Analysis of Meandering River Morphodynamics Using Satellite Remote Sensing Data—An Application in the Lower Deduru Oya (River), Sri Lanka

Abstract

River meandering and anabranching have become major problems in many large rivers that carry significant amounts of sediment worldwide. The morphodynamics of these rivers are complex due to the temporal variation of flows. However, the availability of remote sensing data and geographic information systems (GISs) provides the opportunity to analyze the morphological changes in river systems both quantitatively and qualitatively. The present study investigated the temporal changes in the river morphology of the Deduru Oya (river) in Sri Lanka, which is a meandering river. The study covered a period of 32 years (1989 to 2021), using Landsat satellite data and the QGIS platform. Cloud-free Landsat 5 and Landsat 8 satellite images were extracted and processed to extract the river mask. The centerline of the river was generated using the extracted river mask, with the support of semi-automated digitizing software (WebPlotDigitizer). Freely available QGIS was used to investigate the temporal variation of river migration. The results of the study demonstrated that, over the past three decades, both the bend curvatures and the river migration rates of the meandering bends have generally increased with time. In addition, it was found that a higher number of meandering bends could be observed in the lower (most downstream) and the middle parts of the selected river segment. The current analysis indicates that the Deduru Oya has undergone considerable changes in its curvature and migration rates.

Planform Changes in the Lower Mahaweli River, Sri Lanka Using Landsat Satellite Data

“…The high curvature of rivers drives the meandering process by causing erosion in the outer bank and accretion in the inner bank. The river curvature values are comparable with the values obtained in a similar study done for Deduru Oya in Sri Lanka [15]. However, the maximum curvature of the selected segment of the Mahaweli River is higher than that of the Deduru Oya River.…”

“…The importance of remotely sensed satellite data are their free and global availability and considerably high resolution (about 30 m). Further, some of these data are available for more than 30 years (ex: Landsat satellite data is available since 1984) [15].…”

“…However, other than by Basnayaka et al [15], these recent advances have not been applied in Sri Lanka to understand the meandering behavior of rivers. The River Mahaweli is important due to its flat bathymetry downstream.…”

Digitization of print-based absorption and fluorescence spectra – extracting clarity from clutter

“…Graph digitization programs are used either as (i) rulers for identifying the values of particular data points from a graph, or (ii) tools for extracting entire data traces to re-create the graph. Examples of the latter include ultraviolet polarimetric data [34], x-ray diffraction data [35], oscilloscope data [36], cardiotocography data [37], tide-gauge data [38], earthquake signals [39], meandering river morphodynamics diagrams [40], and absorption and fluorescence spectra [16,[41][42][43][44][45][46][47]. We examined each available freeware program listed in Table 1, concluded that WebPlotDigitizer fits our needs, and downloaded an off-line version.…”