Flood Hazard Zonation from a

GIS/RS perspective in Fiji Islands: a

case study of Vitilevu Island.

Joeli Varo

Presentation outline

1. Introduction

2. History of Flood

3. Data source

4. Aim

5. Objectives

6. Methodology

7. Results & Discussion

8. Conclusion & Recommendation

1. Intro…. UNDP (2009) defines disaster risk as potential disaster losses, in lives, health status,

livelihoods, assets and services, in a community over time. Risk is the combination

of hazard, exposure & vulnerability.

UNISDR definition of hazard, as a dangerous phenomenon, substance, human

activity or condition that may cause loss of life, injury of other health impacts,

property damage, loss of livelihoods and services, social and economic disruptions

or environmental damage.

UNDP (2011), In 2000 – 2011, 1.1 million people had been killed, 2.7 billion peoplehad suffered material loss, and 1.3 trillion USD worth of physical damage.

Mycoo (2014), natural hazard will continue to increase in intensity, severity and

frequency for Small Island Developing States (SIDS).

Fiji Islands….

884,887 population

18,275 Km2

Tourism contributes > 82% GDP

332 islands & atolls

Complex tectonic settings

UNSPO(2002), Fiji has high vulnerability in earthquake, flood & landslide.

Vitilevu Island….

- 10,344 km2 with 76.6%

of the 884,887 total

population.

- (65 people per Km2)

- 9 towns & 2 cities - >60% urbanized

2. History of Floods Since 1840….

Floods

- 31+ recorded

- 2018: Twin flood (2 weeks interval)

- 5 deaths

- $US3m worth of physical damages.

3. Aim….

Is to integrate Geospatial knowledge to investigate and understand

disaster risk reduction and assessment for proper planning on the following

hazards:

- Flood

To prepare different types of thematic layers contributing to differenttypes of disaster.

To investigate and evaluate the relationship of other parametersusing the Analytical Hierarchical Process (AHP), Frequency Ratio (FR),MCA in ArcGIS to provide a readable solutions to disaster,

To formulate disaster risk reduction forward planning measures andmanagement plans for Fiji Islands.

4. Objectives

The main objectives of this research are:

5. Data source….Data Description Source

Landsat 8 ETM & satellite image

(30m spatial resolution – 2016)

PNG University of

Technology

Downloaded from

https://libra.developmentseed.org

/ for verification purposes.

Data source year 2018.

Earthquake PGA, Magnitude,

DepthFrom open source

USGS

https://www.usgs.gov/

Fault lines, Folding & Deep strike Derived from SPC. SOPAC & Fiji Mineral

DepartmentData source year: 2018.

Soil factors & Soil Attributes Derived from Fiji LUP Guidelines. Fiji Ministry of

AgricultureData source year: 2015

Rainfall Derived from Fiji LUP Guidelines Fiji Meteorological

ServicesData source year: 2017

Land Use/Zoning/Built

infrastructures

Derived from Fiji Department of

Town & Country Planning.Fiji Department of Town

and Country Planning

Data source year: 2018

Slope Derived from SPC.

Fiji Mineral DepartmentData source year: 2018

Flood

Analytical Hierarchical Process Parameters Theme

Rainfall

River

Dist.

Elevati

on

Flow

Acc.

Land

use Slope

Soil

Texture

Soil

Drain

Geolog

y

Rainfall 1 2 3 4 3 6 7 8 9

Dist. Drain

Net 1/2 1 2 3 4 5 6 7 8

Elevation 1/3 1/2 1 2 3 4 5 6 7

Flow Acc. 1/4 1/3 1/2 1 2 3 4 5 6

Land Use 1/5 1/4 1/3 1/2 1 2 3 4 5

Slope 1/6 1/5 1/4 1/3 1/2 1 2 3 4

Soil Texture 1/7 1/6 1/5 1/4 1/3 1/2 1 2 3

Soil

Drainage 1/8 1/7 1/6 1/5 1/4 1/3 1/2 1 2

Geology 1/9 1/8 1/7 1/6 1/5 1/4 1/3 1/2 1 Parameters Theme

Rainfall

River.

Dist.

