Relief Ratio Research Articles

Spatial prediction of flood-prone areas using geographically weighted regression

An important non-structural solution in flood management is susceptibility mapping, which identifies the likelihood of flood occurrence in an area. Although various models have been applied in flood susceptibility mapping with different successes, Geographically Weighted Regression [GWR] has not been sufficiently tested despite its effective advantages in interpreting spatially heterogeneous relationships. To test GWR's effectiveness in flood susceptibility modelling, this study included 16 morphometric parameters as the explanatory variables, and historical flood occurrence as the dependent. Multicollinearity was eliminated based on Variance Inflation Factor [VIF], which resulted in six screened parameters: stream order, drainage texture, relief ratio, bifurcation ratio, topographic wetness index, and topographic position index. Five tests were carried out, with the first involving direct inputs of the VIF-screened variables into the GWR modelling process. The other four tests incorporated morphometric parameter normalisation into 1-to-5 ranking scores according to Ordinary Least Square [OLS] coefficients or literature using all or only the VIF-screened parameters. The best-performing model was the first test, indicating that direct input of the screened parameters was the ideal modelling process. This test had the lowest corrected Akaike Information Criterion (160.01), the highest percentage of deviance explained (46.18%), lowest spatial autocorrelation of residuals (0.1122) and transformed residuals (0.2827), highest success accuracy (91.24%), and second-best prediction accuracy (75.15%). These findings show that accounting for spatial variation improved global flood model performance. The results also show that GWR may have the potential for better flood susceptibility mapping when compared with other traditional models such as non-spatial logistic regression and frequency ratio.

Using morphometric and geomorphic indices to assess Western São Francisco Craton neotectonic traces

Recently, geomorphometric properties of river networks and catchments have been described and applied as an efficient tool in the investigation of the landforms' response to neotectonics. Geometric parameters of the Cotovelo River catchment extracted from an Alos-Palsar digital elevation model were used to compute morphometric and geomorphic indices to investigate whether the bedrock structure and recent active tectonics influence the local drainage network. The Cotovelo catchment is situated in the Middle to Upper Proterozoic western foreland basin of the São Francisco craton, in northwestern Minas Gerais, Southeastern Brazil; it is presumed to be a stable piece of earth’s crust. The automatically generated streams were processed at the sub-catchment scale to calculate the hypsometric integral, relief ratio, stream frequency, and drainage density morphometric indices as well as supported a geomorphic study based on the basin shape, asymmetry factor, valley floor width-to-height ratio, mountain front sinuosity, transverse topographic symmetry factor, and stream-length gradient index. Achieved results revealed recent and low-rate tectonic activity and structural control on the fluvial morphology. Prominent knickpoints, aligned with mapped fault scarps, disclose straight erosive fronts away from stratigraphic borders, indicating these features are unrelated to lithological changes. Despite the catchment location, the area exhibits impressive fluvial anomalies, and dissection occurs preferentially along ancient faults and fractures densely occurring in the rocky strata. Channel parallelism in context of medium to high relief and steep slopes, remarkably structurally drive fluvial dissection, asymmetric and elongated drainage catchments, and aligned landforms suggest neotectonic influence on the drainage network.

Use of Geospatial Tools in Morphometric Analysis and Prioritisation of Sub-catchments of the Soungrougrou (Casamance Basin)

