Risk Mapping of Natural Hazards in Shibalaya Upazila of Manikgonj District

Statement of the problem

Bangladesh is known as a disaster prone country in the world. Multifarious hazards, for instance riverine/heavy rainfall flood, drought, dense fog, storm, earthquake, etc. strike this country due to its geographical position, climatic and weather disparity. Since Bangladesh is a riverine country so almost every year it has to face area based river erosion resulting the destitution of the river levee people. On the contrary, canal siltation problem is posing concerned dilemma to the inhabitants of this area. Beside these anthropological and technological/industrial hazards always keep the inhabitants fearful and impede the regular livelihood activities. Due to these hazards the assets, lives, livestock & poultry and crops are affected highly. Thus causes hamper not only to the affected community but also keep immense impact on the national socio-economical condition. Bangladesh, is also lying in the disaster prone area of the world is facing risk of people’s livelihood, society and environment.

Manikgonj is a small district of Bangladesh which is more vulnerable for various natural disasters. Manikgonj is located  in  60 km. far from Dhaka. It is surrounded by many large and small rivers.For these rivers Flood and River bank erosion is a common phenomena of this area.

 The present study Upazila Shibalaya of Manikgonj district is more vulnerable to the natural hazards due to its location. Shibalaya Upazila is exposed to various hazards like river erosion, riverine flood, drought, storm, tornado, heavy rainfall, water logging etc. The study area is situated in low lands and is bounded by the Jamuna, Padma, and Ichamoti rivers and transacted by the numerous khals.For this reason most of the area of this Upazila is highly vulnerable to riverine flood and river bank erosion.So people of this Upazila are very much vulnerable to such multifarious hazards. Almost every year this upazila is affected by area based alternate hazad and causes serious hamper to the livelihood activities and to their lives and assets.

Manikganj is selected as the study area because the area frequently affected by flood. Three  rivers – Padma, Dholeshwri, kaligonga run through this area. Most of the people of this area are vulnerable to flood and experiencing loss due to flood. (Banglapedia, www. Wikipedia.Manikganj_District.htm).

Aim & Objectives:

This research aims to risk mapping of natural hazards in Shibalaya upazila of Manikgonj district. The following aspects have been set for report:

1. To give an overview of the natural hazard of Shibalaya upazila.
2. To identify and mapping the Shibalaya upazila in different  zones in terms of severity of various natural hazards.
3. To assess the risk of different natural hazards such as flood, river bank erosion etc.

Literature Review

Literature review is one of the important part of a report. It will help to get better understanding of a topic. Many literatures are available in the field of natural hazard and disasters risk and vulnerabilities both in Bangladesh and other countries. For this study a lots of book, journals, legislation, policies, plans, Statistical year book etc. have been consulted and observed. Some of these are studied for this study.

Paul (2006) in his research discussed the major impacts of flood on the socio- economic and demographic context of the study areas. According to him the major impacts are loss of land, home, man day of employment and other valuable assets, death and injury of people. Due to flood along with river bank erosion homeless and landless people are forced to migrate and this creates negative impacts on the socio- economic condition of the locality but also create pressure on the towns and cities. Though several flood mitigation services are available in the areas but the services are not satisfactory at all to local people. The main causes of non- satisfaction of the flood mitigation services in this area is lack of proper planning, no involvement of local people in flood management, no local flood action plan.

 Choudhury (2007) the natural location is the major reason of the occurrence natural disasters. Some other reasons are siltation of rivers , deforestation, excessive use of ground water and other natural resources. The natural disaster become the part of life of people in this world. People try to match with this condition to live. Several measures are already taken to mitigate this like construction of embankment and cyclone center, flood and cyclone forecasting warning system etc. but are not sufficient and well planned. As a result every year the country has to face huge damage due to these natural disasters.

Winterscheid (2007) it is now commonly accepted that the management of flood risks has to be fulfilled within an integrated framework. About two decades ago flood risk was managed from a limited perspective predominantly by means of structural measures aimed at flood control. In contrast integrated flood risk management incorporates the complete management cycle consisting of the phases prevention, protection and preparedness. In theory it is a well described concept. In the stage of implementation, however, there is often a lack of support although a consistent policy framework exists. Consequently, the degree of implementation must be rated as inadequate in many cases. In particular this refers to the elements which focus on preparedness and prevention. The study to which this paper refers emphasises the means and potentials of scenario technique to foster the implementation of potentially appropriate measures and new societal arrangements when applied in the framework of integrated flood risk management. A literature review is carried out to reveal the state-of-the-art and the specific problem framework within which scenario technique is generally being applied. Subsequently, it is demonstrated that scenario technique is transferable to a policy making process in flood risk management that is integrated, sustainable and interactive. The study concludes with a recommendation for three applications in which the implementation of measures of flood damage prevention and preparedness is supported by scenario technique.

Balica (2009) et al. Populations around the world are vulnerable to natural disasters.

Such disasters are occurring with increased frequency as a consequence of socio economic and land-use developments and due to increased climate variability. This paper describes a methodology for using indicators to compute a Flood Vulnerability Index which is aimed at assessing the conditions which influence flood damage at various spatial scales: river basin, sub-catchment and urban area. The methodology developed distinguishes different characteristics at each identified spatial scale, thus allowing a more in-depth analysis and interpretation of local indicators. This also pinpoints local hotspots of flood vulnerability. The final results are presented by means of a standardised number, ranging from 0 to 1, which symbolises comparatively low or high flood vulnerability between the various spatial scales. The Flood Vulnerability Index can be used by international river basin organisations to identify and develop action plans to deal with floods and flooding or on smaller scales to improve local decision-making processes by selecting measures to reduce vulnerability at local and regional levels. In this work the methodology has been applied to various case studies at different spatial scales.

