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1 I. Intr oduc t ion
1 .1 Ba c k grounds
Bangladesh is country in South Asia. It is bordered by India to its west, north and east; Myanmar (Burma) to its southeast; and is separated from Nepal and Bhutan by the Chicken's Neck corridor. To its south, it faces the Bay of Bengal. The largest city is Dhaka situated at the center as capital. There are 10 metropolitan cities having a lot of municipal small towns inside each of them. Bangladesh is fourth polluted country in the world; Dhaka, Narayanganj, Gazipur are among top 25 worst polluted cities listed by WHO. Dhaka is referred as ‘Sick City’ (warm humid tropical climate getting worse each day).
Unfortunately, urbanization is taking place too quick ly in unplanned approach and thus many municipalities are unable to find the proper balance necessary for preventing a range of symptoms from developing, which can leave a city rather sick and in turn impact the well-being of residents. Bangladesh is a lan d of tropical climate and rivers which are ended into the longest sandy seashore of the world; and therefore has been very well known for its green agricultural landscape and mangrove forest as well 1 . Recently,
1Simulating Land Cover Changes and Their Impacts on Land Surface
Temperature in Dhaka, Bangladesh - Bayes Ahmed, Md. Kamruzzaman, Xuan Zhu, Md. Shahinoor Rahman and Keechoo Choi
2 rapidlyincreasing economy has lifted a rapid growth of urbanization in Bangladesh. Thus ‘the green’ especially in the cities like the capital-Dhaka, is fast diminishing (Table 1) and rising urban heat island (UHI) effects.Tabassum et al reported that the trend of green space declination in Dhaka city seems to be null within 20202.
Design and application of green landscape on building exterior is an inhalation demand of time. Though a very few practice of green application on buildings as a part of leisure activity had been reported, these small scale practitione rs are not sufficient against the UHI effect. Besides the decorative benefit, green roof or wall plantings may provide food, temperature control, hydrological
2Tabassum, T &Sharmin, S., 2010. The Impact of Green Space Declination in Dhaka’s Local Thermal Environment, Conference proceeding, URBANIZATION, TRAFFIC JAM AND BANGLADESH ENVIRONMENT, ISBN: 978-984-33-5373-3
Table 1. The trend of green space declining in Dh aka city Year Total vegetation(ha) Total built-up(ha)
1975 6585 5551 1985 <6250 >9000 1995 5687 >11682 2005 3992 16105 2010 <2225 >16105 (Estimated) 2020 0 (Estimated) >16105(Estimated)
3 benefits, architectural enhancement, habitats or corridors for wildlife, and recreational opportunities.
To see this plot in a big scale, lack of research interest and technological knowledge stands like barriers. As a result, the rate of developmental research is very slow and involves long interval. Recently, it has become the point of interest among the motivated researchers to a step toward intensive and extensive green roof designing as well as green wall designing in Bangladesh3.
On the other side, urban activities generate large quantities of city wastes including several Biodegradable materials (like vegetables, animal wastes, papers, wooden pieces, carcasses, plant twigs, leaves, cloth wastes as well as sweepings) and many non -biodegradable materials (such as plastic bags, plastic bottles, plastic wastes, glass bottles, glass pieces, stone / cement pieces). On a rough estimate Indian cities are producing solid city wastes to the tune of 50,000 - 80,000 metric tons every day. If left uncollected and decomposed, they are a cause of several problems such as clogging of drains, causing serious drainage problems including the burst leakage of drainage lines leading to health problems, barrier to movement of water, solid wastes have seriously damaged the normal movement of water thus creating problem of inundation,
4 damage to foundation of buildings as well as public health hazards, foul smell - generated by dumping the wastes at a place, increased microbial activities. Microbial decomposition of organic wastes generates large quantities of methane besides many chemicals to pollute the soil and water flowing on its surface. When such solid wastes are hospital wastes they create many health problems - as they may have dangerous pathogen within them besides dangerous medicines, injections. Underground soil in cities is likely to be polluted by chemicals released by industrial wastes and industrial wastes, decomposed and partially decomposed materials of sanitary wastes. Many dangerous chemicals like cadmium, chromium, lead, arsenic, selenium products are likely to be deposited in underground soil. Similarly underground soil polluted by sanitary wastes which generate many harmful chemicals. These can damage the normal activities and ecological balance in the underground soil.4
Land is a natural commodity of environment which is used or various constructive purposes. Land cover is actually defined as the utilization of land by human beings and the natural functions of land. There is a need to develop balance between natural land services and human interruption due to construction. If a state
5 of harmony cannot be achieved then the first thing which is going to be ruined is environment. Land will be completely modified due to
constant urban growth and space for agricultural
growth and natural forests will become less. If forests keep decreasing at the same pace then environmental pollution will increase up to a limit which would be unable to control.
Ecology is defined as the relationship of human beings with environment. Similarly urbanization is directly linked with the environment and environmental resources. It is due to urbanization that human beings are changing the topology of this earth. Forests are becoming extinct due to deforestation and the level of ground water has been decreasing at a very fast rate. The reason is over consumption of water resources d ue to high urban growth. There are many part of the world in which urban areas face water shortage and they have to opt for other ways to avail water rather than ground water.
Urbanization doesn’t only cause deforestation; in fact all other types of environmental pollution also became very common. For instance air pollution in urban areas is increasing just because of elevated use of vehicles. Now cities have expanded so much that without a fueled vehicle it is not possible for access different facilities and to go to their daily work and offices. In order to get to
6 their destination earlier people purchase cars. The exhaust of these cars and other motor vehicles include deadly greenhouse gases such as carbon monoxide. These greenhouse gases not only cause pollution but are also a contributing factor in global warming. It means that urbanization has led human beings enter into a phase
of constant challenges from the environment which
are crucially important to cater for the long term survival.
Decrease in the ground water is not the only problem caused due to urbanization. Pollution of rivers and contamination of different water sources are also caused by urbanization. Cities often face the challenge of proper waste management and due to negligence in this department, water pollution occurs. Waste is usually dumped in the water resource due to which aquatic life gets disturbed. Even plants and animals living in the aquatic ecosystems are exterminating at a very fast rate.5
Bangladesh has been ranked fourth among 91 countries with worst urban air quality in the latest air pollution monitoring report of World Health Organization (WHO). Moreover, three Bangladeshi cities have been put among the top 25 cities with poorest air. The 2014 version of the Ambient Air Pollution (AAP) database consists mainly of urban air quality data of 1600 cities from 91 countries.
7 Pakistanhas been shown as the worst country in the category with Qatar and Afghanistan ranked second and third. Iran, Egypt, Mongolia, United Arab Emirates, India and Bahrain take the other spots in the worst ten. In the city-wise assessment, Narayanganj has been marked as the 17th city with worst air quality whereas Gazipur and Dhaka have been ranked 21st and 23rd respectively. In the report, six of the top 10 cities with highest air pollution were from neighboring India with Delhi taking the first spot. The other Indian cities in the top chart are Patna in the second spot, Gwalior third, Raipur fourth, Ahmedabad ninth and Lucknow tenth. Pakistan's Karachi has taken the fifth position. The report says that almost 90 percent of people living in the cities are being exposed to dangerous levels of air pollution. Outdoor air pollution killed 3.7 million people in 2012 and the WHO says it is now the world's largest single environmental health risk. The report also states only 12 percent of people are living in cities that conform to the WHO air quality guideline levels.
The report was more extensive than a similar database released by the W HO in 2011. The report was prepared on the basis of the monthly air quality monitoring data of 2013 of the Department of Environment (DoE), Bangladesh. The DoE has set up air quality monitoring stations in eight cities, including Dhaka, Narayanganj, Gazipur, Rajshahi, Chittagong, Khulna and Sylhet. Though
8 Narayanganj has the highest level of gaseous pollutants, the report shows the air of the northern metropolis Rajshahi contains the highest level of dust particles6. Among the gaseous pollutants which the DoE measures are carbon monoxide (CO), sulphur dioxide (SO2), oxides of nitrogen (NOx) and ozone (O3), methane and non-methane pollutants.
Plastic has become the most common material since the beginning of the 20th century and modern life is unthinkable without it. Unfortunately, what makes it so useful, such as its durability, light weight and low cost, also makes it problematic when it comes to its end of life phase. Dozens of millions of tons of plastic debris end up floating in world oceans broken into microplastic, the so -called plastic soup. Microplastics are found in the most remote parts of our oceans. Entanglement of turtles by floating plastic bags, sea mammals and birds that die from eating plastic debris and ghost fishing through derelict fishing gear produce shocking pictu res. Moreover, plastic is not inert and chemical additives, some of them endocrine disruptors, can migrate into body tissue and enter the food chain. The massive pollution of world oceans with plastic debris is therefore emerging as a global challenge that requires a global response. The European Union should be a showcase for
9 how to build a coherent strategy to optimize plastic waste policy. A second challenge is linked to resources conservation. Nearly 50% of plastic waste in the EU is still landfilled. Therefore, much energy and processed raw material is lost instead of being recycled into new products. Until now there is no comprehensive policy response to such challenges. Specific aspects are addressed in various pieces of legislation, like the Waste Framework Directive with its 2015 separate plastic waste collection target or its 50% household waste collection target by 2020.7
Although there many
approaches are being
developed for waste
management; the plastic
waste management
seems to be uncontrolled in Bangladesh.
