TY  - JOUR
A1  - Mohr, Christian Heinrich
A1  - Zimmermann, Andreas
A1  - Korup, Oliver
A1  - Iroume, A.
A1  - Francke, Till
A1  - Bronstert, Axel
T1  - Seasonal logging, process response, and geomorphic work
JF  - Earth surface dynamics
N2  - Deforestation is a prominent anthropogenic cause of erosive overland flow and slope instability, boosting rates of soil erosion and concomitant sediment flux. Conventional methods of gauging or estimating post-logging sediment flux often focus on annual timescales but overlook potentially important process response on shorter intervals immediately following timber harvest. We resolve such dynamics with non-parametric quantile regression forests (QRF) based on high-frequency (3 min) discharge measurements and sediment concentration data sampled every 30-60 min in similar-sized (similar to 0.1 km(2)) forested Chilean catchments that were logged during either the rainy or the dry season. The method of QRF builds on the random forest algorithm, and combines quantile regression with repeated random sub-sampling of both cases and predictors. The algorithm belongs to the family of decision-tree classifiers, which allow quantifying relevant predictors in high-dimensional parameter space. We find that, where no logging occurred, similar to 80% of the total sediment load was transported during extremely variable runoff events during only 5% of the monitoring period. In particular, dry-season logging dampened the relative role of these rare, extreme sediment-transport events by increasing load efficiency during more efficient moderate events. We show that QRFs outperform traditional sediment rating curves (SRCs) in terms of accurately simulating short-term dynamics of sediment flux, and conclude that QRF may reliably support forest management recommendations by providing robust simulations of post-logging response of water and sediment fluxes at high temporal resolution.
Y1  - 2014
U6  - https://doi.org/10.5194/esurf-2-117-2014
SN  - 2196-6311
SN  - 2196-632X
VL  - 2
IS  - 1
SP  - 117
EP  - 125
PB  - Copernicus
CY  - Göttingen
ER  - 
TY  - JOUR
A1  - van Schaik, N. Loes M. B.
A1  - Bronstert, Axel
A1  - de Jong, S. M.
A1  - Jetten, V. G.
A1  - van Dam, J. C.
A1  - Ritsema, C. J.
A1  - Schnabel, Susanne
T1  - Process-based modelling of a headwater catchment in a semi-arid area: the influence of macropore flow
JF  - Hydrological processes
N2  - Subsurface stormflow is thought to occur mainly in humid environments with steep terrains. However, in semi-arid areas, preferential flow through macropores can also result in a significant contribution of subsurface stormflow to catchment runoff for varying catchment conditions. Most hydrological models neglect this important subsurface preferential flow. Here, we use the process-oriented hydrological model Hillflow-3D, which includes a macropore flow approach, to simulate rainfall-runoff in the semi-arid Parapunos catchment in Spain, where macropore flow was observed in previous research. The model was extended for this study to account for sorptivity under very dry soil conditions. The results of the model simulations with and without macropore flow are compared. Both model versions give reasonable results for average rainfall situations, although the approach with the macropore concept provides slightly better results. The model results for scenarios of extreme rainfall events (>13.3mm30min(-1)) however show large differences between the versions with and without macropores. These model results compared with measured rainfall-runoff data show that the model with the macropore concept is better. Our conclusion is that preferential flow is important in controlling surface runoff in case of specific, high intensity rainfall events. Therefore, preferential flow processes must be included in hydrological models where we know that preferential flow occurs. Hydrological process models with a less detailed process description may fit observed average events reasonably well but can result in erroneous predictions for more extreme events. Copyright (c) 2013 John Wiley & Sons, Ltd.
