Morphology, sedimentology and origin of an anomalous cut-off along the Pravara river, deccan trap region, India

River meanders have always been an intriguing subject in fluvial geomorphology because of their ubiquity, dynamism, remarkable forms and practical consequences of their movement. Sometimes a relatively straight channel flowing over bedrock may develop a lone meander bend cut-off which is very out of the place from the surrounding area. The occurrence of a sudden bend along a river may not be a meandering bend but may be manifestation of sudden change in the river dynamism due to many reasons, such as, lithology, change in rainfall regime, tectonics etc. The formation of such features highlights the behavior of river in the past. One such striking feature has been observed along the River Pravara in the Deccan Trap Region, Maharashtra, India. Rivers in Deccan Trap Region do not meander and form cut-offs by rule. It is rocky country where rivers flow in deeply incised bedrock. Hence, the observed feature displays a striking anomaly in this region. Hence, an attempt has been made in the present paper to evaluate the mode of formation of this single cut-off along this channel. Morphological and sedimentological data were generated and analyzed for the channel loop and the link channel to understand the competence of the river in the past and present which were directly or indirectly responsible for the development of this channel anomaly in this reach. Based on the results of the analysis and intensive field observations, it has been inferred that this is a classic example of natural morphological adjustment of a river when a set of events occurred, first retardation of vertical erosion encountering bedrock followed by series of floods to induce the channel to divert from the original path to resume the present course. Presence of a tributary further aided to the process of the loop development. The study can provide additional knowledge to the studies involving anomalous channel cut-offs at any part of the world.

The retreat of the delta: a geomorphological history of the Po river basin during the twentieth century

The morphology of rivers and deltas, like many features of the Earth’s physical geography, is today subject to dramatic and rapid changes due to human actions. Deprived of sediment from their basins and besieged by rising sea levels, many deltas are at risk of complete disappearance. Despite a rich historical scholarship on rivers, we know little about the history of these important geomorphological processes. This paper sheds light on the geomorphological history of rivers by investigating the case of the Po River basin and its delta during the twentieth century. By combining the insights of fluvial geomorphology and a historical methodology, the paper analyses three main drivers of geomorphic alterations in the catchment that had an impact on the delta: hydroelectricity, sand and gravel mining, and methane extraction. In each case, it focuses on how experts, policy-makers, and overseers understood and regulated (or not) these geomorphic alterations. During much of the twentieth century, engineers and hydrologists monitored geomorphic processes with increasing detail, while state and business actors practiced multiple forms of sediment management. For most of the twentieth century, however, experts did not acknowledge the scale and nature of human-induced geomorphic alteration. Sediment management, moreover, did not take into account sediment scarcity until late in the century, and remained exclusively motivated by local concerns. Through this particular case, this paper offers insights on the historical limits to environmental expertise and policy when facing long term and large-scale geomorphic processes, and encourages a more sustained incorporation of fluvial geomorphology into the history of water systems.

Fluvial Geomorphology and River Management

This Special Issue deals with the role of fluvial geomorphology in landscape evolution and the impact of human activities on fluvial systems, which require river restoration and management [...]

Mapping of Quaternary river terrace landforms with Unmanned Aerial Vehicle (UAV): A case study in the Sakarya River, NW Turkey

<p>River systems are areas that respond most rapidly to regional and / or local tectonic movements, with global climate changes and general basement fluctuations that occurred during the Quaternary period. The most important geomorphological units where these events can be observed are terrace systems, which are the result of deposition and erosion processes. In fluvial geomorphology research on terrace systems, modern technological innovations are used as well as conventional field methods. Especially low-cost Unmanned Aerial Vehicles (UAV) and modern photogrammetry methods are preferred because they both provide detailed and precise identification of terraces and high resolution topography outputs in spatial and temporal terms.<br>This study aims to put a comprehensive mapping of the terrace systems observed in an area of 1.27 km² around Gemiciköy (Bilecik Province), which is located in the middle part of the Sakarya River valley, the largest river in Northwest Anatolia. Accordingly, we used the Structure from Motion (SfM) method which is based on photogrammetric principles and UAV. During the study, 582 images taken from a height of 100 m and having 80% overlap in line with the flight plans by using the DJI Mavic Mini UAV model were evaluated in Agisoft Metashape Professional software. With the use of image processing algorithms, the dense point cloud was first obtained, and then the orthomosaic and digital surface model with 3.29 cm resolution was produced. Two terrace levels (+10 m and +19 m) detected with digital surface modeling, and these were verified by stratigraphic and sedimentological observations made in the field.<br>As a result, low-cost UAV technologies are quite useful in terms of providing more detailed monitoring, mapping and analysis of river environments, together with the production of sensitive and high resolution topography data required in modern fluvial geomorphology research.</p>