Recycling is processing used materials (waste) into new, useful products. This is done to reduce the use of raw materials that would have been used. Recycling also uses less energy and great way of controlling air, water and land pollution. Effective recycling starts
7Ambitious waste targets and local and regional waste management - Ecologic Institute (Albrecht Gradmann),UmweltbundesamtÖsterreich (Thomas Weissenbach (main author) andHubert Reisinger) and RIMAS (Francesca Montevecchi).
10 with household (or the place where the waste was created). In many serious countries, the authorities help households with bin bags with labels on them. Households then sort out the waste themselves and place them in the right bags for collection. This makes the work less difficult. Paper waste items include books, newspapers, magazines, cardboard boxes and envelopes. Items include plastic bags, water bottles, rubber bags and plastic wrappers. All glass products like broken bottles, beer and wine bottles can be recycled. Cans from soda drink, tomato, fruit cans and all other cans can be recycled.
Plastic use in road construction is another recycling option Recent studies in this direction have shown some hope in terms of using plastic-waste in road construction i.e., Plastic roads. Plastic roads mainly use plastic carry-bags, disposable cups and PET bottles that are collected from garbage dumps as an important ingredient of the construction material. When mixed with hot bitumen, pla stics melt to form an oily coat over the aggregate and the mixture is laid on the road surface like a normal tar road. Use of the innovative technology not only strengthened the road construction but also increased the road life. Rainwater will not seep th rough because of the plastic in the tar. So, this technology will result in lesser road repairs. Plastic will increase the melting point of the bitumen. Roads laid with plastic waste mix are found to be better than the
11 conventional ones. Plastic road would be a boon for India’s hot and extremely humid climate where durable and eco -friendly roads which will relive the earth from all type of plastic waste. Help to improve the environment. Use of the innovative technology not only strengthened the road construction but also increased the road life. The idea of using recycled materials in green roof construction site will be very exciting and needed to be studied in perspective of Bangladesh.
Th e tra d itio n a l wa y of po tte d p la n ting in Ba n g la de sh is n ot ye t e ffe ct ive ly re se a rch e d f o r f ig h ting a g a in st UHI a n d micro clima te o f Dha ka city o ccu rre d b y po llu tio n . Sh o rta ge of e xp e rts an d n o off icia l g u id e lin e f o r ro of to p g a rd en de sig n u sin g re cycle d ma te ria ls . He re , I re p o rt a sta n da rd ro of top g a rd e n d e sign gu id e lin e s wh ich ca n min imize th e g ap be twe e n th e cu rre n t sta tu s of g re en ro of in B a n g la d e sh an d a mo d e l g re e n ro of d e sig ne d b y re sea rch b a sed g u id e lin e s u sin g re cycle d wa ste ma te ria ls .
12 1 .2 Goa l & Obje c tive
Th is stu d y is de sig n e d to cre a te a sin g le so lu tio n to sh o t o ut th e se ma jo r two p ro b le ms i.e . g re e n re d u ctio n a nd p la stic me d ia te d p o llu tio n b y with in sta llin g ro of top ga rd e n with re cycle d wa ste p la stic ma te ria l a ro u nd the Dh a ka city.
Th e g oa l is to u pg ra d e th e ro of top g a rd e n co n cep t of B a n g lad e sh mo re fu n ctio na lly a s w e ll a s a e sth etica lly u sin g re cycle d wa ste ma te ria ls to imp ro ve the city co n d itio n )
Th e ob je ctive of th e stu d y is to ma ke a g u id e b oo k with sa mp le ro o f to p g a rd en d e sign b a se d o n the co ntext of Dh a ka city.
II. S c ope & Me thod 2 .1 S c ope
2 .1 .1 Conte x ts
Ma n u f a ctu rin g is a sun se t in du stry in we st. B e cau se of th e lo w co sts it co u ld b e q u ite re wa rd ing to sta rt a p la stic re cyclin g f a cto ry in B an g la de sh . The ma in p ro sp e cts a re b e lo w: A ffo rd a b ility of the lab o r co st a nd th e fa st d e ve lo p ing re cyclin g in d u stry of p o st -co n su me r p la sti c wa ste s in B a n g lad e sh a re the g re a t a d va n tag e s to co mp e te in th e g lob a l ma rke t. Th e con su mp tio n ra te of p la stic in B a ng la d e sh is 5 kg /ye a r a s co mpa re d of wo rld co n su mp tio n ra te 3 0 kg /ye a r,
13 th e re is a h ug e p o ten tia l f o r the do me stic g ro wth of th e p la stic in d u stry in B an g la de sh . The po p u la tion g ro wth in Ba n g lad e sh is h ig h a n d th e refo re th e co n su mptio n rate will in cre a se a n d if th e p la stic in d u stry ca n ta ke th e co nsu me rs o f lo we r & mid d le cla ss, th e b u sin e ss sh o u ld b e p ro f ita b le8. Th u s, th e co n ce p t of u tilizin g p la stic in th e ro d / co n stru ctio n o r in th e ro o f to p ca n ea sily b e ma n ipu la te d in B ang la d e sh .
2 .1 .2 T ime
B a n g lad e sh h a s th ree ma jo r sea so n s: su mme r, win te r a n d ra in y se a son . W in te r is ve ry sh o rt an d su ita b le fo r a ll the co n stru ctio n wo rks a n d f o r p la n ta tion e n d o f ra in y sea so n will b e th e be st ch o ice to a vo id he a vy ra inf all. P ra ctica ll y it wil l ta ke a lmo st a ye a r to in sta ll su ch a we ll-p la n n ed g ree n ro of. Ho we ve r, th e o re tica lly, it is a lre a d y stud ie d an d su rve yed in my stu d y a n d h op ef u lly th e co n tinu a tio n of s tu d y in ve ry d eta il will n o t ta ke lo n ge r p e rio d of time .
8A Report on Plastic Industry of Bangladesh Mansur Ahamed (Ph. D) Research Department, JBBC Corporation.
14 2 .1 .3 S ite
B a n g lad e sh is lo ca ted in th e In do ma la ya eco zo n e. Its e co lo g y in clu d e s a lo ng se a co a stlin e , nu me ro u s rive rs a n d trib u ta rie s, la ke s, we tla n d s, e ve rg re en f o re sts, se mi e ve rg re e n fo re sts, h ill f o re sts, mo ist d e cid uo u s f o re sts, f re sh wa te r swa mp f o re sts a n d f la t la nd with ta ll g ra ss. Th e B a n g lad e sh P la in is f a mou s f o r its f e rtile a llu via l so il wh ich su p p o rts e xte n sive cu ltiva tio n . Th e co u n try is d o m in ate d b y lu sh ve ge ta tion , with villa g e s o f te n b u ri e d in g ro ve s of ma n g o , ja ckf ru it, b a mb o o, b e te l n u t, co co n ut a nd d ate p a lm9. Th e re a re 60 0 0
sp e cie s of p la n t lif e , in clu d in g 5 00 0 f lo werin g p la n ts10. W a te r b o d ie s an d we tlan d syste ms p ro vid e a h a b ita t f o r ma n y a q u a tic p la n ts. W a te r lilie s a n d lo tu se s g ro w v ivid ly d u rin g th e mo n so o n. The co u n try h a s 5 0 wild lif e sa n ctu a rie s. B e side , h a vin g a ll the se p la n tatio n f rie nd ly f ea tu res, B an g la de sh is my n a tive co un try a n d so it is ve ry co n ve n ie nt f o r me to ga the r a ll n e ce ssa ry inf o rma tio n fo r my stu d y, th e refo re it is se le cte d a s th e site of stu d y.
9Bangladesh | history – geography: Plant and animal life. Encyclopædia Britannica. 10Jump up^ "Flora and Fauna – Bangladesh high commission in India". Bangladesh High
15 2 .2 Me t hod
Mo stly my stu d y ma te ria l in clu d e s re vie win g th e re la ted lite ra tu re s a n d th eo re tica l a n a lysis a s we ll a s a b it o f su rve y stu d y. Me th o d o log y is to a pp lyin g th e kn owle d g e the o re tica lly to e sta b lish a p ro pe r g u ide lin e o f a g reen ro of p ro je ct b a sed o n re cycle d ma te ria ls.
