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Cities, accumulated risk, and GIS

Christopher Morley once said “All cities are mad: but the madness is gallant. All the cities are beautiful, but the beauty is grim”. Morley could be and -in some case- is true in defining the beauty of the modern cities. But I wonder what Christopher Morley would have said if he had been provided time machine to go back in time and pay a visit to ancient cities. My view is that he would have debated about which city in the world hasnt seen war, famine, floods, conflict or revolutions?… Which in ancient, medieval and modern time has seen unsustainable situations and which among them were able to withstand the wrath of time. He would also say that cities like Varanasi in India, Beijing in China, Paris in France have seen it all but still survived to tell the tales. He would have sat with City (if it was a living phenomenon), and discussed with it the stories of various settlement, politics, disasters, war and celebrations of various races, groups, tribes that got into the metropolis.

Madness what Christopher Morley talks of the city has seen riches being accumulated inside and around it. Cities like Florence are best example of accumulation of wealth over time. Hampi in India was also one such exotic example where wealth was so enormous, that pearls and precious stone were sold openly in the market. Both Florence and Hampi had many common things between them, even though being a continent apart.

Both cities flourished and became a great center for trade and commerce during medieval ages. Greatest institutional structures were built in both cities to handle great riches that were passing through the city. However, Hampi today as it stands is in ruins but Florence is still flourishing. Both cities started their journey at a similar time but only Florence survived.

Whereas Hampi faced it calamity in 1565 A.D. immediately after Battle of Talikota. After city was plundered for 7 days and 7 nights, Hampi never came back to its former glory. The point is, it takes biblical strength for cities to recover from the catastrophic events like war, earthquake, massive flooding, natural disasters, diseases and financial collapse.

Globally, on an average, 250 billion to 300 billion dollars are lost due to disasters like earthquake, tsunamis, hurricanes, flooding and war. This is equivalent to GDP of most of 3rd world countries. Most of these losses are in major cities of the world. Cities have been and are the pillars of the region, they give stability to the regions.

If any catastrophic event happens in these cities then it would bring chaos to the whole region. Best examples in the current scenario are the cities of Syria. Catastrophic civil war has brought Syria to its knees. Once an emerging market; now Syrian GDP has dropped to half. During war it is estimated that it lost more than 200 billion USD. All these losses are concentrated in the cities of Aleppo, Homs, Hama, and Damascus. Similarly when Nepal earthquake struck in 2015; it crippled Kathmandu thereby crippling the whole economy. Similar slow down was recorded in India during Chennai (2015) and Kerala floods (August 2018).

Accumulated Risk

Modern world is as vulnerable to shocks as it is connected. These shocks will have impact both at local and regional level. Most of the nation-state or city councils do anticipate these kind of scenario but most fail to stop catastrophic event from happening. It should also be noted that we can’t stop event from happening but we can lessen the losses, so that we can build back quickly and better. This aspect of bouncing back quickly could be learnt from Japanese and Chilean government in handling earthquake-related disaster. What these countries have established is a full life cycle of disaster management; from identifying risk to build back better.

In disaster management 2 words are key; one being risk and the other being disaster. “Disaster” as we define, is a sudden accident that causes high loss of life and property. “Risk” is a probability of the threat that would create a negative effect on the life. By definition, disasters are subset of risk. Every day risk like fire, building collapse, local flooding do not disturb the resilience of urban system. However, risks from massive flooding, earthquake, drought (intensive risk) etc can bring down the resilience or destroy the whole resilience of the system itself. Intensive risks are increasing in frequency and intensity affecting more and more population.

There are around 600 cities with 1.7 billion population generating half of the world’s GDP. Most of these 600 cities are either coastal cities or on the bank of the river which make them highly vulnerable for flooding.

In India we have Delhi, Mumbai, Culcutta, Chennai and Vishakapattanam and Tiruvanantapuram as classical example of highly dense and vulnerable population. Any catastrophic event in these cities will not only have socio-economic slow down but also disturbs the resilience of the city itself. From the economic point of view , its not only the millions of population that are exposed to the risk but also the infrastructure that support these population and investment that are made on existing infrastructure and future infrastructure.

These risk doesn’t stop there, they keeps on growing if investment and population goes on increasing in the area that are designated as risk prone. Favela’s of Rio-de-Janeiro, Dharavi of Mumbai, many informal settlements along the river side, infrastructure on the flood plains etc are the typical examples of risks that is being accumulated due to life and property involved in risk-prone area. Whenever disaster like landslide or flooding happens, most of the losses happen not because risk factor was greater but investment in life and property went on unchecked in these risk prone areas and was accumulating from a long time. Hence most of risk is always derived from the development that is going on in risk prone area.

To understand more on accumulated risk, let us take the example of earthquakes that happened in Nepal and in Chile. Nepal earthquake was of magnitude 7.8 and Chile was 8.3 on Richter scale. Even though Chile earthquake was more compared to Nepal , Nepal earthquake caused massive loss of life (more than 9000) and more than 10 billion dollar of loss. In Chile 15 people lost their life. Socio-economic effect of the Nepal earthquake was much greater compared with that of Chile.

In order to understand this effect, we need to look into the accumulated risk of both Nepal and Chile. Chile, a country that suffers from frequent earthquake has strict building code that are meant for earthquake-prone area, whereas Nepal doesn’t have strict implementation of building code for earthquake-prone area. Risk was present in both Chile and Nepal of major earthquake, but what made difference was the amount of investment that went in risk-prone area without risk mitigation strategies. Nepal lost 10 billion dollars; because there weren’t mitigation strategies for accumulated wealth and Chile from years of experience had developed strategies to reduce risk (in this case its building code for earthquake prone area).

