scholarly journals Assessment of possible uncertainties arising during the hydromorphological monitoring of a Sand-Bedded Large River

2017 ◽  
Vol 10 (3-4) ◽  
pp. 27-33
Author(s):  
Tamás Právetz ◽  
György Sipos ◽  
Zsuzsanna Ladányi
Keyword(s):  
Morphological Changes ◽  
Time Lag ◽  
Large River ◽  
Bedload Transport ◽  
Repeated Measurements ◽  
Anthropogenic Factors ◽  
Variable Environment ◽  
Digital Elevation ◽  
Adcp Measurements ◽  
Elevation Model

Abstract The riverbed morphology of sand-bedded rivers is dynamically changing as a consequence of quasi continuous bedload transport. In the meantime, the dimension, size and dynamics of developing bedforms is highly depending on the regime of the river and sediment availability, both affected by natural and anthropogenic factors. Consequently, the assessment of morphological changes as well as the monitoring of riverbed balance is challenging in such a variable environment. In relation with a general research on the longer term sediment regime of River Maros, a fairly large alluvial river in the Carpathian Basin, the primary aim of the present investigation was to assess uncertainties related to morphological monitoring, i.e. testing the reproducibility of hydromorphological surveys and digital elevation model generation by performing repeated measurements among low water conditions on selected representative sites. Surveys were conducted with the combination of an ADCP sonar, GPS and total station. The most appropriate way of digital elevation modelling (DEM) was tested and 30-point Kriging was identified to be optimal for comparative analysis. Based on the results, several uncertainties may affect the reproducibility of measurements and the volumetric deviation of DEM pairs generated. The mean horizontal difference of survey tracks was 3-4 m in case of each site, however this could not explain all the DEM deviation. Significant riverbed change between measurements could also be excluded as the main factor. Finally, it was found that results might be affected greatly by systematic errors arising during motor boat ADCP measurements. Nevertheless, the observed, normalised and aggregated DEM uncertainty (600-360 m3/rkm) is significantly lower than the changes experienced between surveys with a month or longer time lag. Consequently, the developed measurement strategy is adequate to monitor long term morphological and sediment balance change on sand bedded large river.

Analysis of morphological changes of the island of Hvar beaches using archive maps, old photographs and UAV (Eastern Adriatic Coast, Croatia)

2021 ◽  
Author(s):  
Marin Mićunović ◽  
Sanja Faivre
Keyword(s):  
Morphological Changes ◽  
Beach Erosion ◽  
Surface Model ◽  
Sand Beach ◽  
Aeolian Deposits ◽  
Digital Elevation ◽  
The 1950S ◽  
The 1960S ◽  
Elevation Model ◽  
Gravel Beach

