Making homes safe and disaster proof through appropriate disaster resistant techniques ByAthar Nawaz MalikDirector General, Pakistan Housing AuthorityMinistry of Housing and Works, IslamabadandDr. Qamar ul Islam UNDP-DRR Consultant Conference on Working Together for Disaster Risk Reduction Convention Centre, Islamabad 8th October 2009
Abstract • This paper will show two perspectives to achieve safe homes considering the United Nation’s Millennium Development Goals (MDGs). • The first one represents the nature of various components or preventive measures. • The second perspective deals housing disaster challenges by Earthquakes, Cyclones and Floods in three major aspects: (i) Location and sitings (ii) Layout and design of housing areas and (iii) construction techniques. • Disaster resistant cause homes safe and disaster proof must involve together by government, Non Government Organizations, self help and ownership incentives.
Local level first aid type efforts: • There are being discussed one by one in the following order. • Windows at home: • In case of high winds, one option is to purchase the appropriate wind resistant window and shutters. Another option is to cover windows with plywood if we know a severe storm is on its way. It’s also best not to position beds directly beneath large windows.
Doors at home: • Especially in areas prone to high winds, make sure that lead outside have reliable dead bolts and tight secure hinges. If there are any splits or cracks in the door, repair immediately.
Emergency kits: It is always important to keep 72 hour kit per person in home. These should be kept in easy-to-access places, and should include updated, age appropriate items for each individual. It’s also important to keep a first aid kit in an easily accessible area as well. It is also important to keep a radio with batteries nearby so that we can hear what’s going on and so that we know when it’s over and safe to come out.
Important documents to keep in safe: • One option is to rent a safe deposit box from our post office. A more reliable option is to buy a fireproof home safe to keep our important documents in. This can be kept some other home away from disaster zone.
Fire Proof: • It is very important to keep at least one fire extinguisher in our home. Keep all firewood at least 30 feet away from the home. Avoid clutters in our home. Stocks of papers, boxes and even linen create a strong environment for fires. Extension cords and power bars should be disconnected and taken away from home .
Earthquake proof: • Make sure that our family know the safe spaces in each room. These areas are away from glass and heavy objects that might fall. Place breakable, heavy objects on lower shelves. Secure heavy and tall objects such as book shelves, loose cabinets, tall desks, etc.
Shut off Utilities and gas flow. • When we become aware that a storm is approaching , or after the earthquake, turn the refrigerator thermostat to it coldest. Prior to the storm , turn off the utilities and all gas with the gas shift of wrench. Use reliable candles, matches, flashlights, batteries and a battery or crack powered radio.
Vehicles: • Keeping cars in garages are best during any severe storm as they can be thrown into things if they are not safe in an enclosed area.
Pet shelter: • We should be sure to include our pet shelter in emergency plan. Even for tough winds and rain pet shelters should have an enclosed, waterproof area where the animal can go to seek shelter.
Roof: • We should check our roof at least twice a year. In storm and tornadoes, roofs normally go first. Make sure that your roofs have no loose shingles. Keeping our roofs protected is also part of keeping the entire house protected.
Yards: • We should remember that during severe storms trees often fall into houses which usually causes most of the damage to the house. Other trees can protect a house from severe winds and lightening. It’s important to keep them put away. Things likr rakes, shovels, patio equipment and even garbage cans can be used as weapons by fires winds if they re loose in the yard. It is also very important to repair any existing damage to the home before a disaster occurs.
Flood and Water: • For nearly any type of disaster situation it’s important to store drinking water and water for flushing toilets and taking baths in our homes. Fill the bathtubs, pots and clean pails with water and set in a secure places if you know a severe storm is approaching.
Broad based making buildings safe through disaster resistance construction techniques • We have discussed above about the first hand precautions or conditions which can make our homes safe and disaster proof on the short run. Further for long run measures and protections are being discussed onwards in the broader and macro levels in the light of Disaster Risk Reduction (DRR) processes through disaster resistant construction techniques and technologies. • There are several structural and non structural measures to combat disaster risks. As per the World Disaster Report, the structural measures are meant to keep disasters away from the people. On the other hand non structural measures aim at keeping people away from disasters. • The factors that need to be kept in mind at the time of planning for disaster-resistance housing for Earthquakes, Cyclones and Floods are: (1) Location and siting (2) Layout and design and (3) construction techniques and technologies which are being compiled in a systematic tabular form.
