eChapters

Introduction

Groundwater investigation has a long history. In the past a waterman in the village would walk around the investigation area with a Y shaped wooden fork and identify the location for digging the wells. Certain trees and organic landforms like termite mounds were considered as indicators. The native intelligence of local topography should have played a role in identifying potential location. Successful or otherwise the method can be said to lack scientific objectivity. The optimal groundwater surveying method is no doubt drilling. This method ensures that all necessary information is being brought up from the geological formations. However, in order to obtain a desired degree of information from the subsurface of an area, drilling alone is normally not a feasible alternative.

There are a number of efficient and inexpensive geophysical surveying methods available to the hydrogeologist. It is worth noting at this point that these are, without exception, indirect methods. This implies that no method measures directly what we are actually looking for. With geophysical surveys, the target features are therefore invariably associated features. This implies that unless we understand the water context of these features, our geophysical surveys will be less than meaningful.

Objective methods of investigating groundwater are discussed in this chapter.

Introduction

Normally, water is a liquid substance made of molecules containing one atom of oxygen and two atoms of hydrogen (H₂O). Pure water has no colour, no taste, no smell, turns to a solid at 0°C and a vapour at 100°C. Its density is 1 gram per cubic centimetre (1 g/cm₃), and it is an extremely good solvent.

An extraordinary property of water is its ability to dissolve other substances. There is hardly a substance known which has not been identified in solution in the earth's waters. Were it not for the solvent property of water, life could not exist because water transfers nutrients vital to life in animals and plants.

A drop of rain water falling through the air dissolves atmospheric gases. When rain reaches the earth, it affects the quality of the land, lakes and rivers.

Introduction

Wells are vertical shafts excavated or holes drilled in earth to the level of water table for extraction. Digging of wells is an age old practice. Shallow dug wells supported communities in the past. Well water is drawn to the ground manually or mechanically using variety of containers made of metal, leather, canvass and wood or a combination of them. Draught animals or electrical power are used to draw water for irrigation.

Water table (Fig.6.1) wells extend below the groundwater table and extract free water. Pumping water from these wells lowers the water level. The well first gains water from the water bearing material in its immediate proximity. Subsequently a cone of depression is formed in the immediate vicinity of the well. Water outside the cone of depression but with in the area of influence is diverted to replace the body of groundwater finding its way in to pumping well.

Introduction

Fresh water, a renewable but not an infinite resource, is becoming increasingly scarce. The amount available for use to the world today is almost the same as it was 4500 years ago but global demand has been increasing exponentially. Since 1950, the renewable supply per person has fallen 58 percent as world population has swelled from 2.5 billion to 6 billion. Moreover, unlike oil and most other strategic resources, fresh water has no substitute in most of its uses. It is essential for growing food, manufacturing goods, and safeguarding human health.

According to a World Policy Forum report, the largest and most combustible imbalance between population and available water supplies will be in Asia, where crop production depends heavily on irrigation. Asia today has roughly 60 percent of the world’s people but only 36 percent of the world’s renewable fresh water. China, India, Iran, and Pakistan are among the countries where a significant share of the irrigated land is now jeopardized by groundwater depletion, scarce river water, a fertility-sapping buildup of salts in the soil, or some combination of these factors. Groundwater depletion alone places 10 to 20 percent of grain production in both China and India at risk.

Introduction

All models are but approximations of reality. When we approximate there is always room for uncertainty. The preference of a particular model over the other is the relative degree of uncertainty acceptable to the objective and budget of the study. With the advent of computers, hosts of modeling software promising a lot to the researcher have arrived on the horizon. It is not in the scope of the book to enumerate all the techniques of hydrogeological modeling. Physical modeling using sand tanks was the earliest attempted modeling technique, about 107 years ago. Most recent and significant modeling technique practiced by many in groundwater potential identification is Geographic Information System (GIS) based modeling. After a brief treatment of physical models, concepts of mathematical models and GIS modeling are elaborated. The modeling techniques have involved mathematics and or software specific instructions. Hence it is recommended that relevant text books for individual techniques be referred. This chapter deals more on modeling concepts.

