INTRODUCTION
Hazards have different origins and broadly classified as natural (Geological, Hydro-meteorological and Biological) and human induced processes (environmental and technological hazards). Hydro-meteorological hazards deal with the natural processes or phenomenon of meteorological, hydrological or oceanographic nature and climate phenomena origin. Meteorological hazards are related to atmospheric weather patterns or conditions and are generally caused by factors related to temperature, precipitation, wind speed, humidity, or other more complex factors. These hydro-meteorological phenomena cause a wide variety of natural hazards such as floods including flash floods, drought and desertification, forest fires, tropical cyclones (also known as typhoons and hurricanes), coastal storm surges, avalanches, and extreme weather hazards (e.g. heat waves, cold spells). These events are often catastrophic in nature causing loss of life, famine, loss of livelihoods and services, threat to property and the environment. Hydro-meteorological conditions can trigger other hazards viz. landslides, wildfires, epidemics, and in the transport and dispersal of toxic substances and volcanic eruption material (UNISDR, 2009). The terms ‘natural hazard’ and ‘natural disaster’ are frequently used and exchangeable but differ with respect to vulnerability. The impact of natural hazards depends on human presence and the ability of a population to deal with the hazard. Natural disasters occur when hazards meet vulnerability, however If a hazard occurs in an area outside of human settlement, it would not result in a disaster (Wisner et al., 2004). The country whether it more susceptible to a disaster depends on its infrastructure, levels of development, and social stability. Availability and accessibility of healthcare facilities also affect country’s ability to cope with the disasters and their aftermath. Accordingly, strengthening these aspects helps to reduce the prevalence of natural disasters in the region.
A series of major disasters were witnessed in Asia and it is one of the regions of the world most vulnerable to disasters, experiencing a wide variety of natural hazards. During 1980-2013, the frequency of natural disasters increased globally but the sharpest increase witnessed in the Asian and Pacific region because of increasing exposure and vulnerability (ESCAP, 2013). In the past decade (2000-2013), about 0.824 billion people in the Southern Asian region were affected by natural disasters and almost 53,378 (13% of global fatalities) were killed (Emergency Events Database, EM-DAT). Globally about 2.91 billion people were affected by disasters and total number of fatalities was about 425,737, of which Asia accounted for ~57% (Figure 1).
INSERT FIGURE 1
Figure 1. Number of fatalities across continents during 2000-2013 (EM-DAT).
In recent years, the Asian region has been hit by a series of disaster shocks such as droughts, extreme temperature, floods, storms, etc. These natural hazards are expected to rise under the build-up CO2 concentration in the atmosphere under global climate change. These phenomena have widespread impact on society and a prime concern for governments to deal with the social and environmental impacts. In particular, impact due to such hazards predominantly larger in developing nations than that of industrialized countries. The most frequently occurring and routinely observed hazards in developing nations are in the form of natural origin such as floods, flash floods, drought, extreme temperatures, and tropical cyclones. The livelihood of the majority of people in developing countries is predominantly dependant on rainfed agriculture. Start of rainfall season often early or late but it can cause significant losses to farmers as well as country’s food security.
According to the EM-DAT, since 1970 there are 1059 events of natural disaster in Southern Asia. There are 37 droughts, 316 cyclonic storms, 100 extreme temperature events, and 599 flood events (including flash flood). The decadal values indicate the frequencies are increasing in each category, however, flood and extreme temperature categories shows a striking increase. The pattern of increases has a correspondence with global climate change and monsoon dynamics. In terms of total damage, largest damages occurred in floods followed by storms and droughts (Table 1). Over the period 1970-2013, India battered by historic 218 flood events, 130 storms, 48 extreme events (heat and cold waves), 9 drought events, and 2 wild fires and total economic damages were ~50 % of the total damages of Southern Asia (~52,507,676).
Table 1. Frequency of disasters occurred over Southern Asia during 1970-2013 (EM-DAT).
