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Pakistan floods: Predicted or Predictable, but a disaster nonetheless

Cross-posted at Highly Allochthonous

Unusually heavy monsoon rains in July and August 2010 left large swaths of Pakistan underwater. At least 18 million people were affected by the flood, and it is estimated that, more than six months later, several hundred thousand remain without even temporary shelter. As a result of lost crops and livelihoods from the flood and inadequate relief supplies, malnutrition continues to kill people. Like most floods, the Pakistani poor have suffered far more than those with resources to avoid the flood, or at least its aftermath.

Remains of a school destroyed by flooding, near Jacobabad by DFID - UK Department for International Development, on Flickr

Remains of a school destroyed by flooding, near Jacobabad by UK Department for International Development, on Flickr. Used under a Creative Commons license.

A paper in press in Geophysical Research Letters shows that the 2010 floods were extraordinary. Monsoonal rains tend to occur in pulses, with multi-day wet periods followed by multi-day dry periods, and while the total rainfall over Pakistan during the 2010 monsoon season was not unprecedented, the number and intensity of extremely heavy rains over northern Pakistan was very unusual. The authors are working with very limited historical and satellite data, but they estimate that the number of intense rain bursts that occurred in 2010 had a probability of less than 3% in any given year.

Using data from the European Centre for Medium Range Weather Forecasts collection of meteorological models, the authors of the new paper show that the timing and intensity of northern Pakistan’s monsoon rain bursts are predictable up to 6 to 8 days in advance – including the rains that caused the flooding in 2010.

Lead author, Peter Webster, and his coauthors from the Georgia Institute of Technology, draw the following conclusion from their analysis:

We conclude that if these extended quantitative precipitation forecasts had been available in Pakistan, the high risk of flooding could have been foreseen. If these rainfall forecasts had been coupled to a hydrological model then the high risk of extensive and prolonged flooding could have anticipated and actions taken to mitigate their impact.

The floods really kicked off with a burst of rain on 28-29 July 2010, and according to Webster’s reanalysis, that rainfall was predictable with good skill 7 days in advance (21 July). Webster and colleagues argue that if that forecast was available in Pakistan, lives would have been saved and the immensity of the disaster reduced. But, C. Christine Fair, writing on the Foreign Policy magazine website suggests that the flood was forecast in Pakistan.

In the middle of July, the PMD began tracking a storm brewing in the Bay of Bengal. This eastern weather system developed interactively with a western weather system to produce the massive rains and the subsequent super flood of 2010. On July 24, the PMD issued a flood warning to the provincial government of Khyber-Pakhtunkhwa (KPK). Despite these increasingly severe warnings, KPK’s citizenry did not believe them. … The PMD kept issuing warnings to KPK as the rains began to fall. However, as fate would have it, on July 28, … a passenger jet coming to Islamabad from Karachi crashed …With the media beset upon this tragic spectacle, the PMD’s warnings went unheeded as the rain began to fall.

So the Pakistani government did forecast the flood – at least four days out – in plenty of time to get people in northern Pakistan’s valleys out of the way. The problem was not with the meteorological and hydrologic science either internationally or in Pakistan. Instead, disaster was ensured when flood warnings were not taken sufficiently seriously by regional authorities, media, and residents.

Why wouldn’t flood warnings be heeded? Perhaps more could have been done to communicate to Pakistanis through channels whose authority they respected. Webster cites an example of flood warnings in Bangladesh being disseminated by imams at local mosques. The Foreign Policy article quoted above places some blame on media distractedness.

But there was also a more insidious reason the forecasted flood was ignored. It was a rare event, but it was also part of a new climatic pattern for Pakistan. As the Foreign Policy article describes it:

in recent years there has been a slow but steady change in the location where Pakistan’s major rainfalls concentrate. In the past, monsoon rains fell most intensely over the Punjab. Slowly and steadily, the concentration of rainfall has moved north and west to KPK. This redistribution of concentrated rainfall away from the Punjab and towards KPK explains why no one in KPK had any reason to believe the predicted weather.

Flooding frequency and intensity have increased in Pakistan in the last 30-40 years compared to earlier in the 20th century. Webster and coauthors state, “This recent increase is consistent with the increase in intensity of the global monsoon accompanying the last three decades of general global warming.” The flood warnings were ignored, in part, because the statistics of monsoon rain patterns are changing. Human memory and historical records are not good guidance if the weather system is changing. In situations like this one, the past is not the key to the present.

There are lots of things that should have been improved to lessen the magnitude of the Pakistani flood disaster – reservoir management should have been altered; emergency relief supplies should have been distributed more equitably, broadly, and consistently; international assistance should have been much more generous – but the two big lessons for hazard mitigation coming out of the Pakistan floods seem to be: “find a system for making sure that warnings are issued and that they actually make it to people in harm’s way” and “don’t assume the climate of living memory is a very good indicator of the weather of the present and future.”

