Landform Stability Research Articles

Climate change risks to mine closure

Robust planning for mine closure is crucial for minimising negative environmental impacts and ensuring a positive post-mining legacy. Even though climate is an important factor in the design and management of most post-mine landscape features, general understanding of the multi-facetted nature of climate change risks to mine closure outcomes is limited. An approach is presented to mapping the climate change risk while elucidating the nature of its uncertainty. The approach is demonstrated using five mine closure planning and design considerations, namely: pit lake hydrology, landform stability, flooding, revegetation, and acid and metalliferous drainage. The risk to each of these considerations is quantified with a representative climate index, namely: aridity index, rainfall erosivity, annual maximum 1-day precipitation, extreme drought frequency, and drying period duration. Change in climate indices are derived relative to baseline conditions for two future 30-year periods (2040–2069, and 2070–2099) from an 11-member ensemble of dynamically downscaled simulations from the fifth phase of the Coupled Model Intercomparison Project (CMIP5) for two emission scenarios (Representative Concentration Pathways 4.5 and 8.5). The approach is demonstrated for mines within Queensland, Australia, with future change and uncertainty in indices mapped spatially. Results show that annual maximum 1-day precipitation and extreme drought frequency is expected to become more extreme into the future irrespective of future time period, emission scenario or geographic region; whilst the expected direction of change varies spatially for the aridity index, rainfall erosivity and drying period duration. Most indices suggest that the greatest changes will occur in the Mount Isa mining region, whereas the Weipa mining region projections are highly uncertain. The research demonstrates the multiple facets of climate change risks that need consideration in mine closure planning and design. It provides new insights into the variabilities among indices, across mining regions, over ensemble members and between time horizons that need to be factored in by mine closure stakeholders.

Geomorphological changes and landscape ecosystem services dynamics of the Bhasan Char Island in the Northern Bay of Bengal, Bangladesh

Geomorphological changes have had numerous environmental impacts on landscape features, natural resources, landform stability, and ecosystem services on Bhasan Char Island in the Northern Bay of Bengal, Bangladesh. Therefore, the present study examines the morphological change of the island and its impacts on landscape features, landform stability, and coastal mangrove forest resources since its evolution. Optical satellite images from Landsat (TM and OLI) spanning from 2003 to 2023 have been used to assess geomorphological parameters using the bio-physical indices NDWI and MNDWI. A hybrid classification method involving unsupervised classification, supervised machine learning, and post-classification refinement was employed to precisely delineate landscape features and evaluate ecosystem services. Indeed, to evaluate forest cover health dynamics, the leaf area index (LAI) was estimated using the Google Earth Engine (GEE) cloud platform. The study results reveal that the geomorphology of the island was changed by fluvial and marine processes and responses, whereas only 3% of the landscape ages older than 19 years. Results also disclosed that built-up area construction for Rohingya nations drastically lost ∼ 7% of mangrove plantations over the last 8 years, from 2015 to 2023. The current research delivers crucial management strategies regarding further structural development by evading unplanned construction, hastening reforestation, and evolving the green belt along the existing embankment. The study findings will help policymakers, environmental managers, coastal and marine resource planners, ecologists, and geomorphologists take an eco-friendly sustainable development plan and conserve the coastal island and its landscape resources from the risk of fluvial and marine processes.

Spatio-temporal analysis of geomorphic recovery along an altered ephemeral stream using automated image processing

Ephemeral rivers in the Mediterranean region have been exposed to significant human disturbance over the last century. Recently, there has been a growing interest in restoring their morpho-sedimentary condition, backed by the European Water Framework Directive. Previous research has highlighted the severe geomorphic impacts of sediment extraction, such as reduced channel width and riverbed incision, but the recovery of these channels during annual flows remains poorly understood. This study presents a methodological framework to investigate geomorphologic recovery (signs of landform change) and constraints in the Rambla de Cervera (eastern Spain) from 2018 to 2021. Aerial imagery, LiDAR topography, and field surveys were used for stream segmentation, fluvial landform classification, temporal landform change, and comparison with flow characteristics from a 2D hydraulic model. The study identified three groups of segments with different channel types and recovery mechanisms. Upstream (G1), unconfined valley settings showed minor changes, indicating morphological stability. Middle segments in confined valleys (G2) showed greater alluvial channel recovery and vegetation encroachment in response to flood/no-flood periods. Downstream segments (G3), incised on cemented gravel, were highly responsive to floods but lacked landform stability due to high energy conditions. The findings suggest that channel recovery during annual floods is slow and occurs mainly downstream in degraded areas (G3). Increased sediment flux from upstream and additional sediment storage in new forms are required to recover these channels. This analysis underscores the challenge of interpreting short-term morpho-dynamic changes for long-term river recovery, but provides insight into the morpho-sedimentary conditions required to accelerate recovery of ephemeral streams.