<p>Beaches are dynamic coastal forms. However, nowadays, natural processes are intertwined with anthropogenic influences. The island of Hvar has 247 beaches from which we selected those which evolution could be studied by means of repeat photography method using archive maps and old photographs. More than 150 old photographs dating between the 1900s and 1980s have been collected and analyzed. The recent period is studied using unmanned aerial vehicles (UAV).</p><p>In total 12 beaches have been selected for precise study. The benchmarks from old photographs were marked and geolocated during the fieldwork using GNSS Trimble receiver. In November 2020, all locations were recorded by quadcopter DJI Phantom 4 Pro v2.0 with approximately 80% overlapping. On each beach, 6 - 12 ground control points (GCP), mostly benchmarks from the old photographs, were marked and measured. Data collected from UAV has been generated by photogrammetric techniques in ESRI Drone2Map software. Orthophoto and digital surface model (DSM) has been processed with a spatial resolution of 0,02 m and 0,1 m for the digital elevation model (DEM). All analyses were made using the ArcGIS Pro software. In this work, the analysis will be presented on two sites: Mina sand beach, formed in Aeolian deposits, on the northern side of the island and Mola Milna gravel beach, found on the southern side. Beaches have been studied in three points in time, in the 19<sup>th</sup>, 20<sup>th</sup> and 21<sup>st</sup> century.</p><p>On the Franciscan Cadastre (1834), Mina beach was mapped as an individual cadastral parcel with an area of 222 Klafter Quadrimeter (written in the Cadastral supplement), that is 799 m<sup>2</sup>. Recalculating in GIS we obtained a similar value, that is, 782 m<sup>2</sup>. The beach area from the beginning of the 20<sup>th</sup> century was reconstructed from old photographs and was approximated to 450 m<sup>2</sup>. Consequently, since 1834 the beach area reduced by ~43%. In 2020, the area further drops to 226 m<sup>2</sup>, so its surface diminishes by 55% since the beginning of the 20th century or even 72% from 1834.</p><p>In 1834 the Mola Milna beach was ~1073 m<sup>2</sup>, ~900 m<sup>2</sup> in the 1950s (16% smaller) and finally 802 m<sup>2 </sup>in 2020 (11% less than in the 1950s, or 27% smaller compared to 1834).</p><p>Thus, we observed that during the last two centuries the sand beach Mina reduced for more than 2/3 of its size since 1834, while the gravel beach Mola Milna reduced for around 1/3. Similar results have been observed previously on the Zogon gravel beach which lost ½ of its size since the 1960s. Even if the reconstructions of the beach area from the Cadaster maps and old photographs are less accurate than the model generated from UAV photos, obtained values clearly reveal the trend of beach erosion during the studied period.</p><p>This research was made with the support of the Croatian Science Foundation (HRZZ-IP-2019-04-9445).</p>

scholarly journals Analysis of the Suitability of High-Resolution DEM Obtained Using ALS and UAS (SfM) for the Identification of Changes and Monitoring the Development of Selected Geohazards in the Alpine Environment—A Case Study in High Tatras, Slovakia

2020 ◽  
Vol 12 (23) ◽  
pp. 3901
Author(s):  
Ľudovít Kovanič ◽  
Peter Blistan ◽  
Rudolf Urban ◽  
Martin Štroner ◽  
Monika Blišťanová ◽  
...  
Keyword(s):  
Remote Sensing ◽  
Laser Scanning ◽  
Morphological Changes ◽  
Current Trend ◽  
Unmanned Aerial Systems ◽  
Alpine Environment ◽  
Sensing Technology ◽  
Digital Elevation ◽  
Elevation Model ◽  
Aerial Systems

The current trend in the use of remote sensing technologies is their use as a tool for monitoring hard-to-reach areas, objects or phenomena in the alpine environment. Remote sensing technology is also effectively used to monitor geohazards and the development of human-made changes in the country. Research presented in this study demonstrates the results for the usability of the publicly available national digital elevation model DEM 5.0 obtained by utilizing the airborne laser scanning (ALS) survey to monitor the development of erosion, morphological changes of talus cones, or the dynamics of movement of rock blocks between stages of measurement in the alpine environment of the High Tatras mountains. The reference methods for this study are the terrestrial laser scanning (TLS) and structure-from-motion (SfM) photogrammetric approach using unmanned aerial systems (UASs). By comparing the created DEMs, the ALS point cloud’s accuracy on mostly rocky areas of different sizes was verified. The results show that the standard deviation of the ALS point cloud ranges from 19 to 46 mm depending on the area’s size and characteristics. The maximum difference ranges from 100 to 741 mm. The value of systematic displacement of data obtained by different technologies ranges from 1 to 29 mm. This research confirms the suitability of the ALS method with its advantages and limits for the detection of movement of rock blocks or change of position of any natural or anthropogenic objects with a size from approximately 1 m2.

scholarly journals Testing Different Interpolation Methods Based on Single Beam Echosounder River Surveying. Case Study: Siret River

2019 ◽  
Vol 8 (11) ◽  
pp. 507 ◽  
Author(s):  
Arseni ◽  
Voiculescu ◽  
Georgescu ◽  
Iticescu ◽  
Rosu
Keyword(s):  
Cross Sections ◽  
Interpolation Method ◽  
Morphological Changes ◽  
Numerical Models ◽  
Entire Area ◽  
Single Beam ◽  
Interpolation Methods ◽  
Digital Elevation ◽  
Wide Range ◽  
Elevation Model

