Role In Landscape Evolution Research Articles

Landslides on the Loess Plateau of China: a latest statistics together with a close look

Landslide plays an important role in landscape evolution, delivers huge amounts of sediment to rivers and seriously affects the structure and function of ecosystems and society. Here, a statistical analysis together with a field investigation was carried out on the Loess Plateau of China to address the challenges. The study tracks landslide-related deaths and collects knowledge about this natural hazard. Since the 1980s, 53 fatal landslides have occurred, causing 717 deaths. As the most important trigger, rainfall induced 40% of the catastrophic landslides, while other factors, i.e., human activities, freeze–thaw and earthquake, accounted for 36, 23 and 1%, respectively. Furthermore, landslide frequency and death toll related to human activities were increasing as time went on. Landslide also plays an important role in sediment delivery, especially in areas with steep terrain. Sediment discharge from landslides accounts for a considerable proportion of the total soil loss in the upper and middle reaches of the Yellow River. In some catchments of the Loess Plateau, landslides contributed over 50% of the total sediment discharge. The result shows that landslide is a widespread geologic hazard in the rural area of the Loess Plateau, China.

Evaluation of Shallow Landslides in the Northern Walgau (Austria) Using Morphometric Analysis Techniques

Landslides play a key role in landscape evolution in the Eastern Alps. These geomorphic phenomena are influenced by multiple interdependent and interacting natural and anthropogenic factors. An in-depth evaluation of the spatial distribution of existing landslides enables to gain first insights into potentially hazardous areas. Morphometric analysis techniques of mapped landslides as well as their date of occurrence allow to infer their activity and also potential impacts on affected areas. The prevalent slow moving landslides and inactive slipping areas were mapped and analysed via digital terrain models (DTM), shaded relief images of highly resolved airborne laserscanning (ALS) data and in-field observations. Orthophotos from aerial surveys and ALS data allowed a deferred-time analyses of past landslide occurrences including a record of recent slope movements. All mapped landslides were classified and analysed with geomorphometric indices. Pedological processes, the lithological setting and anthropogenic landscape transformationwere taken into account when interpreting the results. The geomorphometrical evaluation of the sliding areas determine the creation of a multitemporal landslide inventory in the Northern Walgau.

Classification and development of shallow soils (< 50 cm) in the USA

In Soil Taxonomy, soils in lithic subgroups have hard rock within 50cm of the surface. An examination of the digital databases of the USDA Natural Resources Conservation Service revealed that soils in lithic subgroups occur in 10 soil orders (excludes Oxisols and Gelisols, for which there were insufficient data) and can be ranked by area: Mollisols>Aridisols, Entisols, Inceptisols>Spodosols, Alfisols>Histosols, Ultisols, Andisols≫Vertisols. This ranking is comparable to the overall ranking of these 10 orders in the USA, except that Aridisols and Mollisols are over-represented while Alfisols and Ultisols are under-represented in lithic subgroups. Seven soil great groups account for nearly two-thirds (65%) of the soils: Calciustolls, Torriorthents, Dystrudepts, Haplargids, Haplocalcids, Haplustolls, and Argixerolls. For mineral soils, the minimum and maximum average depths to bedrock were 23 and 47cm, respectively. Although 47% of the soil series had either a cambic horizon or no diagnostic subsurface horizon, 26% had a calcic horizon, 21% an argillic horizon, and 5% a spodic horizon. Nearly two-thirds (63%) of the soils on an area basis are skeletal, i.e., contain >35% coarse fragments. More than one-quarter (26%) of the soil series have “no competing series,” meaning that they can be considered endemic to the region. Pedogenic processes in lithic soils appear to be analogous to those in soils derived from deeper unconsolidated materials, with the dominant processes being humification, calcification, argilluviation, cambisolization, and podzolization. There is abundant evidence that lithic soils are as developed—if not more developed—than nearby soils derived from deeper unconsolidated sediments. Lithic soils may be important reservoirs of SOC, clays, carbonates, and dust. In that lithic soils are often in upslope or at higher elevations, they play an integral role in landscape evolution.