Stream Suspended Mud as an Indicator of Post-Mining Landform Stability in Tropical Northern Australia

Mining can cause environmental disturbances and thus mined lands must be managed properly to avoid detrimental impacts in the future. They should be rehabilitated in such a way that post mining landforms behave similarly as the surrounding stable undisturbed areas. A challenge for government regulators and mine operators is setting closure criteria for assessment of the stability of the elevated post-mining landforms. Stability of a landform is often measured by the number and incision depth of gullies. This can assess mass stability and bulk movement of coarse material. However, there is a need for a more sensitive approach to assess catchment disturbances using the concept of waves of fine suspended sediment and thus determine the dynamics of recovery of a post mining landform. A more environmentally meaningful approach would be to assess the fine suspended sediment (FSS, silt + clay (0.45 µm < diameter < 63 µm)) leaving the system and entering downstream waterways. We propose assessing stability through relationships between rainfall event loads of FSS and event discharge (Q) in receiving streams. This study used an innovative approach where, instead of using instantaneous FSS concentration, it used total FSS load in waves of sediment driven through the system by rainfall runoff events. High resolution stream monitoring data from 2004 to 2015 in Gulungul and Magela Creeks, Northern Territory, Australia, were used to develop a relationship between sediment wave and event discharge, ∑FSS α f(Q). These creeks are adjacent to and receive runoff from Ranger Mine. In 2008, a 10 ha elevated waste rock landform was constructed and instrumented in the Gulungul Creek catchment. The earthworks required to build the landform created a considerable disturbance in the catchment, making a large volume of disturbed soil and substrate material available for erosion. Between 2008 and 2010, in the first two wet seasons immediately after construction, the downstream monitoring site on Gulungul Creek showed elevated FSS wave loads relative to discharge, compared with the upstream site. From 2010 onwards, the FSS loads relative to Q were no longer elevated. This was due to the establishment of vegetation on the site and loose fine sediment being trapped by vegetation. Large scale disturbance associated with mining and rehabilitation of elevated landforms causes elevated FSS loads in receiving streams. The predicted FSS loads for the stream as per the relationships between FSS and event discharge may not show a 1:1 relation with the observed loads for respective gauging stations. When downstream monitoring shows that FSS wave loads relative to rainfall runoff event discharge reduce back to pre-construction catchment levels, it will indicate that the landform is approaching equilibrium. This approach to assess landform stability will increase the sensitivity of assessing post-mining landform recovery and assist rehabilitation engineers to heal the land and benefit owners of the land to whom it is bestowed after rehabilitation.

Geochemical Stability of Oil Sands Tailings in Mine Closure Landforms

Oil sands surface mining in Alberta has generated over a billion cubic metres of waste, known as tailings, consisting of sands, silts, clays, and process-affected water that contains toxic organic compounds and chemical constituents. All of these tailings will eventually be reclaimed and integrated into one of two types of mine closure landforms: end pit lakes (EPLs) or terrestrial landforms with a wetland feature. In EPLs, tailings deposits are capped with several metres of water while in terrestrial landforms, tailings are capped with solid materials, such as sand or overburden. Because tailings landforms are relatively new, past research has heavily focused on the geotechnical and biogeochemical characteristics of tailings in temporary storage ponds, referred to as tailings ponds. As such, the geochemical stability of tailings landforms remains largely unknown. This review discusses five mechanisms of geochemical change expected in tailings landforms: consolidation, chemical mass loading via pore water fluxes, biogeochemical cycling, polymer degradation, and surface water and groundwater interactions. Key considerations and knowledge gaps with regard to the long-term geochemical stability of tailings landforms are identified, including salt fluxes and subsequent water quality, bioremediation and biogenic greenhouse gas emissions, and the biogeochemical implications of various tailings treatment methods meant to improve geotechnical properties of tailings, such as flocculant (polyacrylamide) and coagulant (gypsum) addition.

