CHALLENGES ON SEDIMENT- RELATED DISASTER MITIGATION

Dolores M. Hipolito

Project Manager II

DPWH, PMO-FCSEC

Types of Sediment-Related Disasters

A. Direct Disaster

Debris flows

Landslides

Slope failures

Pyroclastic flows

B. Indirect Disaster

Riverbed aggradation

Some Recent Major Sediment Disasters

Year Disaster Damages

Nov. 2006

debris flows >1000 people dead and missing, >113,800houses partially/totally damaged in several municipalities of Albay province

Feb.2006

Landslide inGuinsaugon, St. Bernard, Leyte

A portion of Mt. Kanabag slid and buried the entire community of Guinsaugon 1,132 lives lost

2001 Camiguin flash flood and debris flow

250 people dead and missing; damages to agriculture, infrastructure

1991 Mt. Pinatubo eruption Affected national economy; massive laharflows damaged wide areas of agricultural lands and buried communities

1991 Flash flood and debris flow in Ormoc City

About 8,000 people dead & missing, damages to houses, commercial establishments, etc.

Debris Flows in the Towns of

Albay Province (Typhoon

Reming Nov. 2006)

Landslide at Guinsagon, St.

Bernard, Leyte (Feb 2006)

Flashfloods, Debris Flows, Landslides, Slope Failures

Huge sediment, driftwood and log debris Loss of lives

Features of Disasters in the Philippines

a. Typhoons

Geographical location along typhoon path

20 typhoons/year, with intense rainfall

rain-induced landslides

b. Earthquakes

Induce landslides that cause massive siltation in riverchannels

c. Volcanic eruptions/explosion of pyroclastic materials

Cause rivers to meander and change course

Reduce river conveyance capacity

Natural Conditions: Factors of Sediment-Related Disasters

Degradation of Forests

Unregulated watershed activities(illegal logging,uncontrolled land development, tillage of slopingareas, etc.)

Settlement of people in hazard areas

Others e.g., impacts of land use change (change

in local hydrology)

Anthropogenic Factors of Sediment- Related Disasters

Anthropogenic Factors

Increases and accelerates surface runoff

Erosion and siltation ofrivers decreases theconveyance capacity of riverchannels and waterimpounding structures

Degradation of forests

Mechanisms of Sediment-Related Disasters

insufficient discharge capacity of rivers and weakresistance of slopes against erosion

insufficient mitigation measures against floods andsediment disasters

insufficient guidance to people for early evacuation

insufficient evacuation networks in wider areas

access road problems

insufficient rescue equipment

Wrong evacuation / No safe evacuation / People do not know what to do

Wrong perception of safety behind structural measures

Poor knowledge regarding the present danger and hazard / No technical capability

No warning / Warning was ignored

Main Reasons for Loss of Lives During Disaster

Leyte IslandDecember 2003

Quezon ProvinceNovember 2004

Low Awareness on Sediment-Related Disasters: Mis-evacuation

According to a US study (Choi and Fisher, 2003)

82% of damage from disasters is explained by population density and the density of economic activities

the magnitude of hazard is responsible for only 7% of damage

the effect of disasters is determined primarily by the exposure of people and assets to natural phenomena

The best way to avoid disaster is to displace population and activities from disaster-prone areas

Hazard and Disaster Damage

Countermessures For Sediment-Related

Disaster Mitigation

Structural Measures

Sabo works

Natural slope failure

countermeasures

Bio-engineering

Dredging

Non-structural measures

Hazard/vulnerability maps

Watershed management

Monitoring, forecasting and warning system

Land use zoning and regulations

Information, education and communication programs

Evacuation plans

‘SABO(砂防)’ – is a Japanese word

‘SA(砂)’ means ‘sediment’

‘BO(防)’ means ‘prevention’

So ‘SABO(砂防)’ could be translated to

‘prevention of sediment-related disaster’ .

What is SABO ?

Sabo works are aimed to protect lives, infrastructures,and properties arising from sediment-related disastersin hilly and mountainous terrain.

