the requalification of the palm trees of ziban as a tool for sustainable planning

Procedia - Social and Behavioral Sciences 102 ( 2013 ) 508 – 519

1877-0428 © 2013 The Authors. Published by Elsevier Ltd.Selection and/or peer-review under responsibility of Professor Dr Mohd. Zaidi Omar, Associate Professor Dr Ruhizan Mohammad Yasin, Dr Roszilah Hamid, Dr Norngainy Mohd. Tawil, Associate Professor Dr Wan Kamal Mujani, Associate Professor Dr Effandi Zakaria.doi: 10.1016/j.sbspro.2013.10.767

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6th International Forum on Engineering Education (IFEE 2012)

The Requalification of the Palm Trees of Ziban as a Tool for Sustainable Planning.

Soumia Lalouani born Bouzahera, *, Djamel Alkamaa

a, cité des 104 logts. Participatifs aprt.11 bloc01, Biskra 07002, Algeria

Abstract The lower Algerian Sahara is experiencing an unprecedented urban growth, causing a socio-spatial upheaval and an ecological imbalance of oasis ecosystems that are embodied in the detachment of the palm trees from the urban areas. [1] This detachment actively participates in the increase of the Urban Heat Island, as well as the over-urbanization on the account of farmlands. Hence the abundance of palm groves, participates in the activation of desertification. Date palm tree plays a pivotal role in the conditioning of atmosphere and purification of air from dust particles, in addition to its enrichment with O2 molecules. © 2013 The Authors. Published by Elsevier Ltd. Selection and/or peer-review under responsibility of Mohd Zaidi Omar, Ruhizan Mohammad Yasin, Roszilah Hamid, Norngainy Mohd. Tawil, Kamaruzaman Yusoff, Mohamad Sattar Rasul Keywords: sustainable planning; ziban; oasis identity; module 3m x3m; module 5mx5m;module 7mx7m

1. Introduction

Rapid urbanization, as the result of population growth and migration from rural to urban areas, changes both the structure and function of our cities. It leads to severe changes in the physical, social and environmental conditions [2] by affecting the climatology of cities and their surrounding areas. These changes have a direct, immediate, and significant impact on human settlements, ecological diversity, energy flows, and climatic conditions [3] from local to regional scales. Urbanization is one of the major problems especially in the Saharan region. Dealing with this growth in a sustainable manner is a major challenge. [4]

* Corresponding author. Tel.: +0-000-000-0000 ; fax: +0-000-000-0000 . E-mail address: [email protected]

Available online at www.sciencedirect.com

© 2013 The Authors. Published by Elsevier Ltd. Selection and/or peer-review under responsibility of Professor Dr Mohd. Zaidi Omar, Associate Professor Dr Ruhizan Mohammad Yasin, Dr Roszilah Hamid, Dr Norngainy Mohd. Tawil, Associate Professor Dr Wan Kamal Mujani, Associate Professor Dr Effandi Zakaria.

509 Soumia Lalouani born Bouzaher and Djamel Alkama / Procedia - Social and Behavioral Sciences 102 ( 2013 ) 508 – 519

2. Study Problem

Strong instruments to integrate ecological, economic and social aspects early in the planning of Saharan regions and decision-making process are needed to deal with the major upcoming problems like resource and energy consumption, waste disposal, water salinity and desertification.

A sustainable city can feed and power itself with minimal reliance on the surrounding countryside, and creates the smallest possible ecological footprint for its residents. This results in a city that is friendly to the surrounding environment, in terms of pollution, land use, and alleviation of global warming.

The Ziban illustrated one of the best sustainable and urban forms in fragile-ecosystem oases areas, through adaptation, environment respect and exchange of ecological advantages with this hostile environment. In front of the urban growth, the industrial attractiveness, Ksour and Dachra of these oases were abandoned which entraining a phenomenon of drift from the land. This last one created an ecological imbalance on several plans.

The palm is the backbone of the oasis ecosystem and agricultural character of social life in Ziban. It is the element and the source of life of these human groups. It has an ecological role that limits the advancing desert. Also, it creates an essential microclimate for the proper development of understory crops. On the ground the palm cover very large areas which assigns roof-ground, minimizing the solar gain of the areas under palm trees, creating shaded areas identical to Saharan regions.