Strike–slip faulting, topographic growth and block movements as deduced from drainage anomalies: The Yeşilırmak River basin, northern Turkey

This study aims to understand the various effects of known tectonism on a fluvial network and to interpret the tectonic deformations using described, and analysed systematic anomalies in the drainage basin of the Yeşilırmak River in northern Turkey at countermarch. This region, which is divided into several faulted wedges by right-lateral strike–slip faulting of the North Anatolian fault zone and its individual splays, has experienced several moderate to large earthquakes with high amounts of surface ruptures during the historical and instrumental periods. The Yeşilırmak River basin includes several geomorphic imprints of such widespread and frequent strike–slip deformations. Offsets (between 750m and 19km), aligned drainages, and linear valleys (170km) are expected geomorphic and tectonic responses to strike–slip faulting in the fluvial system. We used such indicators to determine the long term effects of strike–slip faulting in the Yeşilırmak River drainage network. The measured stream offsets represent decreasing values toward southern splay faults consistent with published geodetic data for the region. However, some other large-scale geomorphic anomalies extracted from the drainage network are not explainable by only strike-slip tectonics. Compressional structures, i.e., anticlines, synclines, in the region are responsible for such large-scale drainage diversions (20–24km) along the river courses. Although these diversions, the North Anatolian fault zone is the main driving force shaping present geomorphology on a regional scale. The Sungurlu–Ezinepazarı fault also plays a critical role in landscape evolution. Their activities and associated block movements have resulted with tilting processes. On the other hand, the entire fluvial network should be modified by the sea level changes of the Black Sea, particularly in the late Quaternary.

Episodic post‐rift deformation in the south‐eastern Australian passive margin: evidence from the Lapstone Structural Complex

ABSTRACTIdentifying the influence of neotectonics on the morphology of elevated passive margins is complicated in that major morpho‐structural patterns might plausibly be explained by processes related to late Mesozoic to early Cenozoic rifting and/or differential erosion induced by Cenozoic epeirogenic uplift. The proportional contribution of each process can vary from continent to continent, and potentially even within the same passive margin.In the passive margin setting of the southeast Australian highlands the documented occurrence of neotectonic deformation is rare, and accordingly its role in landscape evolution is difficult to establish. The results of investigations within the Lapstone Structural Complex, which forms the eastern range front of the Blue Mountains Plateau, provide evidence for two periods of Cenozoic neotectonic uplift in this part of the highlands. The first, demonstrated by seismic and structural evidence, is suggested to have occurred in the Paleogene, and is thus unrelated to Cretaceous rifting. The second period, demonstrated by evidence from the Kurrajong Fault (presented herein) suggests that uplift occurred in both the Mio‐Pliocene and the Middle Pleistocene. The cumulative Neogene and younger uplift of ~15 m determined for the Kurrajong Fault is less than 10% of the 130 m of total measured throw across the fault. The apparently minor contribution of neotectonism to the current elevation of the Blue Mountains Plateau supports a predominantly erosional exhumation origin for the topographic relief at the plateau's eastern edge. This finding contrasts with evidence from fault complexes associated with similar topographic relief elsewhere in the south‐eastern highlands, indicating that present‐day topography cannot be directly related to relief generated by Neogene and younger uplift, even from relatively closely‐spaced (&lt; 150 km) structures within the same passive margin. These findings have implications for understanding the spatio‐temporal variability of post‐rift faulting in continental passive margin settings and the evolution of landscapes therein. © Commonwealth of Australia. Earth Surface Processes and Landforms © 2014 John Wiley &amp; Sons, Ltd.

