Quantitative Geomorphic Analysis Research Articles

The role of long-term preparatory factors in mass rock creep deforming slopes: insights from the Zagros Mts. belt (Iran)

The long-term evolution of slopes affected by Mass Rock Creep deformations is controlled by both time-invariant predisposing factors, such as the geo-structural inheritance, and time-dependent preparatory conditions, including regional uplift and landscape evolution rates. However, the relationship among Deep-seated Gravitational Slope Deformations, drainage network evolution, and tectonics remains poorly defined. Here, we focused on an undocumented Deep-seated Gravitational Slope Deformation affecting an area of about 8 km2 in the SE tip termination of the Siah Kuh anticline in the Lorestan arc (Zagros Mts., Iran), upstream to the Mountain Front Fault. To assess the evolution processes which involved the slope up to the present, we integrated quantitative geomorphic analysis, optically stimulated luminescence dating of geomorphic markers, and SAR interferometry techniques. In detail, we semi-automatically extracted the river terrace treads to which we associated an elevation above the thalweg based on the Relative Elevation Model allowing the order definition. The plano-altimetric distribution of the treads and the OSL ages of two levels of strath terraces sampled in the field have been correlated along the river longitudinal profile, allowing the estimation of an uplift rate of 2.8 ± 0.2 mm year−1 and 0.42 ± 0.03 mm year−1, respectively upstream and downstream of the Mountain Front Fault. SAR interferometry was used to spot present-day shallow ground displacements associated with the ongoing slope deformation, by processing 279 satellite Sentinel-1 (A and B) radar images of the ascending and descending orbit spanning from 06 October 2014 to 31 March 2019. Different landslide mechanisms were distinguished across the fold axis, rototranslative to lateral spreading interpreted as two different evolutionary stages of the same process transposed spatially through the fold axis. Indeed, the rototranslative mechanism represents an advanced stage of the strain evolution while the lateral spreading is an earlier one. Finally, we infer that the variability in the spatial distribution of the slope deformation styles and patterns in the Lorestan arc is strictly related to the coupled evolution of the drainage system and tectonics. Involved volumes (from 0.6 up to 44 km3), local relief (from 400 up to 2000 m), incision rates (from 0.8 to 2.8 ± 0.2 mm year−1), and persistence time (from 104 to 105 years) represent the most important preparatory conditions and are predisposed by a moderately dipping downslope (from 8 to 25°) sedimentary sequence characterised by units with significantly different rheological behaviour.

Rift kinematics preserved in deep‐time erosional landscape below the northern North Sea

AbstractOur understanding of continental rifting is, in large parts, derived from the stratigraphic record. This record is, however, incomplete as it does not often capture the geomorphic and erosional signal of rifting. New 3D seismic reflection data reveal a Late Permian‐Early Triassic landscape incised into the pre‐rift basement of the northern North Sea. This landscape, which covers at least 542 km2, preserves a drainage system bound by two major tectonic faults. A quantitative geomorphic analysis of the drainage system reveals 68 catchments, with channel steepness and knickpoint analysis of catchment‐hosted palaeo‐rivers showing that the landscape preserved a >2 Myr long period of transient tectonics. We interpret that this landscape records a punctuated uplift of the footwall of a major rift‐related normal fault (Vette Fault) at the onset of rifting. The landscape was preserved by a combination of relatively rapid subsidence in the hangingwall of a younger fault (Øygarden Fault) and burial by post‐incision sediments. As such, we show how and why erosional landscapes are preserved in the stratigraphic record, and how they can help us understand the tectono‐stratigraphic evolution of ancient continental rifts.

