Geomorphological Reconnaissance Research Articles

Engineering geomorphological reconnaissance of the December 2018 Waimata Valley mud volcano eruption, Gisborne, New Zealand

Gisborne (North Island, NZ) is affected by rainfall-induced landslides, earthquakes and tsunami, as well as mud volcanoes (MVs). The latter form via upward mobilization of Eocene–age sediments, and have not been studied from an engineering geological standpoint, so the 15 December 2018 Waimata Valley MV eruption provided a unique opportunity. The event erupted c. 16 900 m 3 of mud, forming an elevated vent area, and three mudflows propagating north, east and south. Scanning electron microscopy (SEM) identified smectite as the dominant clay in the Sr-rich mud, and Atterberg limits indicate high plasticity. In-situ testing using dynamic cone penetrometer and shear vane (3–168 kPa) revealed wide variability in strength properties with depth, while ring shear values are 11.3–13.5°. A fault extends NW beneath the Waimata Valley MV, coinciding with the pre-existing Arakihi Road MV. The Waimata Valley MV area was subject to uplift and cracking during the September 2016 Te Araroa earthquake ( M w 7.1), which caused increased activity at pre-existing mud volcanoes at that time. Geodetic data for the Gisborne district shows an uplift phase culminating around the December 15 2018 MV eruption, followed by the commencement of a Hikurangi subduction zone ‘slow slip event’. Nevertheless, relationships between tectonics and MV eruptions remain equivocal.

The lower altitudinal limit of the periglacial climazonal belt on Kopaonik Mountain (Serbia)

The morphostructural relief of the highest parts of the central Kopaonik Mt was altered by exogenous agents, by denudation as a primary and periglacial processes as a secondary agent. Previous geomorphological studies were mostly focused on the traces of the Pleistocene glaciation, although no reliable evidence was found for this. Recent research, in the part of the mountain above 1,700 m of absolute height, points to geomorphological phenomena resulting from more recent processes within the periglacial environment. By means of geomorphological reconnaissance, analysis and mapping of the highest part of the Kopaonik mountain massif, forms of relief were studied, the ones that according to their morphology correspond to the periglacial forms and processes described in the conditions of high latitudes and high mountains. Determining the spatial coverage of the periglacial belt, especially its lower limit on Kopaonik Mt, is important for understan-ding the distribution of this climatic morphology both in Serbia and in South East Europe. The research contributes to one of the primary aims of exploring the concept of the periglacial zone, in terms of the regional distribution of its specific relief forms.

A Geomorphological Reconnaissance of Tromelin Island, Indian Ocean

Abstract Marriner, N.; Pirazzoli, P.A.; Fontugne, M.; Geerout, M.; Guillaume, M.M.M., and Reyss, J.L., 2012. A geomorphological reconnaissance of Tromelin Island, Indian Ocean. Tromelin is a small coral reef island (∼1 km2) located in the Indian Ocean, approximately 440 km E of Madagascar and 580 km N of La Reunion. Despite the presence of a permanent Meteo France weather station on Tromelin since the 1950s, a detailed geomorphological study of the island has never been undertaken. In this paper, we describe the geomorphology of the atoll, detailing seven geomorphological zones from the outer reef to the atoll crown. We also discuss Holocene relative sea-level changes in the light of new radiometric datings. Uranium–thorium dating of a remnant mid-Holocene reef-flat yielded an age of 5700 ± 400 years and could be interpreted as a relative sea level approximately 1.2 m above present. Subsequent possible sea-level positions have been inferred from coral conglomerates left by high-energy waves. These conglom...

