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Report on

Climate Resilient Shelter Home in South-Western Coastal Areas of Bangladesh

Dr. Anirban Mostafa

Associate Professor

Architecture Disciple

Khulna University

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TA – 6422 (REG): Main streaming Environment for Poverty Reduction

1. Geographic and environmental characteristics of the project area

The deltaic region of Bangladesh is an ideal breeding ground of tropical cyclones, flood and other natural disasters. For the

particular geography of Bangladesh, almost every year, the country experiences disasters of one kind or another such as -

tropical cyclones, storm surges, tornadoes/thunderstorms, coastal erosion, floods, droughts, and earthquake. Disasters cause

huge loss of human life and livestock, and colossal damage to human settlement i.e. infrastructure, housing, and built

environment. The regular devastation of various natural disasters has become part of millions of people living in abject poverty

in the disaster-prone areas of Bangladesh. The societal exposure to such risks is further enhanced by the vulnerability of the

vernacular settlement patterns in the disaster prone regions.

In the project area, mostly agricultural land use dominates the settlements and its economy in the floodplains and coastal areas.

However, fishing is also a major activity in the coastal zones, while large scale industrial activity has been constrained by the

limited availability of saline-free process water. Shrimp farming is one of the major occupations in South-western coastal

region of Bangladesh. In the project areas almost all the agriculture land and homestead gardens were flooded and the green

vegetation was damaged during Aila. Most of the water sensitive fruit trees and vegetables died due to water logging. The

livestock and poultry death is continuing even after Aila due to food and drinking water shortage. Now most of the houses are

devoid of livestock and poultry resources in the affected area and many farmers are selling their remaining livestock as they

cannot provide them with adequate food and drinking water. The people of the affected area received the highest amount of

sufferings from drinking water shortage and destruction of sanitation facilities soon after Aila attack. However, still the

affected people are suffering from shortage of pure drinking water, which is evident from all respondents’ response and

physical visit to the area. Aila devastated all the drinking water sources (ponds and tube wells). During Aila, high tidal surges

contaminated all fresh water sources with polluted saline water. Many people are compelled to drink such polluted water as

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they do not have any other option and consequently suffer from water borne diseases. Since the 1980s coastal lands have also

been extensively brought under shrimp cultivation primarily in response to the high salinity (Agrawala, et. al., 2003). Land use

in project areas is determined mainly by monsoon climate, the seasonal flooding which affects the greater part of the country,

and the high population pressure which has stimulated farmers to bring virtually all suitable land under cultivation and to use

intensive cropping patterns and practices (Brummer, 2004). Residential land use is located within the agricultural lands in

various patterns depending on the 1) topographical features like rives, canals, forests, slopes etc; and 2) infrastructures like

major communication lines, embankments etc. The location of the settlements in vulnerable project areas is mainly due to its

easy access to farmland. Apart from these, community services like market place (hut), school, health centre, mosque, post

office, disaster shelter etc. are generally found along the major communication lines in the disaster-prone settlements. The

vernacular settlements are developed organically in absence of any formal planning intervention. The scattered settlement

patterns worsen the impact of disasters and make the post disaster management difficult. Unsafe location, orientation and

spatial arrangement of living spaces make the built environment more exposed to the severity of different forms of disasters.

The unplanned settlements also impede the spatial re-distribution of rural land use in response to climate change. The vast

number of helpless people living in such built environment is struggling to adapt to the disasters in their age-old vulnerable

ways which are of marginal measures in face of the increasing frequency and intensity of natural disasters. Major

communication lines i.e. roads and railways are built on embankments to raise them above high flood-levels, and provided

with bridges and culverts to allow the passage of floodwater. The homesteads are away from the main communication lines,

and are accessed through or clustered along the secondary or tertiary pedestrian paths. However, bridges and culverts in such

roads and paths often are inadequate in size and number (usually because of lack of funds), which can lead to the overland

flow of water being impeded during heavy rainfall or high river floods, thus aggravating local flooding situation. In most cases,

secondary and tertiary communication links between the homestead and other areas become inaccessible during flood. There is

considerable movement of people and goods by boat along rivers, khals (canal), and over the land when it is flooded in the

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monsoon season. Cyclones and storm surges usually destroy many boats, thus hampering rescue and relief operations in areas

that are mainly dependent on boat transport.