Moraine crest or slope: An analysis of the effects of boulder position on cosmogenic exposure age

Terrestrial cosmogenic nuclide dating of ice-marginal moraines can provide unique insights into Quaternary glacial history. However, pre- and post-depositional exposure histories of moraine boulders can introduce geologic uncertainty to numerical landform ages. To avoid geologic outliers, boulders are typically selected based on their depositional context and individual characteristics but while these criteria have good qualitative reasoning, many have not been tested quantitatively. Of these, boulder location is critical, as boulders located on moraine crests are prioritised, while those on moraine slopes are typically rejected. This study provides the first quantitative assessment of the relative utility of moraine crest and moraine slope sampling using new and published 10Be and 36Cl ages (n = 19) and Schmidt hammer sampling (SH; n = 635 moraine boulders, ∼19,050 SH R-values) in the northern and southern Pyrenees. These data show that for many of the studied moraines, the spatial distribution of “good” boulders is effectively random, with no consistent clustering on moraine crests, ice-proximal or -distal slopes. In turn, and in contrast to prior work, there is no clear penalty to either moraine crest or moraine slope sampling. Instead, we argue that landform stability exerts a greater influence on exposure age distributions than the characteristics of individual boulders. For the studied landforms, post-depositional stability is strongly influenced by sedimentology, with prolonged degradation of matrix-rich unconsolidated moraines while boulder-rich, matrix-poor moraines stabilised rapidly after deposition. While this pattern is unlikely to hold true in all settings, these data indicate that differences between landforms can be more significant than differences at the intra-landform scale. As ad hoc assessment of landform stability is extremely challenging based on geomorphological evidence alone, preliminary SH sampling, as utilised here, is a useful method to assess the temporal distribution of boulder exposure ages and to prioritise individual boulders for subsequent analysis.

Application of geomorphons for analysing changes in the morphology of a proglacial valley (case study: The Scott River, SW Svalbard)

The progressive degradation of the cryosphere of High-Arctic areas causes an increase in the dynamics of geomorphic processes that shape the valleys of rapidly retreating glaciers. Those especially sensitive to global environmental changes are the small, land-ending valley glaciers that are in the phase of strong retreat. Under these conditions, the river valley's floors that are drained by proglacial waters are constantly undergoing intensive changes. For the analysis of these changes, two methods were used simultaneously (as a synthesis) to allow for quantitative and qualitative evaluation. The first one is the increasingly more common DoD method (DEM of difference), which allows quantifying volumetric changes as a result of topographic differentiation. The second one, which was applied for the first time on a small-valley spatial scale, is the geomorphons method that makes it possible to assess the stability of landforms and to determine the directions of their new development. To judge the applicability (advantages and disadvantages) of both methods for analysis of geomorphic changes in rapidly changing proglacial environments, the study was carried out over a 3.3 km distance of the non-glaciated section of the Scott River valley course (NW Wedel-Jarlsberg Land, SW Svalbard). This area (1.3 km2) is currently shaped by a braided gravel-bed river. More accurately, the study focused on the section spanning from the glacier terminus, which is the source of the Scott River, to its outlet at the Rechersche Fjord (Bellsundfiorden). The foundation for the development of comparative elevation models was a collection of terrestrial laser scanning (TLS) surveys that were taken with a Leica ScanStation C10 scanner during the 2010 and 2013 snowmelt seasons. On the basis of these surveys and with the use of TIN interpolation, high-resolution (0.2 m) digital terrain models (DTMs) were generated. The DTM models that had been prepared in this manner were used for the analysis of surface changes by employing Geomorphic Change Detection (GCD) software, and by simultaneously generating geomorphons maps for four selected test areas that covered characteristic fragments of the valley bottom (1- on the close forefield of the Scott Glacier terminus; 2- in the immediate vicinity of the narrow valley outlet at the foot of the marginal moraine ridge; 3- in the enlargement of the central section of the non-glaciated valley floor; 4- within the alluvial fan (outlet to the fjord)). A comparison of the obtained results (DoD and geomorphons maps; zonal statistics) as well as a compilation of both the quantitative assessment of the scale of changes and the qualitative assessment of the transformation's direction allowed for reconstructing the range and rate of three-year-long changes in morphology at the analysed sections of the valley floor. It was found that the pattern and rate of changes were closely related to the location of the test areas in the Scott River's catchment system. Significant differences in the dynamics of processes shaping the valley landforms along the longitudinal valley course were found.