Transient landscapes: gully development and evolution using a landscape evolution model

Gullies are a common feature of many landforms and play a significant role in landscape evolution. They are transient landscape features that move along a drainage line incising into soil, alluvium or colluvium disturbing the catchment both headwards and along its banks. It is important to understand gully initiation, development and evolution as while they are transient features they are drivers of landscape change and erode and transport considerable volumes of sediment through the channel network. There has been considerable research into understanding gully development with many numerical predictive models developed. Here a computer-based landscape evolution model (SIBERIA) is examined for its ability to predict gully development in a catchment undisturbed by European agricultural practices. The simulations demonstrate that the SIBERIA model is able to produce gullies in the same position that are qualitatively and quantitatively morphologically similar to field data. The modelling suggests that the whole catchment is at risk of gullying and is in accordance with the field data which demonstrated that the presence of gullies was extensive throughout the catchment. The model also produces erosion rates within that of independently measured field data.

Dendrochronological and geomorphological investigations to assess water erosion and mass wasting processes in the Apennines of Southern Tuscany (Italy)

Abstract The Tyrrhenian side of the Central Apennines is located in a lively geological context, in which uplift/denudation dynamics played a key role in landscape evolution. Intense water erosion and gravitational processes led to the development of spectacular badlands on the widespread clayey hillslopes. The Crete d'Arbia badlands (as part of the Crete Senesi of Southern Tuscany) represent one of the most beautiful examples of these landforms developed on Pliocene clays. On the other hand, these rapidly evolving landforms endanger the artistic heritage of the area, as with the Monte Oliveto Maggiore Abbey that was constructed on the top of a badland hillslope and confers additional value to the landscape. In the perspective of monitoring and reconstructing some significant phases of the relief evolution of this area an integrated approach has been used, which is based on dendrogeomorphology and geomorphological monitoring techniques. In particular, the correspondence between the data from dendrogeomorphological indicators and the measured denudation rates on badland hillslopes was tested. The sampling for dendrogeomorphological analysis has been performed in two stages on 45 trees of the Pinus pinea L. species, on hillslopes affected by soil creep and shallow landslides, in order to identify annual ring growth anomalies, compression wood and roots exposure. Trees' local behaviour is not homogeneous but some common trends have been detected on the basis of the anomaly index and compression wood. Since 1993 several monitoring stations at badland denudation “hot spots” have been equipped with erosion pins; quantitative data from monitoring stations, compared to pluviometric series, indicated critical phases of denudation that were supported by dendrochronological data. The integrated approach between dendrogeomorphology and geomorphological monitoring techniques allowed calibration of both tools in order to extend the analysis in the period preceding the field measurements. This kind of approach, capable of implementation in many contexts, could be particularly helpful in order to forecast the relief evolutionary trend.

Weathering in the central Namib Desert, Namibia: Controls, processes and implications

The hyper-arid Namib Desert is an ancient desert of great lithological diversity. Weathering plays a key role in landscape evolution in the Namib which, in spite of its aridity, has a number of sources of moisture – rainfall, fogs, dews and groundwater seepage – which enhance weathering. Among the weathering processes that have been the subject of recent study in the central Namib are salt, thermal and lichen weathering which, in often complex associations of processes, contribute to the array of small scale weathering features found on marble and granite outcrops here. At the landscape scale weathering in the central Namib is also highly interrelated with erosion and the development of geochemical sediments (calcrete, gypcrete, tufas etc), whilst weathering ‘hotspots’ are thought to be important sources of fine sediment production. Over the long term weathering has played important roles in landscape evolution here which, despite localized weathering hotspots, has been very slow for much of the Cenozoic.