Like Nepal story, the story of accumulated risk are in most cities, especially in developing countries like India, China, Brazil, Nigeria etc. Figure below shows settlements built on the steep slope of mountain. These areas are high risk(landslide) areas.

There are some settlements which are along the rivers, some on flood plains and some cities like Carabadella in Venezuela are on alluvial fans of river. These are the areas where there exist high risk of disaster and government as such doesn’t allow any construction in these areas and hence are notified as disaster prone. However over the time these unoccupied and disaster prone area are occupied by migrants who can’t afford to pay for housing in these cities. As time moves on one occupant becomes many and series of social structure comes into being resulting in what we call low income settlements or slum.

These slum in time grow up to become center of economic and social activity . Favellas of Brazil and Dharavi slum of India are best example of this. These informal settlements does have their own dynamics, their own economy , their own social innovations. But these are also the area which were disaster prone and hence would be at high risk . This risk get exasperated due to years of accumulation of both material and human. When impending disaster strikes these would be the areas that would cripple the whole resilience of the city.

Image shows Dharavi Slum and its proximity to sea and river.

Recent 2015 Chennai floods has estimated loss of 200 billion dollar. Investigation has revealed that poor planning of drainage system, encroachment of wetland area and clogging of drains were the main reasons for such a high loss of property. Chennai international airport which is built across river Adyar got flooded. Chennai airport is a classic case of accumulated risk manifesting itself as loss during flood. Figure shows Chennai airport build right across the river.

Chennai airport example is one typical example of high and critical investment. However there are other infrastructure at citizen level i.e. residential building along the floodplains of Adyar that got flooded because they were present in high-risk zones.

Accumulated risk exist here due to non-implementation of strict encroachment policies of floodplain. Half of damage to the property was not due to risk of floodingbut by the accumulated wealth that was present due to unchecked urban growth on floodplains. This story is not just of Chennai; its all across the globe.

To take an example the city of Caraballeda was destroyed by the flooding. Carabadella city sat on the antecedent river’s alluvial fan. Once a tourist city , after disaster, Carabadella was filled with 8 feet of mud. Most of luxury hotels of the area were abandoned due to damage that had happened to building. Resilience of the city was shattered and it never recovered it glory. Huge amount of investment went in vain. Stories of Chennai, Carabadella, Kathamandu forces us ask a simple question… Can we identify, whether areas of high accumulated risk exist in my city? The answer is yes.

Use of GIS and Remote Sensing

Stories of accumulated risk are present in all major cities of India and world. We can easily detect and identify areas under risk using GIS and remote sensing. There are simple raster data and tools that can be used to provide qualitative analysis of risks. In order to go for quantitative analysis, we need numbers related to the investment both at citizen level and at institutional level. Following are the simple datasets that can be used to create risk maps.

  • Digital elevation model (DEM)
  • Slope of the region
  • Delineated floodplains
  • Storm surge data
  • Rainfall data
  • Land surface temperature and vegetation index data
  • Soil Moisture data
  • Near Real Time (NRT) data like fire pixel data, extreme precipitation and seismic activity data
  • Urban density and Impervious layer data
  • Water scarcity data etc.

Most of these above datasets are free of cost. Using these, indices related to risk, vulnerability and exposure can be drawn; which in turn can give maps both for qualitative and quantitative analysis. Softwares like ArcGIS, Erdas, HecHMS , HecRAS have built-in tools that can be used to design both simple and complex models that would be helpful in coming up with indices. Following are the risks that can be easily modeled using free data both at local and regional level.

  • Flash Flood : Just by using slope data and impervious layer data we can have qualitative map that identifies areas which are at high risk of flash floods in cities.
  • Land Slides : Complex event like landslide can also be modeled using methods like Certainty Factor
  • Drought : Risk like droughts can be mapped using simple index like Vegetative condition index(VCI), Precipitation condition index(PCI), NDWI, Temperature Condition Index(TCI). We can also model the complex and integrated index like Integrated Drought Severity Index in matter of days both at regional and national level.
  • Flooding : Using hydrological tools and SAR data we can actually map and simulate the floods.
  • Heat Waves and Urban heat island : Using temperature data and evapotranspiration data derived from satellites (MODIS sensor) , we can produce risk maps.

It’s not only the risks that need to be mapped in order to check risks getting accumulated. We also need to check vulnerability and exposure of these risks to both human and non-human resources. This kind of integrated approach of risk, vulnerability and exposure will give a full picture of accumulated risk. There exist no hard and fast rule to integrate these maps. It is also true that risk, vulnerabilities and exposure are different for different regions. Hence, tools like WRO (Weighted Overlay Analysis for ArcGIS environment both desktop and web) becomes handy in these cases. WRO can generate scenario-based risk, vulnerability and exposure maps or mix of all 3 maps in matter of seconds. GIS industry as whole has such powerful tools, which could be used along with power of free data to map the risks and vulnerabilities that are getting accumulated in our cities, along coast, along rivers, on slopes etc. Its the power of earth observation that gives us an opportunity to map the accumulated risks and plan accordingly to mitigate the losses when disaster strikes.

Note: This is a guest blog by Shivaprakash Yaragal, GIS-Executive(Presales), IHub Team, ESRI-India