KW  - process based
KW  - macropore flow
KW  - catchment scale
KW  - modelling
KW  - semi-arid area
Y1  - 2014
U6  - https://doi.org/10.1002/hyp.10086
SN  - 0885-6087
SN  - 1099-1085
VL  - 28
IS  - 24
SP  - 5805
EP  - 5816
PB  - Wiley-Blackwell
CY  - Hoboken
ER  - 
TY  - JOUR
A1  - Bürger, Gerd
A1  - Heistermann, Maik
A1  - Bronstert, Axel
T1  - Towards subdaily rainfall disaggregation via Clausius-Clapeyron
JF  - Journal of hydrometeorology
N2  - Two lines of research are combined in this study: first, the development of tools for the temporal disaggregation of precipitation, and second, some newer results on the exponential scaling of heavy short-term precipitation with temperature, roughly following the Clausius-Clapeyron (CC) relation. Having no extra temperature dependence, the traditional disaggregation schemes are shown to lack the crucial CC-type temperature dependence. The authors introduce a proof-of-concept adjustment of an existing disaggregation tool, the multiplicative cascade model of Olsson, and show that, in principal, it is possible to include temperature dependence in the disaggregation step, resulting in a fairly realistic temperature dependence of the CC type. They conclude by outlining the main calibration steps necessary to develop a full-fledged CC disaggregation scheme and discuss possible applications.
Y1  - 2014
U6  - https://doi.org/10.1175/JHM-D-13-0161.1
SN  - 1525-755X
SN  - 1525-7541
VL  - 15
IS  - 3
SP  - 1303
EP  - 1311
PB  - American Meteorological Soc.
CY  - Boston
ER  - 
TY  - JOUR
A1  - Heine, Iris
A1  - Francke, Till
A1  - Rogass, Christian
A1  - Medeiros, Pedro Henrique Augusto
A1  - Bronstert, Axel
A1  - Förster, Saskia
T1  - Monitoring seasonal changes in the water surface areas of reservoirs using TerraSAR-X time series data in semiarid northeastern Brazil
JF  - IEEE journal of selected topics in applied earth observations and remote sensing
N2  - The 933 km(2) Bengue catchment in northeastern Brazil is characterized by distinct rainy and dry seasons. Precipitation is stored in variously sized reservoirs, which is essential for the local population. In this study, we used TerraSAR-X SM(HH) data for an one-year monitoring of seasonal changes in the reservoir areas from July 2011 to July 2012. The monitoring was based on acquisitions in the ascending pass direction, complemented by occasional descending-pass images. To detect water surface areas, a histogram analysis followed by a global threshold classification was performed, and the results were validated using in situ GPS data. Distinguishing between small reservoirs and similar looking dark areas was difficult. Therefore, we tested several approaches for identifying misclassified areas. An analysis of the surface area dynamics of the reservoirs indicated high spatial and temporal heterogeneities and a large decrease in the total water surface area of the reservoirs in the catchment by approximately 30% within one year.
KW  - Image classification
KW  - monitoring
KW  - radar imaging
KW  - remote sensing
KW  - synthetic aperture radar (SAR)
Y1  - 2014
U6  - https://doi.org/10.1109/JSTARS.2014.2323819
SN  - 1939-1404
SN  - 2151-1535
VL  - 7
IS  - 8
SP  - 3190
EP  - 3199
PB  - Inst. of Electr. and Electronics Engineers
CY  - Piscataway
ER  - 
TY  - JOUR
A1  - Brosinsky, Arlena
A1  - Förster, Saskia
A1  - Segl, Karl
A1  - Lopez-Tarazon, José Andrés
A1  - Pique, Gemma
A1  - Bronstert, Axel
T1  - Spectral fingerprinting: characterizing suspended sediment sources by the use of VNIR-SWIR spectral information
JF  - Journal of soils and sediments : protection, risk assessment and remediation
N2  - Knowledge of sediment sources is a prerequisite for sustainable management practices and may furthermore improve our understanding of water and sediment fluxes. Investigations have shown that a number of characteristic soil properties can be used as "fingerprints" to trace back the sources of river sediments. Spectral properties have recently been successfully used as such characteristics in fingerprinting studies. Despite being less labour-intensive than geochemical analyses, for example, spectroscopy allows measurements of small amounts of sediment material (> 60 mg), thus enabling inexpensive analyses even of intra-event variability. The focus of this study is on the examination of spectral properties of fluvial sediment samples to detect changes in source contributions, both between and within individual flood events.