Structural and geomorphological features of landslides in the Bhutan Himalaya derived from Terrestrial Laser Scanning

This study presents data on landslides affecting the main west–east transport corridor in the Himalaya of eastern Bhutan close to the Main Central Thrust. The study focuses on the extraction of structural and geometrical information from Terrestrial Laser Scanning (TLS) data utilising a case study landslide, the Namling Landslide. Analyses of the TLS data allow extraction of slide geometry, discontinuity orientations and identification of the mode of failure. The TLS results are compared to a traditional engineering geological survey and prove to yield considerable added value and should form the basis of new approaches to geomorphological studies and site assessment. Macro-scale geomorphological reconnaissance findings are outlined and interpreted within a conceptual model of the evolution of landslide features, here termed hierarchical landsliding. It is concluded that the Nam Ling Landslide is indicative of deeper seated deformation and is not purely a function of road construction.

Engineering geomorphology for road design in unstable mountainous areas: lessons learnt after 25 years in Nepal

Twenty-five years after the publication of the pioneering work in the field of mountain road engineering geomorphology by D. Brunsden, J. C. Doornkamp, D. K. C. Jones and others, the design and construction performance of the Dharan-Dhankuta road in Nepal vindicates the approach that was applied in this geotechnically challenging part of the Himalayas. The use of engineering geomorphology as a forerunner to more detailed geotechnical studies during design and construction proved an extremely worthwhile exercise. Despite this, the wider use of engineering geomorphology in Nepal since then has been disappointingly low. There are instances where a lack of engineering geological or geomorphological appreciation has led to recurrent problems, leading to design and even alignment modifications. Elsewhere, engineering geology has provided sufficient information and interpretation to enable design to proceed effectively, and the evaluation of slope and drainage hazards as past, recurrent and potential future risk elements has required geomorphological assessment as the critical path activity. However, rapid geomorphological reconnaissance mapping remains a largely judgemental exercise, and one that still suffers from outcome uncertainty despite the passage of 25 years of applied Himalayan geomorphology. Nevertheless, as an observational and interpretative technique that attempts to combine past geology with current and predicted future geomorphology, it should be a critical element in any mountain road engineer’s geological tool box. The future for engineering geomorphology is reliant on a greater integration between landforms, processes and hazards, and the development of a wider appreciation and commitment in both the training and industrial spheres.

Stability of streambanks formed in partially saturated soils and effects of negative pore water pressures: the Sieve River (Italy)

Streambanks of alluvial channels are usually composed of loose materials, which are unsaturated in ambient conditions. Unsaturated soils are subject to negative pore water pressures, which cause an apparent cohesion. The latter is the main factor in allowing the stability of near-vertical banks. Even during moderate in-bank flow events, the apparent cohesion can be strongly reduced as the material approaches full saturation; therefore, during the drawdown phase, as the confining pressure of the water in the channel disappears, a bank failure is likely to occur. Channel bed-level lowering along the Sieve River, Central Italy, has caused widespread bank instability. A geomorphological reconnaissance of forms and processes was followed by in situ tests to determine the shear strength of the banks. Interpretation of the tests and a streambank stability analysis were based on concepts of soil mechanics for unsaturated soils, in order to obtain relations between bank angle and height in limit equilibrium conditions. A stability chart was obtained with curves for different apparent cohesion values, and a stability analysis was performed taking into account the effects of flow events. In order to investigate the pore pressure effects, a series of piezo-tensiometers were installed in a streambank of the Sieve River. Data from a 1 year monitoring period show variations in pore water pressure and matric suction as a consequence of rainfall, evapotranspiration, and water stage variations. A planar failure with a tension crack occurred in the upper cohesive part of the bank during December 1996. The safety factor has been expressed as a function of the geometry of the bank and of the shear strength of the material. Safety factor variations through time are therefore shown as a function of seasonal variations in matric suction.