Dey (2009) river bank erosion is a perennial problem in Bangladesh, causing loss of lands and livelihood along major rivers. Structural and non-structural interventions are needed to prevent potential loss of land and livelihoods. River bank erosion is also a serious problem of Bangladesh. In fact the rivers which cover about 3.4 million hectares of lands are susceptible to widespread bank erosion. Riverbank erosion is possible at any riverbank site. Past records of erosion or lack of erosion are not good indicators of the potential for future erosion at any particular site. Records of riverbank erosion are not kept but past aerial photographs may give an indication of past erosion. Long serving staff will have knowledge of some historical erosion sites.

In this country about 70% of the total area is formed by alluvial deposit where silts and silty clays predominate the top 15m to 25m and clays , sandy silts and sands dominate at the deeper depths. The soil in the upper layers are mostly non cohesive and therefore, easily vulnerable to erosion and scouring . A network of 250 rivers having a total length of 2400km cover the country flowing down into the Bay of Bengal in an average year 775000Mm of water flows through the river systems of the Ganges, the Brahmaputra and the meghna and their tributaries during the monsoon month i.e. from june to October .Bangladesh receives an enormous sediment inflow during this period from the upper catchment of this three rain rivers. The marked seasonality of river flow in this country is responsible for erosion during the monsoon due to strong current and sedimentation during the dry season.

Sarker (2004) et al. Bangladesh having an area of 144, 000 sq km and a population of about 110 million (about 800 persons per square kilometer) is a disaster prone country. Almost all types of disasters like flood, cyclonic storms, tidal surges, droughts, tornadoes, riverbank erosion and earthquake occur in Bangladesh regularly and frequently. Cyclones and floods are major disasters in Bangladesh. But other disasters are also creating severe damages. Drought leaves a permanent damage and encourages the desertification process that is going on in some parts of North Bengal. River erosion takes away thousands of hectares of land every year in a country where land is the scarcest resource. Earthquakes may cause millions and billions of Taka worth of damage. Perhaps the most disturbing but ignored fact about disasters is that they are all linked to each other. Now a days it is an important issue to know the disaster prone areas and their effect to any kind of environmental planning in association with the different field of sciences such as engineering, agriculture and fisheries. GIS based disaster database is very crucial and an important aspect for environmental management strategy for planning. This study will find out the disaster prone areas of Bangladesh and also the damages, history, severity of these areas. This information will assist the environmental management and planning of Bangladesh.

According to Asian Disaster Preparedness center (2004) Environment and disasters are inherently linked. Environmental degradation exacerbates the impact of natural disasters. It affects natural processes, alters humanity’s resource base and increases vulnerability. The degree to which environment can absorb impacts, increase overall resilience and provide effective and economical solutions to reduce disaster risks is therefore jeopardized. Furthermore, societies’ traditional coping strategies are challenged. (ISDR 2002) Adaptive capacities of ecosystems to absorb sudden shifts in climatic, geological or biological components are a key feature increasing disaster resilience. (ISDR 2002). Understanding these critical thresholds is crucial for estimating site specific impacts of environmental change and evaluating the potential prevention dividends associated with environmental management. The following sections take a closer look at physical parameters of hazard risk.

In 1987 Haque discussed the general impacts of hazards in the Lower Brahmaputra (Jamuna) floodplain of Bangladesh. The impacts of bank erosion hazards have been assessed in terms of loss of land, change in occupation, and impacts on social ties and relationships. The basis of analysis of impacted was a survey conducted on 547 randomly selected displaces households. It is indicated that a large number of household who had agriculture as their primary occupations became labour following dislocation by the bank erosion hazard. The paper concluded that some social measure should be undertaken to ameliorate this problem. He discussed on the general impacts of erosion hazards in the lower Brahmaputra (Jamuna) floodplain of Bangladesh. The author also focuses on the nature of perception of hazards among floodplain inhabitants and also on the indigenous adjustment strategies to cope with the hazard effects in “Human Responses to Riverbank Erosion Hazard in Bangladesh. Some lessons from Indigenous Adjustment Strategies.”

Nazem, (1988) in his paper gives an overview of environmental disaster in South Asia. Flood, riverbank erosion and drought have been considered as the major types of disaster. The intensity and the extent are not same in all the countries. The author also discussed the impacts of natural disaster under the heading of economic, social and political impacts. The paper concluded that the measures of disaster management in all stages including planning, designing and implementation at the regional levels should be coordinated as a part of an integrated regional system in order to ensure long term variability and effectiveness. Nazem (1988) gives a general overview of environmental disaster in South Asia.

It is pointed out that a large amount of land, which emerged as a result of riverbank erosion, needs proper survey in order to bring this land within government control. It is shown how through selective violence a few land grabbers maintain control over Char land and settlement. The paper cited examples how government backed programme for the distribution of land to landless has been threatened by the unscrupulous jotedars in collaboration with the local politicians and dishonest officials.

