Special Issue "Close-Range Remote Sensing and Modern Field Measurements in Fluvial Geomorphology"

A special issue of Water (ISSN 2073-4441). This special issue belongs to the section "Hydrology".

Deadline for manuscript submissions: closed (31 March 2020).

Special Issue Editor

Prof. Dr. Petteri Alho
Website
Guest Editor
Department of Geography and Geology, University of Turku, FI‐20014 Turku, Finland
Interests: river dynamics; close-range remote sensing in fluvial studies; fluvial processes in boreal and subarctic regions; flood risk studies; computational fluid dynamics; paleoflood studies

Special Issue Information

Dear Colleagues,

Current progress in close-range remote sensing, field measurement techniques, data connections, and processing has enabled new research approaches in fluvial geomorphology. Laser scanning including terrestrial, airborne, UAV-LS, and mobile laser scanning has been used in the detection of small-scale fluvial forms on point bars and flood plains. Sonar techniques and optical imagery have been used for bathymetric mapping and the detection of submerged fluvial forms on a river bed. Lately, structure from motion (SfM) has also been used for a river survey. However, the level of detection has been much coarser on submerged river sections compared to the mapping of forms above the water surface. Moreover, challenges in multisensor data processing are yet to be solved—e.g., merging and georeferring of sonar-based bathymetric data and high-resolution remote sensing data of topography might cause a strong impact on the level of detection. A multi-angular mapping approach is also needed to diminish the shadow effect in data created through steep and changing topography and vegetation of riverine environments. Further, high frequent flow measurements have been undertaken by new ADCP sensors and remotely-controlled platforms. These set-ups enable three-dimensional studies of the flow structures with higher level of detail compared to the classic cross-sectional sampling strategy.  

These abovementioned mapping and measurement methods are still rather young, and hence, more testing and demonstration is needed before these methods are standardized in fluvial geomorphology. Therefore, this Special Issue welcomes fluvial geomorphology studies dealing with state-of-the-art close-range remote sensing and/or field measurement approaches. It provides a publication medium for research and review papers. Topics of interests include but are not limited to:

  1. Laser scanning/SfM for fluvial form mapping;
  2. River dynamics surveyed with close-range remote sensing;
  3. Merging flow measurements and bathymetric mapping;
  4. Topographic/bathymetric data collection and processing in river studies;
  5. Reach scale change detections with multisensor RS data;
  6. 3D flow characteristics with ADCP measurements;
  7. Winter-time field measurements.

Prof. Petteri Alho
Guest Editor

Manuscript Submission Information

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Keywords

  • river dynamics
  • close-range remote sensing
  • mapping of fluvial forms
  • laser scanning
  • ADCP
  • SfM
  • bathymetric mapping
  • UAV

Published Papers (4 papers)

