Lichen communities as a multiscale correlative indicator of elevational and land use-land cover gradients in the Himalayas

Elevation and land use/ land cover (LULC) plays an important role in the diversity of lichens in the Himalayas. The elevation gradients and LULC can be remotely assessed using remote sensing (RS) and geographical information systems (GIS). The current study was done in the Chopta-Tungnath landscape in the Kedarnath wildlife sanctuary, western Himalaya, India. Digital elevation modelling of the study area was done using shuttle radar topography mission data (SRTM-DEM) processed in Esri ArcGIS® ArcMAPTM 10.5, to assess the elevation gradient of the study area and selection of four lichen sampling sites. The LULC maps of the study area were prepared using Landsat 8 and Google Earth Pro 7.3.2.5776 imagery processed using LeicaTM ERDAS IMAGINE® 9.2. An elevation gradient of 2750 m to 3703m was recorded by SRTM-DEM. The LULC analysis resulted in five LULC classes of which the four sampling sites fall in the 3 LULC classes. The principal component analysis (PCA), used to analyse the lichen communities along the RS-GIS recognized LULC classes. The study found lichen communities to be a proxy to the LULC classes in the Himalayas with clear gradients of growth forms and habitat subsets along the increasing elevation gradient.

Characterisation and Prioritization of Micro Watersheds Using Geospatial Techniques: A Case Study on river Bharathapuzha, Kerala

Watershed based interventions are essential for the sustainable land and water management of any region. Watershed prioritisation is a must for the efficient utilisation of available monetary and human resources. One of the most common means of prioritisation is through morphometric analysis as hydrological processes or watershed responses depend on morphometric characteristics of the watersheds. The study contains morphometric analysis of a few number of micro watersheds of river Bharathapuzha of Kerala state. With the help of ArcGIS software and SRTM DEM, all the basic morphometric characteristics and derived morphometric characteristics of 10 micro watersheds are determined and then scores are assigned to the parameters. Finally, combined parameter scores are determined and ranking of each micro watershed is done. The priority scores between watersheds show considerable variation which is an indication of the efficacy of the methods employed. Once the ranking of the micro watersheds are done objectively and scientifically it would be a great support to the soil and water conservationist and planners. This study gives an insight into the applicability of the method to a mid land region in the state of Kerala, India.

Assessment of Slope-Adaptive Metrics of GEDI Waveforms for Estimations of Forest Aboveground Biomass over Mountainous Areas

Waveform broadening effects of large-footprint lidar caused by terrain slopes are still a great challenge limiting the estimation accuracy of forest aboveground biomass (AGB) over mountainous areas. Slope-adaptive metrics of waveforms were proposed in our previous studies. However, its validation was limited by the unavailability of enough reference data. This study made full validation of slope-adaptive metrics using data acquired by the Global Ecosystem Dynamics Investigation (GEDI) mission, meanwhile exploring GEDI waveforms on estimations of forest AGB. Three types of waveform metrics were employed, including slope-adaptive metrics (RHT), typical height metrics relative to ground peaks (RH), and waveform parameters (WP). In addition to terrain slopes, two other factors were also explored including the geolocation issue and signal start and ending points of waveforms. Results showed that footprint geolocations in the first version GEDI data products were shifted to the left forward of nominal geolocations with a distance of about 24 m~30 m and were substantially corrected in the second version; the fourth and fifth groups of signal start and ending points of waveforms had worse performance than the rest of the four groups because they used the maximum and minimum signal thresholds, respectively. Taking airborne laser scanner (ALS) data as reference, the root mean square error (RMSE) of terrain slopes extracted from the digital elevation model of the shuttle radar topography mission (SRTM DEM) was about 3°. The coefficients of determination (R2) of estimation models of forest AGB based on RH metrics were improved from 0.48 to 0.68 with RMSE decreased from 19.7 Mg/ha to 15.4 Mg/ha by the second version geolocations. The RHT and WP metrics gave the best and the worst estimation accuracy, respectively. RHT further improved R2 to 0.77 and decreased RMSE to 13.0 Mg/ha using terrain slopes extracted from SRTM DEM with a resolution of 1 arc second. R2 of estimation models based on RHT was finally improved to 0.8 with RMSE decreased to 11.7 Mg/ha using exact terrain slopes from ALS data. This study demonstrated the great potential of slope-adaptive metrics of GEDI waveforms on estimations of forest aboveground biomass over mountainous areas.