Disaster Types / 1970’s / 1980’s / 1990’s / 2000’s / 2010-13 / Total (Col) / Total damage('000 USD)
Flood / 37 / 93 / 152 / 245 / 72 / 599 / 78,164,500
Drought / 9 / 10 / 4 / 12 / 2 / 37 / 6,040,172
Storm / 50 / 64 / 87 / 86 / 29 / 316 / 19,745,843
Extreme TEMP / 7 / 15 / 23 / 39 / 16 / 100 / 544,133
Wild fire / 0 / 1 / 5 / 1 / 0 / 7 / 11,700
Total (Row) / 103 / 183 / 271 / 383 / 119 / 1059 / 104,506,348
Over the last few decades, geospatial approaches deals with the procedures to acquire, analyze and evaluate spatial information for risk assessment from natural and human-induced hazards viz. geological hazard, hydro-meteorological hazards, environmental hazards and technological hazards. Geographic Information System (GIS) is commonly used as a mapping and analytical tool that support hazard risk and assessment, mitigation, and emergency response planning. Thereby, geospatial technologies have raised pronounced expectations in recent years as potential means of prevention and mitigation of natural disasters, including hydro-meteorological hazards. GIS has the capability to evaluate spatial information from various sources like remote sensing imagery, digital photogrammetry, meteorological radar, etc. and can deliver cost-effective geospatial solutions to policy makers.
This chapter introduces the use of space technology and geographic information systems in Hydro-meteorological hazards for detection, monitoring, and developing early warning systems for disasters. The major disasters and existing assessment methods and approaches were introduced and further selected case studies were presented.
HYDRO-METEOROLOGICAL DISASTERS
Floods
Floods are most common natural hazards resulting from meteorological processes such as prolonged rainfall, intense thunderstorms, onshore winds. Other processes viz. landslides, avalanches, levee breakage, and dam failure can cause rapid and widespread flooding. Floods cause more fatalities and loss of property and livelihoods of people than any other type of hazards. It can disrupt water purification and sewage disposal system, and cause toxic waste sites to overflow. Flash flooding is the result of intense rainstorms within a brief period of time and it occurs with little or no warning. It is often the result of rapid, unplanned urbanization, which can greatly reduce the land’s ability to absorb rainfall. The resulting runoff has nowhere to go and accumulates as quickly as the rain can fall. Drainage systems can be built to alleviate some of this problem, but very heavy rains will often exceed the capacity of even the best-designed systems of the developed countries. Floods have been occurring almost every year in India sub-continent and prevalent during monsoon season June to September. Flood problems are confined to the states located in the Indo-Ganges plains, northeast India and central India (Dhar and Nandargi, 2003) caused by tropical disturbances like cyclonic storms, depressions, low pressure, and thunderstorms.
To identify flood prone areas satellite images with high resolution data and GIS data can be used to create flooded maps. Since flood is a dynamic phenomenon, the period of submergence may vary greatly at different place and take times from hours to weeks. This leads to incapability of mapping the widest spread of flooding (time delay between the peak flood phase and that of satellite observation). Besides, floods prevalence during monsoon season (cloudy condition) cause a problem to acquire information as optical satellite sensors has a limitation which makes it difficult to map the spatial extent of inundation. On the other hand, microwave data/radar image have a limitation in difficult classification of acquired signal because of influence of complex ground and system variables. So an integrated approach of combining all data from different remote sensing based sensors and historical data (e.g. river discharge, past flood events) in a GIS platform could provide firsthand information for flood prevention and decision making.
Droughts
Drought is defined as “a period of abnormally dry weather sufficiently prolonged for the lack of water to cause serious hydrologic imbalance in the affected area” (Glossary of Meteorology, 1959). In a simpler form it is a period of unusually dry weather that has a prolonged existence to cause environmental or economic problems. Droughts are recurring climatic events, episodic in nature and recognized as slow creeping natural hazard. It is a major limiting factor to the region’s economic development by affecting the development of agricultural and water resources and food production. It produces complex impacts especially on agriculture sector by declining food grain production depending upon the intensity, duration, and spatial coverage of drought stress. It can also lead to increased migration from rural to urban areas, posing additional pressures on diminishing food production. Frequent droughts and more erratic nature of rains combined with underlying economic, social and environmental vulnerabilities may increase as a result of climate change and can have an increasingly destructive impact on at risk populations living in poor countries. Drought severity depends on duration, moisture deficiency, and the size of the affected area. It could be widespread and devastating which can cause large agro-ecological damage and disrupt socio-economic life. It often hits South Asia, causing massive water shortages, financial losses and adverse social consequences. In the history of British Rule, The Great Famine of 1876–78 affected severely entire Southern peninsula of India and heads to Central and Northern parts of India. The famine due to intense drought was spread over 16.7 million ha and the mortality was estimated as 5.5 million people. In Late Victorian Holocausts, Davis, M. (2001) explores the impact of colonialism and capitalism during the extreme climactic conditions "El Niño-Southern Oscillation (ENSO)" droughts related famines of 1876–1878, 1896–1897, and 1899–1902 in India. In the second half of the 19th century, India subcontinents witnessed a near-permanent cycle of droughts, bad harvests and subsequent famine. Subsequently, The Bengal famine in 1943 occurred due to crop failures and food shortages and it is estimated that at least 3 million people were died from starvation, malnutrition and related illnesses during the famine.