Dhaka, the capital city of Bangladesh
Polluted city with waste materials diminished green space
Rooftop garden with recycled waste materials
Rooftop garden design guideline
16 III. Lite ra ture Re v ie w
3 .1 From Ba b y lon t o Dha k a : T he His t ory of Rooft op Ga rde ns
A t p re se n t, in Dh a ka th e roof g a rde n ha s b e e n q u ite p o pu la r. Ju st lo o kin g a t th e d iff e re nt type s of ro of ga rd e n s ca n b e s e e n in mo st co n ta ine r b a se d syste m . Ho we ve r, mo st of th e roof top g a rd e n ha s b e en d e ve lop e d in an u n p lan ne d wa y. Th e p la nn e d in itia tive s o n th e ro of of the p la n t, e ve n ve g e tab le s ca n b e g ro wn . Th e co lle ctive lo ve of n a tu re in th e clo u d s h a s e xiste d sin ce th e b e g inn in g of re co rd e d time .
Th e f irst kn o wn ro of g a rd e n s a re th ou g h t to b e th e zig gu ra ts of a n cie n t Me so p o ta mia , th e mo st f a mou s of wh ich is th e Ha n g in g Ga rd e n s of B a b ylo n , o ne of th e Se ve n W ond e rs of th e A n cie n t W orld . Usu a lly lo ca te d in th e co u rtya rd s of ma jo r citie s, th e se e n o rmo u s p yra mid to we rs h a d
Figure 3: Reconstruction of the Hanging Gardens of Babylon, 1924, from the Collection of the New York Public Library
17 sta irwa ys th a t sp ira le d a lo n g th e ir o u te r ed g e s, with tre e s o n th e sta irca se la nd in g s to p ro vid e so me resp ite f ro m th e h a rsh d e se rt su n . Ou r o n ly p ro of of the ir e xiste n ce is cla ssica l writin g s b a se d o n o ra l h isto rie s; n o a rche o lo g ica l p ro of h a s e ve r b ee n f ou n d (a lth o ug h , re ce ntly a B ritish a ca d e mic cla ime d to h a ve id e n tif ie d the tru e lo ca tio n of th e Ha ng in g Ga rd e n s of B ab ylo n .)
Fa st f o rwa rd to Th e Re na issa n ce , whe n Ita lia n s we re c ra zy f o r the ir g a rd e n s th e mo re symme trica l a n d o rd e re d in de sig n , th e b ette r. Th e o ld e st an d be st p re se rve d ro o f g a rd en is f ro m th is time , lo ca te d in th e to wn of P ie n za in S ie n n a , Ita ly. P ie n za wa s th e b irth p la ce of A en ea s S ilviu sP icco lo min i, wh o h ad a p a la ce bu ilt f o r h imse lf th e re whe n he la te r b e ca me Po p e P iu s. On the ro of , a fo rma l g a rd en wa s e re cte d f o r h im to ho ld a u d ie n ce s. The e n tire to wn of P ien za , n ow a UNE S CO W o rld He rita g e site an d its p la ce h a ve re ma ine d virtu a lly u n to u che d sin ce th e 1 5 th ce n tu ry.
Th e tra d itio n a l ro of g a rde n in B a ng la d esh sta rte d f ro m th e ve ry e a rly u n sp e cif ie d time with p o t p lan tin g in re sid e ntia l b u ild in g s a s a h o bb y. Th e n it sta rte d to tra n sfo rm g ra d u a lly sin ce 1 9 8 9 b y d e ve lop in g the te rra ce ga rd e n an d 1 99 4 a s th e rma l co mfo rt fo r u rb a n a re a .
18 B u t th e co n cep t sta rte d to ren o va te a s u rba n ag ricu ltu re f a ste r th a n an y o the r sig n if ican ce s. No w it is p la yin g a n imp o rta n t ro le in e co n o mic se cto r b e ca u se th e re a re ma n y p eo p le wh o se ll ve g e ta b le s in the ma rke t af te r f u lf illin g th e h ou se ho ld d e ma n d.
3 .2 P re se nt c ondit ion of D ha k a
In B a n g la d e sh, th e p ra ctice of ro of top ga rd e n is a n cie n t b u t it is ve ry sma ll sca le a n d a ma ln o u rish ed se cto r d ue to la ck of a wa re n e ss a n d e xten sive re se a rch . Ho we ve r, h e re so me of th e d e ve lo p me nta l ste p s a re me n tio ne d wh ich a re d o ne b y a f e w re sea rch e rs in B an g la de sh .
Ove ra ll, th e a p p ro a ch of g re e n ro of to p d e ve lop me n t in B a n g lad e sh su mma rize d in f ra me (Tab le 2 )
19 T a ble 2: T he de ve lop me nta l ste p s of gr e e n roof top of Ba ngla de sh
Ye a r S c ie ntif ic or non -sc ie nt if ic re ports
S tra te gic P roc e d ure Un sp e
cif ie d
P o t p lan ts in
re sid e n tia l b u ild in g s o f B an g la de sh
Ju st a s h ob b y11.
1 9 8 9 Te rra ce Ho u sin g Na tu ra l ve n tila tio n an d e ffe ct of a ir we ll o n a ir f lo w a n d a ir ve lo city12. 2 0 0 4 Re sid e n tia l V e g e ta tio n Fin a n c ia l a n d e n viro n me n ta l be n ef it13. 2 0 0 5 Ro of Ga rd en in g Imp a ct o n b u ilt co n stru ctio n14. 2 0 0 7 Ro of g a rde n in g Imp o rta n t a sp e cts of ro of
g a rd e n ing1 1 2 0 0 9 Gre e n ro of co n cep t in Re sid e n tia l a p a rtme n t b u ild in g Gre e n ro of in co n te xt of Dh a ka city a pa rtme n t15. 2 0 1 0 Na tu ra l g re e n te ch n o log y Th e effe ct of Gre e n ro of in u rb a n li fe16. 2 0 1 3 A p p lica tio n of e xte n sive an d in te n sive g re en ro of s Co mp a riso n a n d co n tra st b e twe en two ma jo r typ e s of
g re e n ro of in Dh a ka city17.
11Natural Green Application technology on Building in Dense Dhaka City is provide a sustainable, energy saving, comfortable and healthy environment. RumanaRashid ,Mohd. Hamdan Bin Ahmed , Md. Sayem Khan
12Mallick F.H. PhD thesis (unpublished), AA school of Architecture. 13SudiptaBarua, Sarah Bashir, Study of the effect of residential vegetation on built environment; 2005
14Sajjaduzzaman; Analytical study on cultural and financial aspects of roof garden. 15 Shad, Sheikh DibyaPorkash, Dhaka,2007
16 Hossain MM, effects of green roof concept on residential apartment in the context of Dhaka city. (Unpublished)
17Rumana Rashid, Green roof and its impact on urban environment and sustainability, World Journal of Management, Vol 2
20 Fro m th e u p p e r tab le it is cle a r th a t a lmo st still n o w g re e n ro o f is a p ra ctice a mon g th e rich an d u p pe r mid d le cla ss so cie ty. Th is p ra ctice is no t stu d ie d we ll e no u gh to b e a va ila b le f o r g e n e ra l an d ma ss pe o p le , u ltima te ly re su ltin g in effe ctive a p p ro a ch a ga in st UHI e ff e ct.
Ma rko v mo d e l simu la te d la n d co ve r ma p s of Dha ka a rea sh o ws th e la nd co ve r ch a ng e s f o r 20 1 9 a n d 20 2 9 ; a n d th e imp a cts o n L an d S u rf a ce Te mp e ra tu re s in re sp e ctive p e rio d s.
S imu la tio n re su lts sh o w tha t if th e cu rre n t tre n d co ntin u e s, a t th e ye a r of 20 1 9 an d 2 0 29 , 5 6 % a nd 87 % a rea of Dh a ka re sp e ctive ly will f a ce mo re tha n 3 0 °C te mp e ra tu re . Ne ve rth e le ss, with a g rea t lo ss of vege ta tio n rep la ce d b y b u ild u p a rea18.
18Simulating Land Cover Changes and Their Impacts on Land Surface Temperature in Dhaka, Bangladesh - Bayes Ahmed, Md. Kamruzzaman, Xuan Zhu, Md. Shahinoor Rahman and Keechoo Choi
21 Gre e n roof s ha ve man y be n ef its a s p re se n ted a b o ve , bu t g re e n ro of s a lso h a ve n eg a tive a sp e cts. B a se d o n va rio u s
22 re se a rch e s, th e fo llo win g issu e s re q u irin g a tte ntio n of th e d e sig n e rs a re ide n tif ie d :
• Gre e n ro of s h a ve mo re d e man d ing stru ctura l sta n d a rd s. S o me e xistin g b u ild in g s can n o t b e re trof itte d with a g re e n roof b e ca u se of th e lo ad of th e so il a nd veg e ta tio n . Dep e nd in g o n wh a t kin d of ro of it is, th e ma in te n an ce costs co u ld be h igh e r. • Gre e n ro of s a lso p la ce h ig he r d e ma n d s o n th e wa te rp ro of in g syste m of th e stru ctu re b o th b e cau se wa te r is re ta in e d o n th e ro of a n d du e to the p o ssib ility o f ro o ts p e n e tratin g the wa te rp ro of me mb ran e . In sta llin g a d e q ua te wa te rp ro of in g syst e ms a n d ro o t ba rrie rs c a n in cre a se th e co st o f th e roof .