Bathymetric measurements play an important role in assessing the sedimentation rate, deposition of pollutants, erosion rate, or monitoring of morphological changes in a river, lake, or accumulation basin. In order to create a coherent and continuous digital elevation model (DEM) of a river bed, various data interpolation methods are used, especially when single-beam bathymetric measurements do not cover the entire area and when there are areas which are not measured. Interpolation methods are based on numerical models applied to natural landscapes (e.g., meandering river) by taking into account various morphometric and morphologies and a wide range of scales. Obviously, each interpolation method, used in standard or customised form, yields different results. This study aims at testing four interpolation methods in order to determine the most appropriate method which will give an accurate description of the riverbed, based on single-beam bathymetric measurements. The four interpolation methods selected in the present research are: inverse distance weighting (IDW), radial basis function (RBF) with completely regularized spline (CRS) which uses deterministic interpolation, simple kriging (KRG) which is a geo-statistical method, and Topo to Raster (TopoR), a particular method specifically designed for creating continuous surfaces from various elevation points, contour, or polygon data, suitable for creating surfaces for hydrologic analysis. Digital elevation models (DEM’s) were statistically analyzed and precision and errors were evaluated. The single-beam bathymetric measurements were made on the Siret River, between 0 and 35 km. To check and validate the methods, the experiment was repeated for five randomly selected cross-sections in a 1500 m section of the river. The results were then compared with the data extracted from each elevation model generated with each of the four interpolation methods. Our results show that: 1) TopoR is the most accurate technique, and 2) the two deterministic methods give large errors in bank areas, for the entire river channel and for the particular cross-sections.

scholarly journals Structural Analysis and Morphotectonic Interpretation of Ain Sifni Anticline, Northern Iraq

2021 ◽  
Vol 54 (2A) ◽  
pp. 49-59
Author(s):  
Alaa N. Hamdoon
Keyword(s):  
Morphological Changes ◽  
Tectonic Deformation ◽  
Fold Axis ◽  
Study Region ◽  
Northern Iraq ◽  
Model Interpretation ◽  
Digital Elevation ◽  
Dextral Strike Slip Fault ◽  
Regional Tectonic ◽  
Elevation Model

Ain Sifni anticline is located in northern Iraq within High Folded Zone. It contains some tectonic deformations that need to study to determine the source and mechanism of these deformations concerning the geological setting of the study area. This study includes structural and morphotectonic interpretations for the Ain Sifni anticline, such as the visual & digital interpretation of satellite images and the Digital Elevation Model interpretation. These parameters are used to identify the morphogenic criteria and subsequently, to conclude a morphotectonic aspect of the deformations in the Ain Sifni anticline. Because of the regional tectonic evolution in this area, the structural and morphotectonic analysis of this anticline shows much evidence of morphological changes at the southeastern plunge area of the anticline within the Injana and Mukdadiya formations in comparison to the northwestern plunge area of the anticline. In addition, two recent water gaps have been recognized at the southeastern plunge area, one is confirmed and the other is proposed, and then a wind gap has been recognized in the middle of the anticline. A relation has been established between these morphotectonic features with the lateral propagation of the anticline towards the southeast, due to the regional tectonic deformation. A significant main fault has also been detected as a dextral strike-slip fault perpendicular to the fold axis of the anticline. This fault caused a difference in the vergency of the anticline and deformed the outcrops of formations in the study region.

scholarly journals Digital elevation model and satellite images an assessment of soil erosion potential in the Pcinja catchment

2007 ◽  
Vol 87 (2) ◽  
pp. 11-20 ◽  
Author(s):  
Ivica Milevski ◽  
Slavoljub Dragicevic ◽  
Stanimir Kostadinov
Keyword(s):  
Soil Erosion ◽  
Satellite Images ◽  
Outcome Data ◽  
Field Analysis ◽  
Vegetation Coverage ◽  
Anthropogenic Factors ◽  
Soil Composition ◽  
Digital Elevation ◽  
Left Tributary ◽  
Elevation Model

