AUTORÍA MEDIATA

The Fourth Assessment Report of the Intergovernmental Panel on Climate Change (Cruz et al, 2007) predicts that climate change will affect the globe over the next one hundred years.

The main effects of the predicted climate change are:

 _{a rise in temperature}

 _{a rising sea level}

 _{variation in rainfall patterns with increased intensities and greater}

drought and rainfall periods in different places

 _{variation in track and increased intensity of cyclones}

A further consequence for infrastructure is increased saline intrusion. The Philippines lies third in the world’s countries most vulnerable to climate change and disasters caused by natural hazards (ADB, 2013).

The projected rising temperatures and sea levels, and changes in precipitation, are capable of initiating load changes and elevated pore- pressures sufficient to cause a range of geological and geomorphological processes that have hazard potential. There is already significant evidence, according to McGuire et al (2012), that this will cause a modulation or triggering of seismic, landslide and volcanic activity resulting from small changes in environmental parameters such as solid Earth and ocean tides, atmospheric temperature and pressure, as well as in response to specific geophysical events such as typhoons or torrential precipitation.

Specific events already identified include the violent venting of volcanic gases from Mount St Helens resulting from rainstorms, and collapses of the Soufriere Hills’ lava dome on Montserrat linked to intense tropical rainfall.

Table 2-5 shows the hazards identified as potentially being influenced by climate change. All except glacial outburst floods are relevant to the Philippines.

However the research on the effects of climate change on GeoHazards is at a very early stage and no quantitative predictions are available. They can be considered as a higher order of uncertainty compared with the direct assessment of current GeoHazards. Therefore no attempt is made to incorporate the effects of climate change in GeoHazard assessment in this Guide. For major projects where a full risk assessment is undertaken, including consequence-based risk, the potential effects of such climate- change induced changes to GeoHazard risk may be appropriate using, for example, the approaches described in PIARC (2013).

Specific effects of climate change which will affect engineering structures, including sea level change, storm surge and flooding, are addressed in the Guide Volume 3 – Water Engineering Projects Design.

Table 2-5 Relation of Climate Change to GeoHazard

Potential

hazard Mechanism / potential relationship with climate change Relevant climate drivers Environmental settings

Sub aerial landslides and debris flows

Permafrost thaw; pore-water pressurization; intense rainfall destabilizing regolith

Temperature rise; ice-mass

loss; intense precipitation Mountainous terrain; volcanic landscapes

Glacial outburst

floods (GLOFs) Glacier retreat; accumulation of melt water in pro-glacial lakes Temperature rise; ice-mass loss High latitudes; mountainous terrain; glaciated volcanic landscapes

Earthquakes Ice-sheet and glacier wastage; ocean island and ocean margin loading due to sea-level rise

Temperature rise; ice-mass loss; ocean volume increase

High latitudes; glaciated terrain at mid-to-low latitudes; ocean basins and margins Volcanic activity Unloading due to ice-sheet and glacier

wastage; loading due to sea-level rise; pore-water pressurization; intense rainfall destabilizing regolith

Temperature rise; ice-mass loss; intense precipitation; ocean volume increase

Volcanic landscapes at all latitudes

Tsunamis Submarine and sub-aerial slope failures and volcano lateral collapses; gas- hydrate breakdown; ocean load-related earthquakes; ice-quakes

Ocean temperature rise; ocean volume increase; intense precipitation

Ocean basins and margins

3

Preliminary GeoHazard Assessment

Initial project development requires projects to be identified as requiring an Environmental Impact Assessment, an Initial Environmental Assessment or for projects having no significant environmental impact, a Project Description Report. Projects are then reviewed by DENR and where considered appropriate an Engineering Geological and GeoHazard Assessment is required. This is undertaken by MGB.

According to DENR (2007), unless projects are located in an environmentally critical area or are environmentally critical projects DENR are required to issue a Certificate of Non-Coverage if the project proponent submits only Project Description Report. The Proponent is responsible for identifying whether the project lies in an environmentally critical area and there is no single source for identifying the extent of environmentally critical areas. Consequently the great majority of projects are not considered for an EGGA and therefore there was a potential risk that GeoHazards have not been identified.

The introduction of a PGA at the concept development stage of all projects, including rehabilitation and reconstruction work, is therefore to ensure that smaller projects, which may yet be at risk from GeoHazards, are adequately assessed.

The PGA is carried out at proponent level initially. Its purpose is to identify exceptional conditions that may require special investigation, design measures, additional budget or in the extreme case a relocation of the project.

3.1

Required Expertise

The person undertaking the PGA should be a qualified geologist, or engineer who has undertaken at least geology and geotechnical engineering modules in a university degree level course. Alternatively, the person should have extensive experience and job-training sufficient to undertake the assessment.

3.2

Scope of Preliminary GeoHazard Assessment

3.2.1 Desk Study

The PGA cannot be undertaken without a Project Description. If one has not been prepared then this should be done before undertaking the PGA. Procedures for preparing a Project Description are described elsewhere. The desk study for the PGA is similar in nature to the broader study to be undertaken as part of the site investigation and described in Volume 2C – Geological and Geotechnical Investigations. However, for the PGA, the desk study is limited to the GeoHazards and specific sources of information.

The information to be used in the GeoHazard desk study is listed under the relevant hazard in Section 2 of this Guide.

However the available information is expanding rapidly. Annex F summarizes the available information about likely developments in the next few years, which should be taken into account in undertaking the PGA. In addition to the specific sources, the assessment should make use of topographic maps from the NAMRIA Geoportal, aerial photographs where available, land-use maps if available in the region, and agricultural soils maps.

3.2.2 Reconnaissance

The reconnaissance for GeoHazards is most appropriately undertaken as part of a broader field inspection which may include validation of assumptions contained in the Project Description and, for reconstruction works, identification of the causes of deterioration of the asset.

Before undertaking the field reconnaissance, the desk study should be undertaken and a general sketch and list of potential GeoHazards should be drafted. During the reconnaissance, these potential GeoHazards would be assessed, as well as identifying other possible GeoHazards. Field reconnaissance and procedures for identification of specific GeoHazards are described in Section 2.

Where the project consist of or contains rehabilitation of existing assets, the field reconnaissance should identify specifically those GeoHazards which have contributed to the current deterioration of the asset.

Field inspections of areas where GeoHazards may be present require additional safety measures. The basic requirements for safety during field reconnaissance are described in Volume 2C Geological and Geotechnical Investigations. The person leading the field inspection should undertake a prior safety assessment and adopt appropriate precautions for the inspection team.

3.3

Preliminary GeoHazard Assessment Report

The report shall consist of a one-page summary and attachments. The template for the report is included as Annex H. The person that undertook the field reconnaissance for the assessment is the required signatory on the report.

Where GeoHazards have been identified, or there is remaining uncertainty, attachments should be included showing the information on which the assessment was based.