In this chapter, an attempt is made to emphasize the fact that while no country in the World is safe from geohazards, a proper understanding on their causes, ways to mitigate them and surviving techniques would help reduce the life and property loss. Each geohazard has its own characteristic way of potential impact and hence classifying vulnerability of different regions and creating awareness on potential impact is essential. In addition to providing basic information on geohazards, this chapter presents a conceptual model on hazard mitigation, rescue and relief operations.

INTRODUCTION

Every year, thousands of people are killed by volcanic eruptions, earthquakes, landslides and floods. These natural causes damage human settlements and infrastructures (GOI, 2004) inflicting life and economic loss. As human population increases, habitation on hazardous and or vulnerable land becomes more common and the risks posed by these hazards increase. The need to observe their behavior, understand them better and mitigate their effects become ever more urgent (IGOS, 2003). Decades of research may have contributed towards betterment of our understanding on the processes of geohazard formation but still a long way has to be covered to develop better mitigation procedures.

This chapter reviews the published information on tsunami and attempts to characterize tsunamigenic sediments in terms of their microfossil content. Tsunamisare long-period waves generated by vertical displacements of marine watercolumn due to earthquakes, volcanic explosion and landslides. These waves can exceed heights of 25 meters (in shallow water) and lengths upto 100km with a velocity of more than 1000km/hour. Even at this magnitude, they are undetectable in deeper waters owing to very low wave height which in turn reduces significantly the response time, causing sudden havoc along coasts. They can cause flooding of coastal areas and affect areas thousands of kilometers away from their point of origin. These characteristics of tsunami imprint ensuing sediments with unique assemblage of microfossils.

INTRODUCTION

Shallow water progressive waves with very large wavelength and long duration caused by the rapid displacement of ocean water are called “tsunami”. Tsunami is a sudden non-meteorologically induced impulse in water regardless of size. Tsunamis are formed by submarine tectonic activity more often due to earthquakes and less frequently due to volcanic eruption, landslides near the coast, meteor impact and nuclear explosions.

The velocity of the tsunami varies and depends on many parameters such as bathymetry, height of the originating wave, initial pressure changes in the sea, etc. and can travel at a speed of more than 1000 km/hr. At the place of origin (directly above the epicentre of submarine earthquake or any other causative factor), the wavelength may be upto few tens to several hundred kilometres but the wave height is often less than one metre only. Since the velocity is proportional to the depth of the water column, it gets reduced to few tens of kilometres as the tsunami approaches the coast. However, the wave height increases significantly reaching 100 m in extreme cases. As a result, the tsunami strikes the coast with massive force. The effect is colossal in islands with low relief. The tsunami waves appear as flooding with water rushing inside the land more violently and with great force towards a river course. In several cases, when the tsunami arrives, the water level in the sea may drop significantly and the waters receding several hundred metres come back with great speed drubbing the coastal lands doubly from both the directions. Though an event of short duration in terms of geological history, tsunami deposits, owing to their higher rate of deposition and other salient characteristics, find place in stratigraphic records. This chapter is an attempt to review the characteristics of tsunami and tsunamigenic sediments, to find out the ability of microfossil content of such sediments for characterization and to identify tsunami deposits in stratigraphic records.

A review on historic occurrences of tsunamis in the Indian Ocean and their associated characteristics followed by detailed characterization of genetic causes of recent tsunamiarepresented in this chapter. Althoughsubmarineearthquakes occur very frequently, resultant tsunami and its strength relied on many factors including transformation of energy into the ocean water, area of rupturing of ocean floor, duration of rupturing, accompanying submarine slides, kind of material at focus of earthquakes and type of faulting. The direction of tsunami wave propagation plays the decisive role in deciding sites of impacts. Perfect blend of all these parameters is required to make a submarine earthquake to generate devastating tsunami, which is relatively rare in geological history. This is the reason why although there were as many as 77 tsunamis that occurred in the Indian Ocean region during historic past, the recent one of 26th December 2004 is deadly and rare geological occurrence. However, aftermath effects in terms of volcanic eruptions, coastal high wave activities and change in climatic cycles are recorded since then and require constant scientific vigil.

