NATURAL HAZARDS ENVIRONMENT OF THE CARIBBEAN: AN OVERVIEW OF ACTIVE PROCESSES

NATURAL HAZARDS ENVIRONMENT OF THE CARIBBEAN: AN OVERVIEW OF ACTIVE PROCESSES RAFI AHMAD rafi.ahmad@uwimona.edu.jm UNIT FOR DISASTER STUDIES http://www.mona.uwi.edu.jm/uds/ DEPARTMENT OF GEOGRAPHY & GEOLOGY THE UNIVERSITY OF THE WEST INDIES, MONA KINGSTON 7, JAMAICA NOTICE PLEASE DO NOT REPRODUCE THE CONTENTS OF THIS LECTURE WITHOUT AUTHOR S PERMISSION Thank You

We present a geologic, geomorphic, and geophysical background for the management of natural hazards and risks Natural Hazard processes are an essential part of how Earth functions These processes have been shaping the planet Earth for millions of years We often pay a high price for ignoring ground rules As far as possible we must try to match land use with geological constraints

IT IS EASY TO TRY CHANGES TO HUMAN BEHAVIOUR RATHER THAN CONTROLLING NATURAL PROCESSES Natural disasters result from human decisions How we choose to select building sites is critical in risk exposure We must strive to meet with geology, geomorhology, and geophysics We must discover the societal value of geological maps

Physical Caribbean (From: NEIC, USGS)

THE CARIBBEAN Physiography Note: Distribution of land area (brown)

PLATE TECTONICS AND NATURAL HAZARDS IN THE CARIBBEAN The theory of plate tectonics is a simple yet comprehensive basis to explain how Earth works and how landforms were shaped. It is an elegant concept in that the theory allows for predictions to be made which could be tested against observations. The theory of plate tectonics thus provides a platform to address a variety of anthropologic/societal concerns in a quantitative/empirical way. Characteristics of tectonic plates, especially plate boundary zones and their working is critical to our understanding of natural hazard processes, for example, how are earthquakes related to plate motions and what sorts of tsunami-generating sources may be found in different types of plate boundaries.

PLATE TECTONIC MAP, Modified from Munich Re. The Caribbean plate provides vivid examples of why and how natural hazard processes occur in the Caribbean.

EARTHQUAKES AND VOLCANIC ACTIVITY DEFINE THE PRESENT-DAY CARIBBEAN PLATE Earthquake epicentres: black dots and circles. Volcanic centres: red triangles, open-active

Plate boundaries and earthquakes in the Caribbean Region From: US Geological Survey

The Caribbean Plate Modified from National Geographic Magazine

LANDSLIDE TRIGGERS ARE EARTHQUAKES AND RAINFALL. Plate boundary zone of Jamaica, historical tsunami generating earthquakes, and hurricane tracks. The Caribbean Plate is moving east-northeastward at a rate of approximately 18-20mm/yr relative to North America. The plate boundary zone in the vicinity of Jamaica is complex. Hispaniola area: Oblique convergence between the Caribbean Plate and the Bahamas Platform. Jamaica area: Transpression. Cayman area-central America: Strike-slip and transtension. ( Map modified from Grindlay, Hearne, and Mann, 2005) Hurricane Tracks

Rainfall (Modified from MunichRe) Rainy months: VI (June)-XII (December) Maximum 24 hr rainfall in mm: Eastern part: 200-300 Western part: 300-400

CLIMATE CHANGE (Modified from MunichRe) El Nino year: : Increase in tropical storms in the Pacific Basin Decrease in tropical storm activity in the Atlantic BasinB La Nina year: : Increase in tropical storms in the Atlantic Basin Decrease in tropical storm activity in the Pacific Basin Temperature Change: 1-30C 1 in the Atlantic

MULTIPLE NATURAL HAZARDS MAP OF THE CARIBBEAN: VIEW OF THE WORLD S LARGEST RE-INSURER MUNICH RE. (Unit for Disaster Studies Map; modified with permission from Munich Re, 2002).

