GIS-Based Digital Terrain Analysis of Assam-Meghalaya Foothills in Kamrup District, Assam

Terrain characteristics and their evaluation usually come under geomorphological study and more particularly the applied geomorphological study (Prasad & Sarkar 2011). Foothills are a geographically defined zone having a gradual increase in elevation at the base of a mountain or hill range. Detailed assessment of the present terrain parameters of the study area using GIS is significant as it shows the influence on the landscape of the area. It is a prerequisite in effective management of the impact of transition upon the landscape and its natural resources for sustainable management. In the study, an attempt has been made to delineate the foothill belt of the Assam-Meghalaya border in Kamrup District, Assam using Geographical Information system (GIS), and remote sensing techniques. Datasets available from USGS Earth Explorer, i.e. Shuttle Radar Topographic Mission (SRTM) and Digital Elevation Model (DEM) are used for analyzing the elevation, contour, slope, and terrain characteristics. The present study aims at getting an information archive of the geomorphological and terrain characteristics of the Assam-Meghalaya foothills in Kamrup District, Assam, and its spatio-temporal variation.

GEOMORPHOLOGICAL MAPPING OF THE SERIDÓ REGION, RIO GRANDE DO NORTE STATE/MAPEAMENTO GEOMORFOLÓGICO DA REGIÃO DO SERIDÓ, ESTADO DO RIO GRANDE DO NORTE

O mapeamento geomorfológico do Seridó é necessário devido à escassez de produtos dessa natureza, assim como, também, é importante para fins de planejamento e ordenamento territorial, haja vista que a região analisada apresenta cidades em fase de expansão, como, por exemplo, Caicó e Currais Novos. Este trabalho objetivou realizar um mapeamento geomorfológico da Região do Seridó, Estado do Rio Grande do Norte, até o 4º táxon, na escala de 1:100.000. A base de dados utilizada para o mapeamento foi obtida do SRTM (Shuttle Radar Topographic Mission), com resolução espacial de 30 m, onde foram obtidas curvas de nível, sombreamento do relevo, declividade e hipsometria, além de imagens do satélite LANDSAT 8, para distinção de fisionomias. A partir de então, foi possível distinguir as unidades morfoestruturais e morfoesculturais, além de subunidades morfoesculturais e modelados. Os referidos dados servirão de base para o planejamento e gestão ambiental da área de estudo, uma vez que constituem preciosas informações da geodiversidade regional.

New insights on the Ife-Ilesha schist belt using integrated satellite, aeromagnetic and radiometric data

The present study combined analysis of satellite, aeromagnetic and radiometric data for evaluation of structural features within the Ife-Ilesha schist belt. Shuttle Radar Topographic Mission digital elevation data have been enhanced using hill-shading technique for the delineation of morphological features. The superposition of total gradient amplitude lineaments on the 3-D Euler deconvolution map revealed the trends and depth of structural features within the study region. The major trends are NE–SW, NNE–SSW, E–W and minor trends in the N–S direction, including the Ifewara shear zone that trends in the NNE–SSW. The estimated depths to the top of the sources within the shear zone varies from 90 to 200 m. Complementary analysis of the airborne radiometric data revealed that the Ifewara shear zone and adjacent regions are characterized by radiometric anomalies, indicating regional mineralization alteration zone. Generally, there is a good correlation between the satellite, radiometric, aeromagnetic maps which provides new insights and re-evaluation of structural features.

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.

Floodplain mapping and risks assessment of the Orashi River using Remote Sensing and GIS in the Niger Delta Region, Nigeria.