• Ho we ve r, f o r th o se livin g in in cre a sin g ly ta ll b u ild in g s th e ro of g a rd en s a re offe rin g do o rste p re cre a tio n sp a ce s a nd co n ta cts with na tu re in th e ve rtica lity.
Th u s, p oo r in sta lla tio n , wro ng ma te ri a l ch o ice s, ne g lig e nt ma in te n an ce h a s p la ye d a n imp a ctf u l ro le a s b a rrie rs in th is se cto r.
Gre e n inf ra stru ctu re e stab lish me n t can imme d ia te ly b e a p p lie d to th e go ve rn me n ta l o rg an iza tio n s, p u b lic p la ce s, e d u ca tion a l in stitu te s, off ice s e tc. co mpa re d to an y p e rso na lly o wn e d b u ild in g a s we can see f ro m th e we ll -e sta b lish e d
23 e xa mp le s be ca u se th is me ssa g e ca n be first a d o p te d b y th is typ e of po we rf u l, we ll kno wn an d sca tte re d o rga n iza tio n s to cre a te e xa mp le in a g ro win g city. Na tu re is g e ttin g se n sitive d a y b y da y b y cha n g ing its clima te s, f e a tu re s, wea th e r, p ro d u ctivity e tc. It ch a n g e s its f a ce a t d iff e ren t p la ce s of th e e a rth . Th u s it is p o ssib le th a t g re e n inf rastru ctu re is n e e de d to b e stu d ied a t the p la ce wh e re it is g o in g to be ap p lie d co n sid e rin g the clima t e , p la n t re sou rce s, we a th e r an d o th e r n e ce ssa ry pa ra me te rs of th at sp e cif ic p la ce . Ba n g lad e sh is a llo win g o n e of th e fa ste st g ro wth s of u rban iza tio n thu s Dh a ka is o n e of th e f a ste st g ro win g citie s. The re a re ma n y rep u ted u n ive rsitie s in Dh a ka , wh ich a re a l so an e xa mp le of u rb a n iza tio n .
B e in g a co n cre te jun g le b y g ra b b ing hu g e a mo u n t of ve ge ta te d su rf a ce s u nd e r ra p id u rb a n iza tion an d h o u sing p ro ce ss, Dh a ka a s we ll a s re sid e n tia l a re a s is f a cing se ve ra l e xte n sive e n viro n me n ta l p ro b le ms. S o , the imp o rta n ce of veg e ta tion sh o u ld be a n a lyzed f o r th e be tte rme n t of the city’s existence . Ho me o wn e rs of te n wan t to a vo id th is so lu tio n th in king ab o u t th e e xtra lo a d of e ven ly d istrib u te d su b stra te o n th e ro of a s th e y a re fa milia r o n ly with ve ge ta tion like - f lo we r o r f ru i t tre e s in p la n te r b o xe s in ve ry lim ite d sp a ce with a p o o r wa te r irr ig a tio n syste m a lso no t a wa re of the weig h t of th e ga rd e n .
24 B u t, in te n sive o r e xten sive type of ro of ing is mo re co n ve n ie n t a n d re co mme n de d a s su b stra te de p th a n d lo a d ca n be b a la n ced an d e a sy to ma in ta in co mp a red to ve ge ta tion in th e p la n te r b o x. A s the in te n sive g re e n roof is a lmo st a n e w id ea in th e co n te xt of Dha ka , p e op le a re n o t a wa re of its imp o rta n ce and benef its and don’t know exactly whom to contact with for mo re d e ta ils. Th e re is la ck of te ch n ica l info rma tio n - sta nd a rd s a b o u t th e wh o le syste m an d te chn ica l e xpe rtise in th is f ie ld to su p p o rt in te re ste d o wn e rs an d d e ve lop ers. Th e re a re ma n y a d d ed b en ef its f o r o wn e rs su ch a s lo n g lif e sp a n of th e roof , e n e rg y sa vin g s to the b u ild in g , in crea ses te n a n cy. B e sid e s, sto rm wa te r ma n a g e me n t, re du ce d wa te r lo g g in g a nd a ir te mp e ra tu re a t the micro le ve l a re b e nef its f o r d e ve lop e rs a nd co mmu n ity a s a wh o le . Occu p an ts of b u ild in g s a lso g e t b e n ef ite d b y lo w o u td o o r an d ind o o r temp e ra tu re , mo re a ir f lo w, le ss a ir a nd no ise p o llu tio n .
25 Fig u re 6 : Cu rre n t ro o fto p g a rd e n syste m o f Dh a ka
26 V e ry in sp irin g n e ws is, n o w a d a ys, th e g o ve rn men t of B a n g lad e sh is h ig h ly f o cu sin g on en co u ra g in g th e ma ss p e o p le a bo u t roof ga rd e n ing a s a pa rt of th a t th e y to o k a lo t o f in itia tive s a s f o llo ws19:
Th e ma yo r of So u th Dh a ka city co rp o ra tio n , S a ye ed K ho ko n an n ou n ced th a t 1 0 % of ho ld in g ta x will b e re d u ce d who h a s g re e n roof on top of th e ir b u ild in g . Cla rif yin g the misco n ce p tion th a t ro of g e ts wo rs e af te r
g a rd e n ing .
E d u ca ting p eo p le ab o u t mo st eff e ctive a n d safe ro of g a rd e n ing .
Spreading the idea and sense of “Green Dhaka - Clean Dhaka” among all.
A p ro fe sso r of d ep t. of Geo g ra ph y a n d E n viro n me n ta l scie n ce s of Dh a ka Un ive rsity n a me d Dr. Hu ma yu n K ab ir a lso p ro vid in g mo tiva tio na l sp e e ch like , gre e n ro of will n o t o n ly f o r b e au tif icatio n , it will ma ke a b a la n ce in the e n viro n me n t wh ich h a s h igh UHI e ff e ct.
A lo t of o wn e r h a s d imin ish e d a lo t of tre e in la st 2 0 ye a rs.
27 3 .3 Rooft op ga rde n wit h re c yc ling wa s te produc t
Re cyclin g is p ro ce ssin g u sed ma te ria ls (wa ste ) in to n e w, u sef u l p rod u cts. Th is is d o ne to re d uce th e u se of ra w ma te ria ls th a t wo u ld h a ve b ee n u se d . Re cyclin g a lso u se s le ss e n e rg y a n d g re at wa y of co n tro llin g air, wa te r a n d la nd p o llu tio n . Eff e ctive re cyclin g sta rts with h o u se ho ld (o r th e p la ce wh e re th e wa ste wa s cre a ted ). In ma n y se rio u s co u n trie s, the a u th o ritie s h e lp ho u seh o lds with b in b a g s with la b e ls o n the m. Ho u seh o ld s the n sort o u t th e wa ste th e mse lve s a n d p la ce th e m in the rig h t b a g s f o r co lle ctio n . Th is ma ke s the wo rk le ss d iff icu lt. P a pe r wa ste ite ms in clu de b o o ks, n e wsp ap e rs, ma ga zin e s, ca rdb o a rd b o xe s a nd e n ve lo pe s. Ite ms in clu de p la stic b ag s, wa te r bo ttle s, rub b e r b a g s a n d p la stic wra p pe rs. A ll g la ss p ro d u cts like b ro ke n b o ttle s, b e e r a nd win e b o ttle s ca n be re cycle d . Ca n s f ro m so d a d rin k, to ma to , f ru it an d a ll o th e r ca ns ca n b e re cycle d .
P la stic u se in ro a d co n stru ction is n o t n ew. Re ce n t stu d ie s in th is d ire ctio n h a ve sho wn so me ho p e in terms o f u sin g p la stic -wa ste in ro ad co n str u ction i.e ., P la stic ro a d s. P la stic ro a d s ma in ly u se p la stic ca rry -b a g s, d isp o sab le cup s an d P E T b o ttle s th at a re co lle cte d f ro m g a rb ag e d ump s a s a n imp o rta n t
28 in g re d ie n t of th e con stru ctio n ma te ria l. W hen mixe d with h o t b itu me n , p la stics me lt to f o rm a n o i ly co a t o ve r th e a g g re ga te a n d th e mixtu re is la id on the ro ad su rface like a n o rma l ta r ro a d . Use of th e inn o vative te chn o lo g y n ot o n ly stre n g th e ne d th e ro ad co n stru ction b u t a lso in cre ase d the ro a d lif e . Ra in wa te r will n o t see p th ro ug h b e cau se o f the p la stic in the ta r. S o , th is te ch no lo g y will re su lt in l e sse r ro a d re p a irs. P la stic wil l in cre a se th e me ltin g p o in t of th e b itu me n. Ro a d s la id with p la stic wa ste mix a re f o u n d to b e b e tte r th a n the conventional ones. Plastic road would be a boon f or India’s h o t an d e xtre me ly hu mid clima te wh e re d u ra b le a n d e co -f rie n d ly ro a d s wh ich will re live th e e a rth -f ro m a ll typ e o -f p la stic wa ste . He lp to imp ro ve th e e n viro n men t. Use of th e in no va tive te ch n o log y n o t o n ly stre n g th e ne d th e roa d co n stru ction b u t a lso in cre a se d th e ro ad life .