INTRODUCTION

Tsunami is defined as a sea wave of local or distant origin that results from large-scale seafloor displacement associated with major earthquake or submarine slide or submarine volcanic explosion. Many a times it is incorrectly described as tidal wave or seismic sea wave, as both of these terms mislead in regard to its mechanism of generation. In Tamil Sangam literature, tsunami is cited as “Azhipperalai”. In South America, it is termed as “Maremoto”. Other names for tsunami include “Flutwellen”, “Vloedgolven” “raz de mare” “Vagues Sismique” and Kai e’e. Prevalence of specific terms for tsunami in many such regions and languages itself stands testimony to the fact that tsunami is known to ancient human populations and that tsunami occurred frequently the historics past.

Detailed information on tectonic evolutionary history of the Bay of Bengal is presented followed by elucidation of these characteristics towards tsunamigenesis in this chapter. The Andaman-Nicobar Island Arc (ANIA) is situated on a 1000 km long plate margin and represents a key region in the developing oceanic crustal area of Bay of Bengal. Frequent earthquakes including the tsunamigenic earthquake of 26th December 2004 off the coast of Sunda take place in this region. The subduction of Indian plate under Myanmar-Thailand plate drives formation of chain of Andaman-Nicobar group of Islands. These oceanic crust formation, subduction and arc formation are all seismigenic and generate shallow focus earthquakes in the Bay of Bengal. It is also observed that the seismicity is decreasing as the bathymetry increases towards SW of the Bay of Bengal. Thus, in long term, the slow accumulation of stress as tectonic plates converge may result in many more earthquakes in this region. After a dormancy of over 100 years, the Barren Island volcano renewed its activity following recent earthquakes. The seismic activity along the Andaman-Nicobar trench is continuing with earthquakes of magnitude varying from 4.8 to 7.2 Richter scale. All these observations suggest resurgent and intense tectonic and volcanic activities due to which allied hazards such as tsunami may take place in future.

INTRODUCTION

The evolving Earth, depending on its heat flow pattern in the mantle throughout geological time, had passed through stages, which are diagnosed through characteristic geodynamic signatures. This chapter focuses on a very active region in the crust, namely, the Andaman-Nicobar Island Arc (ANIA) to recognize such signatures and decipher relative safety of surrounding regions including east coast of India. As similar active arc systems such as Sunda Arc & Japan Arc generate volcanic, seismic and tsunami hazards, understanding the ANIA would be of help assess safety of surrounding regions. Abundant geoscientific literature exists on the northern part of the Indian plate, which is undergoing compressive stress since collision between the Indian and Eurasian plates about 55-45my. However, the behavior of remaining part of the Indian plate underneath the Indian Ocean is still sparcely studied. Owing to these reasons, this chapter attempts to fill the gap in our understanding as well as to assess the implications of renewed phases of geohazard occurrences including that of catastrophic earthquake and tsunami of 26^th December 2004.

Need for systematic mapping and hazard zonation is emphasized in this chapter. Though prevention of natural disaster is not possible, its destruction could be minimized through implementation of effective hazard management system. With this motive, the coastal region between Tangapatnam and Ovari, Tamilnadu State has been classified into various categories of vulnerability based on its response to the 26th December 2004 tsunami. Based on the extent of seawater inundation and coastal geomorphic features, we have assessed the tsunami impact and estimated the behavior of the beaches in case of similar havoc in future. This study had shown that the maximum seawater inundation recorded in the study area is 750m in Colachel and the minimum is 100m in Kadiapatanam, Mandakadu and Vaniakudy areas. Chinnamuttom, Kanyakumari, Manakudy, Pallam and Colachel areas are under high risk.

