Late Holocene channel pattern change from laterally stable to meandering – a palaeohydrological reconstruction
<p>River channel patterns may alter due to changes in hydrological regime related to changes in climate and/or land cover. Such changes are well documented for transitions between meandering and braiding rivers, whereas channel pattern changes between laterally stable and meandering rivers...
| Main Authors: | , , , , , |
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| Format: | Article |
| Language: | English |
| Published: |
Copernicus Publications
2018-08-01
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| Series: | Earth Surface Dynamics |
| Online Access: | https://www.earth-surf-dynam.net/6/723/2018/esurf-6-723-2018.pdf |
| Summary: | <p>River channel patterns may alter due to changes in hydrological regime
related to changes in climate and/or land cover. Such changes are well
documented for transitions between meandering and braiding rivers, whereas
channel pattern changes between laterally stable and meandering rivers are
poorly documented and understood. We hypothesize that many low-energy
meandering rivers had relatively low peak discharges and were laterally
stable during most of the Holocene, when climate was relatively stable and
human impact was limited. Our objectives in this work are to identify a Late
Holocene channel pattern change for the low-energy Overijsselse Vecht river,
to develop and apply a novel methodology to reconstruct discharge as a
function of time following a stochastic approach, and to relate this channel
pattern change to reconstructed hydrological changes. We established that the
Overijsselse Vecht was laterally virtually stable throughout the Holocene
until the Late Middle Ages, after which large meanders formed at lateral
migration rates of about 2 m yr<sup>−1</sup>. The lateral stability before the
Late Middle Ages was constrained using a combination of coring information,
ground-penetrating radar (GPR), radiocarbon (<sup>14</sup>C) dating, and
optically stimulated luminescence (OSL) dating. We quantified bankfull
palaeodischarge as a function of time based on channel dimensions that were
reconstructed from the scroll bar sequence and channel cut-offs using coring
information and GPR data, combined with chronological constraints from
historical maps and OSL dating. We found that the bankfull discharge was
significantly greater during the meandering phase compared to the laterally
stable phase. Empirical channel and bar pattern models showed that this
increase can explain the channel pattern change. The bankfull discharge
increase likely reflects climate changes related to the Little Ice Age and/or
land use changes in the catchment, in particular as a result of peat
reclamation and exploitation.</p> |
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| ISSN: | 2196-6311 2196-632X |