31 Water related Hazards

Somvir Bajar and Hardeep Rai Sharma

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Objectives

 

1.      Introduction to water related hazards

2.      Occurrence of various type of water related hazards

3.      Understanding the causative factors responsible for water related hazards

4.      Understanding of associated impacts of water related hazards

 

33.1 Introduction

 

A hazard is a natural phenomenon and a situation where there is threat to life, health, environment, property, and society. Hazards take place without taking into account whether the place is highly populated or desolate. While a disaster is an event that completely disrupts the human community and leads to economic, loss of life and has considerable impact on environment. Earthquake, flood, tsunamis, landslides etc. are few examples of both hazard and disaster. But a hazard is called disaster when it affects human population. When any hazard strike an area having no population, although it still has destruction properties, it is not termed as disaster. For example, storms like tornado or typhoon occur in many parts of the world, but come under disaster category only when they take place in built environment and human population.

 

Water related disasters like flood, landslides, droughts, tsunamis cause enormous economic, social and environmental damage, and also cause massive loss of human life. Fig. 1 shows different types of water related hazards. Water is harmful in both ways either in excess or in shortage. Abnormally high rainfall and glacial melting leads to floods and associated water related hazards. On the other hand, drought conditions persist, it may cause massive damages to ecosystem, agriculture and economic system. Trends in natural disasters revealed its continuously increasing frequency in most regions of the world. Among all observed natural and anthropogenic adversities, water-related disasters are undoubtedly the most recurrent and pose major impediments to the achievement of human security and sustainable socio-economic development, as recently witnessed with the disasters caused by the Indian Ocean tsunami in 2004, Hurricane Katrina in America (2005), Cyclone Sidr in Bay of Bengal (2007), Cyclone Nargis in Myanmar (2008), Tsunami in Japan (2011), and many others. Global climate change is expected to affect the frequency, intensity and duration of extreme water- related weather events such as excessive rainfall, storm surges, floods, and drought (Adikari and Yoshitani, 2009). Therefore, such hazards affect millions of people, jeopardizing human security and hampering socio-economic activities (Haque et al. 2012). Both the Johannesburg Plan of Implementation (JPoI), Millennium Development Goals (MDGs) and thereafter, Sustainable Development Goals (SDGs) have stressed the need for closer interaction between hazard risk reduction and sustainable development (Adikari and Yoshitani, 2009).

 

33.2 Types of water related hazards

 

33.2.1 Flood

 

A flood is an overflow of water that submerges land which is usually dry. Floods are of many types which include flash flood, riverine flood, coastal floods etc.

 

33.2.1.1 Flash flood

 

The National Weather Service of USA defined the flash flood as “A rapid and extreme flow of high water into a normally dry area, or a rapid rise in a stream or creek above a predetermined flood level, beginning within six hours of the causative event (e.g., intense rainfall, dam failure, ice jam). However, the actual time threshold may vary in different parts of the country. Ongoing flooding can intensify to flash flooding in cases where intense rainfall results in a rapid surge of rising flood waters” (National Weather Service Manual 10-950, April 26, 2006). Flash flood:

  • Factors contribute to flash floods are: rainfall intensity, duration of rainfall, topography, soil condition, and ground cover.
  • Flash flood occurs due to sudden and intense heavy rainfall, so it’s give least amount of warning time.
  • Flash flood can also occurs due to extreme rainfall released by hurricanes, tropical storm, failure of dam or levee, cloud burst and human activities.
  • The damage caused by flash floods can be more severe than ordinary riverine floods due to high speed and velocity of water, and debris load.
  • Examples: Srinagar (Jammu & Kashmir) India, approximately 300 people died (2014); Uttarakhand flood in India (2013) (Image 1a). Central Texas, USA, more than 25 people died (2015); Cloudburst in Manali-Leh highway, India (2017) (Image 1b), Garut Regency in Indonesia count death of more than 30 people (2016).

 

33.2.1.2 Riverine flood

 

Floods occurs in all type of rivers either they are smallest or largest one. This type of flood caused when water runoff collects in river and start overflowing the banks. Along with rainfall, other factors responsible for riverine flood are snowmelt and ice jams. The dynamics of riverine flood changes along with the terrain. This flood cause extensive damage to the people living in nearby areas of rivers and streams. Example: Kosiriver in Bihar (India) in 2008 (Image 2).

 

33.2.1.3 Coastal flood

 

This type of flood occurs when sea water enters into the low lying area near sea/ocean. Various causative agents for coastal floods includes hurricanes, tropical cyclones and tsunamis along with topography of that area. Example:The port in Sint Maarten (Caribbean Netherlands) after Hurricane Irma (2017) (Image 3).

33.2.2. Drought

 

Drought is an extreme climatic event with deficiency in precipitation over an extended period from months to years. Drought is a temporary dry period as compared to permanent aridity as in arid areas. Drought generally refers to water deficit but may also include meteorological (precipitation), hydrological (stream flow), or agriculture (crop yield) deficits. Various consequences of droughts are shown in fig. 2. The main causes for droughts are: dry season, El Nino, deficiency in precipitation, erosion, human activities and climate change. Drought is often classified into three types as (Drought Public Fact sheet, 2008; AMS, 1997; Wilhite, 2000)

 

Meteorological Drought: Meteorological drought is usually defined based on the degree of dryness (in comparison to some “normal” or average) and the duration of the dry period. It is often accompanied with above-normal temperature. Drought onset generally occurs with a meteorological drought.