Co n sid e rin g th e cu rre n t o ve rp o pu la ted and po llu te d situ a tio n o f sma ll city Dh a ka , it is re a so n a b le wise to p a y a tte n tio n in in cre a sin g th e g ree n ro of . B e cau se it imp ro ve s th e rma l p e rfo rma n ce , cle a n ing th e a ir-co o lin g a city, d e cre a se s u rb a n h e a t isla n d eff e ct, cre a te s & p re se rve s of h a b ita t & e co lo g ica l b io d ive rsity. Mo re o ve r, it in cre a se s p ro p erty va lu e a n d o th e r b e n ef its fo r b u ild in g o wn e rs effe ctive fo r ma n a g in g sto rm
29 wa te r. L a st b u t n ot th e le a st, it o p en s th e d o o r o f ae sth etics, o ffe rs o pe n spa ce an d u rba n fo o d p ro d u ctio n .
3 .4 P la nta t ion in Ba ng la de sh 3 .4 .1 E ffe c ts of S e a son s
B a n g lad e sh ha s a tro p ica l mo n so o n clima te . Th e re a re b a sica lly fo u r sea so n s in a ye a r: win te r (De ce mb e r -Fe b ru a ry), su mme r ( Ma rch - Ma y ), mo n so o n (Ju ne -S e p te mbe r) a n d a u tu mn (Oc to b e r No ve mb e r). Th e a ve ra g e te mp e ra tu re a cro ss th e cou n try u su a lly ra n g e s b e twee n 1 1 °C a n d 2 9 °C in win te r mo n th s a nd b e twe en 2 1 °C a n d 34 °C d u rin g su mme r mo n th s. A n n ua l ra inf a ll va rie s f ro m 16 0 cm to 2 0 0 cm in th e we st, 2 0 0 cm to 4 0 0 cm in th e S o uth ea st a n d 2 50 cm to 4 0 0 cm in the No rth e a st.
Th e clima te is trop ica l in Dha ka . Th e summe rs h e re h a ve a g o o d d ea l of ra infa ll, wh ile th e win te rs ha ve ve ry little . Th e K ö p pe n -Ge ig e r clima te cla ssif ica tio n is A w. Th e a ve ra g e te mp e ra tu re in Dh a ka is 2 5 .9 °C. In a ye a r , the a ve ra g e ra in f a ll is 20 2 2 mm The d rie st mo nth is Ja n u a ry. The re is 6 mm o f p re cip ita tion in Ja nu a ry. Mo st of the p re cip ita tion h e re f a lls in Ju ly, a ve ra g in g 3 7 7 mm.20
30
Figure 7 Climate Graph of Dhaka
31 3 .4 .2 S oil a nd wa te r for P la nta t io n
B a n g lad e sh h a s th ree b ro a d typ e s of so il, n a me ly, Flo o d P la in S o ils (7 9 %), B ro wn Hil l S o ils (1 3 %), a n d Te rra ce S o ils (8 %). S o il scie n tists f u rthe r cla ssif y "Flo od P la in S o ils" of B a n g lad e sh in to 1 4 sub typ e s va ryin g f ro m ca lca re o u s to n on -ca l-ca re o u s, a cid b a sin to a cid su lph ate , g re y to b ro wn P ie d mo n t, p e a t a nd Te ra i so ils.
Th e "B ro wn Hill S o ils" a re lo ca te d in th e h illy re g io n s of Ch itta g o ng , CHTs, a n d Dha ka a n d S ylh et d istricts a n d va ry f ro m b ro wn sa n d y loa m to cla y lo a m.
Th e "Te rra ce S o ils" e xist in th e "B a rin d " a n d "Ma d h u p u r" tra cts of B an g la de sh a nd con sist of b ro wn to g re y cla ys an d lo a ms. Th e co u n try h a s f ive ma jo r rive r s yste ms: th e Ga n ge s o r P a d ma an d its d e lta ic stre a ms, the Me g h n a a n d th e Su rma rive r syste ms, th e Ja mu n a a nd its a d jo in in g ch an n e ls, the No rth B e ng a l rive rs, a n d th e rive rs o f th e Ch ittag o ng Hill Tra cts a n d the ad jo in in g p la in s.
Th e Ga n ge s Rive r syste m is d ivid e d in to two se g me n ts, th e Ga n ge s a nd the P ad ma . The Me g h n a River is th e u n ion of th e S ylh e t -S u rma a n d Ku siya ra rive rs. Th e Ja mu n a a nd its a d jo in in g ch an n e ls sp an a la rg e a re a f ro m No rth Ce n tra l
32 B a n g lad e sh to th e Me g h n a Rive r in th e S o u th ea st. Th e Tista is th e mo st imp o rta n t wa te r ca rrie r of No rth we ste rn B a n g lad e sh th a t mee ts the Ja mu na . Th e Fe n i, th e K a rn ap h u li, th e Sa n gu , a nd the Ma ta mu h a ri a re th e fo u r ma in rive rs th a t co n st itu te the rive r syste m o f th e CHTs a n d th e ad jo in in g p la in s o f Ba n g lad e sh . Ove ra ll, th e so il a n d wa te r so u rce a re ve ry su ita b le f o r p lan ta tio n in B an g la de sh.
3 .4 .3 P la nt t ype s
Th e a re a u nd e r a g ricu ltu ra l u se is su b d ivid e d in to th ree ca te g o rie s, n a me ly th e n e t cr o p pe d a re a , cu rre n t fa llo w, a nd cu ltiva b le wa ste wh ich is a fa llo w f o r mo re th a n a yea r. A g ricu ltu re la n d u se ha s b e en a b le to ma in ta in its sh a re a t a b o u t 66 % of th e to ta l a re a of the co u n try d u rin g th e 1 97 0 s a n d 1 9 80 s bu t its sh a re h a s fa lle n to a bo u t 59 % du rin g the 1 9 9 0 s. Th e sh a re of la n d u nd e r "o th e r u se s" like se ttle me n ts, h o me ste ad , rive rs, e tc. h a s con siste n tl y rise n o ve r th e pa st p e rio d21. Bangladesh is the world’s largest producer of jute. Rice b e in g th e p rin cip le sta p le fo o d , its p ro d u ctio n is of m a jo r imp o rta n ce . Rice p ro d u ctio n stoo d a t 2 0.3 mill io n to n s in th e 1 9 9 6 -97 f isca l ye a rs.
33 Cro p d ive rsif ica tio n p ro g ra ms, cre d it, e xten sio n a n d re sea rch , a n d inp u t d istrib u tio n po licie s p u rsu e d b y th e go ve rn me n t a re yie ld in g po sitive re su lts. The co u n try is no w a t the th re sh o ld o f a tta in in g se lf -suff icie n cy in fo od g ra in p ro d u ction . Fo re st a re a s of Ba n g lad e sh va ry con sid e ra b ly fro m o n e so u rce to a n o the r, a nd the re is a g en e ra l n ee d of relia b le in fo rma tio n in th is re g a rd , e .g. the to ta l fo re st a re a is 2 .5 6 mi llio n h a (FMP , 1 9 9 3 ), 2.2 5 millio n h a (B B S , 1 9 99 ) a n d 1 .4 7 millio n h a (W o rld B a n k, 1 99 7 . Ho we ve r, in Ba n g lad e sh , of th e tota l a re a a g ricu ltu ra l la n d ma ke s u p 6 5 % of the g e o g rap h ic su rf a ce , f o re st la n d s a ccou n t fo r a lmo st 1 7 .5 % (2.5 3 millio n h a ) (FD, 2 0 0 4 ), wh ile u rb an a re a s co ve r 8% of th e lan d . W ate r an d o th e r la nd u se s a ccou n t f o r the re ma inin g 1 0 %. Th e to ta l f o re stlan d in clu d e s cla ssif ied a n d un classif ie d sta te la nd s, h o me ste ad f o re sts a n d te a a n d rub b e r ga rd e n s.
