تحلیل خصوصیات هیدروژئومورفیک حوضه آبریز الندچای به منظور اولویت‌بندی زیر حوضه‌ها از نظر حساسیت سیل خیزی

تحقیق حاضر با هدف اولویت‌بندی زیر حوضه‌های حوضه آبریز الند چای واقع در استان آذربایجان غربی از نظر حساسیت سیل خیزی انجام گرفته است. برای نیل به این هدف، ابتدا حوضه آبریز الندچای بر اساس خصوصیات شبکه زهکشی و توپوگرافی و با استفاده از مدل رقومی ارتفاعی (dem) با قدرت تفکیک مکانی 12.5 متر به 15 زیر حوضه‌ تقسیم شد. در مرحله بعد پارامترهای ژئومورفومتریک هر زیر حوضه از سه جنبه خصوصیات شبکه زهکشی (شامل رتبه آبراهه، تعداد آبراهه، طول آبراهه، تناوب آبراهه، نسبت انشعاب، طول جریان در روی زمین، تراکم زهکشی، بافت زهکشی، نسبت بافت، شماره نفوذ، ثابت نگه داشت کانال و ضریب رو)، پارامترهای شکلی حوضه (شامل مساحت، ضریب فشردگی، نسبت مدور بودن، نسبت کشیدگی، ضریب شکل و شاخص شکل) و خصوصیات برجستگی حوضه آبریز (شامل برجستگی، نسبت برجستگی، عدد سختی یا زبری و نسبت شیب) با به‌کارگیری قوانین ژئومورفولوژیکی هورتن، شوم و استرالر در محیط نرم‌افزار arcgis تهیه شدند. به‌منظور وزن دهی 22 پارامتر مورد بررسی در تحقیق حاضر از روش وزن دهی نوین swara استفاده شده و وزن نسبی هر یک از پارامترها برای 15 زیر حوضه مورد مطالعه مشخص گردید. نتایج وزن دهی و اولویت بندی نشان داد که زیر حوضه‌های 3، 1، 4 و 2 به ترتیب با وزن 0.142، 0.122، 0.091 و 0.087 بیش‌ترین وزن را داشته‌ و از حساسیت سیل خیزی بالایی برخوردار می‌باشند. در مقابل زیر حوضه 13 با وزن نهایی 0.018 و زیر حوضه 6 با وزن 0.020 به ترتیب کم‌ترین وزن را از نظر 22 پارامتر مورد بررسی داشته و درنتیجه در طبقه خیلی کم از نظر حساسیت سیل خیزی قرار دارند.

Analysis of Hydrogeomorphic Properties of Aland Chai Basin to Prioritize SubBasins in terms of Flood Sensitivity

IntroductionFlood is a disaster which causes a lot of economic damages to farmlands, forests, gas and power transmission lines, roads, engineering structures, and buildings. There are numerous floods in the northwest of the country at the beginning of spring and the start of spring rains, which in most cases results in heavy damage. The purpose of this study is Geographic Information System (GIS)based analysis of hydrogeomorphic properties of Aland Chai Basin for preparing flood sensitivity map. To this aim, hydrogeomorphic parameters of subbasins have been studied from three aspects of drainage network characteristics (e.g., stream order, streams number, streams length, stream frequency, bifurcation ratio, length of overland flow, drainage density, drainage texture, texture ratio, infiltration number, constant of channel maintenance, and rho coefficient), basin geometry (e.g., basin area, compactness coefficient, circulatory ratio, elongation ratio, form factor, and shape factor) and relief properties (relief, relief ratio, ruggedness number, and gradient).Study areaAland Chai basin is located between 38, 30´ and 38, 48´ N and between 44, 15´ and 45, 01´ E in the West Azerbaijan province. It covers an area of 1147.30 km2 and it is situated in the northwestern part of Iran. This basin is one of the subbasins of the Aras River basin to which surface water flows after joining the grand Qotour River. Basin elevation variations are from 1093m in the Aland Chai River bed to 3638m above sea level in the Avrin Mountain.Figure 1. The study area location in the West Azerbaijan provinceMaterials and MethodsThe StepWise Weight Assessment Ratio Analysis (SWARA) model was introduced to the provided relational database in weighting of data layers. SWARA technique is one of the multicriteria decision methods which was developed by Keršuliene et al. (2010). In this method, an expert has an important role in evaluating and calculating weights. Based on this method, the most signifcant criterion is ranked as the first, while the least signifcant one is ranked as the last.Results and DiscussionHydrogeomorphic analysis plays an important role in the analysis of hydrological behavior of the basins. In the present study, 22 hydrogeomorphic parameters were analyzed from three aspects of drainage network characteristics, shape parameters, and relief properties in order to investigate the role of these parameters in flood sensitivity of Aland Chai basin. Digital Elevation Model (DEM) with 12.5m spatial resolution and ArcGIS software were used to generate the data layers maps. In the next step, all necessary weights were calculated for factors and Subbasins using SWARA model. According to a comparison between factors for each subbasin, it was specified that subbasins 3, 1, 4, and 2 (weighted as 0.142, 0.122, 0.091, and 0.087) have the highest impacts on Flood occurrence in study area. On the contrary, subbasins 13 and 6 (weighted as 0.018 and 0.020) show the lowest weight.ConclusionIn this study, an attempt was investigated to identify subbasins with high potential for flood occurrence in Aland Chai basin. Based on the effective parameters, flood occurrence inside of Aland Chai basin could be separated into 5 distinguished classes from very high to very low flood susceptibility. According to the SWARAbased flood susceptibility map, subbasins 3, 1, 4, and 2 of the study area have very high potential, subbasin 7, 15 and 11 have high susceptibility, subbasin 12, 5, and 9 have moderate susceptibility, subbasins 8, 10, and 14 have low susceptibility, and subbasins 6 and 13 have very low susceptibility toward flood occurrence. The total area of subbasins in the high and very high class of flood is 656.72 km2, which comprises 57.24% of the total Aland Chai basin. Therefore, according to the results of the study, it is necessary to take protective measures such as watershed planning and dam construction in the subbasins that are highly sensitive to prevent flood or reduce potential damages in case of flooding. & nbsp;