INTRODUCTION

On 26^th December 2004, tectonic disturbances happened near Sumatra Island with an intensity of 9.3 in the Richter scale wrecked havoc on southwest part of India. In addition to inflicting life and infrastructure loss, the resultant tsunami event had also eroded severely the coastal region and modified topography of beach and shallow coastal regions. It did raise the concern of scientists and emergency planners about the impact of larger earthquake and consequent tsunami should there be any recurrence of such event. Despite becoming aware of tsunami hazard, there has been confusion about areas at risk and areas of safety. This chapter is an attempt to assess the vulnerability of part of Tamilnadu coast based on its geomorphological conditions and the impact of recent tsunami. The hazard maps have been generated and are intended for educational purposes, to improve awareness of tsunami hazards and to encourage responsible emergency planning efforts by illustrating the range of possible tsunami events.

This chapter is an attempt to introduce basic facts about earthquake generation and the role of earthquakes in triggering secondary geohazards. Earthquake, unlike manyother geohazards is yet to be fully understood towards occurrence and magnitude for better mitigation measures. Though unpredictibility of this hazard makes it dangerous, earthquakes seldom kill lives. Instead, poor ability of man-made structures against ground-shaking waves has been the real cause of life loss and damage to property in most of the earthquake incidences. Furthermore, earthquakes generate secondary geohazards such as landslide, failure of dams and reservoirs, etc. Thus, earthquake, as a natural hazard has its own characteristic way of potential impactand hence classifying vulnerability of different regions and creating awareness on potential impact among common public is essential.

INTRODUCTION

The term “earthquake” denotes “shaking/vibration/trembling/ quivering/shuddering/ wobbling of Earth”. Earthquake is the quickest and most unpredictable natural hazard. It is nothing but a series of suddenly generated elastic waves occurring in the Earth due to internal and/or external causes from shallow (few kilometers) to about 700 kilometers depth. It is a form of motion of wave energy transmitted through the surface layer (crust) of the Earth. One generalization that can be made out of scientific and mainstream media information about earthquakes is that, “earthquakes seldom kill; but the associated phenomena such as landslides, flooding, volcanic eruptions and collapse of natural and man-made structures cause the real damage to lives and property”. This chapter is an attempt to describe the basic elements of earthquakes and few mitigation measures.

This chapter presents a case of Jind region of Haryana State, Northern India which had experienced mild tremors of ~ 3 on Richter scale magnitudes in the recent past with a gap of 1 to 2 years. Rejuvenation of the lineament controlled volcanoseismic process is identified as the probable cause of these tremors. This chapter describes seismotectonic characters, micro and mega seismicity of the area and few mitigation measures.

INTRODUCTION

The Haryana state consists of Delhi Super Group (DSG), Indo- Gangetic alluvial plain in the form of alluvial fan, sand dune, alluvium of Ambala, Yamuna and Ghagghar rivers and Siwalik Super Group (SSG) in the southern, central and northern parts respectively (Fig.1). The study area Jind is located in the central part of Haryana and comprises 200 – 600 m thick Indo-Gangetic alluvium. The alluvium is of Quaternary Period and composes alternating layers of clay, silt, sand and kankar. The Bhiwani and Tosham areas, located south of Jind, show the occurrence of Neoproterozoic granite and rhyolite of Malani Igneous Suite (MIS). The rocks occur in the form of ring structure/ring dyke on the hillocks amidst the alluvium. The metasediments (mica schist and quartzite) of Delhi Super Group are underling MIS at Tosham (located at 70 km southwest of Jind). As Jind region experiences mild tremors and there is no previous published work pertaining to the geology, tectonics and seismicity of the area the chapter records these aspects for better understanding and mitigation of earthquake hazard.

This chapter introduces the readers about volcanoes and associated features and hazards. Volcanic disasters are like any other geohazards in causing dangerous impacts. However, volcanic explosions are preceded by many surficial expressions that can be detected through satellite imageries, thermal sensors, change in magnetic and gravity anomalies, disappearances of vegetation, sudden appearances of anomalous water vapor, thermal springs and abnormal behavior of animals. Hence, unlike other geohazards, volcanic hazards could be forecast with fairly accurate time limits that may allow evacuation and precautionary safety measures. While avoidance is the best mitigation measure, proper land use planning, provision of scientifically designed damming and diversion methods could save lives and infrastructure from lava flows. Though, atmospheric contamination by volcanic gases, ash cloud and pyroclastic materials could not be thwarted and controlled and thus they could cause havoc.