 Sediment samples from the following three different origins were collected in the Isabena catchment (445 km(2)) in the central Spanish Pyrenees: (1) soil samples from the main potential source areas, (2) stored fine sediment from the channel bed once each season in 2011 and (3) suspended sediment samples during four flood events in autumn 2011 and spring 2012 at the catchment outlet as well as at several subcatchment outlets. All samples were dried and measured for spectral properties in the laboratory using an ASD spectroradiometer. Colour parameters and physically based features (e.g. organic carbon, iron oxide and clay content) were calculated from the spectra. Principal component analyses (PCA) were applied to all three types of samples to determine natural clustering of samples, and a mixing model was applied to determine source contributions.
 We found that fine sediment stored in the river bed seems to be mainly influenced by grain size and seasonal variability, while sampling location-and thus the effect of individual tributaries or subcatchments-seem to be of minor importance. Suspended sediment sources were found to vary between, as well as within, flood events; although badlands were always the major source. Forests and grasslands contributed little (< 10 %), and other sources (not further determinable) contributed up to 40 %. The analyses further suggested that sediment sources differ among the subcatchments and that subcatchments comprising relatively large proportions of badlands contributed most to the four flood events analyzed.
 Spectral fingerprints provide a rapid and cost-efficient alternative to conventional fingerprint properties. However, a combination of spectral and conventional fingerprint properties could potentially permit discrimination of a larger number of source types.
KW  - Isabena river
KW  - Mixing models
KW  - Northeast Spain
KW  - Sediment fingerprinting
KW  - Spectroscopy
KW  - Suspended sediment
Y1  - 2014
U6  - https://doi.org/10.1007/s11368-014-0927-z
SN  - 1439-0108
SN  - 1614-7480
VL  - 14
IS  - 12
SP  - 1965
EP  - 1981
PB  - Springer
CY  - Heidelberg
ER  - 
TY  - JOUR
A1  - Müller, Eva Nora
A1  - van Schaik, Loes
A1  - Blume, Theresa
A1  - Bronstert, Axel
A1  - Carus, Jana
A1  - Fleckenstein, Jan H.
A1  - Fohrer, Nicola
A1  - Geissler, Katja
A1  - Gerke, Horst H.
A1  - Gräff, Thomas
A1  - Hesse, Cornelia
A1  - Hildebrandt, Anke
A1  - Hölker, Franz
A1  - Hunke, Philip
A1  - Körner, Katrin
A1  - Lewandowski, Jörg
A1  - Lohmann, Dirk
A1  - Meinikmann, Karin
A1  - Schibalski, Anett
A1  - Schmalz, Britta
A1  - Schröder-Esselbach, Boris
A1  - Tietjen, Britta
T1  - Scales, key aspects, feedbacks and challenges of ecohydrological research in Germany
JF  - Hydrologie und Wasserbewirtschaftung
N2  - Ecohydrology analyses the interactions of biotic and abiotic aspects of our ecosystems and landscapes. It is a highly diverse discipline in terms of its thematic and methodical research foci. This article gives an overview of current German ecohydrological research approaches within plant-animal-soil-systems, meso-scale catchments and their river networks, lake systems, coastal areas and tidal rivers. It discusses their relevant spatial and temporal process scales and different types of interactions and feedback dynamics between hydrological and biotic processes and patterns. The following topics are considered key challenges: innovative analysis of the interdisciplinary scale continuum, development of dynamically coupled model systems, integrated monitoring of coupled processes at the interface and transition from basic to applied ecohydrological science to develop sustainable water and land resource management strategies under regional and global change.
KW  - Coastal regions
KW  - drylands
KW  - ecohydrological modelling
KW  - feedback
KW  - hyporheic zone
KW  - meso-scale ecosystems
KW  - plant-animal-soil-system
KW  - river networks
Y1  - 2014
U6  - https://doi.org/10.5675/HyWa_2014,4_2
SN  - 1439-1783
VL  - 58
IS  - 4
SP  - 221
EP  - 240
PB  - Bundesanst. für Gewässerkunde
CY  - Koblenz
ER  - 
TY  - INPR
A1  - de Araujo, Jose Carlos
A1  - Batalla  Villanueva, Ramon J.