Changes in tree structure, composition, and diversity of a mixed-dipterocarp rainforest over a 40-year period

Little work has examined the spatial and temporal changes of a tropical rain forest for long time periods. Here, we present an analysis of long-term plot data from a Sri Lankan Mixed-Dipterocarp forest (MDF). The plots were established in 1978 at three different elevations (low - 335m, medium - 560 m, and high - 915 m). At each site we measured all trees ≥ 10 cm DBH in 16 or 18 plots. The total area sampled amounted to 12.5 ha. We recorded 166 tree species, with each site comprising between 95 and 121 species. Stem densities and basal areas were different among sites, and declined over the period from 642.8 stems ha−1 and 41.8 m2 ha−1 for the 1978 census, to 496.2 stems ha−1 and 35.2 m2 ha−1 for the 2018 census. The lowest elevation exhibited the highest recruitment, mortality and turnover among sites but patterns changed and became less marked over time. Forest wide tree recruitment was about 1% y−1, while mortality was twice as much averaging about 2% y−1. Four families made up between 44% (1978 census) and 54% (2018 census) of the trees sampled. Two families – Clusiaceae, Dipterocarpaceae contributed up to 33.4% and 37.3% respectively, depending upon site and year of census. The five most common species represent between 31 and 54% of the basal area and between 25 and 66% of the stem density depending upon site. Percentage dominance by the most common species increased over the 40-year time period. Though many trees showed some degree of spatial differentiation, canopy trees showed greater site overlap in their distribution than understory and sub-canopy species. Our results provide an improved picture of variations in MDF structure and composition across the ever-wet realms of equatorial south and southeast Asia. We suggest that dominance in dipterocarps and the degree of closed canopy structure, as measured by basal area, is influenced by time, elevation, the degree of topographic variability within elevation, and topographic interactions with variabilities in climate (drought and windstorms). We propose higher standing basal areas and super dominance of dipterocarps in MDF are linked to site, succession, and landform stability. Dipterocarps increase in dominance with succession (time), with topography (ridges greater than valleys) and with elevation (lowland < hill < lower montane).

Age and sedimentary characteristics of beach sediments from Yongle Atoll, South China Sea: Implications for sediments supply in a coral reef system

Low-lying reef islands constructed from unconsolidated sediments are of growing interest due to concerns over the future stability of island landforms in response to climatic change and sea-level rise. Sediment characteristics, combined with the constituents and physical processes, are fundamental to understand the links between sediment production and their supply to an island’s beach reservoir. The grain size, constituents, and 230Th age of beach sediments from five islands at Yongle Atoll in the South China Sea were analyzed. Data reveal that coral grains are the dominant constituents of the beach sediments, followed by mollusks, coralline algae, foraminifera, Halimeda, and bryozoans. The mean grain sizes of the beach sediment were within a range of 226–4215 μm, and the coarsest sands were located near the passages in the atoll rim. Transportation by tropical cyclone–generated waves and winnowing by tides are potentially the main factors that influenced the grain-size characteristics. Calibrated 230Th age dates for bulk sand samples date the beach sediment between 424 yr BP and 5953 yr BP. Dating of coral sand samples from the beach sediment provides ages of 686–5780 yr BP; the coral sands from a vertical section (1.2 m depth) located on the beach at Jinqing Island were dated at 1154–3824 yr BP. The age reversal on the vertical section, with similar ages of beach sediment on any single island and different age ranges on different islands in an atoll, indicates that the coral sediment supply processes occurred within a relatively close time period and that different islands had different sediment supply rates. The temporal link between the coral-dominated sediment production and the beach reservoir provides an important insight into understanding the sediments supply mechanism of atoll islands in the northwestern Pacific Ocean.

Hydraulic evaluation of a dewatering scheme in shallow aquifers in Kuwait

In heavily populated residential areas lacking adequate subsurface drainage, leakage from urban water supplies and wastewater discharge causes groundwater levels in underlying shallow aquifers to rise. This may have serious consequences for the stability of building foundations, roads and natural landforms. This paper evaluates the performance of a dewatering scheme comprising of 15 vertical wells in two residential areas in Kuwait. The hydraulic effectiveness is evaluated from pumping tests and preliminary numerical modelling. The results show that the scheme can keep the water table at the desired levels over a limited area. The maximum predicted nodal drawdowns after one year of pumping at 16 835 m 3 d –1 were 4.2 and 5.24 m in the two areas. Further investigations are proposed with the objective of optimizing pumping rates.