Enhancing the Identification and Mapping of Fluvial Terraces Combining Geomorphological Field Survey with Land-Surface Quantitative Analysis

A methodological approach to refining the identification and mapping of fluvial terraces has been applied, combining geomorphological field surveys with the computation and assessment of different morphometric parameters (local, statistical, and object-oriented), derived from a high-resolution digital terrain model (DTM) obtained from a LiDAR survey. The mid-sector floodplain of the Misa River basins was taken as a valid example of the main river valleys draining the northern Marche Apennines (Italy) and was considered an ideal site to test a combination of different geomorphological techniques for enhancing fluvial terraces’ detection and mapping. In this area, late Pleistocene–Holocene fluvial terraces are well exposed, and their geomorphological and geochronological characteristics have largely already been studied. However, a reliable distinction of the different Holocene terrace levels, including a detailed geomorphological mapping of different terrace features, is still lacking due to the very complex terrace geometry and the lack of good-quality deposit outcrops. Land-surface quantitative (LSQ) analysis has been coupled with the available outcomes of previous studies and ad-hoc geomorphological field surveys to enhance the identification and mapping of fluvial terraces. The results of this work provided information for the discernment of terrace remnants belonging to the full-glacial fill terrace generation (late Pleistocene) as well as reconstruction of the terrace top–surface, and can be used to distinguish the inner terrace limits coinciding with the margin of the floodplain. It has also been possible to identify and delimit the late Pleistocene terrace from a staircase of three younger strath terraces formed during the Holocene. The results of this study demonstrated that the investigation of fluvial landforms, at different scales, can strongly benefit from the integration of field surveys and quantitative geomorphic analysis based on high-resolution digital topographic datasets. In particular, the integration of LSQ analysis with ground-truth geomorphological data can be dramatically helpful for the identification and mapping of fluvial terraces.

Geomorphic expression of a tectonically active rift-transfer zone in southern Ethiopia

The Gofa Province and the Chew Bahir Basin of southern Ethiopia constitute tectonically active regions, where the Southern Main Ethiopian Rift converges with the Northern Kenya Rift through a wide zone of extensional deformation with several north to northeast-trending, left-stepping en-échelon basins. This sector of the Southern Main Ethiopian Rift is characterized by a semi-arid climate and a largely uniform lithology, and thus provides ideal conditions for studying the different parameters that define the tectonic and geomorphic features of this complex kinematic transfer zone. In this study, the degree of tectonic activity, spatiotemporal variations in extension, and the nature of kinematic linkage between different fault systems of the transfer zone are constrained by detailed quantitative geomorphic analysis of river catchments and focused field work. We analyzed fluvial and landscape morphometric characteristics in combination with structural, seismicity, and climatic data to better evaluate the tectono-geomorphic history of this transfer zone. Our data reveal significant north-south variations in the degree of extension from the Sawula Basin in the north (mature) to the Chew Bahir Basin in the south (juvenile). First, normalized channel-steepness indices and the spatial arrangement of knickpoints in footwall-draining streams suggest a gradual, southward shift in extensional deformation and recent tectonic activity. Second, based on 1-km radius local relief and mean-hillslope maximum values that are consistent with ksn anomalies, we confirm strain localization within zones of fault interaction. Third, morphometric indices such as hypsometry, basin asymmetry factor, and valley floor width to valley height ratio also indicate a north to south gradient in tectonic activity, highlighting the importance of such a wide transfer zone with diffuse extension linking different rift segments during the break-up of continental crust.

Quantitative Geomorphic analysis in Geoarchaeological Investigations: A Case Study of Man-land relationship of Hanga River basin, Ahmednagar district of Maharashtra

Geomorphology is the study of landforms, their processes, form, and sediments at the surface of the earth which includes the earth's surface processes, such as air, water, and ice, which can mould the landscape. Since, from the beginnings human being attracted towards such suitable landscape for the establishment of their settlements. The present geoarchaeological work involves the study of the characteristics and evolution of landscapes, geological settings based on quantitative morphometric analysis, and availability of the natural resources of these areas with the man-land relationship of the Hanga river basin. The previous history of the region indicates that it is rich in prehistoric and chalcolithic settlements. The present basin is not explored systematically so far. Hence, this work is an attempt to fill these lacunae by the way of a systematic, intensive, village to village survey to understand the man-land relationship in the region. Field surveys and laboratory works were carried out to fulfil the aim and objectives of this work.