Agricultural Drought : Agricultural drought links various characteristics of meteorological (or hydrological) drought to agricultural impacts, focusing on precipitation shortages, soil water deficits, reduced ground water or reservoir levels needed for irrigation, and so forth.

 

Hydrological Drought : Hydrological drought usually occurs following periods of extended precipitation shortfalls that impact water supply (i.e. stream-flow, reservoir and lake levels, ground water), potentially resulting in significant societal impacts. Because regions are interconnected by hydrologic systems, the impact of meteorological drought may extend well beyond the borders of the precipitation-deficient area.

 

 

33.2.3 Windstorms

 

Cyclone is a region of low atmospheric pressure surrounded by high atmospheric pressure resulting in swirling atmospheric disturbance accompanied by powerful winds blowing in anticlockwise direction in the Northern Hemisphere and in the clockwise direction in the Southern Hemisphere.

 

Typhoon, cyclones and hurricanes are the same phenomenon, the only difference in places where they occur. If disturbance occurs in the Atlantic and Northeast Pacific, the term “hurricane” is used, if occurs in Northwest Pacific is called a “typhoon” and “cyclones” when occur in the South Pacific and Indian Ocean (NOAA). It is also called Willie- willie in Australia and Tornado in South America. Various impacts of windstorms:

  • Loss of life and livelihood
  • Loss of crop leading to food scarcity
  • Cause erosion of productive soil damaging existing vegetation and ecosystem as well as areas where the soil and sand blown.
  • Damage infrastructure like buildings, power lines, communication towers, bridges and roads.
  • Increased burden on government to rebuild or repair affected areas.

 

33.2.4. Landslides

 

The term’ landslide’ includes all varieties of mass movements of hill slopes and can be defined as the downward and outward movement of slope forming materials composed of rocks, soils, artificial fills or combination of all these materials along surfaces of separation by falling, sliding and flowing, either slowly or quickly from one place to another. Main causes for landslides are: geological weak material, erosion, intense rainfall, human excavation, earthquake and volcanic eruptions. There are different types of landslides like topple, mudflow, creep, lahar (mudflow or debris flow), lateral spread, slides, falls, flow, debris flow and debris avalanche (Varnes, 1978). Image 4 shows landslide in Uttarakhand (India) in June 2013.

 

Various impacts of landslides or mass movements:

  • Damage to property
  • Adversely affect water supplies, fisheries, forest, dams, and roadways.
  • Affect availability of food and fresh water.
  • Cause injury and death of people in affected areas. Often block rivers and may leads to flood.
  • Disturb communication network.

 

33.2.5. Wave and Surges

 

The term tsunami is derived from a Japanese term and is made up of two words “tsu” meaning ‘harbor’ and “nami” means ‘wave’. It is also called as tidal waves, but they are not related to tides. Three most common causes of tsunamis include earthquake, landslide (occurring under water or above the sea) and volcanic activity (near the shore or under water). Tsunami is not a single wave but it consist ten or more waves, so called as ‘tsunami wave train’. Tsunami wave speed is controlled by water depth. Where the ocean is over 6,000 meters (3.7 miles) deep, unnoticed tsunami waves can travel at the speed of a commercial jet plane, over 800 km per hour (500 miles per hour). There are two ways for the prediction of tsunamis as: international tsunami warning systems and regional warning systems. Image 5 shows the aftermath of tsunami and Fig. 3 shows consequences of tsunami.

33.2.6. Water related diseases

 

Water- related disease is defined as any significant or widespread adverse effects on human health in form of death, disability, illness or disorders, caused directly or indirectly by the condition, or changes in the quantity or quality of any waters (Stanwell-smith, 2009).There are many causes of water related diseases like microorganisms, unhygienic conditions, vectors, toxic chemicals etc.(Kulinkina, 2016). Water related diseases includes both water borne diseases and water associated diseases. Fig. 4 shows different types of water related diseases. When there is any water related hazard, it leads to transmission of water related diseases as shown in Table 1. Detailed modules on water borne diseases available in paper 15 (Environmental Microbiology and Biotechnology)

 

Fig. 5 Various causative agents for water related hazards

 

 

33.4 Some Examples of water related hazards in India

 

33.4.1 Flood in Kaziranga National park

 

