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DISASTER RISK ASSESSMENT

IN

LAND USE PLANNING

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Disaster Risk Assessment (DRA)

Purpose:

To generate disaster risk information relevant to land

use planning;

To serve as basis for understanding implications ofcurrent and future land use management anddevelopment;

To guide planners and policy makers in determiningappropriate measures / interventions therebyreducing risks to people and properties.

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DRA 4-Step process:

1. Hazard Characterization

Assessment of past disaster events and currentobservations affecting the planning area to

determine the pattern of occurrence over time.

STEPS:

A. Prepare an inventory of hazards affecting the city/

municipality.

1. Collect geohazard maps, climate related maps from OCD andCSCAND agencies (e.g. READY maps)

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2. Prepare a hazard map for the city/municipality (preferably in GIS format) byoverlaying the obtained hazard maps to the base map.

3. Identify and describe all natural hazards that the LGU is prone to such as:

Hydro Meteorological hazards

Flood

Landslide Soil Erosion

Climate related hazards

Floods

Rain-induced landslide

Storm surge

Geologic related hazards Earthquakes and natural hazards (ground shaking, tsunami,

liquefaction, earthquake-induced landslides

Volcanic Eruption

- Prepare a checklist of hazards affecting the LGU in tabular form:

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Table 1: Checklist of Hazards per Barangay

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Example of Municipal Hazard Map

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Sample GIS map showing the overlay of different

hazards in the municipality.

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3. Identify and describe past or historical occurrences of

hazards/disasters in your area. Present also in tabular form as

follows:Table 2 Historical Data

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B. Obtain climate projection data from PAG-ASA. This climate data

can be linked to the hazards occurring or will occur in the locality.

Example of ten year climate projection:

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C. Discuss the impacts of climate change

projection/ scenario to the localitys existing

hazard situation / disaster risk areas.

An impact chain analysis determines the connection

between a climate stimuli to the different hazards and to the

affected sectors.

Refer to the following example of an Impact Chain Analysis

flow diagram:

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Water Loss

Increased

Temperature

Tropical

CyclonePrecipitation

Drought

Sea Level Rise

Increased

Temperature

LandslideFlood

Increased

Poverty

Damaged

Trees

Buried

production

area

Buriedlowland

/settlements

FloodedFacilities

Cut off services

Damaged

Facilities

Increased

morbidity/

mortality

Loss of

income

Flooded

Productionarea

Loss of

food

supply

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C. Study and discuss the likelihood of a hazard to occur over time

using the likelihood matrix below:

Measure of Likelihood Score Return Period in Years

Frequent or Very likely 6 Every 1 3 years

Moderate or Likely 5 Every 3 10 years

Occasional, Light chance 4 Every 10 30 years

Unlikely, improbable 3 Every 30 100 years

Highly unlikely, Rare event 2 Every 100 200 years

Very rare event 1 Every 200 300 years

LIKELIHOOD SCORE TABLE

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2. Consequence Analysis

The second step determines WHO and WHAT can beaffected by a hazard event.

An inventory of the elements at risk such as people,property, and environment, is an essential part ofassessing vulnerability to loss and damage due tohazards.

Severity of Consequence is a measure of the degree ofimpact of a hazard event , such as injury, death,damage, and interruption brought to the sector ofconcern.

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Consequence Severity Table

Severity of Consequencescore

Severity Score meaning

1 Very low

2 Low

3 High

4 Very High

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Specific Criteria of Consequences

Consequences Specific Criteria

Human consequences Injury, death (ex. at work place or athome)

Property consequences damage to buildings, equipment, and

other facilities in an affected site damage to infrastructures (ex. roads &

bridges)

damage to critical facilities (ex. firestations, police stations, hospitals)

damage to properties ( ex. houses, landareas)

damage to environment & natural assets(ex. forest areas, agriculture)

Operational consequences Interruption of lifelines (ex. water,communication

Interruption of the economy and societal

functions

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Barangay 1 Risk score Human is 15; Property is 15; Operational is 15

Barangay 2 Risk score Human is 15; Property is 10; Operational is 10

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3. Risk Estimation This step determines HOW the planning units properties or

assets are affected by a hazard event and HOW many liveswill be lost in such event.

At this stage, the risk to fatality (in terms of lives lost) and riskto property damage (in terms of replacement value) forindividual hazards and hazard events are computed andsummed up.

For lack of historical record and other factors for fatality anddamage, the risk estimation process may be simplified as per

the expression given below:

Risk = Likelihood of Hazard X Severity of Consequence

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What does this mean?

Explanation:

The red color with the corresponding score suggests the most severe impact and should be

addressed immediately.

Purple color suggests moderate consequences but are severe but unlikely or rare to happen

Yellow color considered as low risk. However, may need emergency management, special land

use management options and improving hazards information and communication

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Prepare hazard and vulnerability maps for

decision making. Overlay the existing land use map and hazard map over the

corresponding settlement areas or residential areas to determine

their extent of exposure.

Fault Zone Flooding Zone

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The sample map is an overlay of the flooding areas and fault zoneover the urban areas. This illustrates that during severe flooding,

residential areas as well as commercial areas adjacent to the riverare exposed to two types of hazards.

A more detailed analysis can be made if data of each household andhouse structure data in the exposed areas can be gathered todetermine the cost of damages showing greatest potential loss inthe event of a disaster. ( Perhaps the CBMS data if available can beemployed for this activity.)

Although this is a time consuming activity for the LGU requiringmanpower and budget requirements, a good database is very

important for disaster risk reduction and management.

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4. Risk Evaluation

Guided by the results of the risk analysis, decision makers will nowhave to evaluate the level of acceptability of risks.

Risk issues are short listed according to urgency or priority foraction. Consequently, the applicable risk reduction /adaptationmeasures for the hazard of concern are determined.

Risk assessment and evaluation shall be applied to all of thedifferent sectors to provide a picture of how the land usecomponents will be affected and how best to arrange them tosupport other risk reduction strategies and ensure sustainable

development. The discussions should express disaster riskmanagement as a development concern.

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Risk evaluation will show: Association of sector goals with risk reduction

goals

Selection of actions compatible to development

thrusts

identified by the LGU

Clustering of compatible actions to develop

alternativestrategies towards risk reduction

Strategies as components of land usemanagement

approaches which may be location based (ex.

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Sectoral Issues and Needs Matrix

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SALAMAT PO!