Assessment of Neotectonic Landscape Deformation in Evia Island, Greece, Using GIS-Based Multi-Criteria Analysis

This study deals with the assessment and mapping of neotectonic landscape deformation in the northern part of the Evia Island (Central Greece). Multi-Criteria Decision Analysis (MCDA) utilizing Analytic Hierarchy Process (AHP) and Weighted Linear Combination (WLC) procedures were conducted for the calculation of the Neotectonic Landscape Deformation Index (NLDI). The study is based on the combination of morphotectonic, geomorphological and geological parameters. The GIS-based spatial MCDA led to the classification of the study area into five classes of neotectonic deformation (from very low to very high) and to a neotectonic deformation map. The results were compared with the outputs of a relative tectonic activity classification approach based on quantitative geomorphic analysis at a regional scale, including site-specific field observations. Areas of high and very high deformation are related to the major active faults of Dirfis, Kandili and Gregolimano–Telethrio. Other minor active normal faults of medium to high seismic risk level, affecting the northern and northeastern parts of the island, are also associated with areas of intense landscape neotectonic deformation.

A tectono-geomorphological perspective of micro-earthquake swarm activity prone areas around Bhavnagar and Jamnagar in Saurashtra, western India

Areas around Bhavnagar and Jamnagar in eastern and northern parts of Saurashtra respectively, are identified previously as prone to recurrent earthquake swarm activity. Sparse seismotectonic studies so far have not revealed any linkage with known faults in Bhavnagar area while no structures are known to occur in the area around Jamnagar. We carried out detailed tectono-geomorphic studies with contrasting geomorphic settings with a view to provide an insight into the swarm activity from a geomorphological perspective. The study is based on extensive field studies and quantitative geomorphic analysis of landscape and drainage. The area around Bhavnagar is divisible into two tectono-geomorphic domains – the E-W trending Sihor Fault zone located to the west of Bhavnagar (domain-I) and the terrain to its south which shows undulating landscape controlled by N–S trending structural trends (domain-II). The quadrant in the SW between these two domains consists of southward titled trappean hills which form source area for drainages flowing northward through Sihor Fault zone and those flowing eastward through domain-II. Late Quaternary, possibly Holocene tectonic activity along the Sihor Fault is indicated by the northward tilt of alluvial plain surface, knickpoint in rivers and small scale minor faults along the fault zone, prominent decrease in depth of fluvial incision away from the fault zone and youthful landscape indicated by drainage basin analysis. Domain-II comprises the largely erosional pediplain developed over trappean and Tertiary rocks to the south of Bhavnagar. The drainages show an early stage of landscape development due to ongoing tectonic activity. The area around Jamnagar is dominantly a peneplain formed over subhorizontal trappean lava flows. The peneplain is a manifestation of the prolonged period of non-erosion and deposition during the Cenozoic. The rivers show youthful landscape in the central part of the peneplain which includes, large knickpoints, rapids, anomalous river bends, steepening of channel gradient and large potholes. This ENE-WSW trending zone of anomalous fluvial geomorphic anomalies points to the existence of a fault or fold in the subsurface. The structure appears to be active as indicated by the denser cluster of earthquake swarm along this zone. We infer that the generation of earthquake swarm activity comprising low to moderate magnitude shocks is caused by the sheared rocks along the Sihor Fault near Bhavnagar and the ENE-WSW trending subsurface structure near Lalpur which provide avenues for downward percolation of rainwater to deeper levels causing loss of frictional resistance along weak planes.

Geomorphic response to neotectonic instability in the Deccan volcanic province, Shetrunji River, western India: Insights from quantitative geomorphology

