Oldrich Navratil

Effects of urbanization on river morphology of the Talar River, Mazandarn Province, Iran

Abstract In the present study, we investigate the effects of urbanization growth on river morphology in the downstream part of Talar River, east of Mazandaran Province, Iran. Morphological and morphometric parameters in 10 equal sub-reaches were defined along a 11.5 km reach of the Talar River after land cover maps were produced for 1955, 1968, 1994, 2005 and 2013. Land cover types changed extremely during the study period. Residential lands were found to have increased in area by about 1631%, while forest land and riparian vegetation decreased in by approximately 99.9 and 96.2%, respectively. The results of morphometric and morphological factors showed that average channel width (W) for all 11.5 km of the study river decreased by 84% during the study period, while the flow length increased by about 2.14%.

Monitoring Debris Flow Propagation in Steep Erodible Channels

Debris flows mobilize high sediment loads especially during intense rainfall events. The volume of these surges is known to dramatically grow during propagation by scouring of the unconsolidated sediment stored in the channel before the event. The current prediction tools used by engineers to manage debris flow hazards are mostly based on empirical relationships with a high level of uncertainty. This situation arises in particular because of our insufficient understanding of interactions between the flow and the erodible bed of the torrent. In order to address this issue, field monitoring stations were deployed in 2010 in the Manival and the Real Torrents, two very active sites in the French Alps. Several stations were installed in different locations along the same torrent to investigate the spatial variability of the measured parameters. Each station was equipped with rain gauges, flow stage sensors, set of geophones and camera. The collected information allows developing a data base including the rainfall duration-intensity-volume, the flow depth, the front velocity and the surge volume. The objective is to characterize the changing nature of the debris-flow properties along the torrents and then to analyse the effect of channel conditions on debris-flow scouring.