Zaman, (1986) emphasizes on the behavioral approach to natural hazard studies. The author argued that the individual response to natural hazards should be studied in broader socio-political and historical context. This approach is useful for understanding the individual, the family and community response. The author applied this idea by examining aspects of social and cultural life of people who are displaced by riverbank erosion in the Brahmaputra-Jamuna floodplain. Attention has been paid how friends, relatives, corporate groups, village fictions and patronage system influence adjustment and resettlement option of the erosion displaces

The rivers are characterized by channels shifting (Chowdhury, 1959& 1981; Chowdhury, 1979; Kamaludin, 1973; Miah, 1975; Saad, 1975; Rudra & Bandyopadhyay, 1981; Haque, 1997; Mamun & Amin, 1999). The Jamuna has also changed its course since geological past (BWDB, 1973; Coleman, 1968; EGIS, 1997). Geological evidence shows that Bangladesh owes its existence to the rivers and their floods.

Some of the above literature related to riverbank erosion proved useful information on the trend, pattern, and change in bank erosion. There is still a serious dearth of documentation in early define policies and strategies as regarded the bank erosion with context to the population redistribution of the country. This indicates the relevance to research interventions on this and related issues.

The present study of  Shibalaya Upazila focuses upon the risk mapping of flood and river bank erosion of perception in a micro-level context.

 Methodology of the Study

The present study has been carried out mainly based on secondary data and information. Indeed, this report is a desk study and overall the report is based on material available on the Internet and library as well as personal communication with relevant organization of Dhaka city and study area.

A Conceptual Overview of the Natural Hazard Risk Mapping of Bangladesh: Flood and River Bank Erosion has been discussed in order to gain the proper understanding of different aspects including theoretical framework about natural disaster risk mapping. Besides other relevant literatures have been collected through the internet and library. After than an analysis has been carried out on the existing risk of the study area. This analysis has been done by the both maps, tables, graphs, photographs, statistical m and description. Some maps were used directly from the collected sources and were reconstructed. After than some important key social and economic which are mainly affected by flood and river bank erosion have been identified and discussed. Finally some recommendations have been reconstructed to reduce risk of several disasters.

The present report includes the secondary information that were collected from various relevant organizations, for instances Union Parishad Office and other upazila level government offices and validated through the Focus Group Discussions (FGD).

As the second research is based on secondary information these may lead to certain limitations. Different organizations show the different figures for the same issues for the same period. Besides, sufficient updated data are not available for all priority issues. Maps and documentation also indicates past record on different issues rather than recent date.

The following steps will be used in achieving the goals and objectives of the study:

Conceptualization:

First of all the research problem is selected considering the interest field of work and then concept about the research problem is tried to clear.

 Selection of the Study area

Manikganj is a flood and  river bank erosion prone area and almost every year it affects by

flood and river erosion. So, taken into consideration the study purpose study area has been selected.

 Literature Review

To conduct any study a clear idea about the problem is necessary. For this study a lots of book, journals, legislation, policies, plans, Statistical Year Books etc. have been consulted, observed. It will help to get better understanding.

Preparation for Field work

A field survey will be conducted to know the existing scenario of different disasters risk and vulnerability.

Collection of Information

Secondary Information review of literature, relevant journals, published and unpublished materials such as different books, BSc, MSc thesis, reports related to  disaster management etc.

Analysis of Data and Information

After gathering all the necessary data it will be present in a tabular form and cross checked. The tabular data will be present in text, chart etc. and will be tried to provide some recommendation on the basis of some disaster management model.

Report preparation

After completing the above work the study will be present by using MS word software. For map and calculation GIS and Ms Excel will be used respectively.

Structure of the Report

To organize the study, different theme is presented in various chapters.This report has been prepared based on the above methodology and is composed of is five chapters with a number of sections and sub- sections and the sequence of these chapters follow the chronological development of research.

Chapter one

It comprises Outlines the problem formulation, aim and objectives, literature review, methodology and structure of the report.

 Chapter two

It discuss about Environmental setting of the study area. Different environmental aspects have been discussed in this chapter with relevant data and table.

Chapter three

It divides into two sections. First section provides an overview of the hazard, disaster, vulnerability and risk. Second section discusses about an overview Natural Hazard Risk Mapping of Bangladesh and Flood and River Bank Erosion in the study area.

Chapter four

This chapter divides in two sections. First section analyzes the flood risk mapping of the study area and second section analyzes the river bank erosion of the study area.

Chapter five

Draws conclusion with a brief discussion about the result. Some recommendations have constructed to reduce risk of natural disasters also discussed in this chapter.

 CHAPTER TWO

 Physical Environment or structure of the study Area

Shibalaya upazila is formed by old Ganges alluvial land, new Brahmaputra alluvial land and active Brahmaputra alluvial land. The entire region is almost plain to little wavy terrestrial lands along with some depressions (beels). Higher terrestrial lands (settlements) of the area do not inundate during the usual monsoon. In rainy season, some of the medium height terrestrial lands inundate by little depth to medium depth and the depressions inundate by medium depth to high depth. This area falls under the Agro-ecological Zone (AEZ) 7, 8 and12 (SRDI, 2000). Active Ganges alluvial land falls under the Agro-ecological Zone (AEZ)-10. This area is the newly formed sandbar, which is mostly transient but sometimes may be permanent in nature. This land is under the flood and river erosion prone area.

Agriculture

Agriculture is the life of the national economy as well as the life of economy of the present study area. Rainfall and temperature of an area determine the type of naturally grown vegetation and the varieties of crops and their yields. The soil and climate of this area is suitable for growing most of the crops that grow in Bangladesh.

Padma and Ichamoti Rivers feed water to the floodplain of Shibalaya upazila through numerous canals . A decade ago these canals carried alluvium to the croplands of the area during monsoon thus used to enhance the fertility of the croplands. Construction of unplanned roads and embankments reduces the occurrence of normal inundation of croplands significantly during the wet season. In the past, the rivers contained adequate water even during the dry season and these rivers used to recharge the groundwater aquifer. This phenomenon kept the topsoil moist which was suitable for crop production. In the near past ground water table was high and the cultivators could draw water using shallow tube-well and even by boring a shallow hole.

