جستجوی مقالات مرتبط با کلیدواژه « ndwi » در نشریات گروه « جغرافیا »

Estimation of flood zoning is very important in terms of management and determination of flood damages. Remote sensing and the use of high-resolution images can be effective in extracting flood zoning estimator indicators. In this research, Sentinel 2 images in the year of the flood occurrence with a spatial resolution of 10 meters and Landsat 8 images at the same time in the years before and after the flood were used by environment the Google Earth Engine.  In this study, the zoning of the flood was estimated using indices of NDWI, MNDWI, and DVDI. The results showed that the MNDWI, despite the long-time interval (20 days) after the flood of 2019 and the evaporation of most of the water spread over the lands, the area of flooding was estimated better compared to the NDWI  around 330.59 ha. Also, the flood-affected area using DVDI (that indicates the destruction of vegetation due to floods showing negative values) was estimated at 3522.21 ha, which showed a small difference compared to the results provided by the results of Lorestan Governorate research (4750 hectares). Finally, the results showed although DVDI optimally estimated flood zoning due to the use of the 5-year time series of the NDVI before and after the flood if the cloud-free images of Sentinel 2 exist to extract the MNDWI, it probably could perform better than the DVDI. In general, the use of the above indicators is suggested as an important, practical, and low-cost method for management, area estimation, and flood damage determination.

Earth's surface temperature is considered an important parameter in biosphere, ice globe and climate change studies. In this research, LST, NDVI, NDMI and NDWI values were calculated for the Anzali wetland area using the OLI and TIRS measurements of the Landsat 8 satellite. Investigations showed that the minimum LST temperature for the years 2013, 2018 and 2023 was equal to 13.94, 22.36 and 14.6, respectively, and its maximum values for these years were equal to 35.7, 40.58 and 31.6. 31.6 degrees Celsius is estimated respectively. Vegetation status, access to water resources and water stress for the study area were estimated with NDVI, NDWI and NDMI indices. Bands 3, 4, 5, 6 and 10 of Landsat 8 satellite were used to estimate these indicators. The obtained values were compared with LST values. The distribution charts show that the highest negative correlation between LST and NDMI is established at the rate of -0.65 and the highest positive correlation between the NDWI and LST indices is established at the rate of 0.23. In general, the investigations have shown that there is a negative correlation between the NDMI and NDVI indices with the LST index. The Support Vector Machine (SVM) method was also used to investigate land use changes (LULC). The results showed that in the studied area, which has an area of 686.81 square kilometers, agricultural lands have faced significant expansion and reached 487.7 square kilometers from 329 square kilometers in 2013. In the meantime, forest areas have faced a sharp decrease and have decreased from 34.8 square kilometers to 1.73 square kilometers.

Urban rivers are of the most important reasons for flood inundation in cities. This study aimed to investigate the morphological effects of the Gorganrood River in Aq’ Qala City in a case of flood inundation on March 2019. The images of Sentinel-2 and Landsat-8 were downloaded for full flood monitoring. After preprocessing, the NDWI and MNDWI indices were applied on the images to extract the flood zones. The sinuosity index and the number and mean radius of meanders were calculated from Sallaq Yilqi village to Dogonchi village using Google Earth and AutoCAD. The NDWI index was appropriate to detect the permanent and clear waters, while the MNDWI index was appropriate to detect the muddy waters and high humidity terrains. The area of flooded zones which obtained from the MNDWI index was 88% more than those of NDWI index. The sinuosity index was 3.88 (sever meander) in the district of the Sallaq Yilqi village to the Yampi village. Destruction outer arc meanders and low radius of meanders and erosion of soils in upstream were caused overflow the flood in the Gorganrood channel. On the 20th March due to low channel width and very-low gradient of bed river (0.0002) from the Aq Tekeh Khan village to the Dogonchi village were caused slow velocity of flood stream, therefore the water level was raised and the city of Aq’ Qala were flooded. According to the flood maps obtained, the northern and southern of the Aq’ Qala city located at high-risk zone. Canalization of outer meanders curvature, planting the absorbent vegetation around the quantitative buffer zone of the Gorganrood river, widening and dredging the channel and modifying structure of channel on the northern plains of Gorganrood River can be prevented from flooding over the Aq’ Qala city.