Apart from these, the poor people in disaster-prone areas consider the disasters to be part of their life and try to live with the

disasters in their age old ways no matter it works or not. As a matter of fact, poor socio-economic condition does not allow

them to reduce the vulnerability of their settlement patterns. They cannot afford to upgrade their small hut. The poor people

usually are reluctant to leave their homes during times of disaster, mainly for fear of theft of their possessions. Therefore, when

flood water rises above the level of homestead mounds, families first move onto beds or other furniture within their dwelling

and raise their important possessions above water level. Then if the water level continues to rise, they make crude wooden or

bamboo platforms (machans) within the dwelling on which to live during the flood. Eventually, in an exceptionally high flood,

they may move to roofs or trees. Only as a last resort do they abandon their dwelling and move by boat or raft to any available

higher ground: river or road embankments; flood shelters (where they exist); or public buildings. Poultry, goats and sheep are

similarly moved upward in the homestead during a flood, in so far as this may be practicable, and some may be moved to

embankments which provide the only grazing land (FAP16+19, 1993a).

2. Typical settlements, homesteads and housing pattern of project area

The vernacular settlements of project area are characterized by the centuries-old experience in adapting form and material

selection to achieve comfort in relation to the deltaic geography and local climate. Physical forms and spatial patterns are

shaped by the traditional way of life, local climate, topography, socio-economic conditions, and socio-cultural norms and

values.

Spatial sequence –

There exist a common spatial sequence in a village where, few houses (Ghar) form a homestead (Bari), a cluster of

homestead forms a community (Para), and a number community (cluster of Bari) forms a village (Gram).

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Single space houses in the periphery around a courtyard are the basic living units (Figure 6).

The homesteads surrounded by orchards and separated from each other (with a name), usually have their individual ponds.

Spatial Pattern –

Scattered clusters amidst agricultural land.

Clusters normally connected through meandering pedestrian paths linking the community facilities.

Community facilities away from the residential clusters located close to the communication lines and river/canals.

Low density, mostly single storied built forms with indoor and semi-outdoor spaces arranged around open-to-sky

courtyard.

Figure 1: Traditional built environment

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In floodplains, individual homesteads generally are constructed on raised earthen mounds (vita); ponds dug to raise the vita

and create source of sweet water; the height of which is determined by local experience of previous high flood levels. The

slopes of settlement mounds are planted with flood-tolerant shrubs and herbs as a protection against wave erosion at high flood

stages. The homesteads scattered amidst agricultural land; or arranged linearly along the tertiary paths. However, in

floodplains, they usually are located on the highest land available on river-banks and on floodplain ridges which mark the

position of the banks of former meander loops.

Figure 2: Traditional built form Figure 3: Traditional constructions materials

Built Form and Constructions Materials

The vernacular built forms are usually of single story, arranged around a rectangular compound with an adjoining pond used

for domestic water supply, bathing and often for fish production; and an outside kitchen, surrounded by multi-use trees, banana

plants, bamboos, and a kitchen garden. The use of locally available materials and construction techniques is local micro-

climate responsive, need-based, low-cost, and affordable. Thus the house forms, building styles and materials used in

construction have significant variations in different geographic and climatic regions. Most of the houses are temporary (katcha

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house) constructions. Based on number, sequence and enclosure of spaces several types of formal patterns are found; and

based on local construction materials and techniques several types built forms are found in the disaster-prone settlements.

Construction Materials -

Kutcha house – organic materials

Wall – jute stick, straw, bamboo mat, dry grass, mud.

Foundation- earthen plinth with bamboo or timber posts.

Roof – thatch (rice wheat or maize straw, dry grass etc.) with split bamboo framing.

Figure 4: Construction materials

Semi-Pucca house – combination of organic and inorganic materials

Wall – bamboo mats, CI sheet, timber or bamboo framing, earth, brick in part or full.

Foundation - earthen plinth, brick perimeter wall with earth infill, brick and concrete also used.

Roof - CI sheet with timber or bamboo framing.