Design principles and suitability testing for rehabilitation in a flood defence channel: the River Idle, Nottinghamshire, UK

1. The River Idle is a low gradient river flowing through north Nottinghamshire. The river was comprehensively channelized (early 1980s) for flood defence and land drainage. The scheme has produced a trapezoidal channel with a lack of ecological diversity, a poor fishery and low aesthetic value. A rehabilitation design was required to tackle these deficiencies through improvements which did not compromise the other obligations of the managing authority. 2. Rehabilitation proposals were based on a semi-quantitative assessment of the sources and pathways of sediment transport through the system. Geomorphological reconnaissance was used to define conservation value, to prioritize the most suitable reaches for restoration and to identify a reference reach. On this basis, structures were designed to achieve short-term objectives without compromising long-term geomorphological sustainability. 3. After design, the siting and impacts on flow conveyance were tested using appropriate hydraulic models. BENDFLOW was used to refine the positioning of deflectors while the estimated reduction in flow conveyance (HMODEL2 and FCFA) did not exceed 10% of capacity or 0.05 m in water surface elevation (HECRAS) under high flow conditions. 4. As river restoration and rehabilitation schemes become more widely employed in rivers with multi-functional management requirements, so detailed design principles set into their catchment context and hydraulic testing will become increasingly critical to protect designs from the criticism that flood defence and land drainage interests are adversely affected. © 1998 John Wiley & Sons, Ltd.

Characterization of river channel adjustments in the thames basin, south‐east England

AbstractThe increasing involvement of fluvial geomorphology in river channel management has highlighted the desirability of being able to predict spatially differentiated river channel adjustment in relation to prevailing drainage basin characteristics. An exploratory analysis, using data derived from geomorphological reconnaissance surveys and maps, was carried out with the aim of characterizing river channel adjustments in four catchments within the Thames basin. As many of the variables are categorical in nature, logistic regression is utilized to generate multivariate equations which relate four styles of adjustment to catchment characteristics describing rock type, gradient, land use and channel management. Using only the variables which are statistically significant provides a goodness of fit of around 50%. Geomorphological interpretations of the characterizations are provided and, in general, indicate the varying balance between areally extensive natural controls and more localized human influences in shaping the individual styles of adjustment. In the studied lowland environment it appears that few channels are capable of recovering their sinuosity after channel management, thus highlighting the importance of conserving currently sinuous channels and the restoration of previously straightened reaches. Low gradient rural channels set on Chalk or clay favour deposition and thus may be targeted for maintenance operations. Erosive enlargement of the cross‐section is promoted where channel straightening takes place in zones of high gradient; an option which should be minimized to reduce further management expenditure.

Rapid geomorphological reconnaissance survey for road alignment in west Nepal : G.J. Hearn, Bulletin — International Association of Engineering Geology, 48, 1993, pp 59–68

Rapid geomorphological reconnaissance survey for road alignment in west Nepal : G.J. Hearn, Bulletin — International Association of Engineering Geology, 48, 1993, pp 59–68

Rapid geomorphological reconnaissance survey for road alignment in West Nepal

A rapid geomorphological reconnaissance survey of the 112 km Baitadi-Darchula road currently under construction in the Middle Himalaya of West Nepal is described. The first 39 km of the proposed road was under construction when this 5 day survey commenced, to cover both the initial segment as well as an examination of the stability and practicability of the remainder of the alignment. A combination of landslide and erosion mapping along the proposed alignment and interpretation of air photographs led to the recommendation to abandon the remainder of the alignment and adopt an alternative route, considered to be more stable. The findings were later endorsed by a detailed feasibility study and preliminary design thus supporting the cost-effective use of rapid geomorphological surveys for engineering projects in unstable mountain terrain.

A geomorphological reconnaissance of the submarine part of the East Rift Zone of Kilauea Volcano, Hawaii

More than half of the intensely active East Rift Zone of Kilauea Volcano crops out underwater along the crest of the submarine Puna Ridge. I present multibeam bathmetry of the entire ridge, near-bottom photographic and sonar observations of the plunging crest of its deeper distal half, and seismic profiles across the ridge tip and the adjacent structural moat. Analysis of large-scale relief, small-scale topography, and superficial rock types indicates that the rift zone is actively propagating across the moat but is probably a superficial structure that does not penetrate the underlying oceanic crust, that its tip is covered with large lava flows erupted at high rates and is surrounded with extensive debris flow deposits, and that the axial topography at depths of 2–4 km is dominated by gaping fissures and collapse pits, showing a preponderance of intrusive rather than extrusive events. Some aspects of this central-volcano rift zone, such as its geometry at small lateral offsets, resemble those at interplate rift zones along fast-spreading mid-ocean rises, but the great contrast in lithosphere thickness results in fundamental structural differences.