Use of earth observation images and GIS techniques for groundwater exploration in hard rock terrain

Prolonged drought and improper maintenance of water resources increased the demands on ground-water supplies resulting are focuses for the need to evaluate ground-water resources in the hard rock terrain. In recent years, Remote-Sensing methods have been increasingly recognized as a means of obtaining crucial geo-scientific data for both regional and site-specific investigations. This work aims to develop and apply integrated methods combining the information obtained by geo-hydrological field mapping and those obtained by analyzing multi-source remotely sensed data in a GIS environment for better understanding the Groundwater condition in hard rock terrain. In this study, digitally enhanced Landsat ETM+ data was used to extract information on geology, geomorphology. Hill-Shading techniques are applied to SRTM DEM data to enhance terrain perspective views and to extract Geomorphological features and morphologically defined structures through the means of lineament analysis. A combination of Spectral information from Landsat ETM+ data plus spatial information from SRTM-DEM data is used to address the groundwater potential of alluvium, colluvium and fractured crystalline rocks in study area. The spatial distribution of groundwater potential zones shows regional patterns related to lithologies, lineaments, drainage systems and landforms. High yielding wells and springs are often related to large lineaments and corresponding structural features such as dykes. The results demonstrate that the integration of remote sensing, GIS, traditional fieldwork and models provide a powerful tool in the assessment and management of water resources and development of groundwater exploration plans.

Comparative analysis of SRTM, TanDEM-X and UAV-SfM DEMs to estimate lavaka (gully) volumes and mobilization rates in the Lake Alaotra region (Madagascar)

Over the past decades, developments in remote sensing have resulted in an ever growing availability of topographic information on a global scale. A recent development is TanDEM-X, an interferometric SAR mission of the Deutsche Zentrum für Luft- und Raumfahrt providing near-global coverage and high resolution DEMs. Moreover, ongoing developments in unmanned aerial vehicle (UAV) technology has enabled acquisitions of topographic information at a sub-meter resolution. Although UAV products are generally preferred for volume assessments of geomorphic features, their acquisition remains time-consuming and is spatially constrained. However, some applications in geomorphology such as the estimation of regional or national erosion quantities of specific landforms, require data over large areas. TanDEM-X data can be applied at such scales, but this raises the question of how much accuracy is lost because of the lower spatial resolution. Here, we evaluated the performance of the 12 m TanDEM-X DEM to i) estimate gully volumes, ii) establish an area-volume (A-V) relationship, and iii) determine mobilization rates, through comparison with a high resolution (0.2 m) UAV-SfM DEM and lower resolution (30 m) SRTM DEM. We did this for six study areas in the Lake Alaotra region (central Madagascar) where lavaka (gullies) are omnipresent and lavaka surface area changes over the period 1949–2010s are available for 699 lavaka. SRTM derived lavaka volume estimates were systematically too low, indicating that the SRTM DEM is too coarse to accurately estimate volumes of geomorphic features at the lavaka-scale (100–100 000 m2). Lavaka volumes obtained from TanDEM-X were similar to UAV-SfM volumes for the largest features, whereas the volumes of smaller features were generally underestimated. To deal with this bias we introduce a breakpoint analysis to eliminate volume reconstructions that suffer from processing errors as evidenced by significant fractions of negative volumes. This elimination allowed the establishment of an area-volume relationship for the TanDEM-X data that is within the 95 % confidence interval of the UAV-SfM A-V relationship. Our calibrated area-volume relationship enabled us to obtain large-scale lavaka mobilization rates ranging between 18 ± 6 and 289 ± 125 ton ha−1 yr−1 with an average of 102 ± 41 ton ha−1 yr−1. These results indicate that current lavaka mobilization rates are two orders of magnitude higher than long-term erosion rates. With this study we demonstrate that the global TanDEM-X 12 m DEM can be used to accurately estimate volumes of gully-shaped features at the lavaka-scale (100–100 000 m2), where the proposed breakpoint-method can be applied without requiring the availability of a higher resolution DEM. Furthermore, we use this information to make a first assessment of regional lavaka erosion rates in the central highlands of Madagascar.

