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Fan Area (fan + area)

Distribution by Scientific Domains

Earth and Environmental Science	75%

Selected Abstracts

Morphometric controls and geomorphic responses on fans in the Southern Alps, New Zealand

EARTH SURFACE PROCESSES AND LANDFORMS, Issue 3 2004
Fes A. de Scally
Abstract Morphometric variables associated with 41 debris-,ow and 18 ,uvial fans and their basins in the Southern Alps of New Zealand are examined. The results show statistically signi,cant differences in the area, maximum elevation, relief and ruggedness (Melton's R) of the basin and the area, gradient, and apex and toe elevations of the fan between debris-,ow and ,uvial sites. Concavity of the fan longitudinal pro,le also differs between the two fan types, although this could not be tested statistically. Most of these morphometric differences re,ect differences in processes and environmental controls on them. Discriminant analysis indicates that basin area and fan gradient best differentiate the two fan types by process. Moderately strong correlations exist, on both debris-,ow and ,uvial fans, between basin area or Melton's R and fan area. Correlations between basin area or Melton's R and fan gradient are generally weaker. The results of this study also indicate that on debris-,ow-prone fans the fan gradient and basin Melton's R have lower thresholds which overlap little with upper thresholds associated with basins where only stream,ow reaches the fan. These thresholds may therefore have value in preliminary morphometric assessments of debris-,ow hazard on fans in the Southern Alps. Copyright © 2004 John Wiley & Sons, Ltd. [source]

Morphometric Controls and Basin Response in The Cascade Mountains

GEOGRAFISKA ANNALER SERIES A: PHYSICAL GEOGRAPHY, Issue 3 2001
Fes De Scally
Morphometric variables associated with 36 debris torrent, 78 snow avalanche, 45 composite debris torrent and snow avalanche and 14 streamflow basins in the Cascade Mountains of southwestern British Columbia, Canada are examined. The results show significant statistical differences in top and bottom elevations, relief, channel length and gradient, basin area, fan gradient and area, and basin ruggedness between snow avalanche basins and the two basin types affected by debris torrents, reflecting the very different nature of these processes. Only top and bottom elevations and fan area differ significantly between debris torrent and debris torrent-snow avalanche basins, implying that the latter are probably debris torrent basins in origin. As many as six morphometric variables are significantly different between streamflow basins and the other basin types, allowing the former to be differentiated despite their small, steep character. Discriminant analysis indicates that bottom elevation and channel or path gradient are the best variables for classifying the four basin types by process. Generally strong correlations exist between basin area on the one hand and relief, channel length and channel gradient on the other in debris torrent, debris torrent-snow avalanche, and streamflow basins. Fan gradient and area are, however, weakly or modestly correlated with basin area or ruggedness. No such morphometric relations are present in snow avalanche basins. The results of this study also indicate that in debris torrent-prone basins the fan gradient and Melton's R have identifiable lower thresholds while basin area has an upper threshold, but use of these thresholds for identification of debris torrent hazard is complicated by overlapping thresholds for streamflow basins. [source]

Relationships between morphological and sedimentological parameters in source-to-sink systems: a basis for predicting semi-quantitative characteristics in subsurface systems

BASIN RESEARCH, Issue 4 2009
Tor O. Sømme
ABSTRACT The study of source-to-sink systems relates long-term variations in sediment flux to morphogenic evolution of erosional,depositional systems. These variations are caused by an intricate combination of autogenic and allogenic forcing mechanisms that operate on multiple time scales , from individual transport events to large-scale filling of basins. In order to achieve a better understanding of how these mechanisms influence morphological characteristics on different scales, 29 submodern source-to-sink systems have been investigated. The study is based on measurements of morphological parameters from catchments, shelves and slopes derived from a ,1 km global digital elevation model dataset, in combination with data on basin floor fans, sediment supply, water discharge and deposition rates derived from published literature. By comparing various morphological and sedimentological parameters within and between individual systems, a number of relationships governing system evolution and behaviour are identified. The results suggest that the amount of low-gradient floodplain area and river channel gradient are good indicators for catchment storage potential. Catchment area and river channel length is also related to shelf area and shelf width, respectively. Similarly to the floodplain area, these parameters are important for long-term storage of sediment on the shelf platform. Additionally, the basin floor fan area is correlative to the long-term deposition rate and the slope length. The slope length thus proves to be a useful parameter linking proximal and distal segments in source-to-sink systems. The relationships observed in this study provide insight into segment scale development of source-to-sink systems, and an understanding of these relationships in modern systems may result in improved knowledge on internal and external development of source-to-sink systems over geological time scales. They also allow for the development of a set of semi-quantitative guidelines that can be used to predict similar relationships in other systems where data from individual system segments are missing or lacking. [source]

Alluvial fan development and morpho-tectonic evolution in response to contractional fault reactivation (Late Cretaceous,Palaeocene), Provence, France

BASIN RESEARCH, Issue 2 2009
S. Leleu
ABSTRACT Along-strike variability within a Late Cretaceous to early Palaeocene contractional growth structure and associated alluvial fan deposits is documented at the northern margin of the Arc Basin (Provence, SE France). This contribution shows that alluvial fans can be used as high-resolution proxies to reconstruct structural segmentation and palaeo-geomorphological evolution of a source/basin margin system. Facies-based reconstruction allows the spatial and temporal distribution of alluvial fan bodies to be mapped. Relationships between fan area and catchment size from modern alluvial fan systems were used to estimate palaeo-catchment size. Combining alluvial fan morphologies with catchment area, pebble provenance analysis and growth structure reconstruction, we show that: (1) fan distribution and related depositional processes were strongly influenced by intrinsic parameters such as drainage basin evolution, local structural inheritance and lateral facies changes in source area lithologies; (2) Inherited structures trending N100 effectively controlled the first-order location of the fold and thrust structures (Montagne Sainte-Victoire Range) and adjacent depositional areas (Arc Basin); (3) Syn-sedimentary faults trending N010-030 influenced the source/basin margin development and interacted with developing growth structures; (4) Facies changes in Jurassic carbonates controlled fold development and consequently the structural evolution of the source area; and (5) the N010-030 faults and along-strike variability of the source/basin margin system were ultimately controlled by basement structures that controlled where Late C etaceous deformation nucleated. The overall architecture of the source/basin margin system reflects segmentation and strain partitioning along strike, as demonstrated by diachronous alluvial fan distribution. [source]