Organic carbon dynamics in soils of Mid-Atlantic barrier island landscapes

Geomorphic processes associated with coastal wetlands often result in high carbon accumulation rates and relatively large carbon stocks. Barrier islands are an important component of coastal ecosystems and freshwater and brackish wetlands on these islands provide an important habitat for a number of animal and plant species. However, organic carbon dynamics in these landscapes have received relatively little attention. The objective of this study was to document the accumulation of organic carbon and understand the factors influencing soil carbon dynamics on barrier islands. Ten topographic transects were established on different landforms on Assateague Island National Seashore, MD, USA. Soil organic carbon stocks, aboveground carbon inputs, and decomposition rates were compared among landforms (representing differing degrees of landform stability and soil age) and drainage conditions. Soil organic carbon stocks (0–1.0 m) ranged from 0.49 to 18.8 kg C m−2, and increased in magnitude with soil age. Higher carbon stocks in the older soils were partly attributed to the increased time over which carbon had accumulated. Additionally, a shift from herbaceous dominated to forest dominated plant communities led to greater carbon inputs in older soils. Carbon stocks were also greater in the very poorly and poorly drained soils (relative to drier soils) where high levels of carbon inputs (plant biomass) exceed decomposition rates, which were slowed under anaerobic conditions. While rates of carbon accumulation (average 0.021 kg C m−2 yr−1) are somewhat low compared to other more productive systems, barrier island soils have the potential to store large amounts of organic carbon (relative to other soils) as organic-rich surface horizons are buried during overwash events.

Parametrizing tidal creek morphology in mature saltmarshes using semi-automated extraction from lidar

Coastal saltmarshes provide a range of ecosystem services, such as flood protection and carbon sequestration, but face rapid global losses. Managed realignment (MR) is an increasingly popular method to artificially recreate these habitats by reinstating tidal regimes to reclaimed land. However, to improve MR design, better knowledge of the processes that control morphological evolution in natural saltmarshes is needed. In this paper, we develop tools to assist in the monitoring of creek network evolution towards dynamic morphological equilibrium, a state of landform stability under current physical forcings. Using lidar (Light Detection and Ranging) datasets, we combined a semi-automated creek extraction algorithm, based on elevation and slope thresholds, with a novel algorithm for morphometric creek analysis. A comprehensive suite of morphological creek characteristics was extracted for 13 natural British saltmarshes, including: amplitude, length, sinuosity ratio, junction angle, width, depth, cross-sectional area, creek order, bifurcation ratio, drainage density, and drainage efficiency. Results closely matched with field-validated manual digitization results, and were significantly faster and less subjective to produce. Morphological equilibrium relationships from the literature were found to be applicable to the new dataset, despite yielding high prediction errors due to the inherent variety of creek network shapes in saltmarshes. New equilibrium relationships were also defined relating the creek network drainage efficiency to the mouth cross-sectional area and the marsh elevation. To improve future scheme designs, these tools will be used in further studies to monitor rates of evolution towards equilibrium in MR sites depending on their initial conditions.

Performance assessment of a single-layer moisture store-and-release cover system at a mine waste rock pile in a seasonally humid region (Nova Scotia, Canada).

Cover systems are commonly applied to mine waste rock piles (WRPs) to control acid mine drainage (AMD). Single-layer covers utilize the moisture "store-and-release" concept to first store and then release moisture back to the atmosphere via evapotranspiration. Although more commonly used in semi-arid and arid climates, store-and-release covers remain an attractive option in humid climates due to the low cost and relative simplicity of installation. However, knowledge of their performance in these climates is limited. The objective of this study was to assess the performance of moisture store-and-release covers at full-scale WRPs located in humid climates. This cover type was installed at a WRP in Nova Scotia, Canada, alongside state-of-the-art monitoring instrumentation. Field monitoring was conducted over 5years to assess key components such as meteorological conditions, cover material water dynamics, net percolation, surface runoff, pore-gas, environmental receptor water quality, landform stability and vegetation. Water balances indicate small reductions in water influx to the waste rock (i.e., 34 to 28% of precipitation) with the diminished AMD release also apparent by small improvements in groundwater quality (increase in pH, decrease in sulfate/metals). Surface water quality analysis and field observations of vegetative/aquatic life demonstrate significant improvements in the surface water receptor. The WRP landform is stable and the vegetative cover is thriving. This study has shown that while a simple store-and-release cover may not be a highly effective barrier to water infiltration in humid climates, it can be used to (i) eliminate contaminated surface water runoff, (ii) minimize AMD impacts to surface water receptor(s), (iii) maintain a stable landform, and (iv) provide a sustainable vegetative canopy.