INTRODUCTION

The term “Volcano” is derived from the name of Roman mythical God of fire “Vulcan”. A volcano is an opening of different shapes, through which, molten rock and gas get ejected either violently or simply flow over earth’s surface. The molten rock and gaseous materials are drawn from deep inside of crust or mantle of the Earth. Repeated ejection of molten materials through vent, fissures or plate margins forms volcanic mountains on earth’s continental or submarine regions.

Volcanism is a threat not only to the lives and infrastructure, but it also drastically alters landscape, impacts atmospheric quality and renders forests, cities and villages and cultivation lands useless. In addition, volcanic eruptions are capable of causing changes in global atmospheric cycles. For example, the eruptions of El Chicho’n in Mexico in 1982, Laki volcano in Iceland and Asama Volcano in Japan in the year 1783 and Krakatau volcano of Japan in the year 1883 have all impacted global climate and atmorpheric dynamics.

Readers are introduced through this chapter to a geohazard (Landslide) that is most frequently publicized in mainstream media. Systematic examination of landslides and associated structural, tectonic, geological, geomorphological, meteorological, hydrogeological characteristics and land use pattern of Nilgiri hill area had indicated that steep slope, dipping of rockstowards slope, presence of clay layering in weathered rock types, events of continuous heavy rains, flooding on the slopes and improper land use practices play a major role in the genesis of landslides. Inaddition, ongoing seismotectonic activities in Southern Granulite Terrain of South India and reactivation of hidden blind shear zones were identified to be causative factors of recent increase of landslide occurrences.

INTRODUCTION

The downward movement of consolidated and unconsolidated soils and rock en masse from any geomorphic feature due to natural or manmade causes under the influence of gravity is termed as landslide (GSI, 1982). Nevertheless, presence of water, clay material, weak joints, favorable slope and many other characteristics also act as catalysis for this event. Landslides are one of the common geological hazards that affect countless population in India, especially in hilly terrains. Different reasons have been ascribed to different landslides of various terrains. Among them, reactivation of Bhavani shear zone (Prasannakumar and Llyod, 2007), high anthropo-geomorphic intervention (Basu, 2005), local geology, precipitation and slope (Bhattacharjee, 2005), presence of local vertical faults, triangular facets, abrupt deflection of streams and neotectonism

This chapter provides an introduction to cyclogenesis, nature of cyclone disaster and historic events. The mechanism that is in practice in cyclone mitigation, information dissemination and relief and rescue operations are detailed. As the state of Orissa is being battered more frequently by cyclones than any other state of India, special emphasis on cyclone disaster management system of Orissa is also discussed.

INTRODUCTION

Orissa state with immense natural resources is located between 17⁰27’N and 22⁰34’N latitudes and meridians of 81⁰27’E and 87⁰29’E longitudes. Orissa lies on the eastern coast of India with the waters of the Bay of Bengal swirling along its eastern and southeastern boundaries. It shares its boundaries with West Bengal and Jharkhand on the north, Chattisgarh on the west and Andhra Pradesh on the south. Out of the Indian mainland coastline of 7500 km, it constitutes a coastline of about 480 km. It extends for about 155,707 sq.km accounting about 4.74% of the total area of India. According to the 2001 census, it has 3.57 percent of the total population of India. Administratively, it has 30 districts, 3 Revenue Divisions, 58 Sub- Divisions, 51,061 villages and 127 Urban Centers.

