Up to 80 mile an hour wind gusts possible from ex-hurricane Gonzalo

The remains of hurricane Gonzalo is due to strike the British Isles tonight resulting in widespread rainfall and wind gusts up to 80 miles an hour tomorrow morning.

Gonzalo travelled over the island of Bermuda earlier this week, but has since been decreasing in energy and is now downgraded from hurricane status to an extra-tropical storm. The video below, from the Met Office, shows ex-hurricane Gonzalo undergoing extra-tropical transition into an Atlantic low pressure system.

The Met Office has issued a severe weather warning for wind for large parts of the UK. The worst disruption is expected on Tuesday morning when high wind gusts coincide with the morning rush hour.

Severe weather warning for #wind has been updated. Stay #weatheraware at http://t.co/ziqeF8QF1E pic.twitter.com/ZdK4GKuQOK

— Met Office (@metoffice) October 20, 2014

The Environment Agency has asked people to be flood aware and prepared, Although the strong winds might help drive low coastal flood risk on Tuesday and Wednesday. You can keep up to date with updated flood warnings on the Environment Agency’s website: http://apps.environment-agency.gov.uk/flood/142151.aspx

Ekbal

More information:
[1] The Met Office warnings: http://www.metoffice.gov.uk/public/weather/warnings/
[2] The Environment Agency flood risk map: http://apps.environment-agency.gov.uk/flood/142151.aspx
[3] More about hurricanes, typhoons and cyclones: https://climateandgeohazards.wordpress.com/2013/10/07/cyclones-hurricanes-and-typhoons-whats-the-difference
[4] The latest BBC news report at time of writing (21:37 Mon 20th): http://www.bbc.co.uk/news/uk-29685066

Flash Floods in the Holy City of Mecca

The holy capital of the Islamic religion is the ancient and beautiful city of Mecca. Located in the desert climate of Saudi Arabia, with temperatures often exceeding 45 degrees Celsius, this is the last place you would expect to experience heavy floods.

However, since the city is located in a low-lying region it is threatened by seasonal flash floods despite the low amount of annual rainfall. A flash flood is a very rapid flooding event often occurring with little warning.

Heavy rainfall over the past week has resulted in significant flash floods in the city of Mecca today. At the time of writing the floods are ongoing. The pictures below show streets inundated by flood waters and a number of vehicles being swept away by the currents.

All images courtesy of Zakhir Hussain.

Ekbal

Future flood losses in the world’s largest coastal cities

 

Over the next few decades climate change induced sea level rise and subsidence due to ground water pumping is expected to affect a greater proportion of people living in low lying  regions. Coupled with economic growth and increasing populations in coastal cities this trend will result in higher annual losses from flooding.

A recent Nature Climate Change article estimates that the average annual losses from flooding in the world’s largest coastal cities could rise from about $6 billion per year in 2005 to over $1 trillion per year by 2050. Even if investments are made to maintain flood probabilities at current levels, subsidence and sea level rise alone will increase annual losses to around $63 billion by 2050.

The top 20 coastal cities with the most Average Annual Loss increase in 2050. Hallegatte et al. 2013

The above figure, from the article, shows the 20 cities where Average Annual Losses (AAL) increase the most (in relative terms in 2050 compared with 2005) if adaptive measures are taken to only maintain present defence standards or flood probability. Note that this assumes a relatively optimistic sea level rise of about 20cm. Many coastal cities are expected to have much higher sea levels of ~60cm by 2050.

Another way to look at flood risks is to rank them in order of how much much damage is expected from a 100 year repeat flooding event with respect their annual GDP. The table below lists the top 10 cities ranked by 2005 losses as a percentage of its GDP.

	City	Country	AAL (% of GDP)
1	Guangzhou	China	1.32
2	New Orleans	USA	1.21
3	Guayaquil	Ecuador	0.95
4	Ho Chi Minh City	Vietnam	0.74
5	Abidjan	Ivory Coast	0.72
6	Zhanjiang	China	0.50
7	Mumbai	India	0.47
8	Khulna	Bangladesh	0.43
9	Palembang	Indonesia	0.39
10	Shenzen	China	0.38

China currently occupies three of the top 10 positions in this table. Which is why the Chinese government is actively investing in flood defence technologies and climate change research. Many of the countries where the annual losses are a significant proportion of the annual GDP are developing nations. These countries will continue to suffer with greater losses in future years unless something drastic is done to improve their flood defence systems.

It is worth noting that Hallegatte et al. (2013)  do not consider the other issues a rising sea level will have on coastal populations. Higher sea levels coupled with rising temperatures will result in a greater frequency and/or magnitude of coastal storms and cyclones. Historically these single events have been the cause of the greatest loss of lives and damage to infrastructure.

