Application of an index of sediment connectivity in a lowland area

PurposeSediment connectivity at the landscape scale has gained interest in the last few decades. Distributed approaches, such as topographic indices, are widely used to evaluate this connectivity. However, most of the research efforts are concentrated in mountainous areas while little work has been done in lowland areas where evidence of high connectivity has been reported. The objectives of this study are as follows: (i) to integrate landscape infiltration/runoff properties in the assessment of connectivity to account for lowland processes and (ii) to apply this approach to a large territory with both mountainous and lowland areas.Materials and methodsThe topographic index of connectivity (IC) of Borselli et al. (2008) was computed for the Loire–Brittany River Basin (>105 km2). A distributed parameter (IDPR) that reflects landscape infiltration and saturation properties due to underlying geological formation characteristics is introduced. We integrated this parameter in a revised index (ICrevised) as an indicator of landscape hydrologic connectivity. Results at the pixel scale are aggregated at the watershed scale.Results and discussionTwo maps of connectivity are produced, considering the initial IC and the revised form (ICrevised). As expected, the IC gives the highest connectivity in the steepest areas and does not reflect the existing connectivity in lowland areas. On the contrary, the ICrevised computed in this study profoundly modifies the sediment connectivity values. These changes are evenly distributed over the entire territory and affected 51.5 % of the watersheds. As a result, we obtained a better correlation between calculated connectivity and the observed drainage density (which reflects the actual connections between hillslopes and rivers) in areas where slopes are gentle (<7 %).ConclusionsTopographic indices do not reflect the real sediment connectivity in lowland areas, but their adaptation by considering runoff processes of such areas is possible. The ICrevised presents an interesting perspective to define other highly connected areas at the country scale, as 17 % of the French territory is characterized by very gentle slopes with high runoff capacity.

[1]  Artemi Cerdà,et al.  Soil erosion assessment on tillage and alternative soil managements in a Sicilian vineyard , 2011 .

[2]  G. R. Foster,et al.  Predicting soil erosion by water : a guide to conservation planning with the Revised Universal Soil Loss Equation (RUSLE) , 1997 .

[3]  N. Fohrer,et al.  SEPAL – a simple GIS-based tool to estimate sediment pathways in lowland catchments , 2009 .

[4]  Joël Daroussin,et al.  Mapping erosion risk for cultivated soil in France , 2002 .

[5]  Doerthe Tetzlaff,et al.  A comparison of wetness indices for the prediction of observed connected saturated areas under contrasting conditions , 2014 .

[6]  Gerard Govers,et al.  Evaluating the effects of changes in landscape structure on soil erosion by water and tillage , 2000, Landscape Ecology.

[7]  John Wainwright,et al.  Sediment connectivity: a framework for understanding sediment transfer at multiple scales , 2015 .

[8]  Andrea Vacca,et al.  Rates and spatial variations of soil erosion in Europe: A study based on erosion plot data , 2010 .

[9]  Bruno Cheviron,et al.  Vegetated filter effects on sedimentological connectivity of agricultural catchments in erosion modelling: a review , 2011 .

[10]  R. Grayson,et al.  Toward capturing hydrologically significant connectivity in spatial patterns , 2001 .

[11]  Stuart N. Lane,et al.  Representation of landscape hydrological connectivity using a topographically driven surface flow index , 2009 .

[12]  T. Heckmann,et al.  Geomorphic coupling and sediment connectivity in an alpine catchment - exploring sediment cascades using graph theory , 2013 .

[13]  S. Rodrigues,et al.  Morphological evolution of a rural headwater stream after channelisation , 2015 .

[14]  C. Gascuel-Odoux,et al.  Evolution of soil surface roughness and flowpath connectivity in overland flow experiments , 2002 .

[15]  D. Walling,et al.  Suspended sediment sources in two small lowland agricultural catchments in the UK , 2001 .

[16]  Veronique Souchere,et al.  Variability of soil surface characteristics influencing runoff and interrill erosion , 2005 .

[17]  Leo Stroosnijder,et al.  Soil Conservation Through Sediment Trapping: A Review , 2015 .

[18]  Nicola Fohrer,et al.  Incorporating landscape depressions and tile drainages of a northern German lowland catchment into a semi‐distributed model , 2010 .

[19]  R. Dikau,et al.  Sediment connectivity in the high-alpine valley of Val Müschauns, Swiss National Park — linking geomorphic field mapping with geomorphometric modelling , 2014 .

[20]  Lorenzo Marchi,et al.  Geomorphometric assessment of spatial sediment connectivity in small Alpine catchments , 2013 .