SUMMARY NATURAL HAZARDS ON JAMAICA TROPICAL STORMS and HURRICANES: Zone 4 on Saffir Simpson Scale, 210-249 Km/h with an exccedance probability of 10% in 10 years (equivalent to return period of 100 years). MAXIMUM 24 HOUR RAINFALL: 300-400MM (I/M 2 ) LANDSLIDES; FLOODING; SEDIMENT-WATER FLOODS COAST LINE: Tsunami and Storm surge hazard. EARTHQUAKES: Zone 3 Probable Maximum Intensity MMVIII with an exceedance probability of 10% in 50 years (equivalent to return period of 475 years) for medium subsoil conditions. Kingston: A large city with Mexico City Effect.

EARTHQUAKES: Zone 3 to 4: MMI VIII- IX and above Probable maximum intensity (Modified Mercalli Intensity Scale) with an exceedance probability of 10% in 50 years (equivalent to a return period of 475 years) for medium sub-soil soil conditions. Kingston: Large city with Mexico City effect VOLCANOES: Last eruption before 1800 AD Last eruption after 1800 AD Particularly hazardous volcanoes TSUNAMI AND STORM SURGES: Tsunami and storm surge hazard TROPICAL STORMS TRACKS: Probable maximum intensity (SS: Saffir- Simpson hurricane scale) with an exceedance probability of 10% in 10 years(equivalent to a return period of 100 years) Zone 3: SS 3 (178-209 km/hr) Windward Zone 4: SS 4 (210-249 km/hr) Leeward

ACTIVE PROCESSES AND LANDFORMS A MODEL OF TROPICAL MONTANE STREAMS

IN JAMAICA, MORPHOLOGY OF MONTANE STREAMS ARE LARGELY CONTROLLED BY A PLENTIFUL SUPPLY OF COARSE BEDLOAD FROM LANDSLIDES( AHMAD, SCATENA, and GUPTA, 1993, SED.GEOL. 85, 157-169). A CONCEPTUAL MODEL (1) The drainage density is low with the tributaries joining the main stream at high angles. (2) In the mountains the valleys are narrow and deep with landslide ide-affected slopes and confined stream channels. (3) Stream gradient is high, with local rapids at rock outcrops, or boulder and rock block accumulations. HOPE RIVER (AHMAD, 2003) YALLAHS RIVER, MAVIS BANK (AHMAD, 2005) FAN DELTA OF YALLAHS RIVER IN 1963, TYNDALE BISCOE PHOTO Judgment Cliff Landslide, 1692 (4) Valley alluvium is characterized by extremely coarse sediment. (5) Braiding, multiple channels, and bars are found where the valley widens, either locally or near the coastal plains. In meandering streams an enlargement of point bars in in coarse sediment is common at such places. (6) The depositional forms built by sand, pebbles, cobbles, boulders, and rock blocks are related to both the passage of high magnitude floods and size and d age of the nearest large landslide.

Example of a debris fan created by landslides triggered by the rainfall r associated with tropical storm Dennis, June 2005; Yallahs River, Robertsfield, St.Andrew. Note that the sediments in debris fans tend to block the main river course. P. RIVER 2005 LANDSLIDE DEBRIS FAN SEDIMENTS HAVE RAISED THE CHANNEL BY ABOUT 3.0 m Yallahs River

HILL SLOPES: Example: Evolution of hillslopes in the Neogene transpressional plate boundary regime of Jamaica is strongly influenced by landslides. Large landslides are typical manifestations of the gravity-induced erosive processes responsible for shaping the mountains and supply sediment to build alluvial fans and fan-deltas in the lowlands. Significance Hazards of slope instability. Sediment flooding. Land degradation. Alluvial fans are not only of academic interest because they offer relatively flat building sites. Alluvial fan flooding. Landslide debris is an economic resource. TRANSPRESSION ON JAMAICA W E W THROUGHGOING FAULT ZONE MAKES A COMPRESSIONAL BEND IN THE ZONE OF LEFT-LATERAL STRIKE-SLIP DEFORMATION NEAR JAMAICA N

SATELLITE IMAGE OF SPUR TREE FAULT SCARP AND LANDSLIDES Manchester Plateau Fault Scarp Landslides Alligator Pond

Landslide Inventory of Logwood, Lititz, Sea Air, New Forrest, Alligator Pond areas in Manchester. Many of the old landslides were reactivated following the rainfall from tropical storm Emily in July 2005. New Forrest to Alligator Pond Road follows a dry river course.