Presently about 75% of cultivated lands of the area are under irrigation scheme. . The crops, for instances high yielding Boro variety, maize etc. mainly need groundwater for irrigation due to unavailability of surface water and timely precipitation.

Net croplands of Shibalaya upazila stands about 2,672 hectares which are distributed under 4 agricultural blocks. The land elevation profile of Shibalaya upazila along with the hectares of the land distribution is shown in the following table 2.2

Table 2.1 : Total croplands of Shibalaya Upazila based on their the land type

Source: DAE, 2007-08, BBS, 2005 and SRDI, 2000, Shibalaya, Manikganj

Due to diversification of land elevation, cropping pattern is also diversified. This profile of land supports a wide variety of crops. The estimated cropping intensity of this upazila is about 203% (DAE, Shibalaya, 2008). The major cropping patterns along with the respective cultivated areas (Mohadebpur, Shimulia and Ulail) of the Shibalaya upazila are given in the following table.

           Table 2.2 : Major cropping pattern of the Shibalaya upazila

            Source: DAE, 2007-08, BBS, 2005 , Shibalaya, Manikganj

 Landscape features

Landscape feature of this upazila is very simple. The demarcation of the land elevation is not so prominent though the cropping pattern is versatile and changes according to land elevation. The most fascinating features of this upazila are the presence of large depressions and some natural bamboo forests that are scattered elsewhere in the upazila. The settlements are also scattered and mostly along the roads. Most of the houses are built with tin, timber, bamboo and jute stick.  The depressions of this upazila play a vital role to maintain the ecological balance

 Land use

The land of Shibalaya upazila is very fertile and productive. The landuse pattern of this upazila is diversified. Most of the croplands are cultivated with varieties of seasonal crops; some lands are occupied by settlements, market places, terrestrial roads and the rest are occupied by natural forests and water bodies. About 10-12% of the total land of this upazila is not cultivated as those land are used for settlements and other purposes.

 Soil texture

Total area of cultivable land of this upazila is about 2,672 hector. Soil texture of Soil texture of selected unions of Shibalaya upazila includes loam, clay, clay-loam, silt and sandy. Soil textures of the settlements are mostly clay to clay-loam.  Soil class-wise cropland area has been estimated for Shibalaya upazila which is presented in the following table 2.4.

                   Table2.3 : Soil texture and area of Shibalaya upazila

          Source: DAE, 2007-08, BBS, 2005 and SRDI, 2000, Shibalaya, Manikganj

Climate and Hydrology

 Rainfall trend

The average rainfall trend is downward. Although, the recent flood in 2004 occurred due to heavy rainfall. It is seen from the figure 8 below that heavy rainfall usually occurs in the period of June to August. During this period continuous three-day rainfalls generally occur several times in a year.

Source: Banglapedia 2006.

Natural resources

 Water bodies

Some perennial and large depressions (Beel) exist in the Shibalaya upazila. These depressions have high potential to build fish sanctuaries to lessen the fish related complexities. Besides these, some seasonal depressions are also scattered in the upazila. These depressions play a vital role in balancing the whole ecosystem and as a source of foods, goods and services of the area. The depressions of this area have been losing their characteristics and lives for the last decade.

Rivers and canals

Jamuna and Padma river flow from the west side of the upazila. A number of canals criss-crosses the upazila. These canals include Shahily chakar  khal, Kalagariar chakar khal, Maniknagar’s khal, Rogunatpura’s khal, Udir barir khal, Dubliar khal, Kazir barir khal of Mohadebpur union,  Kalshirs khal, Kalnir khal, Munail khal, Monsol barir khal of Shimulia union and Machail khal, Charipara khal, Koira khal, Rupsha khal, Ulail khal of Ulail union etc. These rivers and canals keep vital role in feeding water to the countryside as well as in receding floodwater. These rivers and canals also keep significant role in recharging of groundwater. The in-stream functions of riparian people are manifolds, for instance human and cattle bathing, fishing, etc. and the off-stream functions include kitchen use and surface water irrigation to the croplands, etc.

River system of Manikgonj district

The network of rivers, streams and canals, constitute about 100 kilometers in length and 400 Sq.km in area. The watercourses are obviously not evenly distributed. They increase in number and size from the north-west of the Northern Region to the south east of the Southern Region. There are three major river systems in Manikgonj district, namely the Jamuna (The Brahmaputra-Jamuna), Dhaleswari-Kalinganga and Isamati. Besides, there are many small rivers and channels are present here. Most of the river courses appear to be rather stable. About 95 percent of the area is affected by seasonal flooding. Depth and duration of flooding vary with topographical position and are mainly controlled by the levels of the main rivers and their tributaries. Ridges are mainly seasonally shallowly flooded from few weeks up to four-five months.

 The Brahmaputra-Jamuna river system 

The Brahmaputre-Jamuna River is one of the largest fine-grained sandy braided river system of the world (Bristow, 1987) and the second largest river in Bangladesh (Rashid, 1991). It is a fine grained (Reinec & Singh, 1980) large scale sandy (Alam, 1992) braided river. The river is highly braided channel characteristics (braided indices 5.3 to 6.7) in Assam, India (Goswami, 1983) and in its Bangladesh reach, displays a braided pattern in plan view (Colman, 1963; Alam, 1991) but some reaches are amastomosed or meandering (Bristow, 1987). The Tsangpo-Dihang Brahmaputa-Jamuna originates from Chemayung dung Glacier in the Kailas range of the Himalayas. The Ysangpo is the name of the river while it runs through Tibetan country. During its curse through ‘tribal territory’ the vermacular name Dihang is in use and from its entry in to the plains of Assam it is known as Brahmaputra.