Rock avalanches and the pace of late Quaternary development of river valleys in the Karakoram Himalaya

We discuss the implications of a set of terrestrial cosmogenic nuclide (TCN) ages on blocky, cross-valley deposits of large rock avalanches along upper Indus streams. The dated deposits are key to understanding late Quaternary events that play a major role in landscape evolution in the Karakoram Himalaya. The landslides occurred between 3 and 8 ka ago, challenging existing chronologies of events along Indus streams. The TCN ages may support a mid-Holocene climatic role in preparing slopes for failure, but the balance of evidence suggests that large earthquakes triggered the landslides. Each landslide dammed the Indus or a major tributary and controlled base level and sedimentation for millennia. They produced landforms long regarded as characteristic of the region, including extensive lacustrine deposits, flights of river terraces, epigenetic gorges, and sediment fans. Until the 1990s, most of the landslides were interpreted as moraines; related lacustrine and other sediments continue to be attributed to glacial damming, and stream terraces to tectonic processes. Generally they were seen to originate tens of thousands to hundreds of thousands of years earlier than the new ages require. Instead we argue that they record interactions among different geomorphic processes in landslide-fragmented valleys during the Holocene. Rather than being geomorphic markers of tectonic and climatic events, the landslides have buffered or redirected climatic and tectonic forcing. In such an active orogen, millennia-long episodes of zero net bedrock incision at each site are surprising. However, rates of sedimentation above landslide barriers and erosion controlled by their breaching are close to today9s high measured rates for geomorphic activity. We propose that landslide-fragmented rivers may, in fact, characterize interglaciations and future patterns of upper Indus landscape evolution at time scales of 10 3 to 10 4 years.

The role of mass movements on landscape evolution in the Central Karakoram: Discussion and speculation

Mass movement constitutes an important process in the evolution of landscapes in mountain regions. However, the role of massive slope failures in denudational unloading and landscape evolution has not been extensively studied. Large-scale mass movements in one of the greatest mountain ranges on Earth, the Central Karakoram in Pakistan, were therefore examined to help evaluate their role in landscape evolution in high mountains. Specifically, four major mass-movement complexes (Ghoro Choh rock avalanche, Busper sackung and slope failure, Gomboro slope failure, and Urdokas rockslide), each comprising 10 6 m 3 of debris, were assessed and mapped in detail. Two of these mass-movement complexes, the Ghoro Choh rock avalanche and Gomboro slope failure, were dated using terrestrial cosmogenic nuclides. The ages of occurrence of the mass-movement complexes studied in the Central Karakoram date from the late Pleistocene to the Holocene. The four major mass-movement complexes all involved the removal of mass from the tops of mountain ridges and peaks that failed and were subsequently transported towards the bottom of their respective valleys. Such massive movement of mass is anomalous compared to other forms of mass movement and is generally spatially coincident with exposed deeply buried gneiss-dome structures. These large-scale movements appear to be part of a coupled system involving river incision and glacial debuttrussing, although earthquakes might have triggered these mass movements. This study illustrates the role of climate forcing, which is part of a coupled system of denudational unloading, but it is unclear whether high-magnitude, low-frequency events such as these initiate the isostatic and tectonic influx of mass, or if sustained high-magnitude denudation resulting from a coupled system is responsible for the exhumation of buried structures.

Active tectonics and geomorphology in the Sone-Ganga alluvial tract in mid-Ganga Basin, India

Active tectonics plays a major role in landscape evolution by bringing changes in topography and channel slopes. The alluvial plains in Ganga Basin are divided into a number of tectonic blocks by several active subsurface faults. The associated disturbances along these faults have given rise to a distinctive fluvial regime and geomorphology in the region. In Sone-Ganga alluvial plain in parts of South Ganga Plains in middle Ganga Basin, the Sone and Ganga rivers have responded to the ongoing tectonic deformation in the area. The study reports a classical example of tilt- induced avulsion and channel migration during Holocene from the parts of South Ganga Plains within the extensional half-graben between East Patna Fault (EPF) and West Patna Fault (WPF). The rate of lateral tilt appears to control the style of channel movement, with gradual migration occurring at low tilt rates, and avulsion at higher rates. The river Sone, lying laterally close to the line of uplift, has undergone avulsions at different times of tilting, whereas the Ganga River located at the lower parts of the tilting-block away from the line of uplift has migrated in the down-tilt direction. Various fluvial anomalies such as gradient reversals in the longitudinal profile of channels, sinuosity variations, channel incision, frequency in the braid bar distribution and variation in the cross-sectional parameters of the channels most probably created by tectonics have been studied. Satellite images and maps coupled with relative bank height measurements and other geomorphologic studies in field have helped in identifying such fluvial signatures and their relevance to tectonics. The subsurface faults in the Sone-Ganga plains cut across and also run parallel the river channels, showing the effects of transverse, and lateral tilting manifested in channel avulsions and migrations.