Abstract The prioritisation of catchments, particularly in the context of catchment plans and management programmes, is part of water resources development. In fact, morphometric analysis assisted by geospatial technology is carried out by prioritising sub-catchments according to their natural resource availability characteristics. Information on the geomorphology and erosion factors of the study area is used in the area in the preparation of local models of ungauged sub-catchments, which otherwise lack an adequate hydrological database. The objective of this paper is to use geographic information systems (GISs) in morphometric analysis to prioritise sub-catchments of the Soungrougrou (a tributary of the Casamance River). In this respect, the integrated methodology involving morphometric aspects from geospatial technology is used. To carry out the geospatial research, basic mathematical equations used in a GIS environment were used to measure a series of aspects of hydrology such as flow length, flow length ratio, bifurcation ratio, drainage density, drainage texture, flow frequency, elongation rate, circularity ratio, form factor, relief and relief ratio. The results divided the whole catchment into three priority areas, namely high, medium and low. The results are relevant for establishing soil and water conservation plans in the Soungrougrou basin, as well as adequate groundwater production and management. The high category (sub-basins 6, 8, 14, 17 and 18) is subject to maximum soil erosion, which requires immediate intervention to avoid possible natural hazards.

Quantitative Geomorphological Parameters Analysis for the Aynalem- Illala Streams, Tigray, Northern Ethiopia

Morphometric analysis is the measurement and mathematical analysis of the configuration of the surface, shape, and dimension of landforms. The objective of this study is to characterize the Aynalem and Illala streams using the morphometric parameter. The topographic map at a scale of 1:50,000 taken from the Ethiopian National Mapping Agency was used to characterize the linear and areal aspects. ASTER Digital Elevation Model with 10m resolution was used to characterize the relief aspect. The Arc GIS 10.4.1 was used during the morphometric analysis. The analysis result of the streams is summarized based on the linear, areal, and relief aspects. The area is characterized by a dendritic drainage pattern which is characteristics of massive hard rock terrain. The Aynalem and Illala streams are 4th and 5th order streams. Considering the number of streams in the Aynalem (75.81%) and Illala (74.66%) is composed of first-order streams that indicate a flashy flood and the mean bifurcation value of Aynalem (6.8) and Illala (4.7) shows that the Aynalem area is more structurally affected than Illala but both show less stream integration. The analysis of areal aspects such as elongation ratio, circularity ratio, and form factor has indicated that both streams are characterized as elongated streams, this implies that both streams are flowing in heterogeneous rock material, presences of structural effect, and slow runoff discharge. The other areal aspect such as drainage density, stream frequency, infiltration number, and length of overland flow all show smaller values in both streams. This implies that the streams are characterized by a relatively permeable rock material with a higher infiltration capacity. The relief aspect of the Aynalem and Illala was also analyzed using basin relief, relief ratio, ruggedness number, hypsometric curves, and Hypsometric integral. The streams are characterized by a lower relief ratio and ruggedness number which implies a relatively flat slope and lower relief. The hypsometric curves and the Hypsometric Integral of the streams indicate that the Aynalem and Illala are at the maturity stage. This shows the area is characterized by higher erosion but less affected by recent structures. Based on the morphometric parameter analysis result it is possible to conclude that the stream development is dependent on the topography and geology of the study area and both streams show similar morphometric character.

Morphometric Relief Aspects Identification of Khabour River Basin

Relief Aspects provides data regarding erosion properties of the river basin, such as the morphological properties of the relief, overall slop, and erosion severity. The Khabour River Basin has severe slopes, resulting in high runoff and soil erosion. This creates large latent energy to move water and sediment downward per unit of length. Besides, the ruggedness number of the study area basin is (7.23). The high value indicates that the area is characterized by rugged relief soil erosion and structural complexity. Furthermore, the dissection index (Dis) of the study area which was 0.50, indicates that the basin is still in the youth stage and its reliefs are in constant development instead of morph-metrical Hezel and the sub-Khabour. Hezel River basin has relatively higher values than Al Khabour River main and sub-basin. For example, the slop of the Hezel River basin is (34.73), while the main Khabour Basin (23.7), compared to al- Khabwr sub-Basin (22.60) and the river canal slope (22.1) , while the slope of the sub-Khabour River canal (14.4). The Hezel Basin also has a significant increase in the relief number, relative relief ratio, and ruggedness number. The study area basin is characterized by the modern geomorphology, the activity of water erosion factors, the high proportions of both stripping and transferred materials and basin runoff speed which resulted in a decrease in the percentage of filtered water to the subsurface layers due to the complex nature of the mountain basin, the slop intensity and surface ruggedness.