Pcinja is large left tributary of Vardar River (135 km long, 2877,3 km2 catchment?s area), which drainages surface waters from northeastern Macedonia, and small part of southeastern Serbia. Because of suitable physical-geographic factors (geology, terrain morphology, climate, hydrology, vegetation coverage, soil composition, and high human impact), some parts of the catchment?s suffer significant erosion process. For this reason, it is necessary to research properly spatial distribution of erosion, then influence of physical and anthropogenic factors for the intensity of soil erosion, related erosion landforms (with morphology, genesis, evolution, soil erosion protection etc.). Earlier researches in the area have been performed generally with combination of cartographic and classic field analysis. But in last decades, there are new possibilities available like satellite images and digital elevation models. In this work has been presented the methodology of utilization of satellite images and DEM for erosion research, with analysis and comparisons of outcome data.

scholarly journals Global flood hazard mapping using statistical peak flow estimates

2011 ◽  
Vol 8 (1) ◽  
pp. 305-363 ◽  
Author(s):  
C. Herold ◽  
F. Mouton
Keyword(s):  
Time Series ◽  
Peak Flow ◽  
Flood Hazard ◽  
Large River ◽  
Hazard Mapping ◽  
River Floodplains ◽  
Digital Elevation ◽  
Monthly Discharge ◽  
Elevation Model ◽  
Flooded Areas

Abstract. Our aim is to produce a world map of flooded areas for a 100 year return period, using a method based on large rivers peak flow estimates derived from mean monthly discharge time-series. Therefore, the map is supposed to represent flooding that affects large river floodplains, but not events triggered by specific conditions like coastal or flash flooding for instance. We first generate for each basin a set of hydromorphometric, land cover and climatic variables. In case of an available discharge record station at the basin outlet, we base the hundred year peak flow estimate on the corresponding time-series. Peak flow magnitude for basin outlets without gauging stations is estimated by statistical means, performing several regressions on the basin variables. These peak flow estimates enable the computation of corresponding flooded areas using hydrologic GIS processing on digital elevation model.

scholarly journals Assessing UAV survey performance for geomorphological monitoring of mountain rivers

2020 ◽  
Author(s):  
Bob de Graffenried ◽  
Ivan Pascal ◽  
Tomas Trewhela ◽  
Valentina Martinez ◽  
Christophe Ancey
Keyword(s):  
Morphological Changes ◽  
Control Points ◽  
Mountain Areas ◽  
Mountainous Regions ◽  
Bed Elevation ◽  
Digital Elevation ◽  
Elevation Data ◽  
Alternate Bars ◽  
Elevation Model ◽  
Alpine Watersheds

<p>Characterising morphological changes in mountain areas is of fundamental importance for science<br>and engineering. Intense floods usually involve massive sediment transport, which may significantly<br>alter basin and river characteristics. Sediment erosion and deposition control the dynamics<br>of morphological structures such as alternate bars and meanders. By using unmanned aerial vehicles<br>(UAV), it has been possible to obtain high-precision bed elevation data at the sediment scale.<br>Our project aims to develop a consistent and optimised methodology for monitoring morphological<br>changes in an Alpine watershed using an UAV. Since 2017, we have been monitoring the Plat de la<br>Lé area drained by the River Navisence (Zinal, canton Valais, Switzerland). In mountainous regions,<br>poor accessibility and light conditions make it difficult to set control points on the ground. We first<br>analysed the relevance and influence of certain ground control points (GCP) on the the accuracy of<br>the digital elevation model (DEM) obtained from the UAV’s images. Errors in the GCP localisation<br>were much larger than the DEM resolution. Not only did the GCP number and flight height affect<br>these errors, as expected, but their positions and orientations also played a part. We then carried<br>out an additional monitoring campaign to understand the influence of these parameters on the DEM<br>accuracy. This campaign was ran on two areas: a steep-slope area with irregular topography and<br>a low-slope area that comprises the river channel and its floodplain. We built DEMs for each area<br>considering different GCP numbers (in the 3–18 range with 14 additional checkpoints) and flight<br>heights (in the 40–140-m range). The present study provides guidelines, including an optimal combination<br>of parameters that significantly reduce errors in the DEM, and a methodology that can be<br>used for monitoring Alpine watersheds on a regular basis.</p>

scholarly journals Estimation of River Discharge Solely from Remote-Sensing Derived Data: An Initial Study Over the Yangtze River