Engineering geomorphology of the widentobel catchment, appenzell and sankt gallen, switzerland. A geomorphologuical inventory system applied to geotechnical appraisal of slope stability

The paper presents a method of applied and detailed 1:2000 scale geomorphological and geotechnical surveying, developed in Alpine areas and tested to its engineering consulting value in the Widenbach valley, Appenzell and St. Gallen, Switzerland. The investigation was carried out by a pair of geomorphologists, trained in high relief terrain and well versed in mass movement characteristics. A programme of “Wildbachverbauung” — the controlling of fluviatile erosion by the erection of dams — was already undertaken in the twenties, but this first generation of wooden dams is now being replaced by concrete constructions. The Widenbach valley, situated in the marls and sandstones of the folded molasse zone (untere Susswasserzone) was subjected to glacial scouring and deposition by a branch of the Rhine glacier, transfluencing westwards across the Stosspass, separating the Widenbach valley at 940 m a.s.l. from the Appenzell depression. Postglacially, various earthflows have originated from the instable morainic deposits as well as from the weathered marls and sandstones underlying the glacially oversteepened valley flanks. They have built a two km long earthflow complex filling the Widenbach valley to considerable depth. The townships of Eichberg and Altstätten, situated at the outlet of the system, have since historic times experienced damage to forest and grazing land, houses and roads. In the midstream and upstream valley sections, the Widenbach is flowing on the earthflow morphology, while the downstream part, already constrained by new dams founded in exposed hard rock, is controlled by fluvial processes. The mass movement dynamics of the midstream and upstream sectors make a completely different engineering approach necesssary. When this was made clear by the geomorphological reconnaissance, the lack of data could only be filled by a detailed 1:2000 scale geomorphological site investigation, as time and funds for long-lasting monitoring of the earthflow system were not available. This geomorphological survey contained the following elements: pre-field airphoto-interpretation, mapping of micro-terrainforms, classification of materials, types and order of movement; it placed emphasis on the behaviour of the various discontinuity planes expressed in the terrain.

Orbital photography and the geosciences — a geomorphological example from the Central Sahara

Two types of image-systems have emerged from space research : television pictures and astronauts' pictures. Telemetered imagery is of extremely small scale. Advantages are in the feasibility of polar orbits during which virtually every part of the globe can be surveyed. Astronauts' photos have a larger scale and a high resolution, however, are confinded to a zone between about 30°N.L. and 30°S.L. Gemini and Apollo photos are of particular interest for geological and geomorphological reconnaissance in dry areas. A field survey was carried out in some insufficiently known parts of the Sahara having a good coverage of hyper-altitude images. It related to 1) former shore lines of Lake Chad and dunes E of this lake; 2) the wind relief that characterized large tracts in Borkou and nearby regions; 3) vertical climatic-geomorphological zoning in the Tibesti Mountains; and 4) volcanic and structural features in these mountains.

Glaciological and Geomorphological Reconnaissance in the Antarctic in 1956

AbstractThis paper presents a preliminary account of the glaciological observations made by the Antarctic Expedition of the U.S.S.R. Academy of Sciences in Kaiser Wilhelm II Land, Queen Mary Land and Knox Coast in 1956. The topography of the edge of the ice sheet is described, and the ice regime is discussed, particularly in relation to the existence of ice-free areas such as “Bunger’s oasis”.

Glaciological and Geomorphological Reconnaissance in the Antarctic in 1956

Abstract This paper presents a preliminary account of the glaciological observations made by the Antarctic Expedition of the U.S.S.R. Academy of Sciences in Kaiser Wilhelm II Land, Queen Mary Land and Knox Coast in 1956. The topography of the edge of the ice sheet is described, and the ice regime is discussed, particularly in relation to the existence of ice-free areas such as “Bunger’s oasis”.