Estimating the hazards of floods in the Gulasur Basin in the Sulaymaniyah Governorate - Kurdistan Region of Iraq

The indicators values of the Morphometric Analysis of the Gulasur Basin, which has an area of 556.02 km2, as the ratio of elongation, rotation ratio and form factor, indicated that it is a highly rectangular basin. While the values of the relief aspects, which are represented by the relief ratio, the relative relief and Ruggedness number, indicated the high runoff and the low percentage of leachate in the basin. In addition to other indicators such as stream frequency, drainage density and bifurcation rate. And other hydromorphometric indicators had a hydrological response that reflected the volume of runoff, leg time and discharge rate, which led to a decrease in the reservoir potential of groundwater, and a high contribution to surface runoff. Thus, increasing the chances of water gathering in the main riverbed leads to an increase in the chances of flooding, however, the length of the distance traveled by the water from the top of the basin to the downstream makes the running water, moderately hazards waves with a late arrival.

Interrelations of rainfall and morphometric characteristics in generating geological disasters of Kuranji watershed Padang city

The Kuranji watershed is one of the watersheds in the city of Padang, which is currently experiencing development due to rapid population growth. This has resulted in land conversion from areas that have vegetation to built areas such as settlements. This affects the balance of the Kuranji watershed ecosystem and can lead to geological disasters. Therefore an initial analysis is needed in the development of the Kuranji watershed in the future. This study aims to analyse the interrelation of rainfall and morphometric characteristics that have an impact on geological disasters. The data used are data of maximum rainfall and maximum river discharge in the Kuranji watershed from 2009 - 2018. DEM data (30x30) used to calculate morphometric aspects, consisting of linear aspects, area aspects and relief aspects. The calculation of these aspects is done by a Geographic Information System (GIS) approach using ArcGIS 10.6 software. The result shows that the Kuranji watershed has an area of 22469,55 ha with dendritic drainage patterns. The linear aspect reveals that it has 1894 rivers with a total length of 774,6 km. This aspect explains that with the many tributaries, the Kuranji watershed has the potential to cause flooding. Aspects of the area explain that the Kuranji watershed has an elongated shape, steep slope and causes a rapid and large run-off discharge. Drainage density is at medium level with a value of 3,45 (km/km2) which is close to the high category. The higher the drainage density the smaller the chance of water for infiltration and the greater the river discharge. The relief aspect explains that the Kuranji watershed has a height between 0-1860 meters above sea level. Relief ratio and gradient ratio have a value of 0,08. Gradient ratios with high values result in fast and swift flow of surface and river water flow. This has the potential for landslides, channel erosion and river wall erosion. High rainfall, extreme morphometric characteristics, causes the Kuranji watershed to have a great potential for geological disasters.

Morphometry of AFs in upstream and downstream of floods in Gribayegan, Iran

This study aims to determine the effect of a flood-spreading system on the morphometric characteristics of alluvial fans (AFs) in Gribayegan Fasa, Iran, and its relationship with erosion, age, texture, and type of formations. After determining the AFs using the semiautomatic method and determining their recharged watersheds, 25 morphometric characteristics were investigated. The most important morphometric characteristics were identified using principal component analysis (PCA). The group method of data handling (GMDH) neural network is used to predict erosion, soil texture, age, and formation material based on the morphometric characteristics of the fan. The results demonstrate that the semiautomatic method can effectively extract AF from the landscape. The results of AF morphometry before and after flood spreading show that the fan area, drainage basin circularity (Cirb), fan perimeter, relief ratio of the fan, fan length, minimum fan height, and maximum fan height were higher before flood spreading, and basin shape, St (soil texture), upper fan slope, fan volume, and sweep angle had higher values after the flood. In addition, the results of PCA show that fan area, fan perimeter, fan length, fan radius, fan volume, basin area, basin perimeter, main channel length, basin length, and drainage density are important factors. The results of the GMDH algorithm reveal that this method can accurately predict the formation, age, soil texture, and erosion rate using morphometric characteristics. Therefore, the R2 is 0.92 for the formation age and R2 is 0.86 for the erosion rates, formation types, and soil texture, respectively. Therefore, the most important morphometric parameters can be determined using PCA, and the conditions and processes in the basin, such as formation material, age, soil texture, and erosion rate, can be predicted with high accuracy using the GMDH algorithm.