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3. Justification for improvement of coastal vulnerable housing

People living in the disaster-prone areas have little defense against strong winds, storm surges or severe floods. Absence of

land use planning and development control with proper regards to the degree and extent of floods resulted in low density

scattered settlements in floodplain areas. Big land-owners generally live in inland safer areas, often in urban areas; it is almost

entirely poor families who live in vulnerable rural areas, together with migrant seasonal laborers living in temporary shelter. In

the agro-based rural settlements, prolonged flooding devastates the cultivable lands and leaves people with hardly any income

source to support their livelihood. Scattered homesteads in unsafe areas make the settlements more vulnerable to disasters.

Poor infrastructure and communication heighten the miseries of the flood affected people. Provision of emergency services

(like medical, rescue, relief) is difficult at the best of times in remote areas, and access becomes especially difficult dur ing

floods and after cyclones when land communications are often disrupted.

Most of the rural houses in disaster-prone areas are kutcha construction with natural organic materials. These have shorter life

span, and get easily destroyed by high flood, moderate storm or cyclone (Figure 1). Sitting of the houses in floodplain are

normally above the seasonal flood level, however, they go under water during high flooding of storm surges. Prolonged

inundation causes the bamboo/timber-frame and clay-built houses to collapse. Following are the aspects make the built form

vulnerable to disasters.

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Figure 5: Vulnerable built form and structure.

Source: ADPC, 2005.

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Sitting – below flood level, below communication lines and embankments.

Design –

o Orientation – wider side towards windward direction.

o Shape of roof, slope, overhang – lifting of the leeward roof slope.

o Position and size of openings – any opening on the windward side increase air pressure inside the building and

increase the external suction effect.

Structure/Construction Methods – no foundation, no resistance to lateral wind loads.

Untreated Materials – earthen plinth collapses, structural members rot, breaks for sub-soil water, attacked by sub-soil

insect.

Lack of post-disaster usability - build forms components like roof, walls, posts etc. cannot be removed and re-construct

after disaster is over.

Apart from this, regarding the usability of the spaces, most of the houses have single-space living area with no provision of

storage for life supporting goods like food, drinking water, children’s food etc. to save life during the post disaster crises

period. Thus the poor families suffer additional hardships due to low food stocks and reduced employment opportunities

during and after such disasters.

Most of all, traditionally, the poor people in disaster-prone areas consider the disasters to be part of their life and try to live

with the disasters in their age old ways no matter it works or not. As a matter of fact, poor socio-economic condition does not

allow them to reduce the vulnerability of their settlement patterns. They cannot afford to upgrade their small hut. The poor

people usually are reluctant to leave their homes during times of disaster, mainly for fear of theft of their possessions.

Therefore, when flood water rises above the level of homestead mounds, families first move onto beds or other furniture within

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their dwelling and raise their important possessions above water level. Then if the water level continues to rise, they make

crude wooden or bamboo platforms (machans) within the dwelling on which to live during the flood. Eventually, in an

exceptionally high flood, they may move to roofs or trees. Only as a last resort do they abandon their dwelling and move by

boat or raft to any available higher ground: river or road embankments; flood shelters (where they exist); or public buildings.

Poultry, goats and sheep are similarly moved upward in the homestead during a flood, in so far as this may be practicable, and

some may be moved to embankments which provide the only grazing land.

4. Recommendation for disaster adaptive built environment

Self help housing approach for construction.

Phase wise development with minor financial involvement of user group.

Based on users affordability.

Raised homestead over flood level.

Clustered homesteads connected by secondary communication lines.

Homestead vegetation.

Community based fisheries, forestry, and cottage industry.

Multipurpose community service spaces.

Use of local material, construction technique and expertise in combination with advanced technology.

Adaptive built form, materials and construction.

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Figure 6: Conceptual Framework of Comprehensive Disaster-Adaptive built environment.

Raised homestead over flood level

Clustered homesteads connected by secondary communication lines

Homestead vegetation

Community based fisheries, forestry, and cottage industry

Multipurpose community service

spaces

Use of local material, construction technique and expertise in combination with advanced technology

Adaptive built form, materials and construction

Raised house in coastal areas

Strategic Options

Economic diversification

Sectoral zoning of land use

Compact multipurpose rural centre

Improved water and road communication workable during disaster

Community participation

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5. Demonstration of climate resilient housing

Design Implications

Due to the funnel shaped coast, the deltaic region of Bangladesh is often prone to cyclone, tidal surge and other natural disasters.