34 22
22Simulating Land Cover Changes and Their Impacts on Land Surface Temperature in Dhaka, Bangladesh - Bayes Ahmed, Md. Kamruzzaman, Xuan Zhu, Md. Shahinoor Rahman and Keechoo Choi
1 2
3 4
Figure 7 Present Land cover Map of Dhaka: (1) Buildup Area, (2) Green Area, (3) Water body, (4) Bare land
35 3 .5 Re vie w of the Roof top Ga rde n D e s ign T e c hnique s
3 .5 .1 Rooft op Ga rde n de sig n
In B a n g la d e sh, th e p ra ctice of ro of top ga rd e n is a n cie n t b u t it is ve ry sma ll sca le a n d a ma ln o u rish ed se cto r d ue to la ck of a wa re n e ss a n d e xten sive re se a rch . Ho we ve r, h e re so me of th e d e ve lo p me nta l ste p s a re me n tio n e d wh ich a re d o ne b y a f e w re sea rch e rs in B an g la de sh .
In Dh a ka , u rb a n d we lle rs h a rd ly se en an y g re e ne ry a ro u n d th e m, e ve ry in ch of la n d is o ccu p ie d b y co n cre te stru ctu re s. Th e so lu tio n lie s in p la n tin g a s ma n y tree s a s p o ssib le , a n d th e on ly p la ce to d o th a t se e ms to be ro of to p s. If p eo p le ca n ma ke ve g eta b le , f ru it, f lo we r of o rn a me n ta l g a rd en s, th is will su p p ly f re sh ve g e ta b le s f o r th e m. Fru its a n d ve g eta b le s p u rch a sed in th e city a re of te n mixe d with ch e mica ls, wh ich a re h a za rd ou s f o r h e a lth , b u t a roof to p g a rd e n can b e a sou rce o f f re sh veg e tab le s f o r city d we lle rs, a n d a lso b e a p le a sa n t a n d un u sua l sig h t.23
23NogorKrishor (Urban Farmer) Working for The Greenery of Dhaka City - By M.H.M. BorhannuddinBhuyan
36 3 .5 .2 Ne e d for gre e n roof
Co n sid e rin g th e cu rre n t o ve rp o pu la ted and po llu te d situ a tio n o f sma ll city Dh a ka , it is re a so n a b le wise to p a y a tte n tio n in in cre a sin g th e g ree n ro of . B e cau se it imp ro ve s th e rma l p e rfo rma n ce , clea n in g the a ir, coo lin g a city, d e cre a se s u rba n h e a t isla n d eff e ct, Cre a te s & p re se rve s of h a b ita t & e co log ica l b io d ive rsity. Mo re o ve r, it in cre a se s p ro p erty va lu e a n d o th e r b e n ef its fo r b u ild in g o wn e rs effe ctive fo r ma n a g in g sto rm wa te r. L a st b u t n ot th e le a st, it o p en s th e d o o r o f ae sth etics, o ffe rs o pe n spa ce an d u rba n fo o d p ro d u ctio n .
3 .5 .3 Use of re c yc le d wa s te produc t for r oof ga rde n
P re co n su me r an d p o stind u stria l re cyclin g of p rod u cts mad e f ro m po ly -vin yl ch lo rid e (P V C) is a lre a d y we ll e sta b lish e d in a va rie ty o f ind u stria l se g me n ts. W ith re ga rd s to th e rmo p la stic P V C ro o f ing me mb ra n e s, eff o rts to re cla im a n d re cycle p la n t trimm in g s g o ba ck we ll o ve r a d e ca d e .
37 Th e g rin d in g p ro ce ss is ve r y eff e ctive a t se p a ra tin g scrim, a s we ll a s th e p o lye ste r f e lt b a ckin g u sed in so me ap p lica tio n s, f ro m th e po lyme r ma trix. Th e re sid u a l f luff can b e u sed a s a
re in f o rcin g f ib e r in the p ro du ctio n of ce me n t b lo cks fo r la n d sca p ing a nd re te ntio n wa ll co n stru c tion o r a s f ee d sto ck in wa ste to en e rg y con ve rsio n p ro ce sse s.
A lth o u gh a sig n if ica n t a mo un t, th e rou g h ly fo u r millio n p ou n d s o f trimmin g s ma te ria l p ro d u ce d , p ro cesse d a n d re cycle d a n n ua lly b y on e ma n ufa ctu re r, pa le s in co mp a riso n to th e p o te ntia l vo lu me s a va ila b le fo r p o s t-co n su me r re cyclin g .
38 On e of the ma jo r p rob le ms with cre a tin g a ro of to p g a rd en is th e sh e e r we ig h t of so il. W h ile a typ ica l ro o fto p is de sig n ed to h a n d le a b ou t 20 to 40 po u nd s p e r sq ua re f oo t, so me so il ca n we ig h u p to 1 20 po u nd s p e r sq ua re f oo t. Th a t me an s th a t, wh ile yo u ma y h a ve th e sp a ce fo r a ro of to p ga rd e n , it still mig h t n o t b e fe a sib le . B u t Ga ia So il, a socia l ve n tu re of Ga ia In stitu te , a no n -p rof it co rpo ra tio n , h a s fo u n d a wa y a ro un d th a t p a rticu la r p ro b le m, u sin g a n un e xp e cte d p r od u ct: S tyro fo a m.
E n viro n me n ta lists h a ve lo ng d e crie d th e use o f Styrof o a m, o r p o lystyre n e , be ca u se of its n o n -susta in a b ility, h e a lth concerns, hazardous waste, and polluting qualities. It’s an unlikely coupling, to be sure, but it’s also quite innovative . Ga ia So il u se s re cycle d S tyrof o a m a nd p e ctin to cre a te a syn th e tic so il.
E n d of S e rvice L if e Re cyclin g of Th e rmop la stic P V C Ro of in g Me mb ra n e s B y S .P . Gra ve lin e , V ice Pre sid e n t Te ch n ica l S e rvice s, S ika S a rn af il, a Divisio n of S ika Co rp .
Th e n ea rly we ig h tl e ss S tyrof o a m is co ated with p e ctin , wh ich is a gel that “holds every plant and every f ruit and leaf together,” according to Paul Mankiewicz, creator of the new so il. A cu b ic f o o t of S tyrofo a m an d pectin we ig h s ju st 1 0
39 p o u nd s an d ca n h o ld u p to 2 0 po u nd s of water. That’s a big d iffe re n ce f ro m the 12 0 -p ou n d n a tu ra l p ro d u ct.
S o me a re co n ce rne d ab o u t th e po ssib le risks a sso cia te d with u sin g S tyrof oa m a s so il. Th is is a ma tter o f co n ce rn th a t it mig h t le e ch d a ng e ro u s che mica ls in to p la n ts, b lo w off in to the a ir, o r cre a te oth e r en viro n me n ta l co n ce rn s. B u t so fa r, th e re is no indication of any of those problems. It’s been in use f or ye a rs in so me lo ca tio n s a n d th e re h a ve be e n no p rob le ms.
Th e so il is a lso h e ld d o wn b y a co co nu t f ib e r o r b u rla p co ve r, to p p ed with a n in ch o r so of co mpo st, a n d tie d to g eth e r with a ro o t ma trix—so there’s no real danger of it blowing off . One of th e b e st th in g s a bo u t th is syn th e tic so il—besides the f act that it ma ke s ro of to p g a rd en in g fa r mo re fe a sib le—is that it’s co mp le te ly su sta in a b le. It u se s ma te ria l s th a t h a ve a lre a d y b e e n ma d e an d wou ld oth e rwise go in to o u r wa ste syste m. Th a t ma ke s i t co mp le te ly ca rb o n -n eu tra l24.
40 IV . De ve lop me n t of roo ftop ga rde n de sign guide line
4 .1 T he Ba sic Gre e n Roof Ga rde n
A g re e n ro of is a g re e n sp a ce crea te d b y a d d ing la ye rs of p la n ts on to p of a tra d itio na l ro of in g syste m. Th e la ye rs of a co n te mp o ra ry g ree n ro of syste m, f ro m th e to p do wn , in clu de : The plants, of ten specially selected f or particular
a p p lica tio n s, an in te g ra ted irrig a tio n system a n d co n tro ls an e n g in ee re d g ro win g me d iu m, wh ich g en e ra lly will n o t
in clu d e so il b u t co co nu t h u sk , mu sta rd o il ca ke , wo o d a sh e tc.
A landscape or f ilter cloth to contain the roots
41 A specialized drainage layer, some times with built -in water
re se rvo irs,
The waterproof ing/roof ing membrane, with an integral root re p e lle n t, an d
The roof structure, with traditional insulation either above o r b e lo w.
4 .2 De sign Con s ide ra t ion s
Th e re a re se ve ra l imp o rta n t de sig n s an d stru ctu ra l d iffe re n ce s b e twe en g ro un d le ve l la n d sca p e d e ve lop me n t an d roof top d e ve lo p men ts. The fo llo win g a re th e sp e cia l co n stru ction re q u ire me n ts a nd co n side ra tio n s wh en d e ve lo p ing a ro of g a rd e n .