Waste dump erosional landform stability – a critical issue for mountain mining

AbstractMining is the largest producer of solid wastes which, when released to land or into waterways, can cause harmful environmental impacts. This is mostly due to fluvial erosion, which is highly increased in mountain areas, due to abrupt slopes. We have analysed this situation at a mountain watershed (192 ha), where steep mined sites and their waste dumps are the main source of sediment in a Natural Park. This problem was tackled by building gabion check dams downstream from the mined sites. We used the DEM of Differences (DoD) method to quantify erosion and sediment yield from three waste dumps (5 ha). Their topography and substrate properties were analysed to understand the erosion problem. The sediment trapped by the check dams was quantified by electrical resistivity tomography (ERT). The rainfall characteristics triggering an episode that filled the check dams with sediment in the winter 2009–2010, were studied to confirm whether it was a case of extreme precipitation conditions.The waste dumps sediment yield (353 ± 95 Mg ha−1 yr−1) suggests severe landform instability. Analysis of topographic and substrate properties confirmed long, steep slopes combined with highly erodible materials. The check dams proved to be inefficient in controlling sediment loads, as they had only functioned for four years of 31 of existence, having trapped 13 000 ± 660 m3 of sediment, whereas we estimated that the waste dumps have yielded approximately three times more sediment for the same period. Rainfall analyses showed that neither intense nor extreme conditions (return period of 25 to 35 years) triggered the mobilization of 37 ± 2 Mg ha−1 in a month. This study highlights the fact that mining operations in similar mountainous settings, with equivalent waste dump construction and reclamation practices, are currently unfeasible. We conclude that landform stability cannot be achieved at this site without landform changes. Copyright © 2017 John Wiley &amp; Sons, Ltd.

Geomorphic reclamation for reestablishment of landform stability at a watershed scale in mined sites: The Alto Tajo Natural Park, Spain

This research describes a geomorphic-based process of mining reclamation carried out at the El Machorro mine (at the edge of the Alto Tajo Natural Park, East Central Spain) and its monitoring for five years (2012–2017). The GeoFluv™ method implemented by the Natural Regrade software has been used to design small watersheds as a mining reclamation topographical solution. The procedure included: (i) finding a suitable reference area with stable landforms and acquiring inputs from them; (ii) designing two first-order stream watersheds; (iii) building the planned landscape; and (iv) monitoring the hydrological and erosive – sedimentary response of the reclaimed watersheds. This process is in itself a contribution to global advancement of reclamation best practices, because there are very few geomorphic-based mining reclamation examples, and even fewer that include their multi-annual monitoring. Sediment yields were obtained comparing Digital Elevation Models (DEM) acquired by Total Station (TS), Terrestrial Laser Scanning (TLS), differential Global Positioning System (GPS) and topographic reconstructions (interpretations). An H-flume with turbidity and water pressure sensors allowed quantifying runoff and suspended sediment. Sediment yield progressively decreased with time attaining a current low value (4.02 Mg ha−1yr−1). Water discharge and suspended sediment concentration have also decreased with time.Initially, high sediment yield values were obtained. They are interpreted as being triggered by grading errors that deviated from the design, so that runoff adjusted construction irregularities during that period by erosion and sedimentation. After those adjustments, the reclamation surface became more reflective of the design and the resulting surface remained very ‘stable’. The deduction is that the geomorphic-based reclamation has re-established an approximate steady-state or dynamic equilibrium, where hydrological and erosive – sedimentary functionality operate now at rates comparable to the surrounding natural land. Although further research is required to confirm long-term stability, geomorphic reclamation appears as an efficient mining reclamation alternative solution to the traditional approach of gradient terraces and downdrains, which require frequent and costly maintenance, in the highly erodible setting of the Alto Tajo Natural Park surroundings, as well as in most open pit mines.

