Developments in earth surface processes 

About: Developments in earth surface processes is an academic journal. The journal publishes majorly in the area(s): Climate change & Glacier. It has an ISSN identifier of 0928-2025. Over the lifetime, 309 publications have been published receiving 3771 citations.

9 Modelling river-bank-erosion processes and mass failure mechanisms: progress towards fully coupled simulations

Abstract: This paper reviews recent developments in modelling the two main sets of bank-erosion processes and mechanisms, namely fluvial erosion and mass failure, before suggesting an avenue for research to make further progress in the future. Our review of mass failure mechanisms reveals that the traditional use of limit equilibrium methods to analyse bank stability has in recent years been supplemented by research that has made progress in understanding and modelling the role of positive and negative pore water pressures, confining river pressures, and hydrograph characteristics. While understanding of both fluvial erosion and mass failure processes has improved in recent years, we identify a key limitation in that few studies have examined the nature of the interaction between these processes. We argue that such interactions are likely to be important in gravel-bed rivers and present new simulations in which fluvial erosion, pore water pressure, and limit equilibrium stability models are combined into a fully coupled analysis. The results suggest that existing conceptual models, which describe how bank materials are delivered to the fluvial sediment transfer system, may need to be revised to account for the unforeseen effects introduced by feedback between the interacting processes.

Lowland tropical peatlands of Southeast Asia

Abstract: [Extract] Peatlands are terrestrial wetland ecosystems in which the production of organic matter exceeds its decomposition and a net accumulation results. Several factors influence peat formation and preservation, including a positive climatic moisture balance (precipitation minus evaporation), high-relative humidity, topographic and geological conditions that favor water retention, and low substrate pH and nutrient availability. The majority of the world’s peatlands occur in boreal and temperate zones where they have formed under high-precipitation, low-temperature climatic regimes. In the humid tropics, however, regional environmental and topographic conditions have enabled peat to form under a high-precipitation, high-temperature regime (Andriesse, 1988) and, as a consequence, extensive peatlands occur in southeast Asia, mainland east Asia, the Caribbean and Central America, South America and southern Africa. Most of these are located at low altitudes where rain forest vegetation grows on a thick mass of organic matter accumulated over thousands or tens of thousands of years, to form deposits up to 20m thick (Anderson, 1983). In the tropics, these lowland peatlands are almost exclusively ombrogenous (the peat surface only receives water from precipitation), whereas geogenous peatlands, that are fed additionally by water that has been in contact with the mineral bedrock and soils, are of more limited distribution, being confined to the edges of coastal lagoons, the banks and flood zones of rivers, and the margins of upland lakes. Undisturbed, lowland ombrogenous peatlands support peat swamp forest; freshwater swamp forests are associated with geogenous peatlands.

27 River restoration in the Alps and their surroundings: past experience and future challenges

Abstract: Alpine rivers have undergone significant changes over the two last centuries. Human activities have modified their geometry through engineering measures to gain land for agricultural purposes and settlements, as well as through active mining to exploit gravel resources. Their sediment and water transfers have also been altered by hydropower-plant construction, control works on high-gradient streams, and catchment land-use changes. The resulting river morphological changes have led to abiotic (e.g., river-bed degradation and narrowing) and biotic (e.g., longitudinal and lateral disconnection) disruption. The current critical management situation (channel instability problems, flood effects, biodiversity decrease) has made river restoration a major issue in the Alps and their surroundings. Such an approach is reinforced by the European Water Framework Directive, which aims to ensure that rivers attain a good ecological status by 2015. In the Alps, space is not always easily available and boundary conditions have changed over the long term. A major challenge in river restoration in the Alpine environment is therefore to identify the processes and key parameters for improving both geomorphological and ecological conditions under often-restricted boundary conditions. Early attempts at river restoration mainly focused on small-scale measures. Today, successful restoration projects in high-energy and bedload-transport-dominated conditions must include the full spectrum of scales, striving to initiate self-forming morphodynamics. In this context, we appraise restoration experiences from the Alps, focusing on channel widening and dike enlargement, former channel reconstruction and reconnection, promotion of bedload supply input from floodplains, tributaries, and hillslopes, as well as on bank erosion measures and restoration activities. We discuss the basic arguments behind such actions, their limitations, and research challenges.

20 A review on channel incision in the Polish Carpathian rivers during the 20th century

Abstract: Rivers draining the Polish Carpathians deeply incised over the 20th century and in many sections, the downcutting was especially rapid in the second half of the century Incision has resulted from the increase in transport capacity of the rivers caused by their channelization, and the concomitant decrease in sediment supply to the channels In some of the rivers, in-stream gravel mining has additionally reduced the amount of sediment available for fluvial transport Where the rivers had insufficient energy to destroy the river-control structures and remained laterally stable following their channelization, bed degradation has proceeded at a relatively steady rate On the high-energy rivers, the periods of incision of the regulated channel alternated with the periods of lateral channel migration following the destruction of channelization structures The main phase of incision of the Carpathian rivers occurred progressively later in the upstream direction, this reflecting the variation in timing of the most intense channelization works along their course, the operation of upstream-progressing bed degradation as well as the concentration of the land use changes from the second half of the century in the montane parts of the catchments A marked increase in flood hazard to downstream reaches and a reduction in the potential of Carpathian floodplains for sediment storage have been the most important detrimental effects of the river incision manifested at the regional scale Changes in management of the rivers are necessary to reduce their transport capacity and re-establish the conditions for water and sediment storage on the floodplains