FLOODS IN GHANAJune 5, 2015

Walter Hays, Global Alliance for Walter Hays, Global Alliance for Disaster Reduction, Vienna, Virginia, Disaster Reduction, Vienna, Virginia,

USA USA 

EARLY REPORTS OF SOCIETAL IMPACTS OF THE FLOODS,

FIRE, AND EXLOSION

A PROLONGED SEASONAL RAIN STORMCLOSURE OF ROADS AND SERVICES

POWER OUTAGEFAULTY GENERATOR CAUSED FIRE AND EXPLOSION150 DEAD FROM FLOODING, FIRE, AND EXPLOSION

60 REQUIRED HOSPITAL TREATMENT

FLOODS ARE A PART OF GHANA’S NATURAL

WATER CYCLE

ACCRA: JUNE 29, 1959: 22 CM (7 ½ IN) PARALYZES CAPITAL

GHANA IS IN WEST AFRICA

GHANA (ACCRA IS THE CAPITAL)

ACCRA: THE CAPITAL

ACCRA: THE CAPITAL

The Red Cross of Ghanaprovided blankets, mats and drugs to residents in Accra

and the six other communities affected by the

2015 flooding, fire, and explosion.

Officials blamed the losses from the floods on people

building homes and businesses within the city’s waterways, blocking natural drainage

systems.

TOWARDS FLOOD RISK ASSESSMENT

AND RISK REDUCTION

Officials: 59, 68, 71, 2015, …We have to stop flood disasters from

happening again

PHYSICALPHYSICAL

EFFECTSEFFECTS

ELEMENTS OF RISKELEMENTS OF RISK

EXPOSUREEXPOSURE

VULNERABILITYVULNERABILITY LOCATIONLOCATION

RISKRISK

PHYSICAL EFFECTS OF FLOODS

INUNDATION, HIGH-VELOCITY FLOW, HIGH-VOLUME DISCHARGE, EROSION, AND

SCOUR

DAMAGE FROM DAMAGE FROM INUNCATIONINUNCATION

AN ASSESSMENT INTEGRATES PHYSICAL EFFECTS AN ASSESSMENT INTEGRATES PHYSICAL EFFECTS AND SOCIETAL IMPACTS TO DETERMINE RISKAND SOCIETAL IMPACTS TO DETERMINE RISK

EROSION, SCOUR, AND EROSION, SCOUR, AND LANDSLIDESLANDSLIDES

LOSS OF LOSS OF FUNCTIONFUNCTION ECONOMIC LOSSECONOMIC LOSS

RISKRISK

TYPICAL IMPACTS OF FLOODS

DAMAGE TO CONTENTS, LOSS OF FUNCTION OF BUILDINGS AND

INFRASTRUCTURE, RELEASE OF HAZARDOUS MATERIALS,

TRANSPORTATION OF DEBRIS, AUTOS, AND HOUSES, ENVIRONMENTAL DEAD ZONES,

AND DISEASE VECTORS

VULNERABILITY ASSESSMENT FOR

FLOODS

Vulnerability: A Vital Part of Risk AssessmentVulnerability: A Vital Part of Risk Assessment

FLOOD FLOOD HAZARDSHAZARDS

EVENTEVENT

VULNERABILITYVULNERABILITY

PEOPLESTRUCTURESPROPERTYENVIRONMENTINFRASTRUCTURE

EXPOSUREEXPOSURE

EXPECTED EXPECTED LOSSLOSS

WHAT INCREASES VULNERABILITY

MANKIND’S ACTIONS AND NATURAL EVENTS CAN CHANGE THE

VULNERABILITY OF ELEMENTS AT RISK TO FLOODS

An element’s vulnerability (fragility) is the result of a community’s actions or

nature’s actions that change some part of the regional water

cycle (e.g., precipitation, storage, runoff, transpiration,

evaporation).

MANKIND’S CONTRIBUTIONAn element’s vulnerability

(fragility) is the result of flaws that enter during the planning,

siting, design, and construction of a community’s buildings and

infrastructure.

ACTIONS THAT CAN CHANGE KEY PARTS OF THE WATER CYCLE

• Urban development or industrial development in areas that were formerly wetlands.

• Locating buildings and infrastructure in a river floodplain.

MANKIND’S ACTIONS THAT CHANGE SOME PART OF THE WATER CYCLE

• Actions that increase or decrease river gradients (deforestation, dams, etc).

• Actions that change the runoff pattern or rate (e.g., the city’s concrete footprint)

NATURE’S ACTIONS THAT CAN CHANGE THE NORMAL WATER CYCLE

• A flash flood.• Ice jams/ice dams on the river• Rapid melt of snow and ice• Extreme or prolonged

precipitation caused by stalled low-pressure systems.

LOSS OF FUNCTION OF STRUCTURES IN FLOODPLAIN

FLOODS

INUNDATION

INTERACTION WITH HAZARDOUS MATERIALS

STRUCTURE & CONTENTS: DAMAGE FROM WATER

WATER BORNE DISEASES (HEALTH PROBLEMS)

EROSION AND MUDFLOWS

CONTAMINATION OF GROUND WATER

CAUSES OF RISK

DISASTER LABORATORIES

A RISK ASSESSMENT

• A risk assessment involves the probabilistic integration of:

• The hazard (e.g., floods) and their potential disaster agents (inundation, erosion, etc) that are directly related to the location of the community and what happens in the regional water cycle.

RISK ASSESSMENT (Continued)

• The location of each element of the exposure in relation to the physical demands of the hazard (i.e., inundation, etc.)

RISK ASSESSMENT (Continued)

• The exposure (e.g., people, and elements of the community’s built environment), represents the potential loss when the natural hazard occurs.

RISK ASSESSMENT (Continued)

• The vulnerability (or fragility) of each element comprising the exposure when subjected to the potential disaster agents.

POLICY POLICY ADOPTIONADOPTION

RISK ASSESSMENT

• VULNERABILITYVULNERABILITY

• EXPOSUREEXPOSURE

• EVENTEVENT

POLICY ASSESSMENT

• COSTCOST

• BENEFITBENEFIT

•CONSEQUENCESCONSEQUENCES

FLOOD RISK ASSESSMENT LEADS TO FLOOD RISK ASSESSMENT LEADS TO DISASTER-RISK REDUCTIONDISASTER-RISK REDUCTION

FLOODSFLOODS EXPECTED EXPECTED LOSSLOSS

REQUIRED INFORMATION

• Physical characteristics of the regional drainage system.

• Physical characteristics of each river system and its floodplain.

• Physical characteristics of the regional water cycle.

REQUIRED INFORMATION

• Physical characteristics of catchment basins, reservoirs, and wetlands in the region.

• Physical characteristics of dikes, levees, and dams controlling water discharge and flooding in the region.

REQUIRED INFORMATION

• The hazardous materials located in the floodplain.

DISASTER-RISK REDUCTION POLICES FOR FLOODS

MITIGATION, PREVENTION, PREPAREDNESS, FORECASTS AND

WARNING, EVACUATION, EMERGENCY RESPONSE, RECOVERY AND

RECONSTRUCTION, AND EDUCATIONAL SURGES

MITIGATION

SANDBAGS, ETC

PREVENTION

DAMS, STORM BARRIERS, LEVEES, SPILLWAYS, CATCHMENT BASINS,

RESERVOIRS, WETLANDS, ETC

THREE GORGES DAM: 2309 M LONG, 190 M HIGH, 15 M THICK

FLOOD PREVENTION: LONDON, ENGLAND