Volume XIII |

Estimation of the Quaternary stream erosion in small drainage basins (Vâlcea sub-Carpathians and Olteţ Plateau, Romania)

Abstract: Stream erosion is a widely spread process in the Getic sub-Carpathians and Plateau (including the study sub-units). It is controlled by the high density of small drainage basins on a surface unit. Development of the 4th and 5th order valleys (according to Strahler’s system) in the sub-Carpathians and of the 3rd and 4th order in the Olteţ Plateau was also determined by the high altitude of hillslopes, up to 450 meters in the Vâlcea sub-Carpathians and to 250 meters in the Olteţ Plateau, a consequence of the strong downcutting performed by the Olt river and its main tributaries in this area (Olăneşti, Bistriţa, Cerna and Olteţ). Another control factor is the friable bedrock made of sedimentary deposits: conglomerate, gravel, sand, sandstone, marl, clay, tuffs etc. in the Vâlcea sub-Carpathians and Cândeşti strata (gravels with clayey lens of Villafranchian age) in the Olteţ Plateau.

Volume XIII |

River Change Detection and Bankline Erosion Recognition using Remote Sensing and GIS

Abstract: Bangladesh is mainly formed by alluvial deposits, facing riverbank erosion very frequently due to unvarying alteration of river channels. This study is aimed at computing the actual bank shifting along the Manu River within Bangladesh for a period of thirteen years (1997-2010). The entire course of Manu River from upstream of India Border, Moulvibazar to the confluence with the Kushiyara River at Manumukh, Sherpur for a stretch of around 69 km has been studied using an integrated approach of Remote Sensing and Geographical Information System (GIS). The channel configuration of the Manu River has been mapped for the years 1997 and 2010 using Landsat satellite images. The analysis divulged that the Manu River is a highly meandering river with several very critical sections where the river has been suffering enormously with the erosion problem and shifting characteristics. The enumerated river shifting was found very high as the maximum left bank shifting and maximum right bank shifting had occurred at Rajnagar, Moulvibazar of 656 m and 628 m respectively, in the mentioned period. The results deliver latest and steadfast evidence on the dynamic fluvio-geomorphology of the Manu River for designing and execution of erosion control schemes.

Volume XIII |

Preliminary data on the Jiu River meanders in the lower course (South-West Romania)

Abstract: The aim of this study is the complex monitoring of the Jiu river bed in terms of geometry and complexity of meanders in its lower sector (on a length of 77 km). The detailed analysis of the lower Jiu sector meanders completes the geomorphologic knowledge of rivers in Romania, starting from the identification and determination of the type of meanders: the results that were achieved are represented by the indexes concerning their age and migration rate (wavelength, 1977 – 4721 m; meanders amplitude, 511 – 2862 m; the mean radius of curvature, 270 – 997 m and the sinuosity index, from 0.87 to 2.17). Another aim of this study is the identification of the evolution features of the Jiu river, the relationships between some hydrological factors of control (liquid flow and suspended sediments – annual average values) and the generations of meanders (actual or open meanders, and incised meanders or paleomeanders) distributed in two sectors: Podari – Padea sector and the sector stretching from Padea up to the Danube confluence. In addition, our concern is motivated by the fact that in the last years there were analyzed the landslides and subsidence on the right slope of the Jiu river (next to Bâzdâna and Drănic settlements), strongly eroded and in close connection with the meandering of the watercourse.

Volume XIII |

Remote Sensing data & GIS for flood risk zonation mapping in Varanasi District, India

Abstract: Flood is one of the natural disasters causing colossal loss of life and property. It occurs with a strange regularity in different parts of India, thus devastating those particular areas. The most flood prone areas in the country are in the Ganga and Brahmaputra basins whilst the annual flood damages in the Ganga basin account for about 60 percent of the total. The extent of the damages shows a pattern of increase from west to east (downstream along the Ganga) and from south to north (towards the hills). The present study delineates the application of geographic information system (GIS) in mapping flood risk zones in Varanasi, one of the prominent districts of the Indo-Gangetic plain. The whole district witnesses havoc of flood in rainy season due to impounding of huge amount of water in the Ganga river. The damage and loss of life and cattle due to floods in the area under study are increasing year after year. It could be stated that high magnitude floods occurred in 2013 during the month of August, when the flood plains were mostly used for periodicity and gravity of food. Recognition of flooding parts and flood risk zones in the area under study are the primary steps in the flood control measures. GIS data base has been well utilized in delineating and tackling flood related problems in the area. An attempt has been made to prepare a map of an area measuring about 1526 sq. km. showing flood risk zone with the help of remote sensing data (IRS-P6, LISS III, 2008). A total of five flood risk zones are delineated in Varanasi district. With the help of remote sensing data, flood risk zones in the study area are categorized into low, middle, high, higher and highest level flood zones.

Volume XIII |

Extreme low flow of the Topolovets and Voinishka Rivers (Danube tributaries, Bulgaria)

Abstract: The minimal stream flow is the most sensitive characteristic of stream flow. The aim of the paper is the assessment of the duration and the frequency of low flow through threshold method on daily discharges. The daily data of the two Danube tributaries (the Topolovets and Voinishka) have been used. The results present the following: low flow typically appears in the summer and episodically in the spring and winter; the duration varies between some days to month; the spatial distribution of extreme minimum flow is discrete and depends on climatic and anthropogenic activities. The method of quantiles gives good threshold level for defining extremely low stream flow, but have to apply in keeping with concrete conditions and purposes.