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Research

Open AccessArticle
Image-Based Bed Material Mapping of a Large River
Water 2020, 12(3), 916; https://doi.org/10.3390/w12030916 - 24 Mar 2020
Abstract
The composition or bed material plays a crucial role in the physical hydromorphological processes of fluvial systems. However, conventional bed material sampling methods provide only pointwise information, which can be inadequate when investigating large rivers of inhomogeneous bed material characteristics. In this study, [...] Read more.
The composition or bed material plays a crucial role in the physical hydromorphological processes of fluvial systems. However, conventional bed material sampling methods provide only pointwise information, which can be inadequate when investigating large rivers of inhomogeneous bed material characteristics. In this study, novel, image-based approaches are implemented to gain areal information of the bed surface composition using two different techniques: monocular and stereo computer vision. Using underwater videos, captured in shorter reaches of the Hungarian Danube River, a comparison of the bed material grain size distributions from conventional physical samplings and the ones reconstructed from the images is carried out. Moreover, an attempt is made to quantify bed surface roughness, using the so-called Structure from Motion image analysis method. Practical aspects of the applicability of image-based bed material mapping are discussed and future improvements towards an automatized mapping methodology are outlined. Full article
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Open AccessArticle
Comparative Assessment of Fluvial Suspended Sediment Concentration Analysis Methods
Water 2020, 12(3), 873; https://doi.org/10.3390/w12030873 - 20 Mar 2020
Abstract
The monitoring of fluvial suspended sediment transport plays an important role in the assessment of morphological processes, river habitats, or many social activities associated with river management. However, establishing and operating a well-functioning sediment monitoring system requires the involvement of advanced indirect methods. [...] Read more.
The monitoring of fluvial suspended sediment transport plays an important role in the assessment of morphological processes, river habitats, or many social activities associated with river management. However, establishing and operating a well-functioning sediment monitoring system requires the involvement of advanced indirect methods. This study investigates the advantages and limitations of optical and acoustic devices, to quantify the uncertainties and provide a comprehensive comparative assessment of the investigated indirect methods. The novelty of this study, compared to previous ones, is that four different indirect techniques are parallel tested, i.e., the laser diffraction based LISST-Portable|XR, an infrared based optical instrument, the VELP TB1 turbidimeter, the acoustic based LISST-ABS (Acoustical Backscatter Sensor) sensor, and a 1200 kHz Teledyne RD Instruments Acoustic Doppler Current Profiler (ADCP). The calibration of all the indirect methods was performed based on more than 1000 samples taken from the Hungarian section of the Danube River within a wide suspended sediment concentration range. Implementing a comparative assessment of the different sediment analysis methods, a qualitative and quantitative characterisation of the applicability is provided. Furthermore, a proposal for an optimised sediment monitoring methodology is also suggested. Full article
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Open AccessArticle
Application of Remote Sensing Methods to Study the Relief of Lowland River Valleys with a Complex Geological Structure—A Case Study of the Bug River
Water 2020, 12(2), 487; https://doi.org/10.3390/w12020487 - 11 Feb 2020
Abstract
River valleys of the Central European Lowlands are the zones of the highest dynamics of morphogenic processes. In the case of areas affected by glacial processes, despite their lowland nature, often they also have a complex geological structure. Sub-alluvial bedrock, composed of erosion-resistant [...] Read more.
River valleys of the Central European Lowlands are the zones of the highest dynamics of morphogenic processes. In the case of areas affected by glacial processes, despite their lowland nature, often they also have a complex geological structure. Sub-alluvial bedrock, composed of erosion-resistant deposits, commonly forms morphological protrusions within them. Their presence significantly affects both the course of flood flows and the valley floor relief. Effective forecasting of fluvial processes in such valley reaches requires conducting research within the entire geomorphologically active zone, both in the channel and the floodplain. The effectiveness of such research should be enhanced by simultaneous use of several different remote sensing methods, including short-range remote sensing. The verification of this hypothesis was the aim of the presented works. Such methods were used in the study of morphodynamics of a Bug valley reach. This area is characterized by a complex geological structure. High-resolution multispectral satellite images (VHRs) and a digital elevation model (DEM) based on aerial laser scanning (ALS) were used to examine the terrain relief. The morphology of the river channel itself was determined based on a series of bathymetric measurements made by a research team. Due to induced climate change and increasing maximum flow values, it can be assumed that the effect of a geological structure in the Central European Lowlands will play an increasing role. The threat and losses associated with floods will also increase. Rational flood prevention requires improvement of remote sensing research methods in lowland river valleys, especially those with complex geological structures. The valley reach presented in this article is an example of such a landform. Full article
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Open AccessArticle
Terrestrial Laser Scanning for the Detection of Coarse Grain Size Movement in a Mountain Riverbed
Water 2019, 11(11), 2199; https://doi.org/10.3390/w11112199 - 23 Oct 2019
Abstract
Fluvial transport is a natural process that shapes riverbeds and the surrounding terrain surface, particularly in mountainous areas. Since the traditional techniques used for fluvial transport investigation provide only limited information about the bed load transport, recently, laser scanning technology has been increasingly [...] Read more.
Fluvial transport is a natural process that shapes riverbeds and the surrounding terrain surface, particularly in mountainous areas. Since the traditional techniques used for fluvial transport investigation provide only limited information about the bed load transport, recently, laser scanning technology has been increasingly incorporated into research to investigate this issue in depth. In this study, a terrestrial laser scanning technique was used to investigate the transport of individual boulders. The measurements were carried out annually from 2011 to 2016 on the Łomniczka River, which is a medium-sized mountain stream. The main goal of this research was to detect and determine displacements of the biggest particles in the mountain riverbed. The methodology was divided into two steps. First, the change zones were detected using two strategies. The first strategy was based on differential digital elevation model (DEM) creation and the second involved the calculation of differences between point clouds instead of DEMs. The experiments show that the second strategy was more efficient. In the second step, the displacements of the boulders were determined based on the detected areas of change. Using the proposed methodology, displacements for individual stones in each year were determined. Most of the changes took place in 2012–2014, which correlates well with the hydrological observations. During the six-year period, movements of individual particles with diameters less than 0.8 m were observed. Maximal displacements in the observed period reached 3 m. Therefore, it is possible to determine both vertical and horizontal displacement in the riverbed using multitemporal TLS. Full article
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