Spatiotemporally varying inter-relationships between mainstem riverbed elevation and tributary sediment supply since the last interglacial in the upper Ara River, central Japan

The dynamics of sediment transport processes over millennial time scales in mountain river valleys remain poorly understood, limiting our overall understanding of sediment routing through river basins. Here, we reconstruct changes of the mainstem riverbed elevation, tributary sediment supply processes, and their inter-relationships since the last interglacial in the upper Ara River valley, central Japan. Aggradation of the mainstem river valley began before 100–95 ka and terminated by 41–40 ka. Then, the elevation of the mainstem floodplain remained stable until ~15 ka. Lateral erosion by the mainstem river, and intermittent periods of incision, continued until 5 ka, after which the mainstem river began actively incising. Aggradation of the mainstem riverbed before 41–40 ka elevated tributary junctions, decreasing the slopes of tributaries. Using reconstructed slope changes, and assuming sediment transport by debris flow in tributaries with slopes steeper than 8% and by traction in shallower tributaries, we classified the tributaries into three types: Type-A, with sediment supply by debris flow since the last interglacial; Type-B, with sediment supply by traction during the last glacial period and afterwards by debris flow; and Type-C, with sediment supply by traction since the last interglacial. Based on the relation between relief ratio and drainage area, we subdivided Type-C tributaries into those that plotted along (Type-C1) or markedly below (Type-C2) the regression line of the mainstem river and Type-A and -B tributaries. During aggradation of the mainstem river, sediments supplied by debris flow from Type-A and -B tributaries accumulated around junctions, interfingering with mainstem deposits. During this period, the junctions of Type-C1 tributaries were elevated almost synchronously with mainstem aggradation, while the junctions of Type-C2 tributaries were blocked by mainstem river deposits, forming blocked-valley lakes. Around 30 ka, Type-A and -B tributaries formed fans around their junctions that were subsequently truncated by lateral erosion by the mainstem river during the late glacial period and early Holocene, forming toe-cut terraces. Tributary deposits that had accumulated around the junctions were then reworked while maintaining a dynamic equilibrium state with the mainstem river. We infer that the responses of tributary landforms and sediment supply processes to the changing elevation of the mainstem riverbed during glacial and interglacial cycles varied depending on the drainage area and relief of each tributary. Considering the river basin as a whole, however, tributary deposits stabilized the elevation of the mainstem floodplain.

Hydro-geomorphic characteristics of the Indian (Peninsular) catchments: Based on morphometric correlation with hydro-sedimentary data

In terms of hydro-geomorphic characteristics, catchments in Peninsular India remained mostly unexplored except a few regional and local works that deal with tectonic, structural and paleo-climatic control on geomorphology. Catchment scale morphometric analyses deliver insights into dynamics, erosion capacity, probability of flood occurrence, lithological and structural control, and genetic response to the tectonics. The present study aimed to comprehend hydro-geomorphic characteristics of 12 major catchments in Peninsular India through GIS-based morphometric analysis. A total of 25 morphometric parameters were computed and several statistical analyses performed in establishing inter-correlation and classification of Indian rivers. Most of the rivers in Peninsular India were found 7th to 9th order catchments. Almost all basins showed a moderate relief ratio, hypsometric integral, ruggedness etc. Cauvery, Baitarni, and Brahmani showed exceptionally steeper gradient, high relief ratio, LS factor, and ruggedness index, which indicated higher erosion potential. Correlation among landscape variables revealed moderate scale dependency of few relief factors. Baitarni, Brahmani and Narmada showed higher hypsometric integral. A strong positive association between hypsometric integral and sediment yield suggested critically high erosion potential in catchments with high integral values. The present study provides some generic insights into the hydro-geomorphic characteristics with dissimilarity in lithology in Peninsular Indian catchments as a whole.