From analyzing the previous pattern of cyclonic wind and tidal surge it can be realized that these natural disasters took a route

from south and southwest course. Considering the local climatic condition the dwellers of the locality orient their house along

Uttor Pota (south facing) and Pashchim Pota (East facing). To establish the layout and orientation of the house against cyclonic

wind, it should be kept in mind to put the shorter face of the house (widthwise) across the windward direction of the cyclone.

Wood is popular among the local household to construct vertical supports, joists and truss for roof support. Bamboo is used in

houses that belong to very low to low level wealth ranking, and wood is used in houses belonging to people of medium to high

level wealth ranking. One of the major threats of these traditional building materials like timber or bamboo is that, these are

susceptible to decay due to sunlight, rain, fungi, termite and high humidity when in contact with the ground. The local villagers

practiced a technique to get relief of this problem. They coated the exposed portion of timber with old sump or motor oil which is

called locally as mete tel. Bituminous coating can be a better alternative but more expensive in compare to the previous one.

Coating it with oil prevents further access by insects, and additionally protects from sub-soil water.

The lateral stiffness did not improve at all by providing cross wind bracing at the top. Placing vertical cross braces around the

basic framing made good progress both in the lateral and torsional stiffness by more than 100 times. The inverted V-bracing was a

good alternative where the advancement was visible for lateral and torsional stiffness about 50 and 30 times respectively. Besides,

this type of bracing was also more convenient in terms of putting up doors and windows.

The base of the house in this locality is mostly made of mud according to their traditional way. During storm surge and flooding,

soil washes away from the foundation and plinth. Capillary action through the soil mass aggravates this action in plinth. This

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action leads to subsidence of plinth which end event is the collapse of Column (khuti) of house. As the khuti has no connection

with the foundation, so the houses have every possibility to flush away during tidal surge. Lack of extended roof attic in house

during driving rain enhances the damage of earthen plinth. Various insects, worms, termites and rats burrow in earthen mass and

establish their colonization that eventually weaken earthen plinth. Lack of connection with the foundation also leads to topple

down or even blown away from its original position as a result of strong wind flow during storm.

During survey, floor levels of some houses of the local inhabitants were found satisfactory which were raised from the existing

ground level to get rid of the flood water and locally it is termed as Pota. Heighted stepped earthen plinth was also visible in some

houses and according to their statement this technique is really useful in that locality. Lots of ponds were found in that

neighborhood from where they collected earth to raise their plinth and access road. Introducing of mud concrete or stabilized earth

in plinth may help to withstand the effect of flood. This mud concrete can stand conveniently in flood water without being washed

away. Besides they have good compressive strength. Only 5% cement additive is enough for manufacturing mud concrete with soil

having more than 40% sandy-silt particle. Another option is to surround by 10 inch brick wall to hold the earth of the plinth and as

the base of the vertical posts. So that wooden posts would not get the direct contact of the soil.

Cyclonic storm and high wind in this region is a guiding factor to fix on the form and shape of house. Magnitude of the wind loads

on the structure influences the shape of the roof. Based on the local experience, most of the houses in the village constructed hip

roof (Chouchala) over the Ghar and a lower roof over the verandah which is separated from the hip roof. Expert gave their

opinion that the houses with hip roofs have better record of resistance and the recommended pitch of the roof lies between 30 to 40

degrees (Lewis and Chisholm, 1999).

In the roof structure system, the most sensitive locations are the joinery of beams and columns and the connection between the

rafters and beams. To make the house safe against high wind these connections should be strong. Local builders use iron bolts at

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the connection between vertical supports with beams. In terms of cyclone resistance, experts recommended to use 20 gauge

galvanized metal straps, nails, nuts, and bolts along with nylon rope where necessary (Haq, 2007).