A1  - Bronstert, Axel
T1  - Special issue: analysis and modelling of sediment transfer in Mediterranean river basins
T2  - Journal of soils and sediments : protection, risk assessment and remediation
Y1  - 2014
U6  - https://doi.org/10.1007/s11368-014-1000-7
SN  - 1439-0108
SN  - 1614-7480
VL  - 14
IS  - 12
SP  - 1905
EP  - 1908
PB  - Springer
CY  - Heidelberg
ER  - 
TY  - JOUR
A1  - Medeiros, Pedro Henrique Augusto
A1  - de Araujo, Jose Carlos
A1  - Mamede, George Leite
A1  - Creutzfeldt, Benjamin
A1  - Güntner, Andreas
A1  - Bronstert, Axel
T1  - Connectivity of sediment transport in a semiarid environment: a synthesis for the Upper Jaguaribe Basin, Brazil
JF  - Journal of soils and sediments : protection, risk assessment and remediation
N2  - Hydrosedimentological studies conducted in the semiarid Upper Jaguaribe Basin, Brazil, enabled the identification of the key processes controlling sediment connectivity at different spatial scales (10(0)-10(4) km(2)).
 Water and sediment fluxes were assessed from discharge, sediment concentrations and reservoir siltation measurements. Additionally, mathematical modelling (WASA-SED model) was used to quantify water and sediment transfer within the watershed.
 Rainfall erosivity in the study area was moderate (4600 MJ mm ha(-1) h(-1) year(-1)), whereas runoff depths (16-60 mm year(-1)), and therefore the sediment transport capacity, were low. Consequently, similar to 60 % of the eroded sediment was deposited along the landscape, regardless of the spatial scale. The existing high-density reservoir network (contributing area of 6 km(2) per reservoir) also limits sediment propagation, retaining up to 47 % of the sediment at the large basin scale. The sediment delivery ratio (SDR) decreased with the spatial scale; on average, 41 % of the eroded sediment was yielded from the hillslopes, while for the whole 24,600-km(2) basin, the SDR was reduced to 1 % downstream of a large reservoir (1940-hm(3) capacity).
 Hydrological behaviour in the Upper Jaguaribe Basin represents a constraint on sediment propagation; low runoff depth is the main feature breaking sediment connectivity, which limits sediment transference from the hillslopes to the drainage system. Surface reservoirs are also important barriers, but their relative importance to sediment retention increases with scale, since larger contributing areas are more suitable for the construction of dams due to higher hydrological potential.
KW  - Brazil
KW  - Connectivity
KW  - Sediment redistribution
KW  - Semiarid
KW  - Spatial scale
Y1  - 2014
U6  - https://doi.org/10.1007/s11368-014-0988-z
SN  - 1439-0108
SN  - 1614-7480
VL  - 14
IS  - 12
SP  - 1938
EP  - 1948
PB  - Springer
CY  - Heidelberg
ER  - 
TY  - JOUR
A1  - Heistermann, Maik
A1  - Francke, Till
A1  - Georgi, Christof
A1  - Bronstert, Axel
T1  - Increasing life expectancy of water resources literature
JF  - Water resources research
N2  - In a study from 2008, Lariviere and colleagues showed, for the field of natural sciences and engineering, that the median age of cited references is increasing over time. This result was considered counterintuitive: with the advent of electronic search engines, online journal issues and open access publications, one could have expected that cited literature is becoming younger. That study has motivated us to take a closer look at the changes in the age distribution of references that have been cited in water resources journals since 1965. Not only could we confirm the findings of Lariviere and colleagues. We were also able to show that the aging is mainly happening in the oldest 10-25% of an average reference list. This is consistent with our analysis of top-cited papers in the field of water resources. Rankings based on total citations since 1965 consistently show the dominance of old literature, including text books and research papers in equal shares. For most top-cited old-timers, citations are still growing exponentially. There is strong evidence that most citations are attracted by publications that introduced methods which meanwhile belong to the standard toolset of researchers and practitioners in the field of water resources. Although we think that this trend should not be overinterpreted as a sign of stagnancy, there might be cause for concern regarding how authors select their references. We question the increasing citation of textbook knowledge as it holds the risk that reference lists become overcrowded, and that the readability of papers deteriorates.
