One of the great challenges after volcanic eruptions: Clean-up

A day or so after a volcano erupts media often reports on the clean-up operations undertaken when the volcanic ash (or tephra) is dispersed by winds and deposited on communities. I thought I would use this blog post to summarise a key finding of a recently published review paper by colleagues and myself (available here for free until 14 November).

The video above from the recent Calbuco eruption in Chile shows that ash is incredibly disruptive to society and potentially damaging to property. One of the key methods of reducing the impacts ash can have on a community is to efficiently clean-up and dispose of it where it can be managed. It is for this reason that clean-up operations often involve the mobilisation of large workforces to remove the ash.

A man sweeping ash from the road during the 2014 eruption of Kelud (photo credit: Crisco 1492)

One of the most interesting findings from our paper was that there appears to be a somewhat inherent scale of response across the 30 different clean-up operations all over the world spanning about 50 years.

Removal of volcanic ash during coordinated clean-up operations. Dashed-dotted line indicates 100% removal. (Note: graph changed from published version for copyright purposes, see paper for full details)

I don’t want to dwell on some of the details of the graph (see the paper for specifics) but essentially what it shows is the amount of volcanic ash deposited on a community (x-axis) and the amount of volcanic ash removed and disposed of from the community (y-axis) during coordinated clean-up operations (municipal operations). For clarity, 1,000 m3/km2 is roughly consistent with about 1 mm thickness across a city (10,000 m3/km2 = 1 cm… etc).

If communities removed 100% of volcanic ash the trend would follow the dashed-dotted line. Clearly this isn’t the case. What this suggests is for low amounts of ash (1 mm) just a few percent is removed and disposed (note log scale). Whereas for large amounts (30-40 cm) a much higher percentage is removed. We suggest one of the reasons for this is that the amount of ash removed is consistent with some of the common thresholds given for volcanic ash impacts in urban areas. At low levels municipal authorities concentrate on cleaning roads and leave private property owners to deal with any clean-up on their own. At greater ash thickness it then becomes necessary for municipal authorities to provide assistance to private property owners to clean-up as the volume of ash on a property can become very large.

This provides useful information for municipal authorities as well as for those modelling volcanic impacts and risks which until now have relied on very limited evidence.

The full paper is available free until November 14 from here.

Follow me on twitter: @naturehazard or at The Geohazards Blog.


What is resilience? – 10th Anniversary of Hurricane Katrina

Saturday 29 August marks the 10th anniversary of the Hurricane Katrina disaster, widely viewed as one of the modern western world’s worst failures for disaster response. Not long after the disaster, President G.W. Bush told the world that they would learn lessons from the disaster. So has this pledge translated into increased resilience for the impacted area?

New Orleans, LA, August 30, 2005 — Neighborhoods throughout the city are flooded as a result of Hurricane Katrina. Jocelyn Augustino/FEMA

This government will learn the lessons of Hurricane Katrina. We are going to review every action and make necessary changes so that we are better prepared for any challenge of nature, or act of evil men, that could threaten our people.

— President George W. Bush, September 15, 2005

Hurricane Katrina impact facts

  • Deaths: 1,833
  • Land area damaged: 233,000 km2   (similar to the area of the United Kingdom)
  • Damaged homes: 300,000
  • Economic losses: US$125-150 billion (similar to the annual GDP of Hungary)

What is resilience?

In simple terms, it is the ability of a community to bounce back from a ‘shock’ (in this case, a hurricane).

The resilience of a community in respect to potential hazard events is determined by the degree to which the community has the necessary resources and is capable of organizing itself both prior to and during times of need.

— UNISDR, 2007

So, does this translate to the Hurricane Katrina impact area?

Much has been made of the lessons learned from Hurricane Katrina and certainly many lessons have been learned. Most of these lessons are concentrated on emergency response, as this has been viewed of as the greatest shortcoming leading to the disaster. But there is much more to resilience than emergency response. Recovery, for example, is a fundamental aspect of resilience.

Recovery is something that New Orleans seems to be particularly struggling with. After 10 years, the population is still 100,000 people below 2005 levels. This suggests that opportunities in New Orleans have not been sufficient to entice people to the city. Additionally, less than half of the homes that once stood before the hurricane have been rebuilt. Those that have been rebuilt are often out of the price range of those at lower income levels. As a consequence of the concentration of damage on the affordable housing stock, rental costs are relatively high when compared to the relatively low wages. It is no wonder then that the city has struggled to encourage people to the city.