Earthquakes: • Seismic movements cause relative differential movements in all vertical and horizontal structures of a house making. Therefore for safety against collapse during earthquakes, proper reinforcing of concrete and masonry with steel bars is considered crucial. The idea is to increase the ductility, deformability and damageability of homes so that they perform better during earthquakes without collapsing.
Location & Siting • Buildings constructed on sites with open and even topography are usually less damageable in the earthquakes • Terracing and constructing retaining walls may improve buildings on a steeply sloping site. A site liable to liquefaction or subsidence may be improved by stabilization by sand piling, etc before going in for construction work. • Very loose sand or clay type of soil has a tendency to undergo compaction and should be therefore avoided.
Layout & Design • Buildings which are structurally strong to withstand earthquakes sometimes fail due to in adequate foundation design. • Tilting, cracking and failure of superstructure may result from soil liquefaction and differential settlement of footings. • A building shaped like a box , say, rectangular both in plan and elevation is inherently stronger than one that is L-shaped or U-shaped.Modern buildings in the alluvial soil areas in Europe and Japan use a new concept of shifting the centre of gravity in the earthquake resistant design.
Construction Techniques • Earthquake resistant construction techniques could aid in lessening the destructions after earthquake. Some of the important following techniques and methods must be adopted under the supervisions of structural engineers • All the junctions should be secured with the help of steel so as to impart extra strength to the walls. Load bearing walls can be strengthened with steel reinforcements along with continuous horizontal ties at the sill, roof and plinth levels. • Use steel frame door shutters instead of natural timber. Brittle materials crack under load, the addition of steel reinforcements can add ductility to brittle materials. Projecting parts like large cornices, parapets and all types of ornamentations should be avoided as far as possible, otherwise they should be properly reinforced and firmly tied to the main structure. • Install circuit breakers as most fires are caused by short circuits.
A new concept of isolating the structure from the motions of the ground is now emerging. This is known as base-isolation. This can be achieved by reducing the coefficient of friction between the structure and the foundation One long standing method has been to make a house on short posts, which rests on large stones. So that when earthquake strikes, the posts are pin-connected to the top and the bottom of the building and are thus able to away to and fro. This causes a substantial reduction of the lateral forces and thus, isolates the building from the high frequency movements on the ground. However, in case of massive earthquake, this technology is limited.
Cyclones: • Different types of buildings behave differently under the impact of cyclones. Fully engineered structures are damaged as a result of overturning of bridges, collapse of high steel towers, blowing off of doors, windows and roofing material. • Non engineered structures simply collapse in the aftermath of cyclones. Weak connections among various elements of building lead to failure of structure.
Location & Siting • As far as cyclones are concerned the building sites, which offer shielding from high winds such as main landward side of a hill range, are preferable. • The building site should be much above the probable maximum tide level or the ground should be raised to that level. Piles could be used if site consideration requires so. The sites, which lead to wind concentration, should be avoided.
Layout & Design • The foundation should be taken up to a firm natural soil level, so that the resistance under the footing may not be lost due to flooding. All dynamically sensitive structures in cyclone-prone areas such as chimney stacks, specially shaped water tanks, transmission line towers, etc., should be designed following the dynamic design procedures given in various IS codes.
Construction Techniques • The footing should preferably be built by using stone or fired brick laid with lime mortar. Alternatively, it may be made in constructed on stilts, it is necessary that stilts be properly braced in both the principal directions. • The roof projections should be kept to a minimum, the larger projections must be tied down adequately. For the purpose of reducing wind forces on roof a hipped or pyramidal roof is preferable to gable type roof. Flat roofs should be avoided. • Larger slabs require holding down by anchors at the edges, and reinforcement on top face. As a guide, there should be extra dead load (like insulation, weathering course, etc on such roofs to increase the effective weight.