3. Study Objective

This work proposes the requalification of palm trees as an instrument for town planning, since it is the sustainable factor of oases. We will try to find a simulation of the sunspot, the optimal height of the palm and distance between them to promote an adequate shade on a defined surface. This surface can be used as a planning module

4. Method To do it, we have developed three models of palm 10m heights with distances: 7mx7m and 5mx5m and 3mx3m. These models were exhibited under the Heliodon, which is a device for

adjusting the angle between a flat surface and a beam of light to match the angle between a horizontal plane at specific latitude and the solar beam. [5]

The choice of distances done in imitation of existing situations (farmers use the distances of 7x7 and 5x5 as roof-ground land used to protect the underlying agriculture. The distance of 3x3 was proposed by the team).

5. Definition of the case study, the Ziban:

5.1 Situation and geographic characteristics:

The Ziban lies on the southeast of Algeria, at the southern foot of Saharan Atlas' mountain range. This site makes it deserving "The gate of desert" connotation and allowed the region to play through the different periods of its existence a role of encounter, exchanging and transition between a well equipped north and a disinherited south. (Fig.1.a)


Figure 1. (a) The location of Biskra in Algeria. Source: TDMP,2008 (b) The relief of micro region. Source: Health-mapper

The relief of this micro region is divided into four major groups: the mountain range and high plateaus, great plateaus; steppes and depressions. This whole is irrigated by a set of wadis that form the main gatherer of the

(Fig.1.b) The climate of the micro-region is desert-prone arid and semi-arid, with a high temperature in summer

reaches (48.8°C), in August, and (1.6°C) in February. Because of the desertification phenomena we get a longer and a hotter summer and dry and shorter winter, with a 139, 8 mm / year of average rainfall [6].

5.2. Ziban as self-sustainable urban units

The micro-region was divided into four Zab [7] (Fig.2) each one has its own palm groves, and cultural and architectural heritage, each one is also independent economically and politically, [8] for example Zab Biskra produce some dates and it was the an open market for change all kinds merchandises, Zab Guebli, Zab Dahraoui are specialized in the production of dates and Zab Chergui produce cereals and medicinal plants.


Figure 2. The smaller urban units and their Capitals. Source:. Marc Cote[9]

The urban distribution of the region of Ziban was based on the potentialities of Ksour and Dachra: its palm plantation, its agriculture and quite other constituent elements of the socioeconomic development. Every oasis was independent economically and politically and has its own architecture, its own devices and spatial organizations. Ziban illustrate one of the best sustainable and urban forms in fragile-ecosystem oasis areas, through adaptation, environment respect and exchange of ecological advantages with this environment. [10]

Geographically, the continuum of these oases is an important part of the Lower Algerian Sahara which has several natural resources. These oases have provided since ancient times a prosperous life for its inhabitants. [11]

6. The factor of sustainability in the Ziban:

The number of ancient urban development remains the bedrock of urban reality of today or the rationale for an urban renewal operation. [12] At the time the Ziban's oasis heritage is threatened with extinction, which has allowed us to read cultures and societies traces' that had been experienced this is palm groves and the ruins of old human settlements also made of trunks of palm trees. The initial implantations profit from the proximity of the palm groves that had often surrounded the building ...further had helped to the creation of microclimate. [13] In a palm grove, the temperature drops to 10°C, which can be beneficial to the functioning of: forest and oasis ecosystems, for ecotourism or for life around these spaces. These plants are indeed remarkable markers of ecosystem functioning. [14] What introduces us the sustainability factor in the micro region of Ziban that is the palm tree. The palm tree is the natural, the economic and the social capital of Ziban. The environmental conditions of a city often depend often on the natural environment where it is situated. [15]


6.1 The palm capital of economic sustainability:

Trade always had a significant place in the oases of Ziban, because of fertile soils and palm groves [16] which are the backbone of the oasis ecosystem, and also of the agricultural character of social life essentially by revealing: An ecological role allows to limit desert encroachment The creation of a microclimate permitting the good development of underlying crops; Under these canopies of 20 to 30 m height, light creates luminous pleasant livable atmosphere. The reduction of wind speed, and the curb of cicadas' proliferation; It

improves water reserves in dry soils and the climatic conditions of life. As stabilizer and regulator of cultures, the palm tree prevents landslide and minimizes

6. 2. The palm, capital of urban sustainability:

On the mass, the Ziban Ksour appear as urban groups protected by the palm grove, from sand winds and rays sunlight (Fig.3). Ksour heights does not exceed the ones of the palm trees.