Based on physiography, Orissa can be divided into three broad regions - the coastal plains, the middle mountainous region and the plateaus, and rolling up lands. The coastal plains extend from the River Subarnarekha in the north to the River Rushikulya in the south. The coastal zone covers nine districts namely Ganjam, Puri, Jagatsinghpur, Kendrapara, Jajpur, Khurda, Cuttack, Bhadrak and Balasore. It is narrow in the north, widest in the middle, narrowest in the Chilika coast and broad in the south. The coastal belt of Orissa lacks hills excepting few hillocks and mounds in the northern and southern parts. It has extensive low lands adjacent to the sea, sloping gently towards the shoreline of the Bay of Bengal. The coastline consists of the lakes, lagoons, marshes, bays and islands and natural harbors. The lakes in Orissa are natural and artificial. One of the blazing example of the natural lake is the Chilika lake.There is only one bay in Orissa which is the Hukitola bay. Eventually there are only two islands in Orissa - the Short’s Islands and the Wheeler Islands. Among the natural harbor, there is only one of its type in Orissa i.e. Paradeep which holds its recognition as the deepest natural port in the whole of India. The main drainage system of this area is represented by several rivers at their old stages flowing sluggishly towards the sea, which form topographic features like peneplains, natural levees, deltas, etc. (Fig.1). The major rivers flowing in the coastal belts are the Subarnarekha, the Budhabalanga, the Baitarani, the Brahmani, the Mahanadi and the Rushikulya. This region is the combination of several deltas of varied sizes and shapes formed by these rivers. The coastal belt has an area of 40,166 sq. km with a population of 68,79,379, which is 45 percent of the population of 9 coastal districts of Orissa.

Despite widespread occurrence and its potency to inflict heavy causalities and damage to economy, generalizations could not be made to define “drought” – leave alone characterization, development of predictive model and common mitigation measures. Regional variation, be it definition or symptoms or causative factors or consequences and mitigation measures is the hallmark of drought. This chapter is an attempt to present a review on characteristics of drought for the benefit of devising mitigation and reclamation measures.

INTRODUCTION

“Drought” denotes the meteorological, agricultural, environmental, climatic, social, economic and political consequences of a gap between the water availability and demands for the needs of domestic, irrigational, industrial, commercial and recreational consumption in an area over extended period of time. As these demands vary from region to region and depend on too many parameters such as quantum of rainfall, geological and soil characteristics, land use, population, economic activity, climatic conditions, population and culture, drought conditions of an area may not have characteristics of some other region.

This chapter explains how natural disasters are major catastrophic events, which are often aggravated by human intervention, resulting in adverse conditions affecting both natural resources and human habitats. Though drought is as disastrous as any other geohazard, it differs from other geohazards such that it is a ‘creeping phenomenon’, making its onset and end difficult to determine. Only a continuous monitoring of critical parameters ranging from crop failure to joblessness and shifting population, etc, could indicate drought in an area. In this chapter, we demonstrate a GIS based drought forecasting and monitoring model taking Gubbi Taluk of Karnataka as a case study. The approach includes creation of a spatial database of 17 critical parameters and their integration in GIS environment by developing a suitable rating and ranking scheme for the generation of drought severity map. The results have shown that drought could be monitored with the studied parameters and if suitable remedial measures are implemented, their effectiveness could also be monitored with this GIS model.

INTRODUCTION

India is a large country in terms of geographical area, exhibiting greater agro-climatic variation. The country is susceptible to several natural disasters, which are a major constraint to developmental activities. 

This chapter portrays flooding as a geohazard that can be managed with ease through simple and effective measures. Flooding is a recurrent geohazard that affects vast lands in India and elsewhere. Unlike many other geohazards, flooding event and probable area to be affected could be predicted with fairly accurate levels and hence, proper safety measures could be taken easily. However, as flash floods could not be predicted and the nature of flooding hazard that it brings in added danger of health hazard, crop damage and cutting off of supply and communication networks, flooding is as serious threat as any other geohazard. Scientifically designed urbanization and flood control measures are suggested for minimizing the potential impacts of flooding.