Protection of the integrity of the roof and structure Positive drainage
A long-term, lightweight planting medium
Irrigation for optimum plant growth and sustainability Adaptation to the climatic conditions
Selection of hardscape materials (paving, structural ma te ria ls, site f u rn ish in g s a nd wa te r a s a d e sig n e le me n t) a n d th e ir sp e cia l u se a n d req u ire me n ts a s p a rt o f a ro of g a rd en syste m
42 Provisions for utilities
Public saf ety and security Ease of maintenance
4 .3 P rote c tion o f the S truc ture
4 .3 .1 P rote c tion o f the Roo f a nd S truc ture
Th e sin g le mo st imp o rta n t e le me n t in ro of to p g a rd e n co n stru ctio n is p ro te cting th e in te g rity o f th e roof a nd the stru ctu ra l co mp o n en ts un d e r the ga rd e n . Fo r th is re a so n th e re mu st b e wa te rp ro of in g of e xcep tio na l lo n g e vity to p re ven t d a ma g e a nd to re du ce th e p o ssib ility of lo n g te rm e xp en sive re co n stru cti o n . Fo r th is re a so n it is re co mme n d e d a co mp le te ly n e w wa te rp ro of in g la ye r b e ad d e d to th e e xistin g stru ctu re to in su re th e lon g e vity a nd in te g ri ty of th e wa te rp ro of in g syste m.
4 .3 .2 Loa d Be a ring Ca pa c it y
Th e stru ctu ra l e n g ine e r sho u ld ve rif y th e ma ximu m lo ad b e a rin g ca p a city of th e e xistin g stru ctu re . Th e se f igu re s sh o u ld b e a va ila b le f ro m th e re co rds of the p re vio u s co n stru ctio n of th e h e lip ad . Typ ica lly, a min imu m a d d itio n a l d e a d loa d limit o f 1 50 p sf be twe en co lu mn s is n e e de d to a cco mmo d a te th e con stru ctio n of a ro of ga rd e n . Lo a d s a b o ve
43 columns and at the roof ’s edge can be considerably higher, h o we ve r a stru ctu ra l e n g in ee r sh o u ld b e co n su lte d to e sta b lish the lo ad be a rin g ca p a city of th o se a re a s. The se h ig h e r lo a d b ea rin g a re a s sh ou ld b e u se d to a cco mmo da te la rg e r sp e cime n p la n ting s a nd tre e s.
4 .3 .3 Wa te rproof ing
A s me n tio n b efo re , a co mp le te ly n e w wa te rp ro of in g syste m should be installed to protect the building’s structure. There a re se ve ra l typ e s of wa te rp ro of in g ava ila b le , h o we ve r, e la sto me ric ma te ria ls o ff e r th e g re a te st p ro te ctio n . B itu min o u s wa te rp ro of ing sh o u ld b e a vo id e d . Ove r time th e o rg a n ic co mpo n en ts in b itu min o u s wa te rpro o f ing in te ra ct with th e so ils a n d th e p lan t ma te ria ls a n d th ere f o re in cre a se th e like lih o o d of syste m f a ilu re .
A p ro p e rly in sta lle d wa te rp ro of ing syste m ca n la st th e lif e time o f th e b u ild in g, h o we ve r a sing le sma ll le a k ma y re qu ire th e re mo va l of the en tire g a rde n to f ind an d re p a ir th e d a ma ge . Th e ref o re , in o rd e r to in su re th e in te g rity o f the wa te rp roof in g it is re co mme n d ed a p ro te ctiv e top p in g co a t of con cre te b e a p p lie d , a s soo n a s po ssib le , fo llo win g the in sta lla tio n of th e n e w wa te rp ro of ing .
44 Th e sin g le mo st imp o rta n t co n sid e ra tion re g a rd in g ro of a n d d e ck g a rde n con stru ctio n is p ro te cting the ro of a nd stru ctu re f ro m d a mag e d u e to e xce ssive lo a d in g o r le a ks.
A structural engineer should always be consulted prior to ro of ga rd e n lan d scap e de sig n a n d co n stru ctio n . Roof top structures must typically be able to support a
d e a d lo ad of 1 50 p sf to a cco mmo da te the co n stru ctio n o f a ga rd e n .
The roof must be completely covered by an elastomeric ma te ria l a n d p ro te cte d b y a co n cre te to p pin g sla b .
4 .4 P la nt ing P ro vis ion s
L ike the ro of on wh ich th e g a rde n is to b e b u ilt, a ro of g a rde n is co n stru cte d in la ye rs. Ju st a s fa ilu re in th e ro of co mpo n en ts ca n ca u se sign if ican t d a mag e to th e bu ild in g , so to o ca n f a ilu re of th e p lan tin g co mp on e n ts ca use s sig n if ica n t a nd co stly d a ma g e . The ref o re , it is imp e ra ti ve to ta ke ca re in ch o o sin g a n d in sta llin g ma te ria ls of the h ig h e s t qu a lity a nd species conductive to a roof top’s environment.
4 .4 .1 T he Roof Dra ins
Th e e xistin g ro of d ra in s a re a p p rop ria te f or u se with in th e ro o f g a rd e n . S o me min o r mod if ica tion s ma y b e req u ire d to
45 a cco mmo d a te the n e w wate rp ro of ing a n d to pp in g sla b . Ne ve rth e l e ss, th e f o u r ro of d ra in s a n d their size a re ad e qu a te to support the roof garden’s needs. Special care should be ta ke n an d a cco mmo da tio n s ma de to a llo w a cce ss to th o se ro of d ra in s sh o u ld the re e ve r b e th e n e ed to a cce ss th e m fo r cle a n in g .
4 .4 .2 T he Dra ina ge La ye r
Th e d ra in ag e la ye r, d ire ctly a bo ve th e co n cre te p ro te ctive sla b , sh o u ld be ve ry p o ro u s to p e rmit w a te r to p a ss ea sily th ro u g h it. It mu st b e p e rma ne n t a nd co n tin u ou s o ve r th e e n tire ro of su rf a ce an d stro ng en o ug h to su p p o rt th e we igh t of th e p lan t ma te ri a ls a n d h a rd scap e ab o ve it. Th is la ye r mu st b e ke p t f re e of a n y ma te ria ls th a t co u ld pre ve n t th e f re e f lo w o f wa te r to th e d ra in s. Be ca u se of its lig h twe ig h t an d in te g ra ted f ilte r fa b ric, McCa re n De sig n s re co mme n d s th e u se o f E n kad ra in f o r th is d ra in a ge la ye r. Fu rth e r, its .7 5 in ch th ickn e ss a llo ws f o r mo re p la n tin g me d ia in a re a s n e xt to p a ve d a re a s.
4 .4 .3 Filte r Fa br ic
To p re ve n t th e p lan tin g me d ia f ro m g o ing in to so lu tio n a n d b e in g lo st in o r clo gg in g th e d ra in a ge la ye r a n d ro of d ra in s, a
46 wa te r-p e rme a b le b a rr ie r o f f ilte r f a b ric is n e e d e d . A s me n tio n ed p re viou sly we re co mme n d E n ka d ra in b e cau se th e f ilte r f a b ric is in te g ra l with th e d ra in ag e co u rse .
4 .4 .4 P la nt ing Me d ia
Th e critica l crite ria in th e f o rmu la tio n of a su ita b le p la n ting me d ia fo r ro o f ga rd e n s in clu de : li g h twe ig ht; th e a b ility to h o ld n u trie n ts; a d eq u ate mo istu re ho ld in g ca p a city; a n d the ca p a b ility of d e ve lo p in g a f irm (fo r p la nt sta b ility) ye t e a sily d ra in e d so il stru ctu re . The re a re se ve ra l re a d y mixe d me d ia s a va ila b le tha t me et the se req u ire me n ts. Ho we ve r, ca re mu st b e ta ken in se le ctin g the se lig h twe ig h t soils to b e su re th e re a re a d eq ua te no n -o rg an ic co mp o ne n ts inco rp o ra te d into th e mix. S o il mixe s co n sistin g o f so le ly o rg a n ic ma te ria l wil l d e co mp o se , lo sin g n ea rly 3 0 % of its ma ss e ve ry ye a r, th e re b y re q u irin g f re qu e n t to p d re ssin g to ma in ta in th e so il ma ss. Th e ref o re on e sho u ld in co rpo ra te san d an d e xpa n de d sha le in to th e se p re p a red p la n ting me d ia . W h e n th is mixtu re is p ro p e rly mo ist it wil l we ig h a p p ro xima te ly 6 0 p o un d s p e r cu b ic f oo t.
