Abstract
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.
Highlights
The assessment of water bodies properties makes use of knowledge regarding water quality, temperature, salinity, volumetric and depth measurements
The creation of the digital elevation model of an area depends on the interpolation method
A good digital elevation models (DEM) helps calculating the plan and volumetric areas of the river more precisely; DEM can be very useful for evaluating any morphometric changes
Summary
The assessment of water bodies (lakes, rivers, etc.) properties makes use of knowledge regarding water quality, temperature, salinity, volumetric and depth measurements. The bathymetric models are the best solution to define the bottom surface of any type of lakes or rivers, and these models are obtained by means of depth measurements. The bathymetry measurement method is based on a boat-mounted single-beam or multibeam echosounder device combined with a global positioning system (GPS) with real-time kinematic (RTK) correction. Using this combination of measurements, a series of three-dimensional data (x, y, z) can be collected. According to Liffner [11], and Merwade [12] and Merwade [13], the DEM is affected directly by the type of interpolation methods used
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