Sabo Dam

Slit type, Ormoc, LeyteSabo dam in Laoag, Ilocos Norte

Road Closure Disaster

A road closure disaster (road slope failure) is a disasterwhich causes closure of the whole or partial width of theroad (soil collapse, rock slope collapse, landslide, roadslips, debris flow, river erosion, coastal erosion)

Increasing occurrences

losses from reopening costs of roads, loss of lives, detourcosts, and damages to electricity, communication andother infrastructures installed along the road

Risk Management of Sediment Related Disasters along National Highways

Catch Net

COUNTERMEASURESSediment Disasters Along

National Highways

Catch Fence

Rock Shed

COUNTERMEASURES

Crib Wall

Reinforced Embankment

(Geo-textile)Bio-engineering (Coco-net)

Gabion Wall

Non-Structural Measures

Reduce the community’s vulnerability to the sediment disaster

Avert the loss of life

Reduce damages to properties

Increase community’s resilience towards sediment-related disaster

Ensure the effect of structural measures to mitigate hazard condition

Hazard Maps

Source: MGB

Camiguin barangay hazard map

Precise knowledge to understand its meaning toavoid panic

Enough lead time to induce appropriate reaction

Secure to inform the message to all people

Warning must be conveyed in an easily

understandable manner and in local language

through a legally designated single authority. In

the dissemination, there should be a tool which

is available to poor or far flung people.

WARNING!!!

Public Information, Education and Communication Programs

Foster a disaster-aware culture among the

identified vulnerable communities. Messagedelivery mechanisms include primers, comics,posters, pamphlets, TV and radio ads, printads, messages in movie houses and inclusionof disaster preparedness in school curricula.

Training of Trainers

Table Top Exercise

Community Dialogues

Evacuation Drill

Public Awareness/Disaster Preparedness/IEC

Public Awareness Materials

Land Use Planning, Zoning and Regulations

Generally determine the distribution of landand type of development for allprovinces/municipalities/cities

Important in regulating the use of land toprevent encroachment of waterways by illegalsettlers

Dissuade the settlement of communities inflood plains and in hazard prone areas

Determine areas susceptible to slope collapseand sediment-related hazards

Overview of Disaster Management

Capacity

disaster management system needs to be

enormously improved

there is a critical insufficiency in human

resources, technology, equipment, and funding

need to take an integrated approach, including

establishment of regulations, improvement of

institutional system, acquisition of budgets, and

promotion of training for professional staff and

introduction of equipment

Challenges in Sediment Related Disaster Management

Increasing protection of communities and properties under threat

Improving watershed/river basin management

Strengthening institutional and local capacities for flood mitigation

Establishing a proper management system of data/information

Increasing public and private sector awareness and participation

Pursuing water and sediment related disaster management

Improving enforcement of laws

Addressing climate change

Good governance

Challenges in Sediment Related Disaster Management

Increasing Protection of communities and

properties under threat

Construction of infrastructures that mitigate the sediment disasters for high risk areas

Budget for maintenance of infrastructures

Sabo Dam in Laoag River

Debris Flow breaker along

Kennon Road, Baguio City

Improving Watershed/River Basin Management

Rehabilitation of watersheds

Reforestation

Practice of appropriate land cultivation

technologies to prevent degradation, erosion

and siltation of water bodies

Land use plan and zoning considering the

hazard prone areas

Human resources development (identification ofdisaster prone areas, preparation of hazard mapsand in the monitoring and warning forevacuation)

Introduction of new technologies (hightechnologies for increased accuracy inforecasting)

Provision of logistics such as equipment andbudget (increase rain and stream flow stations,disaster management programs)

Strengthening Institutional and Local Capacities

Establishing a Proper Management System of Data/Information

Establishing a well-structured information system(characteristics, natural, social and economic conditions,that serve as influential factors contributing to disasters)

Updating of topographic maps covering the country at ascale of 1/250,000

Publication of topographic maps of 1/10,000 scalenecessary for planning mitigation measures and forpreparing hazard maps

Increasing the number of rainfall stations and waterlevel stations

Updating and managing land use maps

Increasing Public and Private Sector Awareness and Participation

Community awareness and recognition ofdangers in living in hazard prone areas

Community involvement in disaster riskmanagement

Promotion of education and awarenesscampaign

Improvement of disaster preparedness andresponse

Addressing Climate Change ImpactsPhilippine Climate Change Scenario

Phil. Strategy on CC Adaptation, June 2010

Rise in mean annual temperature by about 0.90C to 1.40Cfor 2020; 1.70C to 2.4 0C by 2050;

Reduction in rainfall in most areas in Mindanao for allseasons by 2050;

Increasing trend in the number of tropical cyclones in theVisayas;

Decreasing trend in the frequency of tropical cyclones inMindanao

Storm rainfall intensity is likely to increase by 11-20% by2050 (Cavite Lowland Study, 2008)

Countermeasures to Sediment-Related Disasters

Combination of Structural & Non-Structural Measures

Structuralmeasures

Non-structuralmeasures

Role of people

Role of LGURole of country To mitigation

of sediment disaster

DPWH

Role of agencies

Thank you for

your

attention!!!

Challenges on

Sediment-Related

Disaster Mitigation