Then the Brahmaputra curve southwards and enters Bangladesh through the Garo-Rajmohal gap and receives on its right bank the Dharla and the Tista Rivers and flows almost due south for approximately 220 km to its confluence with the Padma (Ganges). The combined flow of the two rivers is called Padma River. The Padma flows southeast for about 100 km before meeting the Megna River. The Megna estuary meets the open sea of the Bay of Bengal about 160 km to the south of this confluence. The total length of the Brahamputra-Jamuna from the source to its confluence with the Padma (Ganges) is about 2096 km (Chowdhury, 1989).

The Himalayan watershed of the Brahmaputra comprises four topographic units that rise progressively to the north (Goswami, 1985). The lower most range called the sub-Himalayas (Average Elevation 1000 m) consists mainly of tertiary sandstone and is conspicuous by the presence of many raised, relatively young terraces (Gansser, 1964). The middle Himalayas (average elevatin 4000m) are underlain by a thick horizon of basaltic rocks. The greater Himalayas (average elevation 6000m) consist primarily of granites and gneisses. Further to the north the Trans-Himalayas of Tibet (average elevation 4500m) are made up of sedimentary formations of Paleozoic to Eocene age (Wadia, 1968).

The Brahamputra-Jamuna valley in Assam (India) and in Bangladesh is underlain by recent alluvium approximately 200-300m. thick, consisting of clay, sand and pebbles (Geological Survey of India, 1974; Geological Survey of Bangladesh, 1989). Its present configuration evolved during 2 million years of Pleistocene and recent time (Murthy, 1968; Rao, 1989). Tectonic origin of the Brahmaputra-Jamuna valley and Assam Himalayas is suggested by a number of authors (Holmes, 1964; Evans, 1964; Mittal and Srivastava, 1969; Tapponnier and Molnar, 1977).

The Brahamputra-Jamuna valley and its adjoining highland constitute an extremely unstable seismic region. The earthquakes of 1897 and 1950 each of Richter magnitude 8.7 are among the most severe in recorded history. Both caused extensive landslides and rock falls on hill slopes, subsidence and fissuring of ground in the valley and changes in the cores and morphology of several tributary rivers (Oldham, 1988; Podder, 1952; Coleman, 1969).

During Rennell’s (1781) surveyed time, the main course of the Jamuna River in Bangladesh was the present channel of the old Brahmaputra. The course of the Jamuna River was then occupied by a narrow distributary’s of the Brahmaputra that was called Jhinai in the upper course and the Jamuna in its lower course. The diversion of the Brahmaputra from the old course to the present course was completed by 1830 (Hirst, 1915) and was caused mainly due to tectonic activities (Morgan and Mclnire, 1956). Although LaTouche (1910) offered a different explanation for the diversion of the Brahmaputra. A part of its volume began to flow through the Jhinai. LaTouche (1910) suggested that when the Tista diverted its water from the Ganges to the Brahmaputra in 1778, more water was added to the discharge of the Brahmaputra. The accelerated water in course of time opened a passage through the Jhinai and gradually began to increase the width of the channel, resulting into the present form of the Jamuna.

The Bangladesh reach of the Brahmaputra-Jamuna displays a braided pattern in plain view (Coleman, 1969) with numerous small bars locally called Chars and some reaches are anastomosed or meandering (Bristow, 1987), with few large Chars in the Jamuna are highly unstable and their size, shape and position change radically between each seasonal high flow (Coleman, 1969; Brisow, 1987; Alam, 1992). The overall channel complex of the river is about 15 km width, with individual channels of 3-3 km wide. During flood season, almost all the Chars are submerged, and these individual channels merge into one and the river channels become a gigantic one of more than 15 km wide.

The catchments of the Brahmaputra-Jamuna, excluding the Tibetan portion, forms an integral part of the mosoonal regime of Southeast Asia. Rainfall average 230 cm annually, with a variability of 15-20%. There is a marked spatial variation in the distribution of precipitation over the catchments.

The Brahmaputra-Jamuna is the fourth largest river in the world for average discharge in the month, with a flow of 1980 m per sec (Goswami, 1985). The maximum and minimum discharge recorded in the river is 75700 m per sec and 3950 m per sec respectively in 1984 (Bristow, 1987). Width / depth ratios for individual channels very from 50.1 to 500.1 and gradient in Bangladesh is 0.000077, decreasing to 0.00005 near the confluence with Padma river (Bristow, 1987). The Brahmaputra-Jamuna displays two or three flood peaks. The peak generally occurs during mid June and is characterized by an extremely rapid increase in discharge. Within a few days the discharge may increase from less then .60 m per sec to 1.60 m per sec. There are generally two flood peaks on the Brahmaputra-Jamuna (Coleman, 1969) that occur prior to flooding of the Jamuna. Thus undoubtedly the flood has a major influence on the pattern of the river migration and population displacement.

Table 2.4 : Average width of the Brahmaputra-Jamuna River

Source: EGIS, 1997.