Figure 3. Human and their palm groves Figure 3. (a) Tolga. (b)Bouchagroune (c) Khanguet Sidi Nadji Source: [17]

6.2.1. Rapport between the ksar and its palm grove:

According to a study we find that the surface of the Ksar is almost negligible compared to the surface of its palm grove. We have tried to calculate the ratio which is the result of dividing the surface of the palm grove / on the surface of the Ksar (constructed area). The ratio exceeds greatly the surface of the Ksar. [18] Facing this rapid urban growth that has been done on account of the agricultural land, palm groves, and quality of life; does it become obligatory to curb this sprawl and think about a new manners to reduce energy consumption and outlying environments destruction? To do so, one must bring an end to this triple neglect: of the city, of its ecosystem and of its heritage. [19]

6.3. The palm, capital of architectural sustainability:

Ksour and Dachra meet climatic requirements through ingenious modes of construction, and reveal, in a subtle way, bioclimatic habitats patterns and the workings of the social organizations. [20] The palm tree was used for ecological purposes: its wood and palm provide construction wood and tissue for houses and fences. [21] Fig.4.


(a) It trunks offer planks of construction, poles, beams and lintels (Fig.4. b.c.). From the base of the trunk at the forefront of Palms, everything is recycled and turned into everyday objects. [22]

Figure 4. (a). (b) (c) The trunks used as planks. Source: author

6.4. The palm, capital of social sustainability:

The date palm plays a major role in ensuring social stability of Zibanese oases population: it contributes in keeping knowledge and traditional skills that allow a judicious and sustainable use of natural resources, whether water in irrigation techniques, in the choice of suitable cultivars. Plant biodiversity of palm trees has a real value based on historical, technical and agricultural links between groups and individuals and their cultural and social functioning. [23] The number of palm trees was related to the number of males in the family, because they were the ones who cultivated the palm trees: The more the number of males increased the more they acquired more lands. [24]

6.4.1. Rapport between the population and its palm trees:

A comparative study was based on the choice of important capitals of the Ziban, Zab Chergui, Zab Biskra and Zab El Kantara in the micro-region on the one hand on the other hand, the availability of old statistics.it shows

ratio of 19 palm trees per person was the result of the addition of the whole ratios of 1904 and its division by the number of capitals. But in 2009, the result was a ratio of 4.5 palm trees per person. So from 1904 to 2009, there was a deficit of 14.5 palm trees per person. [25]

7. The palm trees as model for sustainable planning:

7.1. Calculation of Ziban overheated zone:

7.1.1. Thermo-isopleth diagram of Biskra:

This diagram (Fig. 5) highlights the diurnal and seasonal variability of air temperatures. To plot it, first we

5). Then, on a table, we represent the temperatures for each month and draw lines linking between the maximal and the minimal. (Appendix A)

Table 1 Monthly temperatures forecasts of Biskra (2011)

Statements of the meteorological station of Biskra

Months Jan. Feb. Mar. Apr. May. Jun. Jul. Aug. Sept. Oct. Nov. Dec. Max. t. 18°C 18°C 23°C 27°C 31°C 37°C 41°C 40°C 34°C 28°C 22°C 18°C Min. t. 8°C 8°C 11°C 15°C 20°C 25°C 29°C 28°C 24°C 17°C 12°C 8°C


The sunshine is significant; the number of hours of sunshine in warm periods exceeds 14 hours per day. In winter it is around 10 hours. (Fig.5a) (Appendix A) This permits also considering the incidental energy on the ground that, by turns, is not negligible. "In the summer, in July, the amount of incidental energy on a horizontal plane is 6682 Wh / m2 [26] This solar potential offered by the climate of Biskra is promoting the integration of passive architectural processes [27]. Yet, a problem of overheating arises during the period of overheating.

Figure 5(a): Hourly temperature calculator. (b): Source : S. Szocolay, (1979) [28]

According to the thermo-isopleths presented in (Fig. 5b) (Appendix B) shows a close relationship between the average temperature and time of day (hour) and year (month) and from which we can deduct three groups of zones:

A first one known as the zone of sub-heating, it lasts from December to February; A second one known as the zone of comfort, it is defined by the neutral temperature 25°C. It spans the months

of March, October and November; A third one known as the zone of overheating, it spans the months of May, June, July, August and September

when the temperature exceeds 25 ° C especially between 10am and 6pm, where the sun's intensity is high and requires a solar control.