Y1  - 2014
U6  - https://doi.org/10.1002/2014WR015674
SN  - 0043-1397
SN  - 1944-7973
VL  - 50
IS  - 6
SP  - 5019
EP  - 5028
PB  - American Geophysical Union
CY  - Washington
ER  - 
TY  - JOUR
A1  - Bronstert, Axel
A1  - de Araujo, Josè Carlos
A1  - Batalla  Villanueva, Ramon J.
A1  - Costa, Alexandre Cunha
A1  - Delgado, José Miguel Martins
A1  - Francke, Till
A1  - Förster, Saskia
A1  - Güntner, Andreas
A1  - Lopez-Tarazon, José Andrés
A1  - Mamede, George Leite
A1  - Medeiros, Pedro Henrique Augusto
A1  - Mueller, Eva
A1  - Vericat, Damia
T1  - Process-based modelling of erosion, sediment transport and reservoir siltation in mesoscale semi-arid catchments
JF  - Journal of soils and sediments : protection, risk assessment and remediation
N2  - To support scientifically sound water management in dryland environments a modelling system has been developed for the quantitative assessment of water and sediment fluxes in catchments, transport in the river system, and retention in reservoirs. The spatial scale of interest is the mesoscale because this is the scale most relevant for management of water and land resources.
 This modelling system comprises process-oriented hydrological components tailored for dryland characteristics coupled with components comprising hillslope erosion, sediment transport and reservoir deposition processes. The spatial discretization is hierarchically designed according to a multi-scale concept to account for particular relevant process scales. The non-linear and partly intermittent run-off generation and sediment dynamics are dealt with by accounting for connectivity phenomena at the intersections of landscape compartments. The modelling system has been developed by means of data from nested research catchments in NE-Spain and in NE-Brazil.
 In the semi-arid NE of Brazil sediment retention along the topography is the main process for sediment retention at all scales, i.e. the sediment delivery is transport limited. This kind of deposition retains roughly 50 to 60 % of eroded sediment, maintaining a similar deposition proportion in all spatial scales investigated. On the other hand, the sediment retained in reservoirs is clearly related to the scale, increasing with catchment area. With increasing area, there are more reservoirs, increasing the possibility of deposition. Furthermore, the area increase also promotes an increase in flow volume, favouring the construction of larger reservoirs, which generally overflow less frequently and retain higher sediment fractions. The second example comprises a highly dynamic Mediterranean catchment in NE-Spain with nested sub-catchments and reveals the full dynamics of hydrological, erosion and deposition features. The run-off modelling performed well with only some overestimation during low-flow periods due to the neglect of water losses along the river. The simulated peaks in sediment flux are reproduced well, while low-flow sediment transport is less well captured, due to the disregard of sediment remobilization in the riverbed during low flow.
 This combined observation and modelling study deepened the understanding of hydro-sedimentological systems characterized by flashy run-off generation and by erosion and sediment transport pulses through the different landscape compartments. The connectivity between the different landscape compartments plays a very relevant role, regarding both the total mass of water and sediment transport and the transport time through the catchment.
KW  - Connectivity
KW  - Deposition
KW  - Erosion
KW  - Modelling
KW  - Sediment transfer
KW  - Semi-arid
Y1  - 2014
U6  - https://doi.org/10.1007/s11368-014-0994-1
SN  - 1439-0108
SN  - 1614-7480
VL  - 14
IS  - 12
SP  - 2001
EP  - 2018
PB  - Springer
CY  - Heidelberg
ER  -