An interesting map was published by the US Geological Survey shortly after the Turkish-Syrian earthquakes.1 It showed (perhaps somewhat predictively) that there was only one tiny square of the vast affected area in which Modified Mercalli intensity (which is largely a measure of damage) reached 9.0, the ‘violent’ level.2 This is–just about–enough to damage very significantly a well-engineered structure (but not necessarily enough to bring it crashing down). Although the disaster of 6th February 2023 produced, in fact, stronger shaking than this, it should not have caused 5,500 large buildings to collapse. The disaster in Turkey and Syria is very obviously the result of poor construction. This is painfully visible in the video images of buildings collapsing. The patterns of collapse are also the same as those in the last 20 Turkish earthquakes, although they are doubtless more extensive this time around. 

Building codes in Turkey have been upgraded five times in the last 55 years and are now perfectly good enough. The tragedy lies in their non-observance and the paucity of retrofitting. It is a mixture of simple errors, lax procedures, ignorance, deliberate evasion, indifference to public safety, untenable architectural fashions, corruption and failure to enforce the codes. Many, perhaps most, people in Turkey live in multi-storey, multiple occupancy reinforced concrete frame buildings. It is these that collapse. Most of them are highly vulnerable to seismic forces. There is plenty of engineering literature on the typical seismic performance defects of such buildings in Turkey. Perhaps we can grant a small exception for Syria, although before the civil war it did have building codes and earthquake research. However, the comment by a leader of the Syrian Catholic Church that buildings had been weakened by bombardment was something of a red herring. This probably affected about 2-3% of those that collapsed. 

 To know whether a reinforced concrete building is safe to live in would require knowledge of:

• the shear resistance (i.e., quality) of the concrete 
• the presence or absence and connectivity of shear walls 
• whether there are overhangs or other irregularities of plan that distribute the weight of the building unevenly or concentrate load on particular parts of it 
• the presence or absence of a ‘soft-storey’ open ground floor which concentrates the load above columns that cannot support it during seismic deformation 
• the connections between beams and columns, especially how the steel reinforcing bars are bent in 
• whether there are proper hooks at the end of rebars on concrete joints 
• whether the rebars were ribbed or smooth 
• the quality of the foundations and the liquefaction, landslide or subsidence potential of the underlying ground 
• the state of maintenance of the structural elements of the building 
• any subsequent modifications to the original construction. 

 An experienced civil engineer could evaluate some of that by eye, but much of the rest is hidden and only exposed once the building collapses. A short bibliography of sources is appended at the end of this article. 

Many of the news media that have reported the disaster have presented it as the result of inescapable terrestrial forces. While that cannot be negated, it is less than half of the story. The tragedy was largely the result of highly preventable construction errors. Vox clamantis in deserto: to examine this aspect of the disaster one would have to face up to difficult issues, such as corruption, political decision making, people’s expectations of public safety, fatalism versus activism, and more. How much simpler to attribute it all to anonymous forces within the ground! 

A well-engineered tall building that collapses will leave up to 15% void spaces in which there may be living trapped victims. It was notable that, in many buildings that pancaked in Turkey and Syria, the collapses left almost no voids at all, thanks to the complete fragmentation of the entire structure. This poses some serious challenges to search and rescue. In some cases the collapse was compounded by foundation failure, leading to sliding or rotation of the debris. 

There was also an interesting dichotomy in the images on television between the “anthill” type of urban search and rescue, carried out by people with no training, no equipment and no idea what to do, and professional urban search and rescue (USAR), which sadly was in the minority of cases. Nevertheless, it remains true that the influx of foreign USAR teams is, sadly, both riotously expensive and highly inefficient, as they tend to arrive after the ‘golden period’ of about 12 hours in which people could be rescued in significant numbers. 

Among the damage there is at least one classic example of the fall of a mosque and its minaret, the same as that which happened in the Düzce earthquake of 1999. Mosques are inherently susceptible to collapse in earthquakes: shallow arches, barrel vaults, rigid domes and slender minarets. The irony is that the great Turkish architect of the 16th century, Mimar Sinan (after whom a university in Istanbul is named) had the problem solved. He threaded iron bars through the well-cut stones of his minarets, endowing them with strength and flexibility. It is also singular that one of the first short, stubby minarets in Turkey (located in Izmir) was built 300 years after Sinan died in 1588. 

Select Bibliography of Sources on Turkish R/C Construction Practices 

Cogurcu, M.T. 2015.Construction and design defects in the residential buildings and observed earthquake damage types in Turkey. Natural Hazards and Earth System Sciences 15: 931-945. 

Dogan, G., A.S. Ecemis, S.Z. Korkmaz, M.H. Arslan and H.H. Korkmaz 2021. Buildings damages after Elazığ, Turkey earthquake on January 24, 2020. Natural Hazards 109: 161-200. 

Dönmez, C. 2015. Seismic performance of wide-beam infill-joist block RC frames in Turkey. Journal of Performance of Constructed Facilities 29(1): 1-9. 

Erdil, B. 2017. Why RC buildings failed in the 2011 Van, Turkey, earthquakes: construction versus design practices. Journal of Performance of Constructed Facilities 31(3):  

Korkmaz, K.A. 2009. Earthquake disaster risk assessment and evaluation for Turkey. Environmental Geology 57: 307-320. 

Ozmen, H.B. 2021. A view on how to mitigate earthquake damages in Turkey from a civil engineering perspective. Research on Engineering Structures and Materials 7(1): 1-11. 

