Noise/ Sound pollutionThe extent of sound pollution in Dhaka is closely linked with urbanization, Industrialization and motorization.
The World Health Organization (WHO) found the level of sound pollution in Dhaka city exceeds the acceptable limits set by the Department of Environment where noise level is much higher than the acceptable limit in residential areas and vulnerable institutions like schools and hospitals. Chowdhury et al. (2010) measured the noise levels at the roadside as well as at a distance of about 50m away from the roadside and show that the average noise level on the roadside and 50m away from the roadside were about 82 dBA and 73 dBA respectively, which surpasses the acceptable limit for mixed and commercial areas set by the Department of Environment. According to the DOE the perfect sound condition for Bangladesh is 45 dB for the daytime and 35 dB for the night in peaceful areas, 50 dB for the daytime and 40 dB for the night in residential areas, 60 dB for the daytime and 50 dB for the night in mixed areas (residential, commercial and industrial localities), 70 dB for the daytime and 60 dB for the night in commercial areas and 75dB for the daytime and 70 dB for the night in industrial areas.According to the World Health Organization (WHO), generally 60 dB sound can make a man deaf temporarily and Anyone may become deaf for the time being if 100 dB or more noise pollution occurs for half an hour or more in any place. But the noise of any busy street in Dhaka has been estimated at 60 to 80 dB, with the sound of vehicles being 95 dB, loud speakers 90 to 100 dB, mills and factories 80 to 90 dB, restaurants and cinema halls75 to 90 dB, festivals 85 to 90 dB, scooter or motorbike 87 to 92 dB and trucks and buses 92 to94 dB. But the desired sound measure is 25 dB in the bedroom, 40 dB in the dining or drawing room, 35-40 dB in the office, 30-40 dB in the class room, 35-40 dB in the library, 20-35 dB in hospital, 40-60 dB in a restaurant and 45 dB in the city at night. According to a survey of the Department of Environment (DOE), noise causes mental and physical illness among the people.
It causes high blood pressure, tachycardia, headache, indigestion, peptic ulcer, and also affects sound sleep. Working in an atmosphere of loud noise for a long period can cause complete deafness to any person. Any sort of noise pollution seriously affects expecting mothers. (http://en.banglapedia.org/, 2018)Natural and human induced hazardsEarthquakeSeismic zoning in Bangladesh indicates that Dhaka is under Zone II, and as such is at a real risk of an earthquake of significant magnitude.
Major seismic sources (plate boundary faults, Dauki fault and Madhupur fault) exist around Dhaka city. It is one of the most vulnerable cities to earthquake according to the Earthquake Disaster Risk Index of Stanford University (http://www.worldbank.org/, 2018). Natural gas pipelines and connections of electricity can be source of hazard during earthquake with possibility of leakage and explosion.
Absence of critical public facilities (i.e. school, hospital, police station, sewerage system etc) and failure of their proper functioning may have serious impacts on the dwellers, after earthquake. City authorities are ill-prepared to face a high-intensity earthquake event because of little contemporary experience. The urban DRR framework report has found that official building codes was followed by less than 10 per cent of buildings (Shaw, 2013). Comprehensive Disaster Management Program (CDMP,2009) have specified that 78,000 out 326,000 buildings in Dhaka are vulnerable to collapse.
Most of recent housing projects are wetland filled which is highly vulnerable and high damage of sudden earthquake can aggravate from liquefaction (Islam et al, 2015). Again, alarming rate of ground water loss puts Dhaka in high risk.Flood & WaterloggingIn recent years, Dhaka has faced extensive flooding and waterlogging during the monsoon (May to October). Above 50% of Dhaka is low-lying and inundated during monsoon.
Flooding is caused by both the increasing water levels of peripheral river systems, heavy rainfall and seasonal tidal affects. After a flood, parts of the city become waterlogged for several days. Encroachment of rivers and canals increased flood and waterlogging hazard susceptibility. The other main causes of waterlogging are inadequate drainage systems, natural siltation, the absence of inlets and outlets, a lack of proper maintenance of the existing drainage system, filling of water retention areas and the disposal of solid waste into the drains that obstacles drainage paths.