Residents along the shoreline of the Orashi River have yearly been displaced and recorded loss of lives, farmland, and infrastructures. The Government’s approach has been the provision of relief materials to the victims instead of implementing adequate control measures. This research employs Shuttle Radar Topographic Mission and Google Earth imagery in developing a 3D floodplain map in ArcGIS 10.4. The result indicates the drainage system in the study area is observe to be dendritic with catchment of 79 subbasin with 76 pour point indicating the area is floodplain including 3D slope > 8 contain 1.15% and < 8 has 98.85% indicating floodplain area, aspect indicate west-facing slope are dark blue,3D hillshade indicate yellow is very low area and high area is pink and also the buffer analysis result reveals waterbodies reflecting blue with estimated area of 1.88 km2, yellow indicate 0.79 km2 of the shoreline, red indicate 0.81 km2 of the minor floodplain and pink contain 0.82 km2 with length of 32.82km. The result from google earth image in 2007 indicate absent of settlement ,2013 indicate minimal settlement and 2020 indicate major settlement in the study area when correlated with 3D Floodplain mapping before and during the flood in other to analyze and manage flooding for further purpose and majority of the area are under seize with flood like in 2020. Therefore, Remote Sensing and GIS techniques is useful for Floodplain mapping, risk analysis for control measures for better flood management.

A Geomorphic Approach for Identifying Flash Flood Potential Areas in the East Rapti River Basin of Nepal

Basin geomorphology is a complete system of landforms and topographic features that play a crucial role in the basin-scale flood risk evaluation. Nepal is a country characterized by several rivers and under the influence of frequent floods. Therefore, identifying flood risk areas is of paramount importance. The East Rapti River, a tributary of the Ganga River, is one of the flood-affected basins, where two major cities are located, making it crucial to assess and mitigate flood risk in this river basin. A morphometric calculation was made based on the Shuttle Radar Topographic Mission (SRTM) 30-m Digital Elevation Model (DEM) in the Geographic Information System (GIS) environment. The watershed, covering 3037.29 km2 of the area has 14 sub-basins (named as basin A up to N), where twenty morphometric parameters were used to identify flash flood potential sub-basins. The resulting flash flood potential maps were categorized into five classes ranging from very low to very high-risk. The result shows that the drainage density, topographic relief, and rainfall intensity have mainly contributed to flash floods in the study area. Hence, flood risk was analyzed pixel-wise based on slope, drainage density, and precipitation. Existing landcover types extracted from the potential risk area indicated that flash flood is more frequent along the major Tribhuvan Rajpath highway. The landcover data shows that human activities are highly concentrated along the west (Eastern part of Bharatpur) and the east (Hetauda) sections. The study concludes that the high human concentrated sub-basin “B” has been categorized as a high flood risk sub-basin; hence, a flood-resilient city planning should be prioritized in the basin.

Mangrove and Saltmarsh Distribution Mapping and Land Cover Change Assessment for South-Eastern Australia from 1991 to 2015

Coastal wetland ecosystems, such as saltmarsh and mangroves, provide a wide range of important ecological and socio-economic services. A good understanding of the spatial and temporal distribution of these ecosystems is critical to maximising the benefits from restoration and conservation projects. We mapped mangrove and saltmarsh ecosystem transitions from 1991 to 2015 in south-eastern Australia, using remotely sensed Landsat data and a Random Forest classification. Our classification results were improved by the addition of two physical variables (Shuttle Radar Topographic Mission (SRTM), and Distance to Water). We also provide evidence that the addition of post-classification, spatial and temporal, filters improve overall accuracy of coastal wetlands detection by up to 16%. Mangrove and saltmarsh maps produced in this study had an overall User Accuracy of 0.82–0.95 and 0.81–0.87 and an overall Producer Accuracy of 0.71–0.88 and 0.24–0.87 for mangrove and saltmarsh, respectively. We found that mangrove ecosystems in south-eastern Australia have lost an area of 1148 ha (7.6%), whilst saltmarsh experienced an overall increase in coverage of 4157 ha (20.3%) over this 24-year period. The maps developed in this study allow local managers to quantify persistence, gains, and losses of coastal wetlands in south-eastern Australia.

ANALISIS BENTUKAN LAHAN DI SEPANJANG BUKIT BARISAN, KABUPATEN PESISIR BARAT, PROVINSI LAMPUNG

Artikel ini membahas tentang karakterisrik bentuk lahan di Kabupaten Pesisir Barat. Kabupaten Pesisir Barat adalah salah satu kabupaten yang terletak di bagian barat Provinsi Lampung dengan memiliki luas ±2.907,23 Km2 serta memiliki garis pantai 221,5 Km (daratan dan garis pulau-pulau). Penelitian dilaksanakan dengan analisis overlay peta kelerengan dan ketinggian yang berasal dari SRTM (Shuttle Radar Topographic Mission) dengan menghadirkan sebuat peta. Variabel yang digunakan untuk menentukan bentuk lahan pesisir adalah material dan relief. Hasil ini menunjukkan bahwa Kabupaten Pesisir Barat terdiri atas bentuk lahan struktural yang terjadi karena kegiatan patahan semangko dan aktivitas pergerakan bawah laut dengan pertemuan lempeng tektonik.