The Saurashtra peninsula, a Deccan Trap terrain, in western India lacks the studies that document on-land information of tectonically active faults. In the present paper, the tectonogeomorphology of the Shetrunji River basin is investigated to identify the neotectonic signatures of the buried structural element by detailed analyses of the landforms and drainage pattern using quantitative geomorphic analysis, morphostructural studies and Gradient length analysis (GLA) along with field investigation. The basin has been divided into three segments based on channel orientation, (a) Segment-1 (upper reach): oriented in NE-SW direction (b) Segment-2 (middle reach): oriented in an E-W direction and (c) Segment-3 (lower reach): oriented in NW-SE direction. The tectono-geomorphic analysis suggests the neotectonic deformation is mainly demonstrated by the NE-SW oriented Girnar Fault (GF) in Segment-1 and E-W oriented Shetrunji Fault (SF) in Segment-2. The Segment-3 interestingly shows least or no tectonic deformation signatures. For the first time, we report the geomorphic evidence of the two main faults 1) the Girnar Fault (GF) ~ a left-lateral strike slip fault and 2) the Shetrunji Fault zone (SFz) ~ a right-lateral strike slip fault. The interplay between drainage pattern and buried structures are observed in the form of offset channel/offset ridges, deflection in stream and linear valleys. The SFz is characterized by an anastomosing drainage pattern, offsetting/deflection of streams and development of linear valleys in zone which is 52 km in length and 2 km wide. The SL index and Ksn show high values along the fault zone, which is also, supported by the presence of incised river channel, entrenched mender and incised ravine surfaces. The study reveals the prevalent neotectonic activity in the Shetrunji River basin along with the GF and the SFz. The findings are consistent with the geomorphic - structural setup of the region, and coincide with the historical as well as current seismicity distribution.

Tectonic implication of geomorphometric analyses along the Saravan Fault: evidence of a difference in tectonic movements between the Sistan Suture Zone and Makran Mountain Belt

In this paper, remote sensing techniques, as well as field studies, have been used to investigate the geomorphological processes and landscape evolution along the Saravan Fault, SE Iran to highlight how topographic features were influenced by active tectonics. Quantitative geomorphic analysis was carried out using mountain-front sinuosity (Smf), valley floor width–valley height ratio (Vf), drainage basin asymmetry factor (Af), Hypsometric integral (Hi), drainage basin shape index (Bs), mean axial slope of channel (MASC), standard deviation of topography (STD) and index of active tectonic (Iat). Remote sensing techniques, as well as field studies revealed that the Saravan Fault have three parts trending N-S, NW-SE, and E-W. Obtained results show that basins with high Iat index are located at where the strike of the Saravan Faults changes and where several strike-slip faults are crossed the Saravan fault.

Long-term geomorphological evolution of the axial zone of the Campania-Lucania Apennine, southern Italy: a review

Abstract Uplift and erosion rates have been calculated for a large sector of the Campania-Lucania Apennine and Calabrian arc, Italy, using both geomorphological observations (elevations, ages and arrangement of depositional and erosional land surfaces and other morphotectonic markers) and stratigraphical and structural data (sea-level related facies, base levels, fault kinematics, and fault offset estimations). The values of the Quaternary uplift rates of the southern Apennines vary from 0.2 mm/yr to about 1.2–1.3 mm/yr. The erosion rates from key-areas of the southern Apennines, obtained from both quantitative geomorphic analysis and missing volumes calculations, has been estimated at 0.2 mm/yr since the Middle Pleistocene. Since the Late Pleistocene erosion and uplift rates match well, the axial-zone landscape could have reached a flux steady state during that time, although it is more probable that the entire study area may be a transient landscape. Tectonic denudation phenomena — leading to the exhumation of the Mesozoic core of the chain — followed by an impressive regional planation started in the Late Pliocene have to be taken into account for a coherent explanation of the morphological evolution of southern Italy.

QMorphoStream: processing tools in QGIS environment for the quantitative geomorphic analysis of watersheds and river networks

The quantitative geomorphic analysis is a powerful tool for the study of geomorphology and landforms, as it provides objective methods to describe the main properties of drainage basins by means of an appropriate set of parameters. Over the last decades, GIS techniques and processing tools have been widely applied to the geomorphic analysis, and specific applications were developed, essentially using commercial software. In the present paper, the first experimental version of QMorphoStream, an originally developed set of processing tools for quantitative geomorphic analysis in QGIS environment, is presented. Besides the obvious advantage in terms of cost reduction, the choice of an open source development environment allowed us to integrate original algorithms with both QGIS built-in functions and processing tools available in the developers’ community.