Renters with severe housing cost burdens has increased due to Hurricane Katrina. Source: The Data Center analysis of U.S. Census Bureau data from American Community Survey 2004 and 2013

This all raises an important question: If another disaster were to strike New Orleans and destroy the leftover affordable housing, given the current issues with housing affordability, would this force even more people to leave the city permanently? 

Surely, if large quantities of people are forced to permanently leave a city, a resilient city it is not.

It is a common occurrence after a disaster for developers to concentrate efforts on property types that will yield them the most returns. Often this means higher cost housing. A report published in 2007 identified the impending housing affordability crisis for New Orleans, but it has taken until recently for action to be taken to address this issue. The New Orleans City Council has recognised the issue of housing affordability, and is experimenting with a zoning strategy aimed at giving developers an incentive to create low cost affordable housing. The idea is that in exchange for allowing developers to develop on smaller lots, a proportion of the units created will be set aside for low income earners.

No doubt there are many cities around the world (particularly the so called “Global Cities“) where housing affordability is getting drastically out of hand. This raises some serious issues of resilience, particularly with recent studies suggesting climate change related sea rise of at least 1 m over the next 100-300 years is inevitable.

So while we take remembrance of the impacts from Hurricane Katrina, let us not forget that resilience is not just about having the best emergency response practices (although that is important), it is also about what makes a city livable in-between disasters.

What can you make with an earthquake condemned house?

When a large disaster strikes an urban area it is critical for those affected that there is an efficient and timely restoration and recovery process. One aspect of this is to remove housing that is beyond repair or on hazardous land.

The quickest (and probably cheapest) way to do this is by using heavy machinery like diggers and bulldozers to demolish the house and dump the materials at a waste disposal site. Problematically, disasters often create an influx of waste far exceeding the community’s normal waste generation. In Christchurch, New Zealand, a series of earthquakes has led to a large quantity of building debris. It is estimated that if all unprocessed waste was sent to landfill it would take 2o years to complete the demolition and disposal process.

For this reason multiple disposal sites have been needed to be established and some waste recycling is being undertaken.

House being demolished (By Fought70 (Own work) [CC BY-SA 3.0 ( or GFDL (, via Wikimedia Commons)

Although using heavy machinery to demolish houses is most likely the quickest cheapest option, it assumes that the materials that make up the house such as the doors, roof, and kitchen sink are no longer of any value after the decision is made to no longer inhabit the house. Given the problems with disposing of large quantities of waste this begs the question – can we reuse the ‘waste‘ after disaster?

An exhibition at Canterbury Museum aims to show that there is value to the materials from condemned houses, and that the materials that make up a house can be reused for a variety of purposes. The Whole House Reuse (WHR) project displays what can be made from materials salvaged from a house that had been condemned due to the Canterbury Earthquake sequence of 2010-11.

WHR also hopes to visually quantify the irreplaceable material being otherwise lost in the often hasty demolition process, and spark realistic discussion on the pros and cons of deconstruction and demolition.

The Whole House Reuse website states:

Over 250 people from around New Zealand and the world have invented ways of reusing these resources and the result is a huge collection of objects from a delicately carved taonga puoro by master carver Brian Flintoff, to a finely crafted backyard studio by artist Nic Moon and architectural designer Lyn Russell.

The process broadly involved three stages:

  1.  Deconstruction: Professional salvage crew deconstructed the house over 9 days (click here for a short documentary). Care had to be taken to not damage valuable materials and to inspect wood for borer and check for asbestos (some was found in the flooring)
  2.  Design: Materials were carefully cataloged and invitations for people around the country to submit designs for the project
  3.  Reuse: Participants receive materials and begin the process to reshaping the materials into new resources

Below I share some of photos I took of the exhibition (sorry phone quality!).

A dog made from electrical wiring
A chair made from a door
Appropriate 3D Richter shelf.
A table with a rather appropriate looking ‘fault’ acting as the structural bracing
The left over material that could not be reused. Often borer infected wood, rusty nails…and asbestos!

Now of course there are logistical practicalities to deal with, and the above examples might not seem like they would be scalable after a disaster, but the point is that there is indeed value with reusing materials after disasters. As a society we must decide if viewing such materials as waste is the best course of action.

Burwood Resource Recovery Park (photo from Transwaste Canterbury)

In Christchurch about a quarter of all earthquake related debris is currently being taken to Burwood Resource Recovery Park, with an aim to recycle about 50% of the material received. This represents a relatively small proportion of all earthquake debris, but even this modest amount will take until 2017 (12-16 hrs/day, 6 days/week) to filter through. This amounts to over 5 years of work from start to finish.

A mammoth job indeed.