INTRODUCTION

Flooding is defined as a temporary submergence of a large area (that normally remains dry) under water by overflowing rivers and reservoirs as a result of heavy rains, high winds, cyclones, storm surges, tsunami, melting of snow or dam burst (Arya et al. 2005). The term “temporary submergence” denotes a time period ranging from few hours to about few months depending on type and location of flooding. Although flooding is a natural phenomenon that plays a major role in replenishing wetlands, recharging groundwater and supports agriculture, extreme demands on natural resources due to population growth, people and their property move closer to water bodies

Many types of geological hazards namely, tsunami, earthquakes, tsunami, floods and drought affect coastal areas like any other place on the Earth. As coastal regions are thickly populated and have abundant urban, industrial and recreational establishments, impacts of geohazards are always severe along coastal regions. Compliance to coastal zone regulations, with protection of sanddunesandmangroveswillbe the best mechanism to minimizethe damages from such hazards. In future, climate change may result in more hazards such as erratic rainfall and increase the frequency of droughts, floods and storm surges, etc. In this context, proposed coastal management zone for the coastal protection, disaster mitigation and management tools in coastal areas are examined in this chapter. It is suggested that extensive use of GIS and development of Geodatabase for the risk prone areas will serve as efficient tool for planners and policy makers to deal with geological hazards. In addition, it is felt that more efforts are needed in legal and institutional framework for integrated disaster management planning on local as well as national level.

INTRODUCTION

Geologic hazards are natural geological processes that inflict severe damage in areas of their operation if the area is utilized by anthropogenic activity in terms of habitation, industrial, recreational or commercial establishments. Many a times, natural geological processes that operated uninhibited for millions of years turn into geological hazards due to human intervention. These losses – lives and economic are not evenly distributed and are more prevalent in the developing countries due to higher population concentration and low level of economic growth. United Nations had realized the need of reducing these losses due to natural disasters and declared the last decade (1991-2000) as the International Decade for Natural Disaster Reduction. Objective of this proclamation was to reduce, through concerted efforts, the loss of life, property damage and socio-economic disruption caused by the natural disasters particularly in the developing countries (Tewar, 2000).

This chapter documents shoreline changes of the Dakshina Kannada and Udupi districts of Karnataka State for the period between 1967 and 2005 studied by comparing the SOI topographic maps with IRS-1C/1D LISS-III satellite imageries through GIS techniques. Examination of coastal geomorphology, sediment flux and effectiveness of seawalls had indicated that the 130km long coastline of Dakshina Kannada and Udupi districts is essentially stable, but for seasonal variations. It has been estimated that, out of 130km, about 55km long coast is vulnerable to sea erosion, of which, 25km is covered byseawalls and covering another 10km length underway. It is revealed through field examination that protection of coastline through these measures is satisfactory only along few patches while other stretches of seawalls simply shift the zone of erosion to adjacent coastline owing to many reasons including quality of construction, unscientific positioning of seawalls, etc. It is also inferred that same is the case of many other coastlines elsewhere including Kerala coast. These experiences warrant scientific design and implementation of coastline protection measures.

INTRODUCTION

The 130km long coastal zone of Dakshina Kannada and Udupi districts is one of the densely populated coastal zones of India. The coastline is almost straight, regular and oriented towards N22°W, N12°W and N6°W directions at south of Mangalore, north of Mangalore and north of Malpe respectively. Barrier beaches and spits, ancient beach ridges, marshes, swamps and tidal flats characterize this zone. Natural features and man-made structures interrupt the shoreline. The natural features include estuarine mouths of Netravati-Gurpur rivers near Mangalore, Mulki-Pavanje rivers near Mulki, Udyavara river near Malpe, Sita-Swarna rivers near Barkur, Kollur-Chakra-Haladi rivers near Kundapur and rock exposures near Someshwar, Surathkal, Mulur, Kapu and north of Malpe (Fig. 1). The man-made structures include one major and four minor ports; breakwaters at the Netravati-Gurpur estuary, New Mangalore Port and Malpe harbor and a number of seawalls placed at various places along the coastline (Fig. 2). All these structures/features bring about local irregularity and contribute to erosion and accretion along the shoreline to some extent. Apart from these, source of beach material, coastal processes like wave refraction, longshore current, littoral drift etc.