Multi temporal 2D discrete wavelet analysis of a large and deep landslide

The analysis of the landscape evolution before and after a landslide is of paramount importance for investigating the landslide itself and the effects on the involved area. Such analysis can be particularly sharp, when high resolution digital elevation models, e.g. LiDAR, are available at multiple time steps, before and after the event. This work presents some preliminary results of a quantitative geomorphic analysis based on 2D discrete wavelet transform of two LiDARs, ante and post event. In particular, the large landslide of Montescaglioso, south Italy, is investigated. This landslide is a complex large movement, which involved a relatively poor steeping clay slope. Numerical results of this analysis will emphasize the magnitude of variations between the ante and post landslide scenarios

Spatial variations in tectonic activity along the Kachchh Mainland Fault, Kachchh, western India: implications in seismic hazard assessment

The landscape of Kachchh is a unique example of active intraplate region in the world. Various structural features such as domes, faults, folds and associated intrusive suggest early tertiary tectonic history, while youthful topography like youthful nature of the fault scarps and gorges suggests Quaternary tectonic history. Kachchh Mainland Fault (KMF) is a 170-km-long E–W-oriented south-dipping reverse fault situated in pericratonic Mesozoic rift basin in western India. The KMF is a neotectonically active fault substantiated by distinct tectonic geomorphology and seismotectonic history. As Kachchh region experiences an arid climate, it lacks vegetation and provides favorable conditions for assessing the morphology of mountain fronts and gradient of channels using remote sensing to evaluate the relative tectonic activity. We employed the means of quantitative geomorphic analysis extracted from a DEM to access the spatial variation in tectonic activity. The assessment of geomorphic indicators of active tectonics was carried out using tectono-geomorphic parameters such as stream length-gradient index (SL index), mountain front sinuosity (S mf) and valley floor width–height ratio (V f). These parameters were combined to generate the relative index of active tectonics (RIAT) which was further divided into four classes as per degree of tectonic activity. The RIAT classes show segmented nature of KMF, with four segments having decrease in degree of tectonic activity from east toward west. The central and the eastern segments of KMF fall in class 1 and class 2 of RIAT, indicating a relatively higher degree of recent tectonic activity undergone by them. The results of geomorphic analysis are consistent with the landforms present, geological setup and seismicity in the study area. The study would be helpful in accessing the regional seismic hazard from KMF for the entire western India.

Quaternary landscape development, alluvial fan chronology and erosion of the Mecca Hills at the southern end of the San Andreas Fault zone

Quantitative geomorphic analysis combined with cosmogenic nuclide 10Be-based geochronology and denudation rates have been used to further the understanding of the Quaternary landscape development of the Mecca Hills, a zone of transpressional uplift along the southern end of the San Andreas Fault, in southern California. The similar timing of convergent uplifts along the San Andreas Fault with the initiation of the sub-parallel San Jacinto Fault suggest a possible link between the two tectonic events. The ages of alluvial fans and the rates of catchment-wide denudation have been integrated to assess the relative influence of climate and tectonic uplift on the development of catchments within the Mecca Hills. Ages for major geomorphic surfaces based on 10Be surface exposure dating of boulders and 10Be depth profiles define the timing of surface stabilization to 2.6 +5.6/–1.3 ka (Qyf1 surface), 67.2 ± 5.3 ka (Qvof2 surface), and 280 ± 24 ka (Qvof1 surface). Comparison of 10Be measurements from active channel deposits (Qac) and fluvial terraces (Qt) illustrate a complex history of erosion, sediment storage, and sediment transport in this environment. Beryllium-10 catchment-wide denudation rates range from 19.9 ± 3.2 to 149 ± 22.5 m/Ma and demonstrate strong correlations with mean catchment slope and with total active fault length normalized by catchment area. The lack of strong correlation with other geomorphic variables suggests that tectonic uplift and rock weakening have the greatest control. The currently measured topography and denudation rates across the Mecca Hills may be most consistent with a model of radial topographic growth in contrast to a model based on the rapid uplift and advection of crust.