Morphometric analysis and flash floods hazards assessment for Wadi Al Aawag drainage Basins, southwest Sinai, Egypt

Assessment of surface runoff in arid regions is extremely important. Water means life; hence, the best management of flash floods promote groundwater recharge, prevents flood hazards and soil drift that is required for developing purposes. The main objective of the present work is to evaluate the morphometric parameters and flash flood hazards that frequently occurred in Wadi Al Aawag Drainage Basin. The study is based on applying the Arc GIS 10.5 program to draw drainage basins and to compute their morphometric attributes. The hydraulic model (HEC-HMS) in the WMS program was used to compute the peak flow hydrograph of floods for different sub-basin. The calculations of water quantities and peak flow were based on the SCS unit hydrograph approach. Results indicate that all the studied sub-basins have low Rb (1.99–3.7), this tends to give more possibilities to flash floods. The studied sub-basins have high densities ranges between 1.21 (Maier) and 1.62 km/Km2 (Ghewitat), this reflects high relief, impermeable subsurface material, and low contribution for groundwater, especially in the area covered by basement rocks (upstream portions). The decrease in time of concentration of Gebah is associated with an increase in the relief (1900 m) and relief ratio (83.3 m/km), which represent the land has a steep slope. Maier and Habran sub-basin, gives the maximum runoff volume, peak discharge, runoff depth, and runoff velocity during the storms of March 2014 and March 2020. These sub-basins have high CN value, the biggest area, long stream length, and high stream numbers. The study ended with a set of recommendations that mitigate the flash flood risks.

Drainage Morphometric Investigation of Nimni Watershed, Chhatarpur District, Madhya Pradesh, India

The present paper deals with drainage morphometric investigation of Nimni watershed, Chhatarpur District, Madhya Pradesh, India. A morphometric analysis of the Nimni watershed has been carried out to characterize the nature of drainage network. The linear, areal and relief aspects of the drainage basin have been determined. The morphometric parameters have been computed on the basis of drainage map prepared on 1:50,000 scale. These parameters includes Stream order, Lengths of stream, Bifurcation ratio, Drainage density, Length of overland flow, Stream frequency, Form factor, Circulatory ratio, Elongation ratio, Lemniscate’s ratio, Basin relief, Relief ratio, Ruggedness number and Ground surface slope. The drainage area of the Nimni watershed is 98 km2. The stream order of the basin is mainly controlled by physiographic and lithological conditions of the area. The increase in stream length ratio from lower to higher order shows that the study area has reached a mature geomorphic stage. The geomorphic analysis of Nimni watershed reveals that the present drainage basin exhibits uneven topography, presence of hard rock terrain and dendritic to sub-dendritic drainage pattern. The dendritic drainage pattern exhibits the presence of hard and resistant rocks referable to Bundelkhand Granite Complex.