Inversion of Terrain Slope and Roughness with Satellite Laser Altimeter Full-Waveform Data Assisted by Shuttle Radar Topographic Mission

Slope and roughness are basic geophysical properties of terrain surface, and also sources of error in satellite laser altimetry systems. The full-waveform satellite laser altimeter records the complete echo waveform backscattered from the target surface worldwide, so it may be used for both range measurement and inversion analysis of geometric parameters of the target surface. This paper proposes a new method for inversion of slope and roughness of the bare or near-bare terrain within laser footprint using full-waveform satellite laser altimeter data, Shuttle Radar Topographic Mission (SRTM) and topographic prior knowledge. To solve the non-uniqueness of the solution to the inversion problem, this paper used the SRTM and airborne Light Detection and Ranging (LiDAR) data in North Rhine-Westphalia, Germany, to establish a priori hypothesis about real information of topographic parameters. Then, under the constraints of prior hypothesis, the theoretical formulas and rules for slope and roughness inversion using the pulse-width broadening knowledge of satellite laser altimeter echo full-waveform were developed. Finally, based on the full-waveform data from the Geoscience Laser Altimeter System (GLAS) that was borne on ICE, Cloud, and Land Elevation Satellite (ICESat) and SRTM in the West Valley City, Utah and Jackson City, Wyoming, United States of America, the inversion was carried out. The experiment compares the results of proposed method with those of existing ones and evaluates the inversion results using high precision terrain slope and roughness information, which indicates that our proposed method is superior to the state-of-the-art methods, and the inversion accuracy for slope is 0.667° (Mean Absolute Error, MAE) and 1.054° (Root Mean Square Error, RMSE), the inversion accuracy for roughness is 0.171 m (MAE) and 0.250 m (RMSE).

Morphometric analysis of the Crimean river basins relief by using GIS

It is planned to develop projects of basin nature management for the Crimean peninsula. The characteristics of the relief within the river basins is an important stage in the pre-project justification. ArcGIS 10.5 is used for research. The tools of the subset “hydrology”, “Surface”, “Zonal”, “Algebra of maps” made it possible to create morphometric characteristics of the relief, and their visual representation in the GIS environment made it possible to establish spatial patterns and substantiate soil-water conservation measures. Shuttle radar topographic mission with a resolution of 3 arc seconds is selected as input data. Its resolution is consistent with the scale of the study. The morphometric analysis of the relief of 1534 different-order basin structures showed that the height of 64 % of the 3–6-order basins does not exceed 300 m; for them, five steps of vertical dissection of plain territories have been identified. 37 % of the basins are vertically divided into high-mountainous areas. In the plain part of Crimea, where deflationary processes are developed, the average slope steepness is 1°, basins with transversely straight longitudinal-straight slopes prevail, the linear boundaries on which can be rectilinear. In the foothill areas under conditions of agricultural use, soil deflation is added to the processes of water erosion caused by the presence of long slopes with a steepness of more than 3° with the values of the relief factor (LS) exceeding 2, and in some agricultural basins the average value of the relief factor is close to the critical value—4.3. Transversely convex slopes prevail in these territories, here it is necessary to design contour linear boundaries. The density of the river network is on average—0.11 km/km2 in the mountainous part of Crimea, but due to climatic, geomorphological and soil conditions, the redistribution of sediments occurs in the upper link of the erosion network (more developed on the territory of the peninsula). the density of the river network does not exceed 0.2 km/km2 in the flat part of the Crimea. Morphometric analysis of the relief allows describing the hydrogeomorphology of the river basin, identifying the causes of erosion, and substantiating the functioning of ecosystems.