Introduction
Flood is a natural disaster with severe negative impacts, especially on urban and peri-urban areas. The consequences of flood range from loss of life and property to disruption of essential services and infrastructure. Developing countries are particularly vulnerable to these disasters due to factors such as rapid population growth, inadequate infrastructure, and limited resources for disaster preparedness and disaster response. Various methods are used to mitigate the flood risks, ranging from geological and sedimentological approaches to climate change analyses. Among these methods, geomorphological techniques offer a comprehensive approach by integrating endogenous (internal processes of the Earth) and exogenous (external processes of the Earth) agents. By considering the interaction between geological features, surface processes, and climate factors, geomorphological methods provide comprehensive insights into risk zonation and facilitate the development of effective hazard mitigation measures and solutions. The purpose of this study is to locate the zones at risk of floods in the Lavasanat watershed located in Shemiranat County, Tehran Province, Iran. Due to its proximity to Tehran and having a rustic nature, Lavasanat has high economic value; thus, is always exposed to encroachments and illegal constructions. The occurrence of floods can have adverse effects on its watershed area and cause high sediment loads. 

Methods
In this research, the flood risk zoning in the study area was carried out based on the fuzzy logic model. The layers of slope, precipitation, distance from the waterway, land use, elevation and lithology were used to zone the flood risk. All layers were first classified. To implement the fuzzy logic model, it is necessary to first weight the layers based on the membership function. Each layer was thus weighted and converted into raster layers, and the layers were fuzzy in the value range of zero to one. The weighting was done based on the opinions of 30 experts, who were asked to complete a designed questionnaire and score each factor from 0 to 1. The precipitation factor was weighted by considering four categories, while distance from the waterway, slope, land use, and elevation had five categories, and lithology had 10 categories. After weighting the layers, we calculated them using the fuzzy sum model which complements the algebraic multiplication model. In the output map based on this model, the pixel values tend towards 1 (higher membership value). As a result, more pixels are placed in the “very high risk” class. Then, the layers were fuzzified using the fuzzy multiplication model. In this model, all information layers are multiplied together. This model causes the numbers in the output map to become smaller and tend towards 0 (lower membership value); as a result, fewer pixels are placed in the “very safe” class.

Results
Based on the results, the safe zone had an area of 3450 hectares, covering 20% of the area. This zone was mainly located away from waterways and was consistent with the steep and high-altitude areas. The area of the low-risk zone was 4874 hectares. Like the safe zone, this zone was located away from waterways and mainly covered the region’s central areas, which have the largest area in the region. The area of the moderate-risk zone was 4276 hectares. The high-risk zone had an area of 2056 hectares, which were mainly located around waterways on low slopes and in areas with low vegetation cover. The very high risk zone had an area of 1980 hectares, which was located around waterways on low-slope areas, similar to the high-risk zone. 

Conclusion
More than 23% of the region is in zones at high and very high risk of floods, which are mainly located around the main waterway. In urban and rural planning, development, and construction, the requirements for flood prevention and risk reduction, including the provision of retention and storage areas, should be considered.

Ethical Considerations
Compliance with ethical guidelines
This research was conducted in compliance with the ethical principles. Since there was no experiment on human or animal samples, the need for an ethical code was waived.
Funding
This research did not receive any specific grant from funding agencies in the public, commercial, or not-for-profit sectors.

Authors' contributions
All authors contributed equally to the conception and design of the study, data collection and analysis, interpretation of the results, and drafting of the manuscript. Each author approved the final version of the manuscript for submission.

Conflicts of interest
The authors declared no conflict of interest.



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