[21]  Louise J. Bracken,et al.  The concept of hydrological connectivity and its contribution to understanding runoff‐dominated geomorphic systems , 2007 .

[22]  Simon Mockler,et al.  Sediment concentration changes in runoff pathways from a forest road network and the resultant spatial pattern of catchment connectivity , 2005 .

[23]  Pute Wu,et al.  EFFECTS OF LAND USE ON SOIL MOISTURE VARIATIONS IN A SEMI‐ARID CATCHMENT: IMPLICATIONS FOR LAND AND AGRICULTURAL WATER MANAGEMENT , 2014 .

[24]  Josette Garnier,et al.  Assessing the impact of agricultural pressures on N and P loads and eutrophication risk , 2015 .

[25]  Patrick Degryse,et al.  A sediment fingerprinting approach to understand the geomorphic coupling in an eastern Mediterranean mountainous river catchment , 2013 .

[26]  Donald Gabriëls,et al.  Assessment of USLE cover-management C-factors for 40 crop rotation systems on arable farms in the Kemmelbeek watershed, Belgium , 2003 .

[27]  A. Cerda,et al.  The effect of ant mounds on overland flow and soil erodibility following a wildfire in eastern Spain , 2010 .

[28]  O. Cerdan,et al.  Increase in soil erosion after agricultural intensification: Evidence from a lowland basin in France , 2014 .

[29]  Dino Torri,et al.  Prolegomena to sediment and flow connectivity in the landscape: A GIS and field numerical assessment , 2008 .

[30]  Bodis Katalin,et al.  A pan-European River and Catchment Database , 2007 .

[31]  O. Cerdan,et al.  Variability of suspended sediment yields within the Loire river basin (France) , 2014 .

[32]  Doerthe Tetzlaff,et al.  Concepts of hydrological connectivity: Research approaches, pathways and future agendas , 2013 .

[33]  O. Cerdan,et al.  A method for developing a large-scale sediment yield index for European river basins , 2009 .

[34]  J. Daroussin,et al.  Pan‐European Soil Erodibility Assessment , 2006 .

[35]  J. Poesen,et al.  ASSESSING THE PERFORMANCE OF A SPATIALLY DISTRIBUTED SOIL EROSION AND SEDIMENT DELIVERY MODEL (WATEM/SEDEM) IN NORTHERN ETHIOPIA , 2013 .

[36]  V. Vanacker,et al.  Low erosion rates measured for steep, sparsely vegetated catchments in southeast Spain , 2011 .

[37]  R. Horton.  EROSIONAL DEVELOPMENT OF STREAMS AND THEIR DRAINAGE BASINS; HYDROPHYSICAL APPROACH TO QUANTITATIVE MORPHOLOGY , 1945 .

[38]  M. López‐Vicente,et al.  Advanced modelling of runoff and soil redistribution for agricultural systems: The SERT model , 2013 .

[39]  K. Fryirs,et al.  Buffers, barriers and blankets : the (dis)connectivity of catchment-scale sediment cascades , 2007 .

[40]  M. Kirkby.  Do not only connect: a model of infiltration‐excess overland flow based on simulation , 2014 .

[41]  W. H. Wischmeier,et al.  Predicting rainfall erosion losses : a guide to conservation planning , 1978 .

[42]  D. Walling.  The sediment delivery problem , 1983 .

[43]  Karl Segl,et al.  Assessment of sediment connectivity from vegetation cover and topography using remotely sensed data in a dryland catchment in the Spanish Pyrenees , 2014, Journal of Soils and Sediments.

[44]  Stuart N. Lane,et al.  Does hydrological connectivity improve modelling of coarse sediment delivery in upland environments , 2007 .

[45]  D. Walling,et al.  The catchment sediment budget as a management tool , 2008 .

[46]  Catherine Ottlé,et al.  Tracking the early dispersion of contaminated sediment along rivers draining the Fukushima radioactive pollution plume , 2013 .

[47]  Olga Vigiak,et al.  Comparison of conceptual landscape metrics to define hillslope-scale sediment delivery ratio , 2012 .

[48]  Gary Brierley,et al.  Landscape connectivity: the geographic basis of geomorphic applications , 2006 .

[49]  Ronald L. Bingner,et al.  Estimation of Runoff, Peak Discharge and Sediment Load at the Event Scale in a Medium‐Size Mediterranean Watershed Using the Annagnps Model , 2015 .

[50]  Mathieu Javaux,et al.  What indicators can capture runoff-relevant connectivity properties of the micro-topography at the plot scale? , 2009 .

[51]  Arnaud J.A.M. Temme,et al.  Linking landscape morphological complexity and sediment connectivity , 2013 .