Present address: Swiss Re, Swiss Reinsurance Company, Zurich, Switzerland.
Special Issue Article
Ecosystem expansion and contraction dynamics along a large Alpine alluvial corridor (Tagliamento River, Northeast Italy)
Article first published online: 18 SEP 2007
Copyright © 2007 John Wiley & Sons, Ltd.
Earth Surface Processes and Landforms
Special Issue: Multi-scale Characterization and Evolution of Channel Forms in Gravel-bed Rivers
Volume 32, Issue 11, pages 1693–1704, 15 October 2007
How to Cite
Doering, M., Uehlinger, U., Rotach, A., Schlaepfer, D. R. and Tockner, K. (2007), Ecosystem expansion and contraction dynamics along a large Alpine alluvial corridor (Tagliamento River, Northeast Italy). Earth Surf. Process. Landforms, 32: 1693–1704. doi: 10.1002/esp.1594
- Issue published online: 25 SEP 2007
- Article first published online: 18 SEP 2007
- Manuscript Accepted: 20 OCT 2006
- Manuscript Revised: 18 OCT 2006
- Manuscript Received: 15 FEB 2006
- EU Project tempQsim. Grant Number: EVK1-CT2002-00112
- SBF. Grant Number: 02.0072
- flow regime;
- ecosystem process;
- braided river;
- hydraulic exchange;
- temporary river;
Riverine floodplains are pulsing ecosystems that expand and contract with changing flow. In this study we quantified large-scale expansion and contraction dynamics of surface waters along a 41·5 km braided section of the last remaining semi-natural large Alpine gravel-bed river (Tagliamento River; NE Italy). To assess surface–subsurface exchange patterns we measured discharge and vertical hydraulic gradients at multiple locations along the corridor. We identified two river sections delineated by distinct geomorphic knickpoints. In the upper 29 km, Section I (losing zone), surface flow decreased on average by 2·5 ± 0·8 m3 s−1 per river-km. In the downstream 12·5 km, Section II (gaining zone), surface flow increased on average by 0.3 ± 0.1 m3 s−1 per river-km. The losing zone experienced frequent and extensive drying and rewetting cycles. The length of the dry river section was measured over a 1·5 year period using differential GPS. Up to 23 km of Section I fell dry at the surface. Frequent and irregular flow pulses led to rapid expansions of the wetted channel at velocities of up to 3 km h−1, while the subsequent contraction velocities were less than 0·5 km h−1. Water level was linearly regressed against the total length of the dry river section (r2 = 0·74; p < 0·0001). This relationship, in combination with a continuous stage record, was used to evaluate expansion and contraction dynamics over a 4 year period. Timing, frequency, magnitude (spatial extent) and duration of expansion and contraction dynamics reflected the flashy flow regime of the Tagliamento River, including a high intra- and inter-annual variability of surface drying and rewetting. Our study emphasizes that even small changes in flow can cause major increases or decreases of ecosystem size, thereby creating a highly dynamic and harsh environment for both terrestrial and aquatic organisms. Copyright © 2007 John Wiley & Sons, Ltd.