Majority of hillslopes in Jamaica are detachment-limited (or loosening limited) that is transportational process operating on the slopes are capable of removing slope materials at a faster rate than it is produced. These slopes are generally steep and are decorated with amphitheatres or landslide hollows. Photo of the Morant River faulted mountain front near Hillside, St.Thomas. ( A Tyndale Biscoe Photo from Buisseret, 1996) Blue Mountain ridge Mt. Mucango landslide Hillside Morant river

JACKS HILL LANDSLIDE LANDSCAPE. RIDGES ARE RAZOR SHARP, OFTEN ONLY A COUPLE OF METERS WIDE. IN PUERTO RICO, LARSEN AND OTHERS HAVE ESTIMATED SLOPE RECESSION RATES VARYING BETWEEN 0.164 TO 3.8 mm/yr. BARBICAN HOPE PASTURES Three-dimensional model of the Jack s Hill area showing landslide scars (red lines) and debris fans (orange lines). (Source: Virtual Field Trip DVD- ROM produced for 5 th Faculty of Pure & Applied Sciences Conference, 2005)

LANDSLIDE AND FLOOD HAZARDS ALONG THE FAULTED MOUNTAIN FRONT IN LIGUANEA. NATURAL DRAINAGE HAS BEEN COMPROMISED. Sky Line Dr. Sky Line Dr. Forsythe Dr. 2004 debris flows IVAN RAINFALL MUDFLOWS; SEPT. 2004 HOPE PASTURES HOPE ZOO VTDI MUD TOWN MUD TOWN UTECH HOPE RIVER MUD TOWN MUD TOWN Retaining Wall VTDI Drainage outlet Road facilitates runoff

SPATIAL DISTRIBUTION OF MAJOR KNOWN LANDSLIDES ON JAMAICA. NOTE THE LOCATION OF COASTAL TOWNS ON ANCIENT ALLUVIAL FANS BUILT BY LANDSLIDE DEBRIS. ALLUVIAL FANS ( RED DOTS ) AND FLOODING HAZARD. MODIFIED W.R.A MAP

Debris flows, a flow type of landslide, may create spectacular debris fans, for example the Bluefields Debris fan built following the debris flows triggered by 1979 Flood Rains. Bluefields is located on an ancient fan characterized by abandoned dry river channels. Uncertain flowpath flooding is typical of these landforms. DEBRIS FLOWS Bluefields Bay, Westmorland, 12 June 1979 ODPEM WAS ESTABLISHED FOLLOWING THE 12 JUNE 1979 FLOOD RAINS IN WESTERN JAMAICA DEBRIS FAN IN BLUEFIELDS Tyndale Biscoe Photo

MAJOR LANDSLIDE ZONES AND FAULT SCARPS LANDSLIDE ZONES WAGWATER BELT STRUCTURAL MAP FROM DRAPER, 1987 FAULT TRENDS

LANDSLIDE LANDFORMS COVER 19.786 km 2, or 3,57% OF THE AREA IN THE PARISHES OF KINGSTON AND ST. ANDREW.

GRAVITATIONAL FAILURES AND ACTIVE TECTONICS IN THE LONG MOUNTAIN AREA (Aerial photo from the UWI Cooperative Credit Union Calendar 2002). The Long Mountain is an anticlinal uplift feature aligned NW-SE. Inset shows the present-day left-lateral motion on the Jamaica plate boundary zone. Faults: broken black lines. Landslides: red broken lines, arrow is the movement direction. Debris fans: red dotted line. Rubbly limestone, case hardened E W Site of the M5.4, 1993 earthquake damage RA Debris fans Mona Reservoir Site of new housing development BEVERLY HILLS SCHOOL Liguanea Alluvium: gravel, sand & silt