Poor enforcement of laws in protecting the low-lying areas/wet lands in and around the City made the city highly vulnerable.FireMost of the buildings did not follow the building code and lacked arrangements for alternative staircases and emergency exits and firefighting equipment. Lack of open spaces and scarcity of readily available water sources in neighborhood accelerates the exposure to fire vulnerability. High density areas that constructed closely alongside not abide by zoning regulations and code often used for fire prone material storage and industry, without any fire evacuation plan. On an average 80% of roads are twisted, narrow and unplanned that can obstacle fire-fighter and ambulance to enter into the spot. High traffic congestion all over Dhaka city delays to the fire-fighters to control the fire event (http://www.
rajukdhaka.gov.bd/, 2018).Building CollapseThe causes of building collapse are due to bad design, faulty construction, foundation failure, extraordinary loads, unexpected failure modes, combination of causes. According to a recent survey, 78,000 out of 326,000 buildings in Dhaka were detected as risky. Rana Plaza tragedy on 24 April 2013 is considered to be the deadliest garment-factory accident in history, as well as the deadliest accidental structural failure in modern human history.
Low-lying areas and flood-flow zones are being filled up with sand are used for constructing high-rise apartment buildings very often. The recent history of building collapse and slanting in Dhaka city are the results of old and dilapidated building or newly built but faulty design and overloaded weak buildings. Rajdhani Unnayan Kartripakkha (RAJUK) has classified around 1,000 buildings in Dhaka as ‘visibly vulnerable and risky’. Urban specialists believe the actual number is far more that are highly at risk of being collapsed.2. Development control Rules, Regulations as Building Codes in Bangladesh:Standards for planning and building regulations are essential for guiding development, but these must be affordable and relevant to the particular context in which they are applied. When the reality of development control is prohibitively expensive and socially and environmentally redundant or the enforcing authority is weak, the tendency is to bypass these regulations resulting in unauthorized developments.
The following acts have made for regulate and guide building construction in Dhaka so far.The Building Construction Act, 1952Building regulations were first introduced in Dhaka city through the Building Construction Act 1952 later amended in as the National Building Regulation, 1996. To guide setbacks & building heights in urban areas; prevents haphazard construction of buildings and excavation of tanks; controls and regulates safety, comfort, appropriateness of materials, building services this was enforced until the Bangladesh National Building Code (BNBC) was made mandatory through national legislation in 2006 (Mahmud, 2007). The act focused on residential construction and the codes were basically set-back guided layout and there was no limit on the density of built form& permitted to build allowable height fixed by the local authority. The mandatory open space existed only as set-back areas around the building. After construction, these setbacks resulted in narrow strips of land around the building, mostly unusable but narrow strips of ventilation funnel – it channels moving air to interior spaces, provides thermal comfort.
The act had no regulation of green areas on site. Most of setback areas could be paved that resulted in increasing the albedo of the open areas, being exposed to solar radiation. Urban Heat Island effect thus affects. Additional paved decreased the absorption of water by faster run-off of rain water and disallowed recharge of water table. These effects caused the water table to fall considerably, making Dhaka face a water crisis. Increased hard surfaces contributes on creating flash floods even least amounts of rain.
Another limitation of the regulations was, it had no/poor mechanism (less manpower of authorities) to check construction and verify that it had followed the authorized plan that encouraged unlawful construction and violation of regulations. Buildings were mostly found had encroached on the mandatory open spaces, not abiding to the minimum setback limits set by the law, thus denying neighbor’s rights of air and light (Ahmed,2010).The Town Improvement (TI) Act 1953The act regulates proposed building by preparation of master plans, improvement schemes, their implementations; controls development, by improvement and expansion of Dhaka by opening up congested areas; laying out of altering streets; providing open spaces for the purpose of ventilation or recreation; demolition or construction buildings; acquiring land for the said purpose; and rehousing of persons displaced by the exclusion of improvement schemes (Zaman ; Laing, 2013). The major aim was to ensure planned development, promote a healthy urban environment, and prevent development of conflicting land use (among other things) and above all, to ensure the sustainable development of Dhaka City (Mahmud, 2007).