The facade of the traditional houses has windows and perforation over the windows for better ventilation. Obviously this is a good

practice in respect of local climatic consideration in this tropical region. At the presence of too much perforation in the façade

during cyclone build high wind pressure which eventually increases suction pressure under the roof can blow the roof away from

the main structure. To get relief from this effect expert gave opinion to place one door at the center of the wall and add a small

window in the rear wall (Lewis and Chisholm, 1999). The type of shutter in window plays a significant role during cyclone.

Shutters hinged along the top of window frames are preferred as these will not suddenly open and let the wind in during cyclone

which eventually increases internal pressure to cause the roof to blow off. Louvered shutter would be a better choice with this top

hung window. From the same study it was seen that corner openings (door/window) are not safe for the stability of the structure

during cyclone rather than placing the opening in the middle of the facade (Haq, 2007).

Sitting

Raising the level of homestead above the level of flood water

Raise the structure on a mound (killa).

Building on treated bamboo or timber stilts in cyclone prone areas

Floating house with floor level rising along with flood water

Design

Shorter face of house towards the windward direction

Single (flood) or double story house (cyclone), with square or rectangular geometry

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Pitch roof – vertical rise to horizontal spread ratio – 2:3, slope within 30-45 degrees, hip roof over ghar, low roof over

verandah, minimize roof overhangs beyond vertical claddings

Openings – minimize door and window openings, openings at position of external suction reduce the pressure significantly

inside the house thus the risk of lifting off of roof

Structure/Construction Methods

Wall frame – cross bracing, inverted ‘V’ bracing to withstand lateral

Vertical poles – adequate anchoring of vertical poles into ground

Roof frames – cross bracing, adequate anchoring of roof and vertical claddings to basic frame and bracings

Wire lashing at roof/wall/post junctions

Improved local materials

Plinth/base - use of mud-concrete (mixture of rise husk, rise husk ash and cement - 5%) Usability of spaces – single use

Basic frame – bamboo posts treated with bitumen or motor oil coating, insertion of bamboo column in concrete block with

whole

Combination of local and non-local materials

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References:

Agrawala, S., et. al. (2003), “Development and climate change in Bangladesh: focus on coastal flooding and the Sundarbans”, OECD,

(COM/ENV/EPOC/DCD/DAC(2003)3/FINAL), France.

Brammer, H. (2004), Can Bangladesh be Protected from Floods?, University Press Limited, Dhaka.

FAP16+19 (1993a), Charland Study, Vol. 12, FPCO, Dhaka.

Haq, B. (2007), Battling the Storm. Study on Cyclone Resistant Housing. Community Based Disater Preparedness Programme. Bangladesh Red

Crescent Society/ German Red Cross.

Lewis, J and Chisholm, M P, (1999). “Cyclone Resistant Domestic Construction in Bangladesh”, in Implementing Hazard-Resistant Housing.

Proceeding of the First International Housing and Hazards Workshop to Explore practical Building for Safety Solution held in Dahaka, Bangladesh. 3-5

December 1996, edited by Hodgson, Seraj and Choudhury, pp. 29-38.

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Annex 01

ARCHITECTURAL DRAWINGS

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Table of Content:

01. Type 01………………………….Wooden Framework with Brick work up to sill level

02. Type 02……………………………………………Wooden Framework with Concrete post

03. Type 03………………………….Wooden Framework with Brick work up to sill level

04. Type 04 (Duplex) ……… Wooden Framework with Brick work up to sill level

05. Details ……………………….Structural details, water reserver details, base details

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Detailed Plan:

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Elevations:

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Section:

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Layout plan:

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Top view with Structural Frame:

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Structural Frame:

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Perspective View:

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Bill of Quantities:

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Detailed Plan:

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Elevations:

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Section:

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Layout plan:

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Top view with Structural Frame:

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Structural Frame:

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Bill of Quantities:

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Detailed Plan:

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Elevations:

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Section:

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Layout plan:

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Top view with Structural Frame:

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Structural Frame:

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Bill of Quantities:

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Detailed Plan:

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Detailed Plan:

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Elevations:

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Elevations:

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Section:

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Layout plan:

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Top view with Structural Frame:

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Perspective:

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Bill of Quantities:

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Proposed Prototype base:

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Structural details:

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Water reserver detail:

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