DOMESTIC WATER SUPPLY RESRVOIR SILTATION DUE TO LANDSLIDES

EARTHQUAKES HAZARD MAPS INFLUENCE OF GEOLOGY ON EARTHQUAKE PROCESSES CONTROLS

Jamaica Seismic Hazard From: Caribbean Disaster Mitigation Project

How earthquake waves affect us? JACKS HILL GRANODIORITE LIGUANEA PLAINS Hope Pastures KINGSTON HARBOUR PORT ROYAL Limestone LANDSLIDE DEBRIS FANS FAULT ZONE WATER-SATURATED SEDIMENTS IN GULLY COURSES RECENT SEDIMENTS OF THE LIGUANEA FAN THAT WERE DEPOSITED BY THE HOPE RIVER WHEN IT FLOWED WEST OF ITS PRESENT-DAY COURSE CARTOON TO SHOW THE BEHAVIOUR OF A SET OF EARTHQUAKE WAVES AS THEY TRAVEL THROUGH DIFFERENT TYPES OF SUBSTRATE. NOTE THE AMPLIFICATION OF WAVES IN WATER-SATURATED RECENT SEDIMENTS ENCOUNTERED AT THE LAND-WATER INTERFACE OF KINGSTON HARBOUR AND PORT ROYAL.

Seismic Hazard Map for Kingston & St. Andrew

HURRICANES STORM SURGE MODELLING

Maximum Wave Height (m) for a 50 year return period. From Caribbean Disaster Mitigation Project. Stony Hill KINGSTON STORM HAZARD ASSESSMENT MAX. WAVE HEIGHT (metres) - 50 Year Return Period Red Hills Constant Spring Jacks Hill Gordon Town Mavis Bank 50 Year Return Period Roads Spanish Town Central Village Caymanas Estate Gregory Park Waterford Six Mile Three Mile Halfway Tree New Kingston Cross Roads Papine Rivers Contours Waterbody Maximum Wave Height (metres) Bernard Lodge Braeton Greater Portmore Edgewater Port Royal Fort Clarence Kingston Harbour Parade Norman Manley Int. Airport Rock Fort Harbour View Bull Bay 0.1-0.5 0.5-1 1-1.4 1.4-1.8 1.8-2.2 2.2-2.7 2.7-3.1 N Hellshire Hills Hellshire 3.1-3.5 Hellshire Bay 3.5-3.9 3.9-4.4 4.4-4.8 Hellshire Point C a r i b b e a n S e a 4.8-5.2 Manatee Bay Wreck Bay 5.2-5.6 5.7 USAID-OAS CARIBBEAN DISASTER MITIGATION PROJECT KINGSTON STORM HAZARD ASSESSMENT TOAS STORM MODELLING CARRIED OUT BY MARK E. JOHNSON & CHARLES C. WATSON, APRIL 1999 0 1 2 3 4 5 6 7 8 9 10 Kilometers Map produced by NRCA, June 1999.

FLOODING PROCESSES WATER FLOODS SEDIMENT FLOODS

Summary Infrastructure Damage from Hydro-geological disasters (Source: Ahmad, 2004) 1. Flood Rains May- June 1986 Cost of repairs to damage/destroyed road network, $16 million Village of Preston. St. Mary destroyed; 17 families displaced; replacement cost in 1986 at $273,00.002. 2. Hurricane Gilbert, 1988 Approximately 60 percent of island s water facilities damaged, estimated at 10 million; Boar River Water Supply Pipeline damaged; Repairs to island s road network at $19.3 million; 478 landslides along 108km of roads in the Northwestern St. Andrew, 4percent of total roadway blocked by land slides; Landslides delivered an estimated 20,000m3 of sediments to rivers. 3. Flood Rains 21-22 May, 1991 Island wide damage at $30 million; Bog Walk Gorge road blocked by a landslide, and road closed for six months 4. Tropical Storm Gordon, 11-12 November 1994 Approximately 241 km, or 2.3 % of islands total road network damaged; cost $2 million; damage to water systems at $834,000.00. 5. Flood Rains, 3-4 January1998 Portland Total damage $7.84 million, land slide damage$4.7 million (60percent of total Damage. Landslide damage: Agriculture Si.4 million, Water Systems $160,000.00, Roads and houses $3.08 million. Period: 1986 to 1998: Total US$86.25 million

