Document Type : Scientific-Research
Authors
1
Assistant Professor of Urban Planning, Persian Gulf University, Bushehr, Iran
2
Assistant Professor of Environmental Design, Landscape Ecology, Shahid Chamran University of Ahvaz, Ahvaz, Iran
3
Assistant Professor of Architecture, Shahid Chamran University of Ahvaz, Ahvaz, Iran
Abstract
Extended Abstract
Introduction
As an outcome of the expansion of urbanization and over-increasing competition between various organizations including metropolises, urban landscape design is becoming a significant means for the formation of new identities and improving the quality of life. Nevertheless, errors in planning, especially in creating high-rise buildings, have had irreparable damages on urban landscapes. Such examples are the construction of the Jahan Nama Tower in the visual field of Naghshe Jahan Square in Isfahan and the discordant high-rise developments near the River Thames in London that have resulted in the disruption of the skyline. It is totally evident that the necessity of height control only becomes so clear when the irreparable damages have been done to the landscapes. It is evident that height restrictions that are imposed after mistakes will merely prevent further mistakes and are incapable of compensating past damages. Therefore, in order to protect identity-creating urban landscapes, it is vital to consider visual management and height control from the very beginning of the plans.
The landscape of Karoun River in the center of Ahvaz has recently been subjected to unprincipled constructions and its continuation may in the near future result in the disharmony of building heights and create a chaotic appearance for this city. Considering the issue, the mail goal of this study was to develop an effective method for the visual guidance and management of the landscape of this river in Ahvaz. This study endeavored to contribute to the existing municipal documents by determining appropriate protective boundaries, thresholds, and height covers beside the Karoun River which will result in the improvement of the quality of the region’s landscape. To this end, at first the theoretical foundations and existing methods for determining the optimal height of buildings near to the areas were reviewed. Then, a specific practical method was empirically tested at the study area to assess its efficacy and applicability.
Method
This study utilized a mixed-methods approach (quantitative and qualitative methods) and was done in two stages.
Stage 1: Analysis of existing riverine vistas and views
This stage included an exact and comprehensive field study of the existing vistas and views along the Karoun River. The views then were coded and mapped according to standard classifications employed in urban landscape studies (including vistas, serial vision, corridor, panoramic view, etc.). Given the unique characteristics of the central areas of Ahvaz, the views were categorized into two major groups: views emanating from the central zone toward the exterior riverine spaces and views directed from surrounding areas toward the central zone. This dichotomy makes it possible to have a comprehensive look of the entire river and for the precise exploration of the various dimensions of various observers’ (pedestrians, riders, or boaters) visual experiences.
Stage 2: Simulation of the visual surfaces and prediction of height covers
In this stage, the minimum permissible height threshold for buildings in the visual background was determined. This was done by applying the advanced technique of Visual Protection Surfaces (VPS) that is a technique of using 3D-isovist. Finally, Accurate Visual Representation (AVR) was used to present a realistic and intelligible depiction of the proposed scenarios.
Results
Six distinct categories of urban views along the Karoun River were identified and analyzed. The vistas within Ahvaz’s urban areas, despite their gentle slope, have the potential to establish vistas (iconic landscapes) toward the opposite building blocks. Momentary views of organic pathways usually form with bridges or the river’s silhouette as landmark elements. Serial views are along the embankments and bridges and are enriched by such prominent elements as silo and the building of the National Bank of Iran. View corridor directed toward remarkable structures (i.e., bridges and Mo’in al-Tojjar Caravanserai) are significant and require protection, though in some cases inappropriate foreground elements may damage their visual integrity. Threshold views toward valuable buildings, especially the White Bridge (Pole Sefid) are vital and their backdrop need preservation. Moreover, panoramic views that are the most significant riverscapes, are generated in areas around bridges and riverbanks and provide a significant opportunity for showcasing architectural achievements and forming the city’s skyline. The optimal locations for these views are urban open spaces as the White Bridge that are publicly accessible and of high quality.
For predicting the height cover, the optimal depth-to-height ratio (D/H) was determined for the historic texture of Ahvaz to be in the range of 3/1 and 2/1. Since the river corridor's average width is 20 meters, the base height is 6.5 to 10 meters. Then, the Visual Protection Surfaces (VPS) technique was utilized to determine the minimum allowed height threshold for each background block. Finally, using Accurate Visual Representation (AVR), a comparative analysis between the existing and proposed scenarios was presented case by case. The comparison between the proposed values and current urban development plans showed that the current approach for development will make severe damages on the riverscape.
Discussion and Conclusion
This study showed that in spite of the current spatial disharmonies, it is still possible to create a harmonious view for the Karoun River. The measures showed that that development more than 15 meters in height and in the distance of 150 meters of the
river will do severe damage on its landscape. It is necessary for high-rise building (up to 20 stories) to be build in a minimum setback of 400 meters from the riverbed. The implementation of stepped height restrictions using the isovist method will have many benefits such as protecting pedestrian views, preventing the obstruction to wind flows, benefitting all blocks of the riverscape, and creating various specific panoramic, threshold, serial vistas for Ahvaz. This study used quantitative and computational methods. It investigated landscape modifying through taking a holistic, three-dimensional, and technical perspective and putting aside two-dimensional and subjective method. This systematic method can be sued for similar cases.
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