was significant accretion between 1990 and 1993. However, erosion has taken place between 1994 and 1996, such that beach levels in 1996 were lower than just after Hurricane Hugo in early 1990. There was very dramatic erosion here following the 1995 hurricanes, profile area decreased by 78% and the width narrowed by twenty four metres. There has been some recovery since then but not to pre-hurricane levels.

BUNKUM BAY

This site followed a similar pattern to Woodlands Bay, showing accretion between 1990 and 1993, followed by erosion between 1994 and 1996. Again there was significant erosion following the 1995 hurricanes, profile area decreased by 61% and profile width decreased by nineteen metres. During 1996 there was some recovery, but not to pre-hurricane levels.

CARR'S BAY

A site was established at the southern end of the bay in 1990 and a second site was established at the northern end of the bay in 1995. However, this northern site was destroyed at the beginning of 1996. The southern site has shown steady accretion over the period 1990 to 1996. This despite significant erosion after the 1995 hurricanes, when the profile area decreased by 26% and the profile width decreased by eleven metres. However, in 1996 the profile recovered to exceed pre-hurricane levels. While little data was collected at the northern site, the record does show that this site accreted after the 1995 hurricanes by 26%, although the profile width showed little change. Again sand may be moving back and forth within this bay, and the southern headland appears to be promoting significant accretion at the southern end of the bay.

LITTLE BAY

Two sites were established here, one at the southern end in 1990 and the other at the northern end in 1995. The southern site showed accretion between 1990 and 1993, although with some fluctuations. However, between 1994 and 1996 there has been erosion. After the 1995 hurricanes, profile area decreased by 50 % and width by thirteen metres at the southern site. There has been some recovery, but not to pre-hurricane levels. The northern site showed a similar pattern after the 1995 hurricanes, profile area decreased by 51% and width by sixteen metres, and while there has been some recovery, the profile has not recovered to pre-hurricane levels.

FARM'S BAY

A site was set up at the southern end of Farm's Bay in 1990, however, the reference mark was lost in 1992. Between 1990 and 1991 profile area at this site decreased, although the width increased. A new site was established in 1992 and between then and 1996 there have been considerable fluctuations.

Since 1993, Farm's Bay has been the designated beach for controlled sand extraction. Prior to that date, large scale uncontrolled mining took place at Farm's Bay as well as other beaches.

Some of the fluctuations may be related to the volume of sand removed, see the following table. 781 m3 were removed during eight months in 1994, while 482 m3 were removed during a similar period in 1995. Average profile areas were lower in 1994 than in 1995.

Year Number of Permits Issued Cubic Metres of Sand
1993 (5 months) 56 222
1994 (8 months) 121 781
1995 (7 months) 86 482

Source: Gunne-Jones, A., Christopher, W., 1997, Sand Mining a Position Paper from Montserrat, pp87-95. In Cambers, G. (Ed), 1997, Managing Beach Resources in the Smaller Caribbean Islands, Coastal Region and Small Island Papers 1, UPR/SGCP-UNESCO, Mayaguez, 269 pp.

A site was established at the northern end of the bay in 1995. The northern site has shown slight accretion between 1995 and 1996. Both sites showed slight accretion after the 1995 hurricanes.

  Introduction    Activities   Publications   word
search
Wise Practices   Regions   Themes