Tropical Storm Lili and Isadore, September 2002: Summary of Damage (Source: ODPEM, Rapid Impact Assessment Report Tropical Storm Lili and Isadore, 2002) Ministry of Water and Housing: $74,304,938.00 Ministry of Agriculture: $309,267,150.00 Roads and Infrastructure: $206,100,00.00 Public Utilities: $140,004,831.00 Ministry of Health: $54,917,964.00 Manufacturing: $55,800,000.00 TOTAL (Jamaican $) $ 840,394,883.00 (US$1.0 = J$ 50.00)

COMPETING CHANNEL PROCESSES IN SMALL DRAINAGE BASINS

DEBRIS AVALANCHE Sediment load by weight (%) 70-90 Bulk Density Mg/m 3 10-20 Shear strength N/m 2 >20 Fluid Type Flow rheology Visco-plastic Landform deposits Levees and lobes of largely unsorted material, large clasts on top and at face of lobes

1979 FLOOD RAINS IN WESTERN JAMAICA: House at Bluefields almost completely buried as a result of debris flow; Source: The Jamaica Information Service, Photo Library. DEBRIS FLOW Sediment load by weight (%) 70-90 Bulk Density Mg/m 3 10-20 Shear strength N/m 2 >20 Fluid Type Flow rheology Visco-plastic Landform deposits Levees and lobes of largely unsorted material, large clasts on top and at face of lobes

DEBRIS FLOW DAMAGE IN THE BYBROOK AREA, PORTLAND, 2001 RAIN STORM. Levees and lobes of largely unsorted material, large clasts on top and at face of lobes

DEBRIS FLOODS: Following the 25-29 October 2002 rainfall, the Chalky River channel in South Eastern St. Andrew was choked by debris. This blockage diverted some of the debris and water east thus aggravating the effects of flooding in the Bull Bay area. This is an upstream view of the silted Chalky River channel. The Bull Bay housing area is located immediately to the right-hand side of the photograph.

WATER FLOOD: STREAM FLOW, RIO MINHO, 2004 Sediment load by weight (%) 1-40 Bulk Density Mg/m 3 1.01-1.3 Shear strength N/m 2 <10 Fluid Type Flow rheology Newtonian Landform deposits Sorted, stratified (Help in identifying with bedforms floods of the past)

Tropical Storm Dennis, TRMM Rainfall Image from NASA Impacts of rainfall: Forsythe Drive, Mona Heights & Barbican

IN 2004 following hurricane Ivan rainfall and also in 2005 landslide debris again covered the intake. Simple solution: cover the aqueduct, to sustain water supply

EARLY WARNING FOR EXAMPLE, LANDSLIDES and SEDIMENT FLOODING RAINFALL THRESHOLDS EARTHQUAKE MAGNITUDE

RAINFALL THRESHOLDS FOR LANDSLIDES AND SEDIMENT-WATER FLOODS. THE THRESHOLD RELATIONS REPORTED HERE ARE REASONABLE FIRST APPROXIMATIONS. In Jamaica, rainfall threshold relation is defined for storms that had durations between 1-168 hours and average rainfall intensities between 2-93 mm/h. The threshold relation indicates that for rainfall of short duration (about 1 h): Rainfall Intensities > 36 mm/h are required to trigger landslides. These storms trigger mostly shallow landslides by causing an excess pore pressure in shallow colluvial zones. Such landslides were typically associated with 2001-2002 type storms. Low average intensities of about 3mm/h appear to be sufficient to cause landslilding as storm duration approaches approximately 100 h. These storms triggered the largest, deepest landslides in eastern Jamaica, e.g., Flora, Gilbert, 2001 rainfall.

Threshold for earthquake-induced landslides in Jamaica. The earthquakes of June 1692 and January 1907 created hundreds of landslides which caused severe deforestation and erosion on the island.

