Abstract
Lorestan bridges have been of particular importance in different eras due to being located on ancient roads. Bridges built for various purposes, including political, religious and economic, have acted as valley bridges in addition to linking different areas through crossing ravaged rivers of Lorestan at the time such as Kashkan and establishing road safety. Lack of awareness by the local people, the country and the international community of the value of these properties, the destruction of their properties and their associated environments by indigenous peoples and domestic tourists, the lack of a comprehensive and integrated conservation program and the lack of proper budget allocation for their restoration, Their natural context for conservation and restoration has all made these valuable and indigenous properties in the process of destruction. Accordingly, the purpose of the research is to identify the cultural landscape of historical bridges attributed to the Sassanid period of the Kashkan River and to establish a structuralist framework through the analysis of national and international laws, charters, conventions, and treaties to conserve their cultural landscape. In this research, library and field data were collected and four bridges: Kashan, Kelahor-e-Mamulan, pol-e-dokhtar, and Gavmishan were selected as study samples due to historical and architectural values. In the following, recommendations for the conservation of selected bridges’ cultural landscapes were categorized into two categories, generic and specific to the selected bridges themselves using qualitative research method, data analysis, and coding operations at three levels to reach the final results of the research. 
Keywords: Conservation of Cultural Landscape, Historic Bridges, Sassanid Period, Lorestan, Kashkan River.

Introduction
Lorestan province, with its rich and important rivers such as Seymareh, Kashkan and Cesar, has one of the richest flowing water networks. In addition to communicating with the two capitals (Susa-Ekbatan), this province has always established the connection between the old Babylon, then Ctesiphon, and then Baghdad, to Isfahan, through Khorramabad. (Siroux, 1978: 32-33). From other roads, separated from Lorestan, we can refer to Susa to Bisotun and Susa to Masbazan road (Minorsky, 1937). The need for quick and easy access and constant communication between these areas, despite the rich rivers and deep valleys, has led to the construction of huge bridges that makes a man wonder7 (UNESCO, 2016). These bridges have been built to connect large civilizations and some extent of the realization of human rights, religious, ethnic, economic and cultural ties, as well as development, prosperity, security and comfort in difficult mountainous regions (UNESCO, 2016). The undiscovered identity and value of these works for the indigenous people of Lorestan and at higher levels, the country and the international community, the destruction of the works themselves and the natural environment, associated with, by indigenous people (intentionally interfering with the cultural landscape of the bridges), lack of comprehensive conservation and restoration plans and lack of necessary credit allocations from organizations, entrusted with these works, the non-formal and mere physical restoration of some properties, regardless of the context in which, they are formed, have all made these valuable properties of art and cultural landscape associated with, to increasing degradation. In Lorestan cultural domain, these properties have been constructed with the highest quality of locating and building, and study of these works and conservation challenges of their cultural landscapes, can certainly Conserve bridges, with addition follows:
• To illuminate and conserve various historical layers of the region;
• To preserve the natural environment (including river, valley, etc.) where the bridges are located;
• For legibility and conservation of the region’s indigenous culture and
• To achieve construction technologies of bridges, for future conservation and restoration of these properties.
This research seeks to identify the Cultural landscape of Historic Bridges on the River Kashkan and its conservation challenges, in order to provide a basis for helping, define a systematic model to conserve its cultural landscape. In this regard, the following question is defined as:
• What is the definition of the cultural landscape of historic Bridges on the River Kashkan?
• How can a systematic, structuralist model be achieved to conserve the cultural landscape of historic bridges over the Kashkan River?

Discussion
According to the epigraph left by the bridge, Badr-ibn-Hasanwayeh has introduced himself as a constructor to this bridges. The cultural landscape of these Bridges is an integrated collection, interacting with humans over time in the geographical domain of middle Zagros. Despite the vagueness of the “cultural landscape” meanings, today this word has become one of the most controversial words in the World Heritage Convention. Challenges are coming into place when modern science cannot face the challenges of different levels and disciplines (Zibalkalam, 2018). Conservation is also no exception to this and has undergone various changes over time to respond to problems, encountered in conservation. The analysis of this research is carried out through “codifying” at three levels: first cycle codifying, second cycle (middle) codifying, and third or final cycle codifying (post-coding). The codes were reviewed and stored to verify the qualitative data, in order to identify conservation principles of the cultural landscape of these Bridge (the core of the research), at the final stage (Afshar, 2014). In the following, by integrating, the results of code analysis are compatible with the dispersive components of the image (Giviyan, 2016). In the following, recommendations for the conservation of selected bridges’ cultural landscapes were categorized into two categories, generic and specific to the selected bridges themselves using qualitative research method, data analysis, and coding operations at three levels to reach the final results of the research.

Conclusion
This research, in the form of fundamental-applied research, was able to identify the conservation of the cultural landscapes of the studied historical bridges and make them applicable to other similar historical bridges in Lorestan. This study was able to introduce recommendations in two general categories Generic and specific to the bridges themselves. In response to the first part of the research question, the concepts and constituent elements of the cultural landscape of historical bridges were identified through the library, field studies, and analysis of various concepts in the subject literature and in accordance with the native conditions of the cultural landscape under study. In answer to the second part of the research question, it can be said that by analyzing the collected literature and taking a look at field studies, by examining and analyzing the challenges of conserving cultural landscapes and the meanings and concepts of conservation in national charters, conventions and treaties, and International; Investigating and analyzing the meanings and concepts of cultural landscapes in national and international charters, conventions and treaties. These recommendations, since taken from the very context of the aforementioned research and context, have been categorized into a specific framework and have created a systematic model for the conservation of the cultural landscapes of the historical bridges studied.