In the last three decades, rapidly ballooning populations has added to the growing demand for water, food and other natural resources in the region. The drought in 2000-2004 across Southern Asia affected more than 462 million people, with severe impacts felt in western India (Gujarat and Rajasthan States), in Pakistan’s Sind and Baluchistan provinces, as well as in parts of Iran and Afghanistan (Thenkabail et al., 2004). During the last three decades (1980-2013), more than 833 millions of people across Southern Asia affected due to the consequences of drought, and millions were forced to abandon their land (EM-DAT). Assessment and monitoring drought development becomes critical issue in most parts of South Asian countries as droughts are expected to rise in these regions under climate change.
Desertification
Desertification is land degradation in arid, semi-arid, and dry sub humid areas resulting from various factors including climatic variations and human activities and has several definitions. It is a process leading to reduced biological productivity, with consequent reduction in plant biomass, which leading to the intensification or extension of desert conditions (UNCOD, 1977). The degradation types as described by Oldeman (1988) are:
a)by displacement of soil material through water erosion (e.g., loss of topsoil, flooding) and wind erosion (top-soil loss, terrain deformation/overblowing) and
b)by internal soil deterioration through chemical (e.g., pollution, salinization), physical (e.g., soil compaction ) and biological deterioration (biological imbalance in the topsoil).
There are several factors, causes and processes are involved in the complex process of desertification and to assess desertification all factors need to consider. Broadly, the causes can be classified as Environmental (climate, geomorphologic, quality of soil water sources) and Anthropogenic (vegetation, water, land/soil resources degradation) (Sepehr et al., 2007). The factors responsible for soil degradation are wind and water erosion and salinity. Desertification in the arid regions of Southern Asia is characterized by frequent droughts, intensive agriculture, overgrazing, deforestation, soil erosion, and salt damage to irrigated land.
Tropical cyclones
The Tropical cyclone occurs between Tropics of Cancer and Capricorn. The tropical cyclones develop over the warm waters of the North Indian Ocean including Bay of Bengal and the Arabian Sea. Tropical cyclone is a rotational low-pressure system in tropics when the central pressure falls by 5 to 6 hPa from the surrounding and maximum sustained wind speed reaches 34 knots (~62 kmph). Tropical cyclones are severe storms that form over Asia is called ‘typhoons’. Tropical cyclones are called hurricane over the Atlantic Ocean. The low-pressure systems over Indian region are classified as Depression, Deep Depression (DD), Cyclonic Storm (CS), Severe Cyclonic Storm (SCS), Very Severe Cyclonic Storm (VSCS), and Super Cyclonic Storm (SuCS). The associated maximum wind speed (kmph) are 60-90 for CS, 90-119 for SCS, 119-220 for VSCS and >220 for SuCS (RSMC, 2013).
Tropical cyclone significantly affects coastal zones but can travel far inland under certain conditions. These storms are marked by a combination of high winds, heavy rainfall, and coastal storm surges. Climatologically, cyclones are noticed in the month of May-June and October-November but higher frequency of dissipation of cyclones occurred in the month of October in the Bay of Bengal, India because of strong easterly winds aloft. The frequency of tropical cyclones in the north Indian ocean revealed a significant increasing trends during November and May over the past decades (Singh et al., 2000). Based on EM-DAT, about 69 million people were affected by cyclones in India over the period 1980-2013. There were 62 events of tropical cyclones that caused 20,465 causalities with total economic damage of 9,051,375 ('000 USD). The most affected states are located in the east coast such as Andhra Pradesh, Odisha, TN, and WB. The damage and destruction due to storms are increasing however loss of life has been minimized as a consequence of better weather forecasts and warnings, and disaster management strategies.
