2024年洪水：风险和影响

Flood 2024:Risks and Impacts Introduction As Thailand’s rainy season progresses through the second half of 2024, there is a growing risk thatextensive flooding will affect parts of the country. Indicators pointing in this direction include: (i) theweakening ONI, which is expected to swing from currently neutral conditions to a La Niña, thereby likelypushing rainfall above normal; (ii) the impact of regular tropical storms; (iii) the fall in the PDO and IODindices, which are in or moving to a negative phase (i.e., below-0.5), indicating that Thailand is likely to bemore exposed to storm conditions; and (iv) the fact that the monsoon index, which reflects short-termweather conditions, is close to normal, thus adding to the likelihood that areas around Thailand willcontinue to receive their seasonal rains. Krungsri Research expects that the northern, central andnortheastern regions together with parts of the South will be the most heavily impacted parts of thecountry, though flooding will be a particular danger in the lower parts of the North and across the centralregions; in the former case, this area acts as a channel funneling rains towards the sea, while the latter isessentially a large flood plain that is routinely exposed to widespread inundation. This will then have thepotential to generate significant economic impacts on households,factory,machinery, crops, infrastructureand utilities. Krungsri Research expects that in the baseline scenario, flooding will affect 8.6 million rai in2024, leading to property and asset losses of THB 3.1 billion and agricultural output losses of THB 43.4billion. Consequently, total losses could reach THB 46.5 billion, reducing annual GDP by 0.27%. Chaiwat Sowcharoensuk Senior Analystchaiwat.sowcharoensuk@krungsri.com+662296 2000 Ext. 50880 Disclaimer Unlessexplicitlystatedotherwise,thispublicationandallmaterialthereinisunder the copyright ofKrungsriResearch. As such, the reuse, reproduction, oralteration of this text or any part thereof is absolutely prohibited without priorwrittenconsent.Thisreportdrawsonawiderangeofwell-establishedandtrustworthysources,butKrungsriResearchcanmakenoguaranteeoftheabsolute veracity of the material cited. Moreover,KrungsriResearch will not beheld responsible for any losses that may occur either directly or indirectly fromany use towhich this reportorthe datacontained therein maybe put.Theinformation,opinions,andjudgementsexpressedinthisreportarethoseofKrungsriResearch, but this publication does not necessarily reflect the opinionsof Bank ofAyudhyaPublic Company Limited or of any other companies withinthe same commercial group. This report is an accurate reflection of the thinkingand opinions ofKrungsriResearch as of the day of publication, but we reservethe right to change those opinions without prior notice. For research subscription, contactkrungsri.research@krungsri.com Flood risks through the last 4 months of2024 Across the first half of 2024, the tail end of the earlier El Niño left Thailand with hotter, drier weather thatthen undercut agricultural outputs, especially for field crops such as off-season rice, cassava and sugarcane.The resulting supply shortages meant that in some industries, companies were unable to deliver orders, whilerising prices also had knock-on effects on the overall economy. The weakening El Niño then transitioned to neutral conditions, though with enough momentum to carry theclimate rapidly towards a La Niña, which may then trigger flooding across large parts of the country. Severalclimate indicators support this analysis. 1)The Oceanic Niño Index (ONI)is based on sea surface temperatures in the equatorial Pacific that are thenused to indicate the likelihood of El Niño/La Niña conditions emerging. As of July 2024, the ONI stood at 0.1,in the center of the neutral zone1/(Figure 1) but the index has been weakening since the start of the year,and there is a growing chance that La Niña conditions will emerge2/. This is now expected to happen inOctober (Figure 2), and as ocean temperatures dip below their normal range, the chance that rainfall will beheavier than normal will rise correspondingly3/. Official NOAA CPC ENSO Probabilities Based on-0.5oC/+0.5oC thresholds in ERSSTv5 Niño-3.4 index The ENSO phenomenonBox 1 TheElNiñoSouthernOscillation (ENSO) is a climate phenomenon that occurs as a result of theinteraction between changes to sea surface temperatures in the equatorial Pacific and air pressure andweather systems overlying the Pacific Ocean. During the ‘warm phase’ of the ENSO, more usually called an El Niño, higher than normal sea surfacetemperatures in the central and eastern parts of the equatorial Pacific cause changes to dominant winds,which then move from west to east. This in turn increases moisture and rainfall on the eastern side ofthe Pacific and a corresponding drop in rains on its western side. The ENSO’s ‘cold phase’, or the La Niña, occurs when this situation runs in reverse. Thus