关键词:
Multi-thread river
Human impact
Channelization
River restoration
Sediment budget estimation
Moravka River
摘要:
Multi-thread gravel-bed rivers in Europe have undergone distinctive changes in morphology related to progressive narrowing and incision during the last 100 years. In many cases, the post-effects of multi-thread channel transformations are associated with sediment deficits caused by channelization, damming, or land use changes. Similar trends of channel narrowing and incision can be observed in the Moravka River in the Czech Carpathians, where damming, in particular, has led to sediment deficits and decreases in flood events. Evaluation of the planform dynamics of vegetation in the active channel, lateral and vertical erosion in the channel and calculations of the dominant discharge were used as tools to define potential measures for the protection and sustainability of the close-to-natural multi-thread Moravka River channel. The successive vegetation rapidly colonised originally non-vegetated gravel-bar patches, controlling sediment material reinforcement. This process strongly contributed to a decrease in the number of gravel bars in recent decades and a decline in multi-thread channel dynamics. The total volumes of approximately 36,000 m(3) and 3000 m(3) of sediment material were eroded in an approximately 1-km-long reach during a high-magnitude flood (with similar to 20-year recurrence interval of mean daily discharge) and the ordinal high-flow event (with similar to 1-year recurrence interval of mean daily discharge), respectively, which led to an overall sediment material deficit in the studied reach. No single value of dominant discharge for sediment transport was found by bedload transport simulations because the volumes of transported material continuously increased with the magnitude of a particular discharge and its duration. Based on these findings, the main potential measures for the protection and sustainability of multi-thread channels are recommended. The artificial disturbance of successive vegetation cover on gravel bars and the occurrence of artifi