2018 ◽  
Vol 10 (9) ◽  
pp. 1385 ◽  
Author(s):  
Arthur Sichangi ◽  
Lei Wang ◽  
Zhidan Hu
Keyword(s):  
River Discharge ◽  
Empirical Relationship ◽  
Time Lag ◽  
Initial Study ◽  
Roughness Coefficient ◽  
Novel Approach ◽  
Digital Elevation ◽  
Resultant Velocity ◽  
Moderate Resolution Imaging Spectroradiometer ◽  
Elevation Model

A novel approach has been developed to estimating river discharge solely using satellite-derived parameters. The temporal river width observations from Moderate Resolution Imaging Spectroradiometer (MODIS), made at two stream segments a distance apart, are plotted to identify the time lag. The river velocity estimate is then computed using the time lag and distance between the width measurement locations, producing a resultant velocity of 0.96 m/s. The estimated velocity is comparable to that computed from in situ gauge-observed data. An empirical relationship is then utilized to estimate river depth. In addition, the channel condition values published in tables are used to estimate the roughness coefficient. The channel slope is derived from the digital elevation model averaged over a river section approximately 516 km long. Finally, the temporal depth changes is captured by adjusting the estimated depth to the Envisat satellite altimetry -derived water level changes, and river width changes from Landsat ETM+. The newly developed procedure was applied to two river sites for validation. In both cases, the river discharges were estimated with reasonable accuracy (with Nash–Sutcliffe values >0.50). The performance evaluation of discharge estimation using satellite-derived parameters was also analyzed. Since the methodology for estimating discharge is solely dependent on global satellite datasets, it represents a promising technique for use on rivers worldwide.

STUDY OF THE LANDSLIDE MORPHOLOGY BASED ON GNSS DATA AND AIRBORNE SOUNDING (ON THE EXAMPLE OF A SECTION OF THE PROTVA RIVER VALLEY)

2018 ◽  
Vol 12 (5-6) ◽  
pp. 50-57 ◽  
Author(s):  
I. S. Voskresensky ◽  
A. A. Suchilin ◽  
L. A. Ushakova ◽  
V. M. Shaforostov ◽  
A. L. Entin ◽  
...  
Keyword(s):  
Digital Elevation Model ◽  
Geodetic Network ◽  
Aerial Survey ◽  
River Valley ◽  
Ease Of Use ◽  
Digital Elevation ◽  
Loose Deposits ◽  
Positioning Method ◽  
Landslide Body ◽  
Elevation Model

To use unmanned aerial vehicles (UAVs) for obtaining digital elevation models (DEM) and digital terrain models (DTM) is currently actively practiced in scientific and practical purposes. This technology has many advantages: efficiency, ease of use, and the possibility of application on relatively small area. This allows us to perform qualitative and quantitative studies of the progress of dangerous relief-forming processes and to assess their consequences quickly. In this paper, we describe the process of obtaining a digital elevation model (DEM) of the relief of the slope located on the bank of the Protva River (Satino training site of the Faculty of Geography, Lomonosov Moscow State University). To obtain the digital elevation model, we created a temporary geodetic network. The coordinates of the points were measured by the satellite positioning method using a highprecision mobile complex. The aerial survey was carried out using an unmanned aerial vehicle from a low altitude (about 40–45 m). The processing of survey materials was performed via automatic photogrammetry (Structure-from-Motion method), and the digital elevation model of the landslide surface on the Protva River valley section was created. Remote sensing was supplemented by studying archival materials of aerial photography, as well as field survey conducted immediately after the landslide. The total amount of research results made it possible to establish the causes and character of the landslide process on the study site. According to the geomorphological conditions of formation, the landslide refers to a variety of landslideslides, which are formed when water is saturated with loose deposits. The landslide body was formed with the "collapse" of the blocks of turf and deluvial loams and their "destruction" as they shifted and accumulated at the foot of the slope.

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