Once the temperatures are transformed in hours per month (Fig.5b) we can carry them on the chart to

determine the solar superheating zone. (Fig.6) (Appendix C)

Figure 6. Polar diagram of Biskra, presentation of the superheated zone in red.


The solar diagram of the micro region of Ziban latitude 35 ° confirms that the superheated zone is spread over all months of the year except December, November, January and February. Summer is the period of overheating. It starts from 6 am until 7 pm. This fact calls for the protection of outdoor areas where the need for occultation is a priority.

7.2. The date palm a tool of solar occultation in Ziban:

The proposed sustainable planning module is the deficit of 15 palm trees per person. For agricultural reasons, there are 02 picket palm trees methods over the Sahara (Fig. 7) the "Quintral System" and the "Square System", we will use it since it is the most common.

Figure 7(a) "the Square System" Figure 7 (b) "the Quintral System" Source: SECAAR

7.2.1. The tools of the experience:

Three models of palm trees with varying distances, and height of 10m.

7.2.1.1 The 7mx7m module:

Several studies in the field of agronomy have confirmed that a distance spaced from 7m up to 10 represents the best spacing. [29], [30], [31]. The date palms plantation high density has detrimental effects on yields and the ventilation of palm trees, as it hinders mechanization and handling inside the palm groves and makes difficult any development effort [32]. Besides, The high density from one hand, creates a quality an unfavorable microclimate, on the other hand, requires more work since the operations applied individually to each palm tree are even more numerous. [33]


This experiment aims to protect outdoor areas. Yet the old palm groves have been designed with a dense spacing, this fact optimizes the shade, comparing with the new palm groves; but does not foster the maintaining of palm trees and


Traffic spaces in the region of Ziban are more or less narrow (maximum distances in the streets and traffic lanes are 20m for divided highway including pedestrian traffic areas. This latter includes an area of 3m to 1.5m

These three models were exposed to the sun of July 21st, the hottest month of the year. The sun's path is

simulated by the heliodon.


Table 2 capture of the solar occultation of July 21st, the hottest day of the year by three different modules of palm groves (2012)

Module 3mx3m Module 5mx5m Module 7mx7m 8 am

10 am

12 am

2 pm

4 pm

6 pm


8. Analysis and discussion:

By comparing the three modules we notice that: The 3mx3m spacing allows more solar occultation. The 5mx5m spacing: from 12 am till 6 pm the spaces are not shaded. The 7mx7m spacing does not offer a great opportunity for occultation.

For the modules 3mx3m and 5mx5m starting from 8am to 10am there are enough shaded areas allowing

protected movement for users.

Under the 5mx5m module:

Figure 8 (a): the umbra of 5mx5m module Figure 8 (a): the umbra of 5mx5m module At 11 am we find an umbra and penumbra nice light ambiance. (Fig. 8) At 12 am we note a minimum of shaded space that promotes solar occultation under the palm trees. From 2 am to 6 pm the shade disappears from the limits of the module and occupies its interior, this fact

favors its use as a solar occultation.

Under the 7mx7m module: We notice a kind of detachment of the shade from its palm groves during all hours of the day.

The module 5mx5m, we think, is more favorable for solar occultation in arid and semi arid region as Ziban.

3mx3m and 7mx7m modules can be used in other areas.

9. Conclusion:

This study has shown that the palm tree square system used by farmers to preserve the underlying cultures can be a tool of local and sustainable management of outdoor spaces for these regions. As we have seen, the module 5mx5m is the most favorable for solar occultation in the arid and semi arid regions.

The reuse of the palm tree as a tool of planning can help restore the oasis ecosystem by first the resumption between the urban and natural heritage, second the rootedness of society itself in its natural context. This reuse must necessarily be a promoting factor to the recovery of the oasis identity of Ziban.

The return to palm trees agriculture, which is the original culture of Ziban particularly and the desert generally, becomes a necessity. In order to promote the use of palm trees, they must be integrated in development and urban planning.

The sustainable planning, according to the Canadian Council of Forests Ministers intends "to maintain and improve the long-term ecosystem health ... for the benefit of all living beings ... while providing for present and future generations good environmental, economic, social and cultural prospects "[34]


Hence the need for this scientific approach to find the modeler between the oasis trilogy: population, human establishments and palm trees. Especially the last one since it represents both economic and environmental capital of Ziban and any Saharan regions.

References

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Appendix A

Appendix B

Appendix C

the requalification of the palm trees of ziban as a tool for sustainable planning

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