 Dhaleswari-Kaliganga River System 

The Lohajang River branches off from the Jamuna north-west of Tangail town and the Dhaleswari branches off seven km to the south-west. These two join near Elashin and flow southeast as the Dhaleswari. The Dhaleswari bifurcates and the southern arm flows south of Manikgonj and joins the main stream, which flows north of Manikgonj 48 km to the south-east. Just north their confluence the again bifurcates, the southern arm retaining the name, while the northern is called Buriganga (Old Ganges). It flows past Dhaka and joins the Dhaleswari at Fatulla. The Laklya at Narayanganj joins the Dhaleswari

Conceptual Overview of the Hazard related terms

Bangladesh is a riverine country and during June-September, with the commencement of yearly monsoon rain, flood and bank erosion appears as conspicuous features in about 40 of its major and minor rivers. Bank erosion and flood hazards in nearly 100 thanas have become almost a regular feature in recent years. Of these recurrent banks erosion has become most extensive in about 40 thanas. It is estimated that about 1.5 million people are directly affected each year by bank erosion in the country. Most of them suffer from the consequences of flood hazard many end up as landless displaces. The total monetary loss is estimated at the tune of Tk.20000 million a year.

Hazard

Hazard is referred to the potential for harm that is brought about by interactions between people and nature or by interactions between people and technology. A potentially damaging physical event, phenomenon or human activity that may cause the loss of life or injury, property damage, social and economic disruption or environmental degradation

Hazardous Condition:

Hazardous conditions set stage for future harm. They may go unrecognized until a disaster calls attention them.

 Classification of Hazard

A hazard is therefore a phenomenon or a process, either natural or human made, that can endanger an group of people, their belongings and their environment, if they do not take precautions.

 “…phenomena that poses a threat to people, structures, or economic assets and which may cause a disaster. They could be either manmade or naturally occurring in our environment.”

 Hazard Classification:

i) Natural Hazards: Natural hazards are purely natural and not induced by, or controlled by, humans. Example: earthquake, volcanic eruption, floods, landslides, etc.

 ii) Mixed Hazards: Mixed hazards are natural in character but influenced by human actions. Example: landslides in developed areas, river floods in developed areas, dam failure, etc.

 iii) Technological Hazards: Technological hazards are generated by human actions. Example: subsidence in subsurface mines, failure of nuclear power plant, disposal of toxic wastes, etc.

 Disaster

Disaster is a compound function of the natural hazard and the number of people, characterized by their varying degrees of vulnerability to that specific hazard, who occupy the space and time of exposure to the hazard event.

 Disaster is an event, concentrated in time and space, in which a community undergoes severe danger and incurs such losses to its members and physical accessories that the social structure is disrupted and the implementation of all or some of the essential functions of the society is barred.

 Therefore,        Disaster = Hazard × Vulnerability

Disaster is an unexpected natural or man-made catastrophe of substantial extent causing significant physical damage or destruction, loss of life or sometimes permanent change to the natural environment. (Disaster Report 2002).

“any occurrence, that causes damage, ecological disruption, loss of human life, deterioration of health and health services, on a scale sufficient to warrant an extraordinary response from outside the affected community or area”

… WHO, 2006

“Disasters are an outcome of the interaction of a ‘hazard’ event and a vulnerable set-up of the physical and/or social environment”

…Wisner et al, 20

Vulnerability

It is defined as “the extent to which a community, structure, service, and/or geographic area is likely to be damaged or disrupted by the impact of particular hazard, on account of their nature, construction and proximity to hazardous terrain or a disaster prone area”

 Risk

Risk is a measure of the expected losses (deaths, injuries, property, economic activity etc) due to a hazardous event of a particular magnitude occurring in a given area over a specific time period. Risk is a function of the probability of particular occurrences and the losses each would cause. The level of risk depends on:

i.     Nature of the Hazard

ii.    Vulnerability of the elements which are affected

iii.   Economic value of those elements

Risk is expressed as the product of a monetary value and a probability; therefore, the units of risk are the units of monetary value.

Equation of risk,         R = p × L

             Where, R = Risk,

                         p = Probability of occurrence of an event or consequence,

                         L = Loss (value of consequence arising from an event)

Hazard assessment

The objective of a hazard assessment is to identify the probability of occurrence of a specific hazard, in a specific future time period, as well as its intensity and area of impact. For example, the assessment of flood hazards is extremely important in the design of engineering facilities and in zoning for land use. Construction of buildings and residences is often restricted in high flood hazard areas. Flood assessments should be developed for the design of sewerage treatment facilities, as well as for sites having industrial materials of a toxic or dangerous nature.

        Table 3.1: Difference between risk assessment and risk perception.

            Source: Wikipedia, 2007.

 Vulnerability and capacity assessment

Vulnerability/capacity assessments are an indispensable complement to hazard assessment exercises. Despite the considerable efforts and achievements reflected in the improved quality and coverage of scientific data on different hazards, the mapping and assessment of social, economic and environmental vulnerabilities of populations are not equally developed. Some aspects of the social nature of vulnerability/capacity pose different challenges to risk assessment. A great deal of work has been focused on the assessment of the physical aspects of vulnerability. This has been done mainly in relation to more conventional hazardous phenomenon, such as windstorms, earthquakes and floods. The spatial overlapping of hazard zones with infrastructure such as airports, main highways and health and power lines is commonly used in the examination of the physical aspects of vulnerability.