Identification of latent faults using a radon test

This paper discusses the use of 222Rn concentrations in water of natural springs as a geomorphological method to identify latent faults in low-mid term activity areas. The identification of this type of active fault may be crucial in hazard analysis, structural geomorphology and in landscape evolution analysis. The test used to identify these faults is based on the measuring of 222Rn concentrations in water of springs linked to faults, and comparison with those obtained from springs which, although exactly the same lithological context, are not linked with faults (reference values). If the difference between the measured value and the reference value is positive then an anomaly is identified and that measurement indicates a spring linked to a latent fault. The test was applied and validated in springs linked to faults with a latent behaviour in Cantabria, Northern Spain. These faults have shown an intermittent movement over the last 50,000 years, and have contributed towards landslide processes playing a significant role in landscape evolution of the area.

On the formation of couplet-style stratifications

Couplet-style stratifications refer to the sedimentary sequences that consist of alternating coarse-grain-dominated bed and fine-grain-dominated bed, with or without a sandwiched middle-sized bed. The formation mechanism is complicated due to the interplays of varying driving force (s), sediment supply & transport and topographic configurations. This paper presents a comprehensive overview of such characteristic bedforms, which emerge during the transport and deposition of non-uniform sediments. The leading formative models include water-stage variation, gravel-overpassing process, superimposition of bedload sheets and avalanching process (inverse grading). Each process might produce similar or distinct sedimentological features with respect to grading, matrix content, grain attitude, bounding faces between beds and internal longitudinal/transverse geometry. The couplet-style stratified strata might play an active role in landscape evolution.

Hydraulic geometry, river sediment and the definition of bedrock channels

A growing literature deals with bedrock channels, erosion processes within them, and their role in landscape evolution. Formal definitions currently in use classify channels as bedrock when alluvial cover is discontinuous or thin. This is equated with a physical property of the flow. Using up-to-date erosion laws and descriptions of channel dynamics, we show that existing definitions are difficult to apply and may lead to conflicting classifications. We propose the definition: A bedrock channel cannot substantially widen, lower or shift its bed without eroding bedrock. Applied to channels in Taiwan, this leads to a different classification than previous definitions. By analysing at-a-station hydraulic geometry of these channels, we show that the classification exposes different controls of sediment effects on dynamics of channels classified as alluvial and bedrock.

Predictions of steady state and transient landscape morphology using sediment‐flux‐dependent river incision models

Recent experimental and theoretical studies support the notion that bed load in mountain rivers can both enhance incision rates through wear and inhibit incision rates by covering the bed. These effects may play an important role in landscape evolution and, in particular, the response of river channels to tectonic or climatic perturbation. We use the channel‐hillslope integrated landscape development (CHILD) numerical model with two different bedrock incision models that include the dual role of the sediment flux to explore the transient behavior of fluvial landscapes. Both models predict that steady state channel slopes increase in landscapes with higher rock uplift rates. However, the incision models predict different transient responses to an increase in uplift rate, and the behavior of each incision model depends on both the magnitude of change in uplift rate and the local drainage area. In some cases, the transient channel behavior is indistinguishable from that predicted for transport‐limited alluvial rivers. In other cases, knickpoints form in some or all of the drainage network, as predicted by the detachment‐limited stream power model. In all cases the response in the lower parts of the network is highly dependent on the response in the upper parts of the network as well as the hillslopes. As the upper parts of the network send more sediment downstream, channel incision rates may rise or fall, and slopes in the lower parts of the channel may, in fact, decrease at times during the transient adjustment to an increase in rock uplift rate. In some cases, channel incision in the upper parts of the network ceases during the transient while the hillslopes adjust to the new uplift rate; drainage density may also change as a function of uplift rate. Our results suggest that if the sediment flux strongly controls bedrock incision rates, then (1) the transient fluvial response will take longer than predicted by the detachment‐limited stream power model, (2) changes in channel slope may be much more complex than predicted by the detachment‐limited stream power model, and (3) changes in the fluvial system will be closely tied to sediment delivery from the hillslopes. Importantly, our results outline quantitative differences in system behavior produced by competing models and provide a framework for identifying locations in natural systems where differences in channel morphology can be used to discern between competing fluvial erosion models.