IS EXPOSURE TO NATURAL HAZARDS INCREASING? URBAN CENTRES WITH POULATIONS IN EXCESS OF 1000 ARE CONTINUALLY BEING CREATED---INCREASING CONCENTRATION OF PEOPLE AND VALUES COMPLEX UTILITY NETWORKS ARE BEING CREATED THESE ARE EXPOSED TO ALL THE CLASSICAL RISKS THEIR EXPOSURE AND VULNERABITY ARE DISPROPORTIONATE FUTURE DECISIONS ON SITE SELECTION MUST TAKE INTO CONSIDERATION EXISTING KNOWLEDGE AND NEW FINDINGS THE LOSSES THAT MAY BE CAUSED BY NATURAL HAZARDS AND TECHNOLOGICAL RISKS MUST BE IDENTIFIED AND MODELLED IN ADVANCE WE NEED TO DEVELOP NATURAL HAZARD INDEXING AND GEOCODING CRITERIA OF OUR ASSETS- PEOPLES LIVES FIRST WE MUST STRIVE FOR GREATER TRANSPARENCY REGARDING HAZARDS INVOLVED.

GROWTH OF KINGSTON DURING 1940 1990 HAS TAKEN PLACE ALONG THE LAND-WATER INTERFACE, LANDSLIDE SLOPES AND NATURAL WATER COURSES. FLOODING PROBLEMS: NATURAL WATER COURSES HAVE DISAPPEARED. HOUSING DEVELOPMENT IN DUMPED GULLIES ARE EXPOSED TO SEDIMENT FLOODS AND LIQUEFACTION.

Demographic change in Kingston and St. Andrew From STATIN, Jamaica

Landslide Isopleth Map illustrating percentage of area covered by landslides, Kingston & St. Andrew; red 45-50 % area under landslides

MANAGEMENT Recommendations from Yokohama Strategy (1994) and World Conference on Disaster Reduction (2005) Disaster response alone is not sufficient to achieve disaster management as it yields only temporary results at a very high cost. Prevention and mitigation activities undertaken before a disaster strikes contribute to lasting improvement in human safety, economic well being, healthy environment and social justice deemed essential to integrated disaster risk management.

The challenge for the scientific and technical community is to provide practical strategies for preventive maintenance. It is the statutory obligation of the elected and appointed officials of the government to manage hazards affecting people, infrastructure, and environment. It is argued that preventive maintenance should be based on research, continuous investigation and assessment of hazards, provision of publicly available documentation of hazards, and performance evaluation of preventive maintenance measures.

NUTS AND BOLTS FOR MAKING SOUND TECHNICAL DECISIONS TO SUSTAIN SUSTAINABLE DEVELOPMENT IN HAZARD- PRONE TERRAINS AVAILABLE: HAZARD INVENTORY MAPS and HAZARD MAPS WAY FORWARD: VULNERABILITY MAPS and RISK MAPS are required for different hazard magnitudes to decide on acceptable risk and a safe built environment.

AVOID BUILDING IN HAZARD PRONE AREAS

ROLE OF EARTH SCIENTISTS Natural disaster events are not just a consequence of natural hazards, but an avoidable economic and social catastrophe. Disaster strikes when societies are unable to recognize their responsibility for the proper management of the disaster risks. Jamaica faces several types of geological hazards. A range of geological and geotechnical investigations will form the basis for a comprehensive preventive maintenance programme for disaster mitigation. These are summarized below.

Digital surface systems including groundpenetrating radar, electrical resistivity, seismic reflection and refraction, GPS, remote sensed imagery, groundwater movement in slopes, high resolution digital video imaging will dominate digital data collection and interpretation of hazardous geological processes in the new millennium. Excavation techniques have been refined. A National Core Group of practitioners needs to be formulated to oversee the acquisition and application of new technology in preventive measures and practices.

It is appropriate at this time to discuss the view put forward by Mr. Roger T. Jones (SOPAC) at the October 2005 Natural Disaster Mitigation Workshop for SIDS in Mauritius: National governments, in pursuance of the principles of good governance and in order to protect the lives and well-being of the peoples they serve, need to recognize their responsibility for the proper management of the disaster risks which may result from the hazards to which their communities may be subject. The scientific community stands ready to assist national governments by informing natural disaster risk management processes.