It is clear that flood risk and exposure needs to be reduced to below current levels if we are to avoid large financial and human losses in the future.

CGS academic Professor Nigel Wright explores the links between flood vulnerability and climate change and is currently helping to develop a Coastal City Flood Vulnerability Index (CCFVI) based on exposure, susceptibility and resilience to coastal flooding.

Read more about his recent work here: http://link.springer.com/article/10.1007/s11069-012-0234-1

Ekbal

Plight of the Bangladeshi

 

Lying on the floodplains of the mighty Ganges, Brahmaputra and Meghna rivers Bangladesh is a rich, fertile land. These giant river systems meet in the centre of the country and flow together into the Bay of Bengal which, at over 1600km wide, is the largest delta system in the world.

Flood potential map of Bangladesh. Source smeagol.terrace.qld.edu.a

Rising Sea Level

Bangladesh is often cited as one of the countries that will be most affected by rising sea levels from human induced climate change and with good reason. Two thirds of the country lies less than 5m above of sea level. With vast regions to the south much less than a 1m above sea level. The Intergovernmental Panel on Climate Change (IPCC) 2007 report claimed that just 1m rise in sea level could directly expose nearly 14 million people and result in potentially 20% land loss! Although it is unlikely that the actual figures will be so high, the numbers are worrying large.

Floods

Most of the country receives on average more than 2.5m of rainfall a year, 80% of which falls in about 4 months during the peak monsoon season. Contrast that with the UK, which in 2012 had an annual rainfall of less than 1.3m. Combine this with poor flood defences and you have large annual floods. The flood waters bring nutrient rich clays and silts from the high Himalayas and deposit them on the river floodplains during these events. These rich soils produce vast harvests of rice and other crops. Not surprising then that agriculture is the most common livelihood.

Floods in Bangladesh. Source NASA

However floods, once welcomed by farmers and their families are now harbingers of disaster. Human induced climate change has resulted in more erratic monsoonal weather patterns with often larger the normal volumes of water being delivered in shorter time intervals. The resulting floods have had devastating effects on the Bangladeshi people. In 2012 three large floods hit the country in swift succession between the months of July and September directly affecting more than 5 million people. These are now a common annual occurrence.

Cyclones

Bangladesh is also annually subject to devastating tropical cyclones, tidal bores and tornadoes. Some of the worst natural disasters in recorded history were results of cyclonic storms in the Bengal region. Among them, the 1970 Bhola cyclone which claimed over 500,000 lives! Worryingly new research into the effects of human induced climate change has shown that large cyclonic storms will become a more common occurrence in the years and decades to come.

Earthquakes

The foothills of great Himalayan mountain belt has historically been the location of many large earthquakes. Earthquakes in the continents tend to be more infrequent compared to regions such as Japan and California. However this makes them more unpredictable and often unexpected. But when one does occur it can result in significant ground shaking. The 1897 magnitude 8.1 and 1950 magnitude 8.7 Assam earthquakes were two of the biggest to hit the region in recent times.

Aftermath of an earthquake. Source crschools.net

Bangladesh has a population of over 160 million and among the highest population density of any country in the world. With the majority of the country built on river floodplains combined with widespread corruption and ignorance a large earthquake could quite possibly result in the greatest natural calamity to have ever hit the country!

So what can we as earth scientists do?

Bangladesh needs to increase its resilience if its people are to survive the multitude of natural hazards they face. Earth scientists are well placed to understand the risks involved from these hazards and can play a key role in all aspects of building a resilient infrastructure.

Climate science research is ongoing and needs to continue to better understand the affect human induced climate is having and will have on the annual monsoon. This knowledge then needs to be translated into rainfall variation and flooding potentials. The socio-economic issues of a rising sea level can be addressed by the sustainability community. How can we feed millions of people displaced as a direct result of climate change? How can we provide clean drinking water in flood prone regions? The hydrogeologists and geochemists can help find sustainable clean, arsenic free water sources for drinking and farming during the non-monsoon season. The seismologists and earthquake scientists can better assess the seismic risk; produce more accurate hazard maps and importantly identify the active faults within the region.

These are to name but a few of the ways earth scientists can get involved. I believe it is our moral duty to translate the practical aspects of our science into real benefits for people. Only then can we ever hope of helping these people.

Ekbal

Source news24ca.com

Further Reading:

http://www.ipcc.ch/ipccreports/tar/wg2/index.php?idp=446
http://www.guardian.co.uk/global-development/2013/jan/23/bangladesh-floods-harbingers-disaster
http://reliefweb.int/disaster/fl-2012-000106-bgd
http://en.wikipedia.org/wiki/List_of_Bangladesh_tropical_cyclones
http://www.banglapedia.org
http://blogs.ei.columbia.edu/2011/07/13/lurking-under-bangladesh-the-next-great-earthquake