Webster, P. J., Toma, V.E., & Kim, H.-M. (2011). Were the 2010 Pakistan floods predictable? Geophysical Research Letters : 10.1029/2010GL046346

Flooding in Pakistan

A post by Anne Jefferson For the past two weeks, unusually heavy monsoon rains have deluged Pakistan, resulting in flooding and landslides. Pakistan is heavily populated all along the Indus River valley, so this is a slow-moving disaster of epic proportions. The latest news reports estimate that flooding has displaced 14 million people – more than the number of people affected by the 2010 Haiti earthquake, 2005 Kashmir earthquake, and 2004 Indian Ocean tsunami combined.

In the first 10 days of August, parts of Pakistan received almost 24 mm per day more rainfall than usual – during what is usually the wettest part of the year, when the monsoon rains fall. During June-September, the relatively cool Indian Ocean has high atmospheric pressure system, while the intense summer sun heats up the Indian subcontinent and forms a low pressure system. Much like a river flows downhill, air in the atmosphere flows from high pressure to low pressure areas. So moisture rich air from the ocean flows toward India and Pakistan – bringing months of cloudy weather and intense rain. The images below are from true color images from NASA’s MODIS satellite showing the Indus and Chenab rivers in the area around Islamabad. The top image shows the clearest day from recent weeks (9 August), while the bottom image shows a more typical day (6 August).

NASA MODIS image on Northern Pakistan from 9 August 2010

NASA MODIS image on Northern Pakistan from 9 August 2010

NASA MODIS image of northern Pakistan from 6 August 2010

NASA MODIS image of northern Pakistan from 6 August 2010

This year, the monsoon precipitation has been especially intense in Pakistan, because the jet stream is experiencing a blocking event – when the normal eastward progression of weather patterns in the midlatitudes gets stalled out and you get the same weather for weeks on end. This created an additional low pressure zone over Pakistan’s northern mountains, bringing even more moisture to the headwaters of the Indus River. The rain also seems to be exacerbating the landslide and landslide dam problems in the region of the Hunza River, a tributary to the Indus in the northern mountains. (Update: Jeff Masters has a nice explanation of this jet stream blocking event and how it links the Russian heat wave and Pakistan floods.)

Flooding on the Indus is not an instantaneous disaster – it is one that will continue to occur for weeks, with consequences that last years. Because the flooding is being caused by prolonged intense precipitation, there can be multiple flood peaks – where the water level crests, starts to fall, and then rises again. There are already two flood peaks moving downstream, and if further rain falls, there may be three peaks to the flooding, and it could last through the end of August. Also, since much of the rain has fallen in the north, closer to the headwaters of the Indus, the flooding began in the north, and the flood waves are transmitted downstream over a matter of days to weeks. While river levels are now slowly declining in the north, the first flood peak is just reaching Hyderabad – the largest city along the river, with a population of 1.5 million. How fast the flood moves downstream depends on the storage properties of the channel and floodplain. There is some possibility that if the first flood peak stalls out in an area with lots of floodplain storage or obstruction of flow by debris-choked bridges, the second flood peak could catch up, creating an even larger disaster. NASA has a series of wonderful images showing the flood progressing downstream from Sukkur, north of Hyderabad, from 8 -12 August. The latest image is shown below.

Flooding on lower Indus River, 12 August 2010 (NASA MODIS image, combination of infrared and visible light)

Flooding on lower Indus River, 12 August 2010 (NASA MODIS image, combination of infrared and visible light)

Even when the final flood peak reaches the ocean and the Indus River returns to its banks all along its course, the human disaster will continue to unfold. 14 million people have been displaced by this flood – and those people may have lost everything they own. Beyond the personal losses, there has been devastation to infrastructure such as roads and bridges, complicating relief efforts and even making access to some areas nearly impossible. The Indus is the source of water for irrigation canals throughout Pakistan and damage to them is likely to be intense, especially near the river, so agricultural productivity will suffer even in areas that escaped inundation. Village wells will have been contaminated by floodwaters, so access to safe drinking water will be an issue for months.

That’s a lot for any nation to handle – 1 in 12 residents directly affected by the flood – but for Pakistan’s already fragile national government it will be an especially difficult challenge. As the flooding has unfolded, Pakistan’s government has appeared less equipped to provide immediate relief to flood victims than Islamist charities, which will probably increase their support as they fill empty stomachs and provide shelter. There are other aid groups working to ameliorate the suffering. Two of my favorites are MercyCorps, providing clean water, food, and clean up tools in the Swat Valley, and Medecins Sans Frontiers/Doctors Without Borders, which is providing sanitation kits and basic supplies in Kyber Pakhtunkhwa and Baluchistan. Dave Petley, who has worked in Pakistan, recommends FOCUS Humanitarian Assistance.