Controls on sediment distribution in a volcanically-affected basin: insights from the Ethiopian Flood Basalt Province

This study provides a comprehensive examination of the Oligocene–Miocene Ethiopian Flood Basalt Province (EFBP) within the Blue Nile (Abay) Basin (BNB), Ethiopia. Extensive logging through 29 new sections has enabled an updated stratigraphic account of the BNB to be elucidated and reveals the significance of intravolcanic sedimentary systems within the EFBP. Five sub- and intra-volcanic surfaces were modelled using spot heights to generate isopach maps that were used to constrain the thickness variations within the stratigraphy. Additionally, lineaments, Strahler stream segments and volcanic cones were mapped out from digital elevation models (SRTM DEM) and satellite data (ASTER and LANDSAT 8 imagery). These data were used in conjunction with the isopach maps to better understand the basinal controls on the distribution of intravolcanic sedimentary systems within the BNB. The study reveals how NNE and ESE/SE structural trends have influenced the distribution of volcanoes within the basin, which has in turn disrupted the distribution and lithofacies architecture of the volcanic sequences. The presence of intrabasinal ridges parallel to the major structural trends are also revealed, which formed relatively short-lived drainage divides. The implications of these intrabasinal highs on the composition and the reservoir potential of intravolcanic sedimentary successions are discussed.

​The Significance Impact Assessment of Morphological Parameters on Watershed: A Review

Watershed morphological analysis is momentous for controlling floods risk, forethought and management of the watershed area, as well as it is foremost useful to perceive catchment hydrology. Remote sensing and geographic information system are used in recent times as a tool for watershed delineation and its planning. Many types of input parameters generally use for watershed delineation such as Toposheet, ALOS, SRTM DEM, ASTER DEM and CARTOSAT DEM. Based on analysis SRTM DEM gives meticulous and clear results compared to other DEM files. Morphometric based prioritization of watershed was given in many research papers but an appropriate result of priority range was not given and this type of study confusing to evaluate the rank of priority based on its erosional behaviour. In many papers results of morphometric parameters were not indicate how to retaliate these results of morphometric parameters to a watershed. This paper deals with the implication of different values of morphometric parameters with adequate contextual information. This review paper can give useful information for the morphometric analysis of watersheds.

Relationship Between Dams, Knickpoints and the Longitudinal Profile of the Upper Indus River

Mass movements in mountainous areas are capable of damming rivers and can have a lasting effect on the river longitudinal profile. The long profile is commonly used to retrieve regional tectonic information, but how much dams may compromise geomorphometry-based tectonic analysis has not been systematically researched. In this study, we investigate the relationship between river dams and the longitudinal profile of the upper Indus River basin, based on interpretation and analysis of remote sensing imagery and digital elevation models (DEMs) and local field work. We identified 178 landslide, glacier and debris flow dams. Using TopoToolbox, we automatically extracted the river longitudinal profile from the 30 m SRTM DEM, determined the location of convex knickpoints and calculated the channel steepness index. One hundred and two knickpoints were detected with heights above 148 m, of which 55 were related to dams. There is good spatial correspondence between dams, convexities in the river longitudinal profile and relatively high steepness index. Different dam types have different impacts on the river profile; on the upper Indus, debris flow dams have a greater impact than landslide and glacier dams and can form knickpoints of up to 900 m. Therefore, dams may have a significant influence on the river longitudinal profile, knickpoints and steepness index, and should be considered when extracting information on regional tectonics using these indices.

Generating and analyzing Terrain characteristics from Shuttle Radar Topographic Mission (SRTM), DEM

Terrain analysis is the quantitative analysis of topographic surfaces. The purpose of a digital terrain system is to provide the digital representation of terrain so that environmental problem like soil erosion may be approached accurately and efficiently through automated means. Traditionally this was (and still is!) being done manually by using topographic/contour maps. With the availability of Digital Elevation Models (DEM) and GIS tools, watershed properties can be extracted by using automated procedures. Remote Sensing and Digital elevation models (DEMs) are known to be very useful data sources for the automated delineation of flow paths, sub watersheds and flow networks for hydrologic modelling and watershed characterization. The digital terrain model was extracted from a 90m resolution Shuttle Radar Topographic Mission (SRTM) of the study area. The SRTM data was corrected by removing voids, striping, tree offsets and random noise. The SRTM DEM data was projected from geographic coordinate WGS 84 to UTM zone 32 of the study area. The 3-D analysis tool of the ArcGIS 10.1 was used for this process. The DEM was processed to obtain the Slope, Contour, Flow direction, Flow accumulation, Flow length, Stream power Index of the study area. The study proved that SRTM elevation dataset has the ability to obviate the lack of terrain data for hydrologic modelling using ArcGIS where appropriate data for terrain modelling and simulation of hydrological processes is unavailable.