Explaining Strategies for Increasing Physical Resilience against FloodCase Study: Cheshmeh Kile River, Tonekabon River

The intensity of flooding in different parts of the country or in other words in different catchments, depending on climatic conditions, topography and other factors, such as: vegetation varies from point to point. Existing studies based on hydrological statistics and flood events show that the southwest and southeast are the most flood-prone parts of the country. According to studies, about 40 small and large floods occur annually in all parts of Iran. Land leveling, encroachment on rivers and canals, changes in the pattern of natural drainage and flooding in urban areas; The roads will be flooded and the city's maintenance costs will increase.Natural disasters, which are part of the process of human life and are increasing in number and diversity every day, pose a major challenge to achieve sustainable development. In recent years, considerable damages have been caused to the physical fabric of Tonekabon due to the floods and its effects are mainly on the urban fabric around the main river of the city (Cheshmeh-Kileh River). Therefore, the purpose of this article is to elaborate strategies that lead to increased physical resilience against the flood of the Cheshmeh-Kileh River in Tonekabon.

The present study uses a descriptive-analytical method. Therefore, prior to starting the SWOT model steps, variables and indicators were extracted using previous researches in theoretical foundations and then, the conceptual model was developed. Subsequently, using the Content Validity Analysis (CVR) method, the essential variables and indicators were identified to be analyzed using the SWOT model. The methodology of this research is a combination of quantitative and qualitative methods that utilize GIS, AHP and SWOT softwares. Flood risk simulation software (HEC_GEORAS) was used to map the flood risk in the fabric. Three flood risk zones (river privacy, high risk, and medium risk zones) were then identified and then the indicators and variables applied in the study were prioritized. These variables were extracted from different sources and the validity of selected cases was determined and finally strategies were applied to reduce the risk of flooding in the surrounding of Cheshmeh-Kileh River.

Out of 7 indicators, 6 indicators were selected as land use indicators to increase the physical resilience of Tonekabon city against floods, which can be identified in the next step using a hierarchical analysis model. Out of 10 variables, 7 variables were considered useful by urban experts (municipality, Tonekabon water department and governorate) as functional variables to increase the physical resilience of Tonekabon city against floods.
Since the impact of variables and indicators on the issue of physical resilience is not the same, it is necessary to adopt strategies and policies according to their prioritization. To prioritize the variables and indicators, using a hierarchical analysis model, two questionnaires were set separately, one for the variables and the other for the indicators, as a matrix to compare them in pairs, and with the help of a survey of 30 urban planning experts, their importance coefficient was determined.

The results show that there is a coherent relationship between the physical structure in the fabrics around the Cheshmeh-Kileh River in Tonekabon and the increasing physical resilience of Tonekabon against flood. Therefore, by applying the principles and strategies formulated in this article, we can improve the city's performance during floods through planning, designing and implementing the appropriate fabric structure around the River.