Niayesh Fendereski; Mohsen Masoudian; Klaus Röttcher
Abstract
Over the last two decades, the need to restore rivers to the natural and near-natural state has become noticeable. One of the most important tools to achieve this goal, is to assess the hydromorphological changes of the river due to human intervention. In the present study, in order to evaluate the hydromorphological ...
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Over the last two decades, the need to restore rivers to the natural and near-natural state has become noticeable. One of the most important tools to achieve this goal, is to assess the hydromorphological changes of the river due to human intervention. In the present study, in order to evaluate the hydromorphological conditions of the Tajan River along the middle to lower parts (city of Sari) the Morphological Quality Index (MQI) and Hydromorphological Quality Index (HMQI) has been used. Seven reaches in 50 m riparian buffer width were selected and three quality main indicators including geomorphological, artificial, and channel adjustment were studied using satellite images of Landsat 4 in 1975 and Landsat 8 in 2019, aerial photos in 1960 and 2006, hydrological data, and data collected during the field surveys. The results showed that the studied reaches of Tajan River mainly classified as the moderate-quality class for the MQI, while it is classified as one quality class lower for HMQI, mainly as the poor-quality class. The main reason is that all the studied reaches (except reaches 1 and 7), located downstream of the Shahid Rajaee Dam, within the 30 km, which change considerably the river discharge and sediment transfer, also the extreme human impact and anthropogenic stresses in the catchment, such as land-use change. The results also showed that the method, which was used in this study, is effective, in general, index-based assessment, diagnosis of the hydromorphological problems, and an exact comprehensive realization of the response to the mentioned stresses.
Noorangiz Gholami; Karim Solaimani; Ataollah Kavian; Vahid Gholami
Abstract
Destruction of the riverbed and activities in the river area, including mining activities, road construction, non-standard bridges, etc., often increase the risk of floods. Due to importance of this issue in the present study, the effect of mining activities on determination of channel boundary of Haraz ...
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Destruction of the riverbed and activities in the river area, including mining activities, road construction, non-standard bridges, etc., often increase the risk of floods. Due to importance of this issue in the present study, the effect of mining activities on determination of channel boundary of Haraz River, (Noorrud junction to Kelerd forest area as a given reach) has been investigated with a length of 40 km. In this regard, to study changes in river mineral activity levels during the years 1985 to 2021 from satellite images, to simulate the hydraulic behavior of the river from the HEC-RAS hydraulic model and to compare changes in river area during the study period the DLSRS model were used. Thus, satellite data with visual interpretation techniques were used to determine the level of mining activities. Then, a 1: 2000 scale topographic map of the riverbed in the HEC-GeoRAS (GIS) extension and the HEC-RAS model was used to simulate the hydraulic behavior of the river. Finally, by estimating the five parameters of the DLSRS model, the quantitative values of the river at 10-year intervals were determined in the period 1300-1399. The results of changes in the levels of mining activities indicate geometric changes of the bed of the given reach such as displacement and narrowing process. The results of the study of the factors of channel boundary changes also showed that increasing human activities and changing the river flow regime increase the quantitative boundary of the channel. The results also showed that during the last century, the level of mines in the study area has increased from 3.35 to 13.57 ha in 2021, the maximum development of which has been since 2011. As a result, the quantitative area of the river has increased from 9 m in 1922 to 17 m in 2021.