Reef Habitat Type and Spatial Extent as Interacting Controls on Platform-Scale Carbonate Budgets

A coral reefs carbonate budget strongly influences reef structural complexity and net reef growth potential, and thus is increasingly recognised as a key “health” metric. Despite this, understanding of habitat specific budget states, how these scale across reef platforms, and our ability to quantify both framework and sediment production values remains limited. Here we use in-situ census data from an atoll rim reef platform in the central Maldives to quantify rates of both reef framework and sediment production and loss within different platform habitats, and then combine these data with high-resolution habitat maps to quantify contributions to platform wide carbonate budgets. The net reef framework budget for the entire platform is extremely low (0.12 G, where G = Kg CaCO3 m-2 yr-1), with a very high proportion (143,745 kg or 65.1%) of total framework production generated within the platform margin reef zones, despite these comprising only ~8% of platform area. Net platform-scale sediment budgets are higher (1.04 G), but most is produced in the reef and platform margin hardground habitats, of which ~80% derives from parrotfish bioerosion. Significant quantities of new sediment (up to ~1 G derived from the calcareous green algae Halimeda) are produced only in one habitat. All lagoonal habitats have negative or neutral net carbonate budgets. These data demonstrate the marked inter-habitat differences in reef carbonate budgets that occur across reef platforms, and the major dampening effect on overall platform scale budgets when rates are factored for habitat type and size. Furthermore, the data highlights the disproportionately important role that relatively small areas of reef habitat can have on the maintenance of net positive platform scale budgets. Because of the intrinsic link between carbonate production rates and reef-associated landform development and maintenance, these findings also have implications for understanding reef-associated landform stability. In this context the reef island at this site has been highly mobile over the last ~40 years, and we hypothesise that such instability may be being exacerbated by the measured low overall rates of framework and sediment generation.

Tracking rapid landscape change with repeated photography, Gros Morne National Park, Canada

At various coastal and inland sites in and around Gros Morne National Park in western Newfoundland, photographs taken periodically over many decades illustrate the physical stability of landforms. ἀese images provide a convenient, qualitative way to track the development of stone rings and patterned ground, the movement of rocks along intertidal platforms, changes to marine estuaries and to alluvial rivers and fans, temporal trends in late-lying snow beds along mountain tops, and slope failure by landslides and rock falls. ἀis study has established a spatial and temporal photographic record of slope failures along the steep cliḀs of Western Brook Pond, showing that nearly all of the sites identiᴀed in earlier studies as high risk of failure have remained stable. In contrast, thin-skinned landslides along Winter House Brook have remained active for at least 100 years. Little evidence of physical changes in patterned ground features in Trout River Gulch was found, other than frost-heaving in soils disturbed by road construction. Fluctuations from year to year in the level of gravel beaches along parts of the coast are common, and blow-outs continue to modify coastal sand dunes. Apart from certain engineered sites where change was obviously driven by direct human activities, the immediate cause or “driver” of change was natural (non-human), the result of gravitational instability, heavy precipitation, wave and storm action, frost heaving, and other background processes of the sort that long pre-date the coming of people to the region. Continuation of this kind of inexpensive, non-invasive monitoring can assist in assessing ecological integrity, managing public safety, and interpreting landscape processes for Park visitors.

Selective coal mine overburden treatment with topsoil and compost to optimise pasture or native vegetation establishment

Overburden at a coal mine in the Hunter Valley, New South Wales, was stored in a flat-topped artificial mound with 14-degree side slopes. Topsoil was scarce, dispersive and readily eroded. A split-plot factorial experiment applied an enhanced municipal solid waste compost at 0, 60 or 100 t ha−1 to untreated overburden or to overburden covered with 0.1 m of topsoil. Two seeding treatments, of trees and shrubs or of pasture species, were applied to two 0.5-ha replicates of each surface treatment. Substrate physical and chemical properties and vegetation attributes were assessed 2.5 years later. Compost application to both topsoil and overburden significantly increased total N, P, Cu and Zn, soluble K, Ca and Mg, and significantly reduced soluble Na and pH. Mean tree density, size and total canopy cover were significantly greater with compost applied at 60 t ha−1 to overburden than with all other treatments, especially those on topsoil where tree growth was inhibited by undesired species. Compost application to overburden and topsoil at 100 t ha−1 significantly increased biomass of desired pasture species and significantly reduced undesired species cover compared with unamended topsoil and the extent of bare ground compared with unamended overburden. Successful development of woody species on overburden and pastures on both overburden and topsoil treated with compost provides opportunities for new combinations of landscape design, surface preparation and plant species introductions to increase the stability of final landforms, the effectiveness of resource use, and the delivery of commercial and biodiversity benefits from mine site rehabilitation.