Possible pingos and a periglacial landscape in northwest Utopia Planitia

Hydrostatic (closed-system) pingos are small, elongate to circular, ice-cored mounds that are perennial features of some periglacial landscapes. The growth and development of hydrostatic pingos is contingent upon the presence of surface water, freezing processes and of deep, continuous, ice-cemented permafrost. Other cold-climate landforms such as small-sized, polygonal patterned ground also may occur in the areas where pingos are found. On Mars, landscapes comprising small, elongate to circular mounds and other possible periglacial features have been identified in various areas, including Utopia Planitia, where water is thought to have played an important role in landscape evolution. Despite the importance of the martian mounds as possible markers of water, most accounts of them in the planetary science literature have been brief and/or based upon Viking imagery. We use a high-resolution Mars Orbiter Camera image (EO300299) and superposed Mars Orbiter Laser Altimeter data tracks to describe and characterise a crater-floor landscape in northwest Utopia Planitia (64.8° N/292.7° W). The landscape comprises an assemblage of landforms that is consistent with the past presence of water and of periglacial processes. This geomorphological assemblage may have formed as recently as the last episode of high obliquity. A similar assemblage of landforms is found in the Tuktoyaktuk peninsula of northern Canada and other terrestrial cold-climate landscapes. We point to the similarity of the two assemblages and suggest that the small, roughly circular mounds on the floor of the impact crater in northwest Utopia Planitia are hydrostatic pingos. Like the hydrostatic pingos of the Tuktoyaktuk peninsula, the origin of the crater-floor mounds could be tied to the loss of ponded, local water, permafrost aggradation and the evolution of a sub-surface ice core.

Interactions among topographically induced elastic stress, static fatigue, and valley incision

Gravity acting on topography creates differential stress, which, for sufficiently high, steep topography, can fracture intact bedrock. If static fatigue governed the time dependence of that fracturing, a feedback should exist between incision of the landscape and fracturing. The timescale for static fatigue decreases exponentially with differential stress. By creating deeper, steeper valleys, incision should increase the differential stress and, as a result, accelerate fracturing of intact rock. Because both fluvial systems and hillslopes can transport fractured rock much more easily than they can both erode intact rock and then transport its products, topographically induced fracturing could play a crucial role in landscape evolution, especially of steep terrain. Predicting differential stress useful for general rules in geomorphology, however, appears to be difficult, in part because the stress distribution depends sensitively on the precise form of the topography and, perhaps more importantly, because the differential stress for specific topography can differ not only in magnitude but also in sign for small differences in Poisson's ratio. Nevertheless, it appears possible that in steep terrain where rivers are capable of moving bed load sufficiently rapidly, the rate‐limiting process for incision might be static fatigue of the rock under stress due to gravity acting on the adjacent topography.

