Ongoing monitoring of tagged bed particles

We continue with the monitoring of bed particles marked by pit-tags, which have been installed into stream beds of two contrast small streams (check-dam impacted and close-to-nature pool-riffle stream) with similar catchment areas. The monitoring covered one bankfull event and several close-to-bankfull discharge events in following months. After ca. 21-month period, up to 350 m transport distance was measured for tagged particles in the check-dam managed stream; some of grains passed through four check dams. Similar transport distance (up to 300 m) was obtained in the pool-riffle stream. However, there were large differences in recovery rates of pit-tag-marked grains. We reached up to 65% recovery rate in the check-dam managed streams, but only 20-25% recovery rate prevailled in the pool-riffle stream. This notably low recovery rate is likely caused by higher morphodynamics of the pool-riffle stream, which caused frequent burying of the marked grains into gravel-bed deposits during sediment transport-effective discharges. We are planning to continue this monitoring also in the following year; this will also include a development of rating curves for both studied streams, which will allow us to create direct relations between the critical discharge and transported distance (or size) of tagged particles. 

Monitored check-dam impacted stream

Monitored pool-riffle stream

Abandoned channelization works in Beskydian steep streams

The major part of the Moravskoslezské Beskydy Mts. was unaffected by human activities until the 17^th century. Since that times, local forests started to be managed as sources of timber and first villages have been built the valleys. At the turn of 19^th and 20^th century, the first large flood-protective structures had been constructed, which mainly consisted of long stone embankments and check dams. Some of these structures were later not needed and local authorities did not attempt to repair them after damages caused by flood events. We are still able to find their remains in some headwater parts of the mountains. Nowadays, they can act as disconnectivities in lateral sediment flux by abruption of effective hillslope-channel coupling or by contrast, they can serve as sources of coarse (for the most time except extraordinary floods immovable) sediments into stream channels. Nevertheless, their presence clearly documents past vital activities of local people in relatively inaccessible headwater parts of the mountain valleys.      

Long stone embankment, the Slavíč Stream

Remains of check dam, the Slavíč Stream