پهنه‌بندي خطر سيل‌گرفتگي توسط معادله انرژي جريان و سيستم اطلاعات جغرافيايي

Flood Risk Mapping Using Flow Energy Equation and Geographic Information System

دو پارامتر عمق و سرعت سيل تعيين‌كننده ميزان خطري است كه سيل در هر نقطه دارد. معادله حاكم بر انرژي جريان از آن جهت كه داراي هر دو معيار سرعت و عمق جريان است، براي تحليل در اين زمينه مناسب به‌نظر مي‌رسد. به‌منظور تدقيق در پهنه‌بندي سيل با دوره‌هاي بازگشت مختلف و خطر مواجهه با آن در اراضي حاشيه رودخانه‌ها، روشهاي متعددي پيشنهاد شده است. دخيل نمودن عواملي نظير تحليل سيلهاي گذشته در منطقه تحت تاثير سيل، عوامل هيدرولوژيكي منطقه و درنظر گرفتن مولفه‌هاي هيدروليكي موثر در پهنه‌بندي سيلاب نظير سرعت جريان از اين دسته هستند. در اين مقاله تاثير پهنه‌بندي سيل توسط انرژي جريان در نقاط تحت تاثير سيل بررسي گرديد. همچنين خطر سيل از نظر انرژي جريان، در هر مقطع از مسير رودخانه، با ارايه يك نمودار پيشنهادي بازه‌بندي خطر با ديگر پهنه‌بندي‌هاي انجام گرفته در اين زمينه مقايسه گرديد. در اين مقاله رودخانه فردو از رودخانه‌هاي بخش كهك استان قم كه داراي مشخصات كوهستاني و جوان در بالادست و بالغ و پايدار در پايين‌دست جريان است و در فصلهاي مختلف سال مورد آسيب سيل قرار مي‌گيرد، مورد بررسي قرار گرفت. روش پيشنهادي در اين تحقيق، علاوه بر بالابردن دقت شناسايي خطر سيل در نواحي سيل‌گير، شناسايي قسمت‌هايي از بستر و حاشيه رودخانه كه تحت تاثير شديد سيل قرار مي‌گيرد را براي تصميم‌گيري به‌منظور ساماندهي رودخانه‌ها تسهيل مي‌كند.

Flooding and its damages are not only found uplift water level in a region. In other words, the depth and speed parameters together have determining the level of flood risk at each point. This subject is visible in flooded plain with low height and high speed of 2 meters per second, which damages are extensive. According to the criteria of having both velocity and flow depth in the governing equation to the flows energy, this equation seems appropriate to analysis in this study. Various methods have been proposed for increase accuracy in flood zoning with different return periods and risks associated with it in land border of river. For example, some of these methods are considered factors such as analysis of past flooding in the area affected by floods, hydrological factors and consideration of hydraulic elements affecting in flood zoning (such as flow velocity). This paper investigates the effect of flood zoning by the energy flow in the areas affected by floods. Also risk due to flood based on energy flow in each section of the river is compared by the proposed graphs of hazard interval and other done flood zoning in this field. In this study, the FORDO river has been selected as the case study. This river is part of the rivers located in the city of QOM KAHAK. The characteristics of river in upstream and downstream are mountain, young and stable and adult, respectively. Also this river in different seasons is exposed the flood damage. The proposed method in this study can be improving recognition accuracy of flood risk in areas affected by flood. Also, this method facilitate the identify parts of the river bed, that is affected by severe flooding, for decision making to improve rivers organizing.