Slope failures in the Blue Nile basin, as seen from landscape evolution perspective

The Blue Nile basin is severely affected by slope failures, and the characteristics of its deep gorges and rugged valley walls called for a study on the relationships between topography and the process of landsliding and rock falling. Work was commenced with the conception of nine types of landforms on the basis of a one-to-one combination of lateral and vertical slope profiles and thence the determination of the effect of these landforms on the occurrence of slope failures. Observations showed that topographic surfaces with concave lateral profiles shelter mudflows and some retrogressive rotational slumps while slopes characterized by planar lateral profiles are sites mainly for translational slides. Landslides are rare in convex-shaped slopes but when they occur, they are big and deep-seated. As an effort to understand the significant contributions of landslides and rock falls to landscape development, direct and indirect methods are employed. Direct methods are based on quantitative relationships between the volume of material that had been removed from the area and the amount that could, in principle, be taken away based on available erosion rates. Indirect methods used the nature of river incision and the effect of the present-day landslides on the landscape. In general, discrepancy in calculated figures in the first, and the overall drop and form of the Abay River gorge coupled with the observed landslide-caused landform changes in the second, led us to deduce that slope failures were part of the mega-forces that shaped the entire Blue Nile basin, and in fact, played the dominant role in landscape evolution.

Tectonically driven landscape development within the eastern Alpujarran Corridor, Betic Cordillera, SE Spain (Almerı́a)

The Betic Cordillera is a topographic manifestation of Miocene to recent collision between the African and the European plates. Mountain ranges in the Internal Zone of the Betic Cordillera are exhumed massifs of metamorphic and sedimentary rocks, and are surrounded by low-lying sedimentary basins. The Neogene history of mountain range uplift and basin formation in the Betics is well studied, but Quaternary topographic development and its relation to convergent plate boundary tectonics is less understood. Deformation, rates of stream incision and factors controlling landscape evolution on the flanks of the highest mountains in the Betic Cordillera are studied to gain insight on the relationship of Quaternary tectonics to topographic development. Specifically, geomorphic processes that led to formation of topographic relief within the Internal Zone of the Betic Cordillera are assessed. This paper is based on a field study conducted in the eastern Alpujarran Corridor (EAC), which is the eastern half of a 4–6-km wide and 80-km long inverted sedimentary basin. The Mid to Late Quaternary history of basin denudation is deduced on the basis of morphostratigraphic, geochronologic and structural–geologic analyses of oxygen isotope Stage 8-time fluvial deposits in the EAC. Results of these analyses indicate that climate and faulting played only a minor role in landscape evolution in the EAC. Instead, the EAC topographic trough was excavated by a drainage network whose axial stream (Rı́o Andarax) was incising at a rate between 0.3 and 0.7 m/ka since oxygen isotope Stage 8. This paper demonstrates that these incision rates are the same as regional rock uplift rates in the EAC. During the Mid and Late Quaternary, topographic relief between the EAC and adjacent mountain ranges developed largely as a result of fluvial denudation driven by regional uplift. The implications of the results of this investigation are used to propose a model of Quaternary topographic relief development in the Internal Zone of Betic Cordillera. Topographic relief between Internal Zone bedrock massifs and adjacent basins formed largely as a result of fluvial denudation driven by regional uplift. Faulting also played a significant role in areas that are within a few kilometers of crustal-scale fault zones.

Drainage rearrangement by river capture, beheading and diversion

Drainage rearrangement, involving stream piracy (capture), drainage diversion and/or beheading, may be significant for sediment budgets (including sediment provenance) and biotic distributions, as well as for its more usually considered role in landscape evolution. The processes involved in drainage rearrangement are not as self-evident as its abundant literature indicates. This is especially the case with the commonly invoked stream capture. The key process in stream capture, namely, drainage head retreat, is difficult to envisage as a normal part of drainage net evolution, especially in the light of recent findings on drainage hollow evolution. Stream capture may therefore be a relatively rare event in drainage net evolution. This, and uncertainties with interpretations of supposed elbows of capture, mean that stream capture should not be routinely invoked in interpretations of long-term drainage evolution. Further uncertainties associated with the maintenance of drainage lines during the erosion of significant crustal sections, especially in faulted and folded terrains, diminish the likelihood of many supposed examples of stream capture. It is more likely that examples of drainage rearrangement attributed to stream capture were generated by drainage diversion, but even this may involve special conditions.