4 .4 .5 Irr iga t ion
Th e re la tive ly th in , we ll -d ra in e d so il mi xtu re s u se d in ro of g a rd e n con stru ctio n ca n no t p ro vid e the p la n tin g s with th e
47 su b su rf a ce wa te r n o rma lly a va ila b le to g rou n d le ve l p la n ting s. Ca re mu st b e e xe rcise d to p re ven t th e soil ma ss f ro m d ryin g o u t an d ca u sin g d a mag e to th e p la n t ma teria ls. Ha n d wa te rin g is to o la b o r in ten sive a n d is no t co st eff ective . Th e ref o re , we re co mme n d th e in sta lla tio n of a se nso r co n tro lle d d rip irr ig a tio n syste m. Drip irrig a tio n is p ref erre d in ro of g a rde n a p p lica tio n s be ca u se the effe ct s of wind ca n cau se ab o ve g ro u n d syste ms to pe rfo rm in co n siste n tly.
4 .4 .6 Mu lc h
Dryin g a n d o ve rh ea tin g of th e so il ca n be p re ve n te d b y the a p p lica tio n of 2 -3 in ch e s of sh re d de d h a rd wo od mu lch . B e sid e s p ro vid in g p ro te ction of th e p la n t ma te ria ls th is mu lch se rve s to h id e th e d rip irrig a tio n lin e s a n d e mitte rs.
Ke y P oin ts: P la n t ing P rov is ion s
A n imp o rta n t co n sid e ra tion re g a rd ing roo f a nd d e ck g a rd en co n stru ctio n is the su b stra te su pp o rtin g th e p la ntin g s.
The existing roof drainage system is adequate to su p p o rt th e in sta lla tio n of a ro of ga rd e n .
48 Planting media and the drainage course should provide f o r fa st p e rco la tio n of wate r an d b e f ree of f ine silts tha t ca n clo g th e f ilte r b la n ket a nd b lo ck d ra ina g e .
Planting media should contain suff icient mineral content to sta b ilize th e p la n ting s a nd ma in ta in so il ma ss.
On a regular basis soils require topdressing to re p le n ish me n t de ca yed o rg an ic ma te ria l.
Drip irrigation is the pref er method of providing moisture to th e p la n ting .25
5 .1 P e ople a nd food c ulture / ve ge ta ble g ro wing c u lture of Dha k a
5 .1 .1 Curre nt Use o f Re s ide nt ia l Roo ftop s in Dha k a
P re se n tly the roof top s of the re side n tia l b u ild in g s a re be in g u se d fo r va rio u s p u rp o se s: f o r d ryin g an d wa sh in g clo the s, a s p la yg ro u nd f o r ch ild re n , fo r e n te rta in ing g u e sts, fo r co o l a ir d u rin g the su mme r, to sun b a th e in the win te r. On mo st of the
49 ro o f s, so me f o rm of p lea su re g a rd en e xists, so me time s th e re a re f ru it g a rd en s a nd le ss of te n , veg e ta b le g a rd en a s we ll.
6 Fruits a nd V e ge ta ble s P roduc e d:
A b o u t 6 0 va rie tie s of f ru its an d ve g eta b le s a re p ro d u ce d in B a n g lad e sh . No t a ll typ e s ca n b e p rod u ced o n th e ro of to p . The typ e s an d mix a re cho se n in the city d ep e nd in g up o n in d ivid u a l h o u seh o ld f o od p ref e re n ce s, a va ila b ility o f see d s typ e s tha t ca n b e g ro wn o n th e ro of to p , clima te an d a va ila b ilit y of so ils. In th e fo o d ga rd e n the fo llo win g f ru its a n d ve ge ta b le s a re co mmo n ly g ro wn ; Gu a va , L e mon , P ap aya , Gra p e s, Gree n Ch ili, P u mp kin , S qu a sh , On ion , Ga rlic, Co ria n d e r le a ve s, To ma to , Mu sh ro o m, L e af y ve g e tab le s (e .g ., Ca lla lo o , Ju te L e af an d Red A ma ra n th u s), a nd o the r (e .g ., Cu cu mb e r, Fla t b e a n , B itte r g ro u n d , Rib be d g ro und , L a d ie s f in ge r, A ma ra n th u s, Dhu d i, Co wp e a a n d B rin ja l). S o me fa milie s a lso cu ltiva te sp ice s a nd p lan ts u sed f o r me d icin a l p u rp o se s.
7 Owners’ Determination to Rooftop Garden:
Mo stly th e o wn e rs e n jo y g a rd e n ing . A b o u t 6 8 % of th e re sid e n ts sp e nd 5 0 -8 0 Ca na d ia n $ pe r a nn u m. Ma n y o f th e m h a ve p la n s to in itia te f o od ga rd e n ing in th e f utu re . On ly le ss th a n 5% of ho u se o wn e rs a re willin g to a llo w te n a n ts to ro of to p g a rd e n ing . Th e y a lso d o n o t w an t to in cre a se re n t to a llo w
50 th e ir te n a n ts to ro ofto p ga rd e n a s the y mig h t lo se th e te na n t if re n t is in cre a sed .
8 Le a sing:
A lth o u gh ma n y ro of s a re cu rre n tly b e ing u n de ru tilize d th e o wn e rs se e m to b e re lu cta n t to a llo w ou tsid e rs in the ro of s. Th e y wo rry th a t th is ma y ha mp e r th e ir p riva cy.
9 Ma npo we r Ava ila b ilit y:
Ma n p o we r d o e s n o t see m to b e a p ro b lem, sin ce on e o r two p e rso n s a re a va ila b le in e ve ry h ou se . In mo st of th e ca se s so me o n e in the f a mily is a va ila b le to lo ok af te r the ga rd e n . Mo re o ve r, mo st o f th e fa mily h a s me mb e rs wh o h a ve kn o wle d g e ab ou t a n d e xp e rie n ce in a g ricu ltu re a n d ga rd e n ing .
1 0 Ma te r ia ls f or Ga rde ning:
Ob ta in in g ga rd e n ing ma te ria ls (su ch a s soil, se e d s e tc.) is n o t a p ro b le m. Th e y a re e a sily a va ila b le in th e lo ca l ma rke t a n d in th e nu rse rie s.
1 1 Wa te r S upply:
W ate r a cce ss is b e co min g a se rio u s p ro b le m in Dh a ka . Ho we ve r, mo st of th e re sp on d en ts sta te d th a t wa te r is no t a p ro b le m fo r th o se who ca n p a y f o r it. Th o se wh o o wn b u ild in g s ca n a lso affo rd wa te r. In 9 8 % ca se s th e y ha ve a cce ss to wa te r
51 o n th e roof s, a n d the re a re a lre a d y wa ter p ip e s in sta lle d on th e ro of s fo r o the r p u rp o se s (su ch a s clo th wa sh in g e tc.).
1 2 S uita b ilit y of the Roof top s:
E ve ry h o u se o wn e r th in ks th at th e ir ro o f s a re su itab le fo r g a rd e n ing an d d o n o t re qu ire imp ro ve me n t wo rk. In mo st of th e ca se s sh ed d in g f ro m th e n e xt bu ild in g we re n o t p e rce ive d a s a p ro b le m. Mo st of the m a lso d id no t id e n tif y an y p h ysica l b a rrie rs.
1 3 As s is ta nc e Re quire d:
Mo st o wn e rs a re re lu cta n t to ta ke a n y o utsid e h e lp so u rce s. Fe w re sp o n d en ts so ug h t p a rtia l h e lp (fro m n u rse rie s a n d f rie n d s). Ho we ve r, so me o wn e rs a re will in g to jo in Ro o f to p Ga rd e ne rs A sso cia tio n if f o rme d in th e fu tu re .
1 4 P roble ms Ide nt if ie d:
Th e po ssib ility o f bu rg la ry se e ms to b e a ma in p ro b le m. Oth e r a n ticip a ted p rob le ms in clu d e a tta ck of th e g a r d e n s b y in se cts, b ird s a n d mo n ke ys.
52 1 4 .1 Ma inte na nc e
5 .3 .1 . Growin g ve ge ta b le s
It is ve ry imp o rta n t to stud y ab o u t the typ e s of su ita b le ve g e tab le wh ich will b e se le cte d fo r g ree n ro of in sta lla tio n . He re a list o f p la n ts tho se a re ea sily g ro wn ve g e tab le s in B a n g lad e sh26.
English name
Local
name Scientific name Family
Cabbage Bandhako pi
Brassica
oleracea var capitata
Cruciferae
Cauliflowe
r Phulkopi
Brassica
oleracea var botrytis
Cruciferae
Kohlrabi Olkopi Brassica
oleracea var gongyloides
Cruciferae
Chinese
cabbage China kopi Brassica chinensis
Cruciferae
53 Petsai Natishak Brassica chinensis
Cruciferae
Saishin China
shak Brassica parachinensis
Cruciferae Mustard green Sarisasha k Brassica campestris Cruciferae
Turnip Shalgom Brassica rapa
Cruciferae
Radish Mula Raphanussativus
Cruciferae Brussels
sprouts ---
Brassica
oleracea var gemmifera Cruciferae Water
cress Sachi Nasturtium officinale Cruciferae
Pea Motor Pisumsativum Cruciferae
Hyacinth
bean Sheem Lablab niger Leguminoseae
String