Lithostructural controls in Douala-Buea Region landscape (SW Cameroon margin): Insights from morphometric analysis

The Douala-Buea Region (DBR; 4°–5°N, 9°–10°30′E), a portion of the southern Cameroon passive margin, developed on the Proterozoic granito-gneissic basement and the Cretaceous to Recent volcano-sedimentary cover, was explored in order to evaluate the lithology and tectonics controls on its landscape using the qualitative and quantitative geomorphological analyses based on 30 m resolution Digital Elevation Models (DEM) and field evidences. This area displays an uneven and complex landscape differentiated into four morphological units: Douala, Nkondjock, Kumba and Buea Units. The Douala Unit corresponds to the Coastal Plain and is extended on the Douala-Kribi/Campo sedimentary basin. The Nkondjock Unit represents a middle plateau developed on a Proterozoic granito-gneissic basement. The Kumba Unit matches with the southernmost volcanic Western Cameroon High Plateau. The Buea Unit corresponds to the Mount Cameroon stratovolcano. The relief analysis through mountain-front sinuosity (Smf, 1.19–1.43) and relative relief ratio (Rr, 0.10–2.31) vary from one unit to another. The drainage network analysis including drainage patterns, stepped longitudinal river profiles, the associated morphometric indexes, notably the concavity index (IC, 0.56–0.88), deviation (D, 267–2912 m), basin asymmetry factor (A f, 6.37–42.12), hypsometric integral (HI, 0.10–0.29), valley floor width to valley height ratio (Vf, 0.36–2.75), elongation ratio (Re, 0.30–0.50), watershed slope (S, 6.88–88.88) and stream length gradient index (SL, 0–3332) vary from one basin to another too. These results also show the heterogeneous and uneven DBR landscape controlled by its lithology and active tectonics. The drainage system reveals concave to concavo-convex longitudinal river profile shapes with knick points, asymmetric basins, and fault reactivations, and highlights the tectonics activity that used to occur through the time and their control on the morphology. Together, they document the lithostructural controls on the DBR landscape evolution, extendable in the whole SW Cameroon margin.

Morphometric Analysis of a Drainage Basin: A Study of Ghatganga River, Bajhang District, Nepal

This study attempts to study the morphometric characteristics of the Ghatganga basin by using Geographical information system (GIS). This analysis has shown that the relation of stream order (U) and stream number (Nu) which gives a negative linear pattern that order increases with a decreasing number of stream segment of a particular order. Different morphometric parameters such as stream length (Lu), bifurcation ratio (Rb), drainage density (D), stream frequency (Fs), texture ratio (T), elongation ratio (Re), circularity ratio (Rc), form factor ratio (Rf), relief ratio (Rh) and river profile have revealed the basin has a dendritic pattern of drainage, indicating high relief and steep ground slope with less elongated young and mature landforms in which geological structures don’t have a dominant influence on the basin.

GIS and DEM Based Watershed Characteristics of Wadi Al-Adaira Basin, KSA

The study aimed to evaluate the possibility of using the digital elevation model (DEM) technique based on GIS in the automatic extraction of the drainage basin network and calculating its parameters. The study used the digital elevation model from ASTER DEM (30 m) data for Wadi Al-Adaira basin and its sub-basins using Arc GIS 10.5 and its extensions: spatial analyst tools, 3D analyst tools and ArcHydro and then computed the morphometric parameters for the drainage of sub basins. Morphometric parameters for drainage basins include: Area (ranged between 92.5 km2 and 3323.06 km2), Max. Length (ranged between 17.06 km and 152.93 km), average width (ranged between 4.51 km and 21.73 km), perimeter (ranged between 62.45 km and 610.03 km), elongation ratio (ranged between 0.43 and 0.77), circulation ratio (ranged between 0.11 and 0.32), and form factor (ranged between 0.14 and 0.46). Morphometric parameters of drainage networks include: Stream order (ranged between 4 and 5), Stream number (ranged between 44 and 1448), Stream lengths (ranged between 93.74 km and 3383.04 km), bifurcation ratio (ranged between 0.71 and 0.83), drainage density (ranged between 0.86km/km2 and 1.13 km/km2), Stream frequency (ranged between 0.40 strm/km and 0.50 strm/km) and drainage texture (ranged between 0.52 strm/km and 2.37 strm/km). Drainage basin relief parameters include: relief (ranged between 58m and 815m), mean slope (ranged between 2.55 deg. and 10.19 deg), slope aspect, relief ratio (ranged between 0.002 and 0.028), relative relief (ranged between 0.001 and 0.009), ruggedness number (ranged between 0.05 and 0.829), geometric number (ranged between 19.28 and 155.64) and Hypsometric integral (ranged between 0.17 and 4.08). The study concluded that the use of a digital elevation model based on GIS from ASTER DEM data is a more effective and successful method in the automatic extraction of morphometric parameters for drainage basins, integrated with topographic maps and satellite images.