Elevati

on

Flow

Acc.

Land

use Slope

Soil

Texture

Soil

Drain

Geolog

y

Rainfall 0.35 0.42 0.40 0.35 0.21 0.27 0.24 0.22 0.20

Dist. Drain

Net 0.18 0.21 0.26 0.26 0.28 0.23 0.21 0.19 0.18

Elevation 0.12 0.11 0.13 0.17 0.21 0.18 0.17 0.16 0.16

Flow Acc. 0.09 0.07 0.07 0.09 0.14 0.14 0.14 0.14 0.13

Land Use 0.07 0.05 0.04 0.04 0.07 0.09 0.10 0.11 0.11

Slope 0.06 0.04 0.03 0.03 0.04 0.05 0.07 0.08 0.09

Soil Texture 0.05 0.04 0.03 0.02 0.02 0.02 0.03 0.05 0.07

Soil

Drainage 0.04 0.03 0.02 0.02 0.02 0.02 0.02 0.03 0.04

Geology 0.04 0.03 0.02 0.01 0.01 0.01 0.01 0.01 0.02

Sum 1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00

Ratings & Weightage

Scale Reciprocal

Values

Definition

1 1 Equal Importance pair

2 0.5 Equal to moderate Importance

3 0.33 Moderate Importance

4 0.25 Moderate to strong Importance

5 0.2 Strong to very strong Importance

6 0.17 Strong Importance

7 0.14 Strong importance to very strong

importance

8 0.13 Very strong to extremely strong

Importance

9 0.11 Extreme importance

0.01

Factors prepared with

Multi – criteria Analysis

(AHP)

Flood Hazard

demarcation

Parameters

7. RESULTS AND DISCUSSION

Flood Hazard Vulnerability Zone

Flood &

man-made

features

7.46 82.3 10.1

High, 20

Moderate, 80

Low, 0

0

10

20

30

40

50

60

70

80

90

100

0

10

20

30

40

50

60

70

80

90

100

High Moderate Low

% o

f In

fra

stru

ctu

re

% A

rea

% of Infrastructure on each flood zone

% Area % of Infrastructure

Low

8%

Moderate

82%

20%

Infra.10%

Flood Zones

Low Moderate High

Contribution to knowledge:

1)Conceptual

2)Contextual

3)Temporal

8. Conclusion

Mapping and demarcating hazard zones (earthquake, flood,landslide) zones are the common effective readable solutionthat technology such as GIS could produce nowadays.

Disaster risk reduction is possible through technologicalsolution and effective planning to accommodate >60% ofurban population.

76.6% of the total population (884,887) could possibly bewell informed and educated on the location of flood hazardand DRR measures.

90% of infrastructure could be re-designed and futureplanning be better organized.

Recommendations

Disaster risks reduction planning shall be

mainstreamed into development control and

approval by planning agencies.

Development should be focused on low zones.

Land budgeting and inventory

Approved building codes must be used.

Enactment of Acts, Policies, Regulations

Publications

1. Demarcation of Liquefaction Potential Zone and risk reduction in Fiji Islands: a case study of Vitilevu Island (Springer – 29 April 2019)https://link.springer.com/article/10.1007/s41324-019-00265-1

2. Earthquake hazard zonation in Fiji Islands: a case study of Vitilevu Island (Elsevier Scopus IJITEE – 10 September 2019) https://www.ijrte.org/wp-content/uploads/papers/v8i2S11/B12570982S1119.pdf

3. Landslide Hazard Zonation of Central – eastern Vitilevu, Fiji Islands (Elsevier Scopus IJITEE – 14 September 2019) https://www.ijitee.org/wp-content/uploads/papers/v8i12S/L109110812S19.pdf

4. Flood hazard zonation from a GIS/RS perspective in Fiji Islands: a case study Vitilevu Island (Elsevier – under review)

Acknowledgement

Principal Supervisor – Associate Professor Sujoy

Kumar Jana

PNG UNITECH

BULA scholarship

Fiji Government (Min. Lands & Mineral Resources,

Dept. Town & Country Planning, Min. Infrastructure,

Transport, Disaster Management & Meteorological

Services)

SOPAC

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