Insights into deglaciation of the largest ice-free area in the South Shetland Islands (Antarctica) from quantitative analysis of the drainage system

A quantitative geomorphic analysis of the drainage system on Byers Peninsula, Livingston Island, has been carried out in order to study the relief evolution, glacial history and possible neotectonic influence on the largest ice-free area of the South Shetlands archipelago. Aerial photographs, SAR data from RADARSAT-2 satellite, field work, a digital elevation model and GIS spatial analysis have been used to identify, map and study the existing drainage basins. A series of morphometric parameters have been studied in 30 selected basins in order to characterize their shape as well as the drainage network. Results in morphometric parameters reveal elongation trends in the shape of basins and a limited hierarchical network, common of a youthful stage of landscape evolution models.Several morphometric indexes (hypsometric integral, hypsometric curves, SL index, transverse topographical drainage basin asymmetry-T-Factor) have been used to study possible controls on drainage development. Results have been discussed in relation to relief and drainage evolution linked to the spatial distribution of lithological units and structural framework. T-Factor shows an apparently disorganized pattern and absence of tectonic influence. However, there are local values of second order basin asymmetry directions and magnitudes, which could reflect a succession of master rills through time, related to the changes in water supply during the deglaciation history of Byers Peninsula. Hypsometric values and curves of basins are also mainly related to a young stage of landscape evolution. Analysis of hypsometric integrals together with T-Factor index has allowed us to establish a possible deglaciation model on Byers Peninsula, which successfully explains the results. Areas of different landscape evolution stage are linked in space and support the hypothesis of local glacial centers during the ice cover retreat process. SL index results do not show the same pattern in results, which could be due to differences between incision and lateral shifting ratios.Quantitative geomorphic analysis indicates that during the deglaciation of Byers Peninsula, at least three areas acted as local glacial centers (NW, central and Rotch Dome area). Changes in index results clearly show a different behavior between two areas; distal areas and proximal areas close to the glacial centers. Morphometric indexes have demonstrated their being useful tools to provide information on the glacial history in recently deglaciated Antarctic areas.

Landscape response to tectonic and climatic forcing in the foredeep of the southern Apennines, Italy: insights from Quaternary stratigraphy, quantitative geomorphic analysis, and denudation rate proxies

ABSTRACTWe present new data about the morphological and stratigraphic evolution and the rates of fluvial denudation of the Tavoliere di Puglia plain, a low‐relief landscape representing the northernmost sector of the Pliocene‐Pleistocene foredeep of the southern Apennines. The study area is located between the easternmost part of the southern Apennine chain and the Gargano promontory and it is characterized by several orders of terraced fluvial deposits, disconformably overlying lower Pleistocene marine clay and organized in a staircase geometry, which recorded the emersion and the long‐term incision history of this sector since mid‐Pleistocene times. We used the spatial and altimetric distribution of several orders of middle to late Pleistocene fluvial terraces in order to perform paleotopographic reconstruction and GIS‐aided eroded volumes estimates. Then, we estimated denudation rates on the basis of the terraces chronostratigraphy, supported by published OSL and AAR dating. Middle to upper Pleistocene denudation rates estimated by means of such an approach are slightly lower than 0.1 mm yr‐1, in good agreement with short‐term data from direct and indirect evaluation of suspended sediment yield. The analysis of longitudinal river profiles using the stream power erosion model provided additional information on the incision rates of the studied area. Middle to late Quaternary uplift rates (about 0.15 mm yr‐1), calculated on the basis of the elevation above sea level of marine deposits outcropping in the easternmost sector of the study area, are quite similar to the erosion rates average value, thus suggesting a steady‐state fluvial incision. The approach adopted in this work has demonstrated that erosion rates traditionally obtained by quantitative geomorphic analysis and ksn estimations can be successfully integrated to quantify rates of tectonic or geomorphological processes of a landscape approaching steady‐state equilibrium. Copyright © 2014 John Wiley & Sons, Ltd.

DEM and GIS analysis of sub-watersheds to evaluate relative tectonic activity. A case study of the North–south axis (Central Tunisia)

Morphotectonic analysis using geomorphic indexes has been developed as a basic tool to identify recent tectonic deformation in specific areas.This study was undertaken to develop an integrated quantitative geomorphic analysis of tectonic activity in the North–south axis, central of Tunisia. Different geomorphic indexes, including elongation ratio (E), drainage basin asymmetry (Af), hypsometric integral (Hi), Valley floor width-to-height ratio (Vf), mountain front sinuosity (Smf), and stream length gradient index (SL) were calculated. The relationships between the calculated indexes, their correlations and their significance (based on p-values) were also investigated.. Using the hierarchical cluster analysis based on Ward’s method, these indexes were classified into three classes describing the relative, different effect of tectonics in each fault segment. The higher deformation is concentrated in the NE-SW Boudinar fault, followed, in order of decreasing activity, by Goubrar, Gouleb, and Majoura normal faults. This pattern of variation in the relative degree of tectonic activity is consistent with field evidence.