Sezen, H., A.S. Whittaker, K.J. Elwood and K.M. Mosalam 2003. Performance of reinforced concrete buildings during the August 17, 1999 Kocaeli, Turkey earthquake, and seismic design and construction practise in Turkey. Engineering Structures 25(1): 103-114.

David Alexander is Professor of Risk and Disaster Reduction. He has conducted research on disasters since 1980. His main foci of interest are emergency management and planning, earthquake science, disaster epidemiology, and theoretical issues in disaster risk reduction.

Note from editor: We offer our commiserations to all those affected by the tragic events of this week. UCL staff and students can find support here. Find out where and how to donate to the earthquake appeal here.

Following the UK’s exit from the European Union, the legacy leftover from the EU’s Water Framework and Flood Directives, which jointly encourage sustainable management of flood risk, lives on. The UK has seen a number of similar national policy frameworks implemented aiming to reduce flood risk while improving water quality and biodiversity, with over 100 river restoration projects seen in London alone between 2000 and 2019. Most of these efforts are geared towards sustainability in the face of climate change, but, with regards to the long-term, the river itself is often left out of the plans.

The historic human efforts to manage rivers have been progressively called into question over their sustained maintenance costs and an incongruity with environmental and ecological health. An alternative solution is to renaturalise and restore natural processes—reconnecting rivers with their floodplains, reintroducing wild species, run-off targeted tree planting—but this would also be to submit to a changing and dynamic landscape. Rivers can change course—sometimes very suddenly—or silt-up and become unnavigable. True sustainability should therefore account for the long term changes of rivers, but these changes are rarely accounted for in flood risk management policy. As Andrew Revkin asks: “sustain what?”

The problem with “natural”

The problem is partially semantical. The terms renaturalisation, restoration, and rewilding carry with them the image of an implied prior state or a “Lost Paradise”. Ironically, it is precisely the long legacy of human engineering, which some modern schemes are trying to reverse, that denies us the knowledge of a natural state; it is difficult to look into the past, when the waters are so muddied by our imprint. As a result, our ability to assess the future impact of renaturalisation is equally hindered. 

Arguably nowhere in the UK is this problem illustrated better than in the Somerset Levels, which as far back as the roman occupation of Britain has seen artificial drainage and reclamation in order to take advantage of its pastoral and arable potential. At present, the flat, largely reclaimed floodplain relies heavily on a vast network of excavated drainage ditches (rhynes in the local vernacular), sluice gates (clyces), and pumping stations that push the water through the highly banked and augmented river channels; a £100 million tidal barrier has just been approved on the River Parrett, while existing rivers continue to be enlarged to carry extra flood water. Clearly, it is hard to imagine what natural means in this context.

A clyce (sluice gate) in Highbridge that stops in the inflow of tidal water.

Seeing Into the Past

Fortunately, remnants of abandoned rivers—palaeochannels—that have long since stopped flowing through the Levels litter its landscape and offer a glimpse into the past. There are numerous examples of such ancient rivers still visible on the Somerset landscape today, which often surface during high flood stages, but are now easily identifiable with the advent of Light Detection and Ranging (LiDAR) technology, which provides high-resolution elevation data. Palaeochannels have been of interest to researchers in this area because they reveal historic drainage patterns, showing in which direction rivers used to flow before being redirected or abandoned long ago.

Where archaeological records are unavailable—often early in or before human occupation—the reasons for change are less clear. Were the causes human made, or related to a historical climatic shift? And could this inform the way we plan rivers today? To find out more, it is necessary to dig deeper into the landscape. 

The Somerset Levels have experienced their own fair share of devastating floods and are intensely embroiled in the debate between hard engineering measures and natural flood management, which has previously culminated in fierce criticism of the Environment Agency for not carrying out regular dredging. This image reveals an ancient river channel emerging from the flood waters of 2013/2014 around Burrowbridge, Somerset.

Seeing Beneath the Surface

Beneath the sediment that buries them are rivers preserved from a past time. Within the sediment is contained information from the processes and conditions that presided over the river’s eventual abandonment. Here we can see the geometry of the river and look for signs of erosion and migration, and indicators for the causes of abandonment.

A seismic refraction survey conducted in the Somerset Levels.

To overcome the logical problem of seeing buried features, geophysical methods offer a quick and non-invasive way of imaging the subsurface. By applying a force to the ground and measuring a response from beneath, a model of the rivers can be produced. These methods have been tested extensively by scientists for many years in a variety of environments, including floodplain sediments, and are in the UK probably most famously associated with Time Team’s “geofizz”, due to their strong archaeological applications. 

This research uses a combination of electrical resistivity, seismic refraction, and ground penetrating radar methods to image the buried cross-section of ancient rivers. In this way, the river acts as an archaeological feature for investigating the past, and is hoped to provide reference states for river systems that have existed prior to and throughout different periods of human occupation. Surveys have been completed on two sites on either side of the River Parrett, clearly showing the extent of the historical river systems. More are to follow at different sites across the Somerset Levels. 

Imagery of a buried channel as depicted by measurements of resistivity to an electrical current.

Glimpsing into the past of ancient river systems could help in planning for the future development of renaturalised rivers, by exploring scenarios where the measures that humans (and rivers) have grown accustomed to are absent. It may be that, like a river, management plans must be dynamic and adaptable to natural change; otherwise, a one-size-fits-all approach to sustainability is bound to become unsustainable.

To find out more about this project, email me at joshua.anthony.19@ucl.ac.uk

Josh Anthony is a PhD Candidate at IRDR and Editor of the IRDR blog.