Using morphometrics to distinguish between debris flow, debris flood and flood (Southern Carpathians, Romania)

Debris flows and debris floods are rapid mass movements that occur in rugged mountain areas. The differences between them consist in the quantity of water input, which in turn influences the type of flow. For practical reasons, these two process types should be differentiated because different remedial measures should be applied for planning purpose. Due to the lack of historical data covering a long period of time, a morphometric analysis of the factors that control the flow type was chosen for the present study. Only those morphometric parameters with the most important role were selected. Based on statistical analyses, we noticed that only six parameters have a substantial contribution to debris flow occurrences. These are: Melton number, basin relief ratio, basin length, basin area, fan slope and source area ratio. The results show debris flow basins are characterized by Melton ratio > 0.55, basin relief ratio > 0.4, basin length < 1.7 km and basin area < 1.1 km2, debris flood basins by 0.3 < Melton ratio < 0.55, 0.2 < basin relief ratio < 0.4, 1.7 km < basin length < 5.1 km and 1.1 < basin area < 8.2 km2, while flood basins correspond to values of Melton ratio < 0.3, basin relief ratio < 0.2, basin length > 5.1 km and basin area > 8.2 km2.

Morphometrical analysis of torrential flows-prone catchments in tropical and mountainous terrain of the Colombian Andes by machine learning techniques

Assessment of susceptibility to torrential flows at the catchment scale is a necessary step for prioritising zones that can be identified by hazard and risk maps. In the Andean region of Colombia, where these phenomena are common and highly destructive, few studies have been carried out on the subject. Considering that the effects of torrential flows will likely increase in the future due to extreme weather events and urbanisation of low prone areas, effective land management plans should include the assessment of susceptibility to this type of event. In this study, machine learning techniques were applied with morphometric parameters of mountainous catchments in the northern Colombian Andes to analyse torrential susceptibility in tropical environments. Several feature selection methods were implemented using statistics to evaluate the relationship between morphometric parameters and torrential susceptibility. The parameters that showed the strongest relationship with torrential catchments were selected for application of machine learning techniques, along with evaluation of performance and prediction ability. The analysis was carried out on morphometric parameters regarding the catchment’s drainage network, basin geometry, drainage texture, and relief characteristics. According to the results, the catchments characteristics related to relief and drainage texture are the most important for the study of torrential susceptibility. Within these groups of predictor parameters, relief ratio and constant of channel maintenance are the highest ranked variables. Although the Melton index shows a good prediction capacity, thresholds proposed in the literature are not valid in the Colombian Andes.

Assessment of tectonic control on the development of low mountains moderate relief in the Outer Carpathians (Southern Poland)