Weather Hazards: Heat Waves and cold Waves
Heat waves or extreme heat is a temperature-related hazard connected with a significant deviation above normal high temperatures for a given geographical region. Heat waves are global phenomena and most significantly affect human beings, livestock, Wildlife and habitats, agriculture, infrastructure and water resources. This phenomenon occurs during the period March–July across the Indian subcontinent, and causes fatalities attributed to sun stroke. The duration of the heat wave generally varies from 5 to 6 days but may go up to 15 days (Chaudhury et al., 2000). According to the India Meteorological Department (IMD), criteria for heat waves in India are defined as:
a)When normal maximum temperature of a station is less than or equal to 40° C
●Heat wave departure from normal is 5° C to 6° C whereas severe heat wave departure from normal is 7° C or more.
b) When normal maximum temperature of a station is more than 40° C
●Heat wave departure from normal is 4° C to 5° C whereas severe heat wave departure from normal is 6° C or more.
c)When actual maximum temperature remains 45° C or more irrespective of normal maximum temperature, heat wave should be declared.
In the last century (1901-1999), the maximum number of heat waves occurred over Uttar Pradesh (134), Bihar (113), Maharashtra (99), and Rajasthan whereas the minimum number of heat waves reported in Delhi NCR (3), Gujarat (2) and Punjab (1) (De et al., 2005). With respect to fatalities, highest number reported from Rajasthan (1625), followed by Bihar, Uttar Pradesh, Odisha during the period 1978-99 (De and Sinha Ray, 2000). Notably, a significant increase in the frequency and spatial coverage of heat wave has been observed during the decade 1991-2000 as compared to the two earlier decades 1971-80 and 1981-90 (Pai et al., 2004). More frequent and extreme heat waves witnessed during 1991-2000 coincided with highest temperatures increase as a result of global warming, which is also the warmest decade during the past 140 years (WMO, 2001). Global warming induced heat waves might lead to serious implications in the developing countries. According to EM-DAT, human and economic losses in India from heat wave disasters that have occurred between 1980 and 2013 revealed that there were 18 events with 7,725 number of fatalities and total damage was 400,000 ('000 USD). On the other hand, number of cold waves reported were 24 events with 4,567 number of fatalities and total damage was 144,000 ('000 USD). In terms of death toll and total economic damages, cold waves have lesser repercussion against heat waves in India.
Cold waves or extreme cold temperatures are short-lived or may persist for days or weeks which can have severe negative consequences. According to World Meteorological Organization (WMO) report, wind chill factor brings down the actual minimum temperature that depends on wind speed. The actual minimum temperature of a station is reduced to “wind chill effective minimum temperature (WCTn)” based on wind chill factor. For declaring cold wave, IMD uses WCTn indicator and If WCTn is 10°C or less, then only the conditions for cold wave are considered. Criteria for cold waves as defined by IMD:
a)When normal minimum temperature is equal to 10°C or more.
●Cold wave departure from normal is -5°C to -6°C whereas Severe cold wave departure from normal is -7°C or less
b)When normal minimum temperature is less than 10°C.
●Cold wave departure from normal is -4°C to -5°C whereas Severe cold wave departure from normal is -6°C or less
c)When WCTn is 0°C or less, cold wave is declared irrespective of normal minimum temperature of the station. However, this criteria is not applicable for those stations whose normal minimum temperature is below 0°C.
In India, western disturbances cause cold waves mainly affect the areas to the north of 20° but in association with large amplitude troughs, cold wave conditions are reported in different parts of the country except Southern India. In the last century (1901-1999), the maximum number of cold waves occurred over Jammu & Kashmir (JK), Rajasthan, Uttar Pradesh, and Madhya Pradesh whereas the minimum number of heat waves reported in Assam and Andhra Pradesh (De et al., 2005). In terms of causalities, highest number reported from Uttar Pradesh and Bihar during the period 1978-99 due to lack of shelters to the workers and homeless people (De and Sinha Ray, 2000). People lacking shelter are the most vulnerable and IFRC (2013) reported that about 78 million people are homeless and are unprepared to cope with the extreme cold weather conditions.