Natural-Historical Landscape Regeneration of Urban Green Infrastructures based on AWOP and Gravity Models (Case study: District 3, Isfahan)

1. Introduction
The present cities are so far from sustainability indicators and living standards. At present, no balance is observed between urban networks and natural patterns while urban networks are more dominant over ecological networks.
The presence of nature in the city is considered as a vital environment to enhance the quality of biological, environmental, and landscape characteristics. The question of this study was that due to the dense and worn-out texture of some urban areas like District 3 in Isfahan where the designing a green infrastructure network is impossible due to the lack of spatial openness such as green spaces and urban spaces, what will be the solution for the current problems and future developments?
Green infrastructure is a response to modern human need for sustainable development and can be regarded as an approach focusing on the protection of natural environments and their performance as well as the human need results in a comprehensive framework for environmental, social, and economic sustainability results. In this regard, regeneration is a strategy which reorganizes the economic, social, and environmental structures, leads to the restoration of environmental quality or ecological balance, and combines them within the framework of sustainable development goals.
In this approach, considering landscape is similar to a vast mosaic, identification of the disturbances created in the natural process of the inherent natural patterns forming such mosaics, regeneration and design through for restoring the patterns, streams, corridors and green networks. The goal of designing the green infrastructure of many activities is based on ecosystem and human health.

*AUTHOR: EMAIL: F.VAHIDZADEGAN@YAHOO.COM
In order to regenerate historical-natural landscapes, the current models in the field of green infrastructure planning were studied and reviewed and then in accordance with their criteria, the optimal natural-historical patch and corridors were selected. Then, the framework of strategic policies and actions in the areas of strengthening, protecting, improving and restoring the landscape was presented to enhance the quality of environmental life - landscape at the regional level after field observations in accordance with the criteria of quantitative and qualitative methods for urban green infrastructure matrix.

2. Materials and methods
In this study, the combination of both quantitative and qualitative models was used with the regeneration of natural-historical landscape to increase the degree of reliability and efficiency.
The studied area
District 3 of Isfahan is located on the northeast part of central Isfahan in the old city of Isfahan. After examining the satellite images, the percentage of mass to space, the study of social-cultural problems, the amount of worn-out texture and its comparison with the standards and models of urban green infrastructure were used by examining the current potentials (including stream axis, etc.), this area was selected to regenerate the natural-historical landscapes and approach the naturalistic cities and sustainable development.
Patch, corridor, matrix
The structural elements of landscape are introduced as patch, corridor, and matrix based on Forman model. This model itself is part of AWOP model. patchs include urban parks, gardens, cemeteries, vacant lands, urban spaces, semi-private-public green spaces, etc., and corridors include rivers, canals, streams, linear parks, energy transfer paths, streets, etc. After analyzing the structural elements of landscape based on patch and corridor at the regional level, an appropriate pattern of green and open spaces network in an interconnected system at the regional level was presented.
Natural- historical landscape regeneration
In this method too, based on Forman model, the valuable natural- historical patchs of the region were selected for regeneration and simultaneously used in the design cycle of green continuous network.
AWOP Model
This model identifies the landscape elements and presents solutions after overlapping the extracted layers. Based on this model, the small patchs and corridors should be protected and then connected to larger patchs and corridors with ecological function to have a strong connection. This model is of a qualitative type and does not alone respond to the design of green infrastructure. For this reason, the patchs being selected in this method were determined with other quantitative and computational criteria through Gravity model. Then, the aforementioned layers were identified, extracted, and overlapped while the valuable patchs were highlighted and interconnected.
Gravity Model
Gravity model examines the ecological impact of patchs and corridors on each other based on the extent and distance between them and ultimately achieves the optimal matrix in terms of complexity, connection, and the ratio of manufacturer/user cost.
After overlapping the layers in with the principles and criteria of AWOP model, the patchs and corridors were selected based on the criteria and at the same time the patchs which could be regenerated in the region and having common conditions with the model were selected. Finally, they were weighted and formulated based on the principles and criteria of Gravity model.
The studied and measured items:
1. Weighing the selected non-historical patchs
2. Weighing the selected historical patchs
3. Studying the interaction of both non-historical patchs based on the extent of patchs and the distance between them
4. Studying the interaction of both historical patchs based on the extent of patchs and the distance between them
5. Valuing the selected natural- historical-traffical corridors based on ecological indicators
6. Weighing the scores of selected ecological corridors

3. Results
Based on the physical, structural, functional, and other situations, several networks can be produced and evaluated in this model based on green network typology such as the combination of hierarchical and Beckman models.

4. Discussion and conclusion
Cities have converted in such a way that the natural and historical layers at their surfaces have disappeared into dense urban masses. As a result, the city has suffered from lack of self-purification, climate change, and the spread of mental, physical and mental diseases. In this regard, the idea of the interconnected urban green infrastructure network is one of the raised strategies to achieve a balance between the natural and artificial environment in the city and the sustainable structure of the city. It should be noted that each of the above-mentioned methods (not only with a merely qualitative model and not merely a quantitative one) could not respond to the local needs of the region and urban management. Thus, by combining AWOP model and Gravity models, it is the best and most applicable model for responding to the research goals regenerating the past self-sustainable city.
5. Suggestions
This method can also be generalized to other cities and towns with similar conditions to the sample under study such as worn-out, historical, natural textures, and so on. Based on the results, the large patch of Isfahan's Tabark Castle, which has been the oldest part of the city and the center of government in past times but has been neglected, at the same time the natural-historical landscape regeneration of the castle, that can work as the biggest ecological- landscape node in the central loop of hierarchical and Beckman patterns.
Finally, some strategies can be presented separately for each zone in the framework of strategic actions in the domains of strengthening, preserving, improving, reparation and regenerating the natural and historical landscape.