Inherited tectonic structures, ongoing tectonic deformation, and variations in relative rock uplift rates play an important role in conditioning the processes of relief development. Their influence among other factors, such as climate and lithology, can be quantified using landscape analysis, and geomorphometric indices, in particular. The usage of landscape analysis in recent years is increasing systematically due to the constant improvement of the digital elevation models and GIS software that significantly facilitate this approach. In this study, we aim to recognize the influence of tectonic structures and processes on relief development in the low mountains with moderate relief of the Soła River catchment in the Western Outer Carpathians. To this end, we calculated geomorphometric indices (river longitudinal profile, stream-length gradient index, minimum bulk erosion, relief ratio, circulatory ratio, elongation ratio, and hypsometric integral) for the Sola River and its 47 sub-catchments using a 25-m spatial resolution Digital Terrain Elevation Data Level 2. Additionally, we identified lineaments and knickpoints and correlated the computed results with local and regional fault networks, variations in lithology, and climate fluctuations. Obtained results indicate a significant impact of inherited tectonic structures on the relief development of the Soła River catchment, i.e., directions of principal ridges and valleys follow the orientation of main folds and faults recorded in this area. Anomalously high values of minimum bulk erosion, river gradient, and stream-length gradient index allowed us to define two areas with higher relative uplift rates: 1) the Sola Gorge and 2) the Beskid Żywiecki Mts. Polish Outer Carpathians are generally considered as an area of low strain rate and low seismic activity. However, the possibility of neotectonic processes should be considered in geohazard estimations. Observed bends in the direction of river valleys that do not correspond with changes in lithology could be related to active strike-slip faults. These are probably the reactivated basement structures, copied in the thin-skinned nappe cover, as a result of the accommodation of the Mur-Žilina Fault Zone resulting from the tectonic push of the Alcapa (Alpine-Carpathian-Pannonian) microplate against the European plate. Thus, the role of recent tectonic activity in relief development of the Sola River catchment even though appears to be subsidiary at the most, should not be excluded.

Comparison of different digital elevation models for drainage morphometric parameters: a case study from South India

With a plethora of digital elevation models (DEM) available for elevation extraction and catchment morphometric analysis, it is essential to compare and investigate their accuracy and parameter uncertainty derived from them. To serve that purpose, in this study, we have compared the DEMs of different resolution obtained from Shuttle Radar Topography Mission (SRTM), CARTOSAT, and topographic maps (1:25000) in terms of vertical accuracy and morphometric parameters. The investigation was performed on a sub-basin of Champavathi River which is located in Andhra Pradesh, the southern part of India. The vertical accuracy of the DEMs was estimated using elevation from about 1180 points obtained from the Differential Global Positioning System (DGPS) survey. The morphometric analysis showed that the basin is elongated with low relief ratio, mild/rolling slopes, and medium drainage density, and the results were comparable from different DEM sources indicating that most of the morphometric parameters were not significantly dependent on the scale and source of the DEM. Further, vertical accuracy estimation showed that the CARTOSAT DEMs (10 m and 30 m) have a lower root mean square error (4.53 m and 5.89 m) when compared with the SRTM DEMs (6.11 m and 7.19 m).

Morphometric analysis of debris flows basins in the Eastern Rhodopes (Bulgaria) using geospatial technologies

Debris flows are considered as a rapid movement of highly water-saturated colluvial and proluvial deposits. Besides the intensive rainfall and snowmelt, there are several other factors—prerequisites to debris flows: morphometric characteristics, rocks composition, active tectonics and deforestation. The current research is directed to the analysis of morphometric parameters of debris flow areas located in Eastern Rhodopes (Bulgaria). Two types of debris flows are analysed—gully-induced debris flows and stream torrent section with debris flood occurrence. The aim is to determine morphometric indicators to be used for discrimination of debris flow types and further susceptibility assessment. The following parameters are calculated: basin area and length, basin relief, relief ratio, Melton index, slope, topographic wetness index, stream power index and curvature. The analysis shows that slopes in a range 30–45° have most important role, among the other topographic factors, for debris flow initiation. Melton index is a meaningful indicator for discrimination of debris flow types. It is greater than 1 at gully-induced debris flows and much lower at the debris flood section (0.14–0.16). The analysis of curvature rasters, generated as a second derivative of digital elevation model (DEM), shows that the considered gullies are subject of intensive erosion and the process is still active. The research is elaborated in GIS environment on the basis of DEM and field investigations. Terrestrial laser scanning (TLS) of the low part of the basins and debris flow fan is done, and detailed terrain models are developed for the purpose of morphometric analyses.