Water related hazards leads to loss of biodiversity and also changes the landscape of that area. Water related hazards have both significant long-term and short-term effects on biodiversity. Flood in Kaziranga National park greatly affects the biodiversity of national park as well as the landscape of the area. The national park is a relatively small national park in the flood plains of Brahmputra River, however, the area occupies around 60% of the world population of the Indian one- horned rhinoceros, about 50 %of the endangered Asiatic wild water buffalo (Bubalus arnee) and has the only viable eastern swamp deer (Cervus duvaucelli). Brahmputra River is one of the most sediment-charged rivers of the world and also having highest flood potential in the Indian subcontinent. The park was designated as a natural World Heritage site in 1985 on the basis of its outstanding universal value representing significant ongoing geological processes, biological evolution and man’s interaction with his natural environment (criterion ii) and for conserving important and significant habitats where threatened species of plants and animals of outstanding universal value from the point of view of science and conservation still survive (criterion iv). According to the census held in March 2015, which was jointly conducted by the Forest Department of the Government of Assam and some recognized wildlife NGOs, the rhino population in Kaziranga National Park is 2,401. It comprises 1,651 adult rhinos (663 male, 802 are females, 186 unsexed); 294 sub-adults (90 males, 114 females, 90 unsexed); 251 juveniles and 205 cubs. Perennial flooding and heavy rains have resulted in death of wild animals and damage to the conservation infrastructures

 

33.4.2 Flood in Uttrakhand 2013

 

Uttarakhand state of India is considered as devbhoomi (the lands of Gods) and is famous for its chardham yatra. Every year a number of pilgrims visit these places along with other holy places also. But in June 2013, torrential downpour and subsequent deluge wreaked havoc in Uttarakhand. In June, 2013 (June ,14-17), Uttarakhand (India) received heavy rainfall as compared to normal monsoon along with multiple cloud burst caused devastating flood and landslides which becomes the country’s worst natural disaster after 2004 tsunami. Occurrence of heavy rainfall, on June 16, 2013 night, in high hills of Uttarakhand including Kedarnath Valley resulted in massive deluge in the river basin and water level in River Mandakini increased. The heavy rainfall caused the melting of Chorabari Glacier and eruption of the Mandakini river which led to heavy floods near Gobindghat, Kedar Dome, Rudraprayag district in Uttarakhand. The heavy rainfall resulted in large flashfloods and massive landslides. Chardham i.e. Gangotri, Yamunotri, Kedarnath and Badrinath, hindu pilgrim centers are badly affected by this rainfall. A number of people were stuck in various regions because of damaged or blocked roads. The multi-agency rescue operation involved IAF, Army; Indo-Tibet Boarder Police (ITBP); National Disaster Response Force (NDRF) and Border Road Organization (BRO). These multi- agency rescue finally claimed for evacuation of all stranded pilgrims, about 1, 10,000.

 

33.4.3. Cyclone Ockhi 2017

 

The cyclone Ockhi, start from the Gulf of Thailand and ends near the coast of Gujarat (Western India). This cyclone affects India, Sri Lanka and Maldives. The meaning of Ockhi is ‘eye’ and this name was given by Bangladesh. The Cyclones worldwide are named by 9 regions‒North Atlantic, Eastern North Pacific, Central North Pacific, Western North Pacific, North Indian Ocean, South West Indian Ocean, Australian, Southern Pacific, South Atlantic. And in North Indian Ocean, eight countries‒Bangladesh, India, the Maldives, Myanmar, Oman, Pakistan, Sri Lanka and Thailand, are involved in naming of cyclone. A consolidated list of total 64 names were prepared as each country gave 8 names and from this list one word is picked in an order to name the cyclones (for more detail of naming of cyclone, see World Meteorological Organization Technical Document WMO/TD no. 84 Tropical Cyclone Programme, Report no. TCP-21, Edition 2015). The cyclone Ockhi originated on November 21, 2017, as a low pressure area in the gulf of Thailand. On November 29, 2017, in Sri Lanka, this cyclone caused damage to property and life. Then, this cyclone enters into the mainland of India and affects Lakshadweep, Tamilnadu, Kerala, Maharashtra, and Gujarat.

 

33.5. Management of water related hazards: Natural water related hazards like tsunamis, floods, are difficult to control but we can reduce the extent of damage by adopting different disaster management strategies. Early detection systems followed by quick evacuation of people before the hazard proved to be very effective in reducing the lives and property damage in many parts of the world. Further, initiation of rapid recovery actions and assistance to victims and community awareness and involvement is very important in mitigating the impacts of water related hazards.

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References:

 

  • Adikari, Y and Yoshitani, J., 2009. Global trends in water-related disasters: an insight for policymakers. UNESCO, 2009 ISBN 978-92-3-104109-9
  • American Meteorological Society (AMS). Meteorological drought—policy statement. Bull Amer Meteor Soc1997, 78:847–849.
  • Drought public Fact sheet, NOAA National Weather Service, January 2008.
  • Haque, U., Hashizume, M., Kolivras, K.N., Overgaard, H.J., Das, B., Yamamoto, T., 2012. Reduced death rates from cyclones in Bangladesh: what more need to be done? Bull World Health Org., 90(2): 150-156
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  • Varnes  DJ  (1978)  Slope  movement  types  and  processes.  In:  Schuster  RL,  Krizek  RJ  (eds)
  • Landslides,  analysis   and   control,  special   report   176:  Transportation   research                    board,
  • National Academy of Sciences, Washington, DC., pp. 11–33
  • Wilhite DA. Drought as a natural hazard: concepts and definitions. In: Wilhite DA, ed. Droughts: Global Assessment. London: Routledge; 2000, 3–18.
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