Climate and hillslope degradation vary in concert; 85 ka to present, eastern Sierra Nevada, CA, USA

Degradation in the landscape results when the interactions of climate, substrate, and biota dislodge and transport sediment that is mantling landforms. Rates of degradation through time control landform stability and resiliency. Therefore, records of past degradation rates can be used to inform us on how a given landscape responded to significant changes in past climates. For example, climate has varied at many temporal scales, and some of the largest recent shifts enabled the glacial advances and retreats in time scales of 20–100ka. Therefore, it is reasonable to expect that the rate of landscape degradation has also varied at similar time scales. However, the general hillslope diffusion equation that is commonly used to model cross-profiles of hillslopes on time scales of thousands to tens of thousands of years typically relies on a constant and optimized rate parameter to generate a model cross-profile approximating the current observed landform cross-profile. Using a time-varying diffusivity parameter, we generated three separate degradation scenarios for the Mono Basin moraine in the eastern Sierra Nevada, CA, USA, in order to assess the potential impact of varying past climates on sediment transport. We used published paleoclimate records in the study area and modern rates of surface degradation from climates that correspond broadly to those paleoclimates. The results indicate that, in this case, the climate driven and, therefore, time-dependent degradation model produces a good fit between the modeled and observed landform profiles. Results showed that, when the surface elevations of the reference case (constant optimized diffusivity) were compared through time to the surface elevations of the time-dependent model, the differences were relatively small. The largest deviation was found to occur during the Last Glacial Maximum (LGM). We found that for investigations into the geological effects of climate change in glacial and polar regions, the use of time-varying diffusivity offers improved estimates of landform degradation through time. The rates of surface lowering that change through time are important for analyses of the depths of past exposures, exposure dating, and renewal or preservation of surfaces, all of which are relevant in landscape dating, in interpretation of paleoecology, and in modeling landscape evolution.

Genesis and Classification of Soils from Subtropical Mountain Regions of Southern Brazil

Soils formed in high mountainous regions in southern Brazil are characterized by great accumulation of organic matter (OM) in the surface horizons and variation in the degree of development. We hypothesized that soil properties and genesis are influenced by the interaction of parent materials and climate factors, which differ depending on the location along the altitudinal gradient. The goal of this study was to characterize and classify the soil, evaluate soil distribution, and determine the interactive effects of soil-forming factors in the subtropical mountain regions in Santa Catarina state. Soil samples were collected in areas known for wine production, for a total of 38 modal profiles. Based on morphological, physical, and chemical properties, soils were evaluated for pedogenesis and classified according to the Brazilian System of Soil Classification, with equivalent classes in the World Reference Basis (WRB). The results indicated that pedogenesis was strongly influenced by the parent material, weather, and relief. In the areas where basic effusive rocks (basalt) were observed, there was formation of extensive areas of clayey soils with reddish color and higher iron oxide contents. There was a predominance of Nitossolos Vermelhos and Haplicos (Nitisols), Latossolos Vermelhos (Ferralsols), and Cambissolos Haplicos (Cambisols), highlighting the pedogenetic processes of eluviation, illuviation of clay, and latosolization in conditions of year-long, large-volume, well-distributed rainfall and stability of land forms. In areas with acid effusive rocks (rhyodacites), medial or clayey soils were observed with lower iron oxide content, invariably acidic, and with low base content. For these soils, relief promoted substantial removal of material, resulting in intense rejuvenation, with a predominance of Cambissolos Haplicos (Cambisols) and lesser occurrence of Nitossolos Brunos (Nitisols) and Neossolos Litolicos (Leptosols). Soils formed from sedimentary rocks also tended to be more acidic, but with higher sand content, and the soils identified were Cambissolos Haplicos and Humicos (Cambisols). Cluster analysis separated the soil profiles into three groups: the first and largest was formed by profiles originating from sedimentary rocks and rhyodacites; the second, smaller group was formed by four profiles in the Agua Doce region (acidic rocks); and the third was formed by profiles derived from basalt. Discriminant analysis was effective in grouping soil classes. Thus, the study highlighted the importance of geology in the formation of soils in this landscape associated with climate and relief.