 Risk assessment

A methodology is  to determine the nature and extent of risk by analyzing potential hazards and evaluating existing conditions of vulnerability that could pose a potential threat or harm to people, property, livelihoods and the environment on which they depend. Risk assessments include detailed quantitative and qualitative understanding of risk, its physical, social, economic and environmental factors and consequences.“Risk assessment is a required step for the adoption of adequate and successful disaster reduction policies and measures.” Risk assessment encompasses the systematic use of available information to determine the likelihood of certain events occurring and the magnitude of their possible consequences. As a process, it is generally agreed that it includes:

• identifying the nature, location, intensity and probability of a threat;
• determining the existence and degree of vulnerabilities and exposure to those threats;
• identifying the capacities and resources available to address or manage threats; and
• determining acceptable levels of risk.

Table 3.2: shows the basic stages undertaken in a risk assessment process. The identification of hazards is usually the starting point for a systematic assessment of risk.

Source: Wikipedia, 2007.

 Risk Mapping

Risk MAP combines flood hazard mapping, risk assessment tools and Mitigation Planning into one seamless program. The intent of this integrated program is to encourage beneficial partnerships and innovative uses of flood hazard and risk assessment data in order to maximize flood loss reduction.

Flood risk mapping of Bangladesh

Bangladesh is a riverine country and during June-September, with the commencement of yearly monsoon rain, flood and bank erosion appears as conspicuous features in about 40 of its major and minor rivers. Bank erosion and flood hazards in nearly 100 thanas have become almost a regular feature in recent years.

Floods are also common phenomena in Bangladesh. The people of this country have a long history of coping with flood. They have demonstrated a variety of responses are basically uncoordinated, unorganized and are not well internalized with the rural development activities.

Source: Disaster Report, 2007,

The devastating floods of the recent past occurred in 1974,1987,1988,1998,2004 (Rainfall) and 2007. In 2004, Bangladesh experienced one of the most devastating floods in nearly 50 years. About 38% of the country went under water. The damage caused by the flood was to the tune of US$ 2 billion. The most affected were the poor the most vulnerable in such disasters.

Table 3.3: Risk Statement Associated With Flood Hazard

      Source:  mahmudul.islam@cdmp.org August 2009

Erosion as a Hazard

Hazard is defined as a natural or artificial destructive process, which affects the human civilization, nature and environment. The devastating process, which does not do any harm to the nature, is not defined as hazard (Hossain, 1984). Natural hazard depend on the interface between the physical environment and human use system and the state of natural event system (Kates, 1971:438). There are so many natural processes, which sometimes occur as hazard, such as flood, riverbank erosion is a common problem for Bangladesh, which destroys lots of lands, houses, and crops and makes man landless. There is a difference hazard and disasters. Cannon (1977; 1994) makes a distinction between hazards and disasters in the context of vulnerability. As he puts it “hazards are natural but in general disasters are not and should not be seen as the inevitable out come of hazards impact” (Cannon, 1994; 13). The emphasis here is on the condition of the people. Which creates the context for a hazard to become a disaster. This includes the degree and types for their vulnerability in association with the technical of how society interfaces with the hazard in terms of mitigation and preparedness. Cannon insists that opportunities and risks in the environment for the society at as well as for individual members are conditioned by varying characteristics of the social systems. This implies that there are no actual generalized opportunity and risks in nature but instead there are varying sets of access to opportunities and exposures to risks. These features are invariably related to the socio-economic system.

The Jamuna is naturally unstable river (Coleman, 1969). It swings at different directions at different reaches. As a result, Erosional hazard is going on along both banks of the river at different rates. In this research the term “Hazardous Zones” is used to indicate areas along the riverbank, which is under serious threat of river erosion.

Riverbank Erosion in Bangladesh

Riverbank erosion is one of the worst natural calamites in Bangladesh. Every year this render’s thousands of people homeless and destitute yet until 1993, the government did not river erosion in list of national disasters.

Riverbank erosion a quiet disaster takes place round the year but is not known to general mass because it is not publicized widely in the mass media. However a large number of peoples become homeless in Bangladesh due to riverbank erosion. Realizing its destructive nature river erosion was officially recognized as a disaster in 1993.

In this rivering Bangladesh more or less everywhere riverbank erosion continues. Generally in the rainy season the river takes its formidable form. High velocity of river current cuts the base of the riverbank causing erosion. But the erosions occur most by at the end of the monsoon. However, it has been observed from our experiences riverbank the erosion takes place just before monsoon sets in.

River erosion is a constant and age-old disaster that has rendered the formation of the char land of Bangladesh. Previously the population was a sizable one, but as it has risen in number, habitations have increased and extended to greater areas making erosion a matter of greater concern. Erosion is a continuous process for which the disaster fails to generate concern that other forms of disaster are capable of creating. Yet it causes enormous loss of lives and properties as any other. According to the satellite data the river consumes about 8,700 hectors of arable land every year. About 10,00,000 peoples are affected it (Disaster report, 1997). In 1998 6,00,000 households, about 5,00,00,000 peoples directly affected by the riverbank erosion (Disaster report, 1998). The populations are tillers of the land, who don’t have the capability of retrieving their loss and thereby migrate to the cities seeking means of sustenance. They are considered the floating populations with no defined job or social status.

 Riverbank Erosion in Manikgonj and the study area

Harirampur, Shibalaya and Daulatpur thanas of Manikgonj District have been subjected to severe erosion by the river Jamuna, Padma and Dhaleshwari. Erosion continued along the 87 km long banks under these thanas. In the last five years eleven educational institutions, nine mosques, one health complex and six river ports went into the water. These rivers also devoured 25000 acres of lands 4000 thousands farmers have been rendered shelter less and about 8000 families comprising of 50000 people were the victims of erosion. Due to its continuous erosion the total land area of the district was reduced. In Harirampur, 30% of the total land area has gone into the river. Out of the thirteen unions nine have already gone into the water. Three refugee shelters were erected in 1998 in Harirampur to provide shelter to the destitute out of which the Padma has already destroyed one. Within a span of hours the second largest trade centre of the district along with 500 shops went into the water of the Padma. Many houses, Zafarganj, Dublia Primary School, Mosque and temple of Shibalaya thana of the district also went into the water.