Quantitative geomorphic analysis along Narmada – Son Fault (NSF), Gujarat, Western India: Implication for late Quaternary tectonic activity

Quantitative geomorphic analysis along Narmada – Son Fault (NSF), Gujarat, Western India: Implication for late Quaternary tectonic activity

Active tectonic assessment around Rudbar Lorestan dam site, High Zagros Belt (SW of Iran)

The aim of this study is to improve a method to develop an integrated quantitative geomorphic analysis of tectonic activity around the Rudbar Lorestan dam site and powerhouse in the High Zagros Belt (HZB), southwest Iran, using several tectonic geomorphic indexes including stream length–gradient index ( SL), drainage basin asymmetry ( Af), hypsometric integral ( Hi), ratio of valley floor width to valley height ( Vf), and transverse topographic symmetry factor ( T). Considering the results obtained from each of the above indexes, as combined and weighted by the “analytic hierarchy process” (AHP) and plotted on the “index map of relative active tectonics” ( Iat) by El Hamdouni et al. (2008), four classes are recognized in the study area; i.e. low, moderate, high, and very high, according to the rate of tectonic activity in the subbasins. Low to moderate intensities correspond to the northeast (along the Main Zagros Reverse Fault: MZRF) and southwest parts of the study area; whereas subbasins in the middle parts, along the Saravand–Baznavid strike-slip fault, are classified into high or very high intensities because of recent activity and the oblique-slip movement of the Saravand–Baznavid fault. The results show that the Rudbar Lorestan dam site and powerhouse are located in an active strike-slip fault zone and that a seismic hazard may occur along this zone in the future.

Estimating Long to Short-Term Erosion Rates of Fluvial vs Mass Movement Processes: An Example from the Axial Zone of the Southern Italian Apennines

Estimates of erosion rates related to fluvial and landslides processes have been performed for several temporal ranges on the basis of different viable methods. The study area includes three catchment sub-basins of the north-eastern flank of the Agri Valley, a tectonically active morpho-structural low located in the axial zone of the southern Apennines and affected by desertification processes in its middle part. Long and mid-term rates have been estimated evaluating the missing volume of eroded rocks, on the grounds of GIS-aided calculations linked to geomorphological markers corresponding to ancient base-levels of the erosion. Short-term rates have been calculated converting the parameter related to the turbid transport of streams (Tu), derived from the quantitative geomorphic analysis, adopting an average value for the specific weight of the outcropping rocks, Such an approximation has to be considered acceptable because of the presence of conditions of lithological homogeneity in two of the chosen basins. In the light of this, the third basin, characterized by a certain geological heterogeneity, has been assumed as test-site with regard to the other two sub-basins. The average value of the long-term erosion rate from the entire study area is 0.25 mm/y, mainly due to fluvial processes. The comparison of the erosion rates related to the fluvial network activity from early Pleistocene to Present with those related to the mass movements occurred in a more recent (and shorter) time-span indicates that mass movements contribute just for the 1% of the whole erosion estimated in the two homogeneous basins, but they refer to a short time-span (10 ky to Present). A theoretical extrapolation to the past (0.5 to 1 My) allows to consider the contribution of landslides to the total erosion inside the catchment areas as almost equal to the fluvial aliquot. The conversion of the Tu values shows that the short-term rates are generally greater than the rates calculated on the basis of the “volumetric” method, being the average value about 0.46 mm/y. This may mean that the present-day trend of the linear erosion rate could increase respect to the long- and mid-term trend as a response to climate triggering (i.e. more rainfalls and/or sediment supply), or simply represent an instantaneous trivial fluctuation in the long-lasting behavior of the fluvial nets under variable climate conditions. The comparison of all these data with the uplift rates calculated on a regional scale (0.6-1.1 mm/y) confirms that the southern Apennines may represent a non-steady state system.