The wood used in cyclone-resistant houses should be well treated with preservative, so that it is durable against weathering and insect action. • Height of the stone masonry walls should be restricted to two storey in lime-sand mortar and one storey when clay mud mortar is used.
Floods: • During coastal floods, many houses subjected to a large mass of water striking them with force collapse totally. The kind of damage is typical of coastal waves followed by cyclone. • The sea wave may reach several meters above sea level and strikes the structures with great force. Flash floods also bring upon sudden pressure on the structure due to high velocity of water, often causing complete destruction. • Even buildings constructed with RCC may get damaged. Katcha structures made up of thatch, mud, etc., are wiped out completely. In location where the houses are built on loose soil, complete collapse of the structure is likely in the event of inundation.
Location & Siting • Taking into account the variability of the flood hazard in the river, the zones are demarcated into prohibited, restricted and warning zones. The construction of houses should be restricted to the zones involving least risk. Development of any kind in the prohibited zone should be totally disallowed to avoid damage to property and to avert flood situation upstream threatening settlements there.
A limited building activity and planned agricultural activities can be taken up in the restricted zone. In this area minimum ground floor level, flood proofing arrangements, etc, should be provided in the houses. • People wishing to settle down in the warning zone be informed of and advised on the risks involved. Buildings should be constructed on the best bearing soil on the highest ground available locally.
Layout & Design • Layout and design for flood-resistant construction lays emphasis on flood prone area planning. The rural areas traditionally have a large amount of vegetation and a forestation. resulting in reduced runoff in small watersheds. Thus there are chances of flash floods due to heavy rainfalls in such small catchments. • Changes in the land uses patterns have a great impact on the hydrology of the region and increasing the flood potential of the catchments areas.
Damage to individual buildings and structures may be prevented to some extent by incorporating in their design, the ability to withstand the nature of inundation and high water velocity. • Layout of the settlement should be such that it does not block the flow of water. Ground drainage and escape lane should be incorporated in the settlement layout. Growing of vegetation and afforestation in the catchment areas and along river banks should be promoted.
Construction Techniques • To withstand the negative impact of floods, flood-resistant construction techniques must be strictly followed in flood-prone areas: • (i) Houses should not be constructed in low lying areas, wetlands, lagoon mouths, edges of island lakes. Flood plains, narrow defile or gorges, downstream banks and flow ways should be avoided. • (ii) The houses if built on raised mounds, should be thoroughly compacted and made of locally available soil. When houses are built on silt, they must have a rigid framework construction. • (iii) Houses constructed with mud must be given water proofing treatment.
(iv) The roof levels should be sufficiently above the danger level in order to provide emergency protection. The choice of roof type should be such that it gives protection for a minimum period of one day to the people who take shelter while waiting to be evacuated to safety. • (v) Many of the traditional methods are still valid and should be adopted because they are cost-effective and environment- friendly. Provision needs to be made for channelisation ponds and floodwalls. • (vi) Repeating and strengthening and undamaged buildings need to be taken up regularly. This could vary from superficial repair to structural strengthening.
Conclusion: • However in addition to location and siting, layout and designs and construction techniques as discussed above, disaster-resistant construction must go hand to hand with the rehabilitation package should incorporate housing and infrastructure redevelopment, social rehabilitation programme and economic rehabilitation schemes. • An effective disaster risk reduction plan must consist of preparedness schemes for health services, resurrection of education activities and rehabilitation of disadvantaged sections especially, the women, children and elderly. • Disaster risks could be effectively reduced if the development of infrastructure, agricultural rehabilitation, growth of alternative employment opportunities, livelihood options and viable disaster-resistant construction methods are given due emphasis in the development schemes.
Disaster-resistant construction, though a very pertinent disaster risk reduction method, becomes redundant if seen in isolation of the broader economic, social and cultural requirements of the target groups. • All risk reduction strategies draw sustenance from development-disasters interface. Unless the aftermath of disasters is turned into development opportunity with due focus on the requirements of the target groups availability of infrastructure and mobilization of the resources and agencies involved, disaster risk reduction through disaster-resistant construction will not prove useful on the long run.