                                                                                                                      Continued

 Source: CDMP,2009.

CHAPTER FIVE

Recommendation

The research evidence has shown that the hazards has been partly caused by both the natural (siltation) and human (river bed cutting) system. Most have not also recovered from the disaster though it occurs almost every year. Poor disaster management policies and practices are partly to be blamed for the poverty and poor living conditions of the victims that seems to be a key determinant for their social vulnerability to the effects of the past disaster and subsequent hazards. It is also very clear that the disaster zone residents place their livelihood activities above any risk they may face in the region.

Complete flood control in the geographical context of Bangladesh is not at all a feasible option.

• Structural methods of flood protection are neither economically viable nor these are environment friendly.
• Non-structural methods are becoming popular in mitigating flood disaster.
• Indigenous solutions such as changing the housing structures and crop patterns can help reduce flood damage.
• Good governance, appropriate environmental laws, acts and ordinances will be necessary to achieve sustainable economic development and to reduce any environmental degradation like flood and river bank erosion.
• People of the flood prone areas should be more conscious about the flood vulnerability.

Preference of solutions/managements for mitigation of the risks

Embankment and Construction of Sluice gate

Construction of embankment for controlling flood and protecting river erosion  .To conserve water in the wet season, to control water, to drain out polluted water and to irrigate water in the dry season it needs to construct sluice gate where necessary and need based repairing. It needs to appoint efficient operator and regular monitoring. Adoption of plan for the construction of flood protection embankment and implement the plan through BWDB

 Construction and repairing of roads

For easy access and rescue activities it needs to construct new roads and repairing of risky roads. Heightening of the roads Repairing the roads which were damaged by the flood. Conduction of research work for undertaking the construction of flood protection embankment project and implementation.

Supply of fertilizer and seeds

Supply timely and adequate fertilizer and seed to the affected farmers with the assistance of Ministry of Agriculture.

 Assistance in irrigation

To assist the irrigation activities through deep tube-well it needs to supply and regularize electricity during the irrigation period and at the places where no electricity supply arrange adequate fuel with subsidy.

 Skill and consciousness developing training

Capacity building training needs to be introduced significantly. Informing the doings and preparedness during and after hazards through awareness building programme involving mass people.

Loan

Make available the soft loan to the sharecropper and affected farmers.

Construction of Shelter

Construction of adequate number shelter for emergency shelter during flood hazard.

 Re-excavation of river, khals and  Canal

Re-excavation of the rivers, khal and drainage canal that are scattered in the Shibalaya upazila

 Flood early warning

Dissemination flood early warning for ensuring emergency evacuation and exploring safer places.

Construction of bridge, culvert and repair

Construction of adequate bridges and culverts on roads of the upazila for rapid recession of logged water along with the repairing of risky bridges and culverts.

 Social afforestation

Both edges of the roads and premise of homesteads and the khas lands need to be planted with trees socially to protect the community from various severe hazards and proper implementation of the forest policy.

 Work expansion of Sub-Asst. Agriculture Extension Officer

Work expansion of Sub-Asst. Agriculture Extension Officer for helping farmer to cultivate verities crops

 Structural management

By taking following new technological management with necessary upgrade, such as construction of embankment and sluice gate, construction and repairing of roads, construction of shelter, construction and repairing of bridges & culvert, re-excavation of river, khal and drainage canal and river erosion protection measures it will be possible to protect the lives, crops and wealth of the affected community of the area.

Table 5.1 : Risk reduction work plan proposed by the community

Continued

Conclusion

Bangladesh is a riverine country and during June-September, with the commencement of yearly monsoon rain, flood and bank erosion appears as conspicuous features in about 40 of its major and minor rivers. Bank erosion and flood hazards in nearly 100 thanas have become almost a regular feature in recent years. Of these recurrent banks erosion has become most extensive in about 40 thanas. It is estimated that about 1.5 million people are directly affected each year by bank erosion in the country. Most of them suffer from the consequences of flood hazard many end up as landless displaces. The total monetary loss is estimated at the tune of Tk.20000 million a year. Shibalaya Upazila once upon a time known as granary of Manikgonj district as well as Bangladesh. Now every year silent famine swoops the area. The cause of the famine is nothing but river bank erosion and flood. The impact of river bank erosion is immediately the variations or changes in population. Most of the Charlands are of this nature.These characteristics are found in Shibalaya thana.

There is no doubt that the flood and river bank erosion have a devastating economic impact on the population. At the micro level, the erosion increases the percentage of landless and also contributes to the surplus agricultural labor force. Flood is also responsible for severe under employment among the agricultural laborers and further improverization of the rural population. Majority of the people have been moving from one place to another.The people of Shibalaya Upazila are experienced with this event.

The findings suggest that the flood and river bank erosion vulnerability is mainly a function of socio- economic vulnerability . As such, there is a need for integration of these disaster management activities with rural development. It has also been identified that the planning for risk mitigation activities should be done at the grassroots level with the provision for direct participation of the people concerned. While the local govt. institution has more or less failed to attain this objective, some of the non- govt. institution has made some remarkable examples. However the activities of the non-govt. institutions are limited to a segment of the population.

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