Popular Science: Even partial river restoration can help
There have been efforts in recent years to improve the river habitat quality and to achieve good hydromorphological conditions within the ecological status, and not only in the Czech Republic. Their status is evaluated according to biological, hydromorphological, chemical and physical-chemical and biochemical parameters and there is a requirement to achieve this status under the Water Framework Directive 2000/60/ES.
When evaluating the river status and proposing restoration measures, it is first important to determine the reference conditions in the locality itself. Reference conditions represent the natural state of rivers with only minimal anthropogenic influences. These conditions can be determined from historical sources, such as old maps and aerial photographs.
The authors of this research focused on the evaluation of the river status and on proposing restoration measures for the Slubice River, the left site tributary of the Chrudimka River in the northern edge of the Vysočina Region. The river was divided into parts, with 17 parameters (divided into 4 mapped zones) being evaluated in each part. At the end of this process, each part of the river was assigned one of five hydromorphological status classes.
The great issue was river straightening and the deepening and reinforcement of the channel. The calculation shows a shortening by 31% in the upper course of the Slubice River and 48.8% in the lower course. These numbers are higher than the Czech average of river network modifications (28.4%). According to the hydromorphological status, almost half of the river was denoted as average and almost half of the river length was characterized with a status of very good and good. The water quality was influenced by nutrients, particularly nitrates from agriculture, and by organic contamination.
Two parts of the river which have the worst hydromorphological status were selected as restoration localities. The authors proposed a new meandering channel with a shallow and wide cross-section profile including the riparian zone vegetation. The simulation of the proposed restoration measures resulted in an improvement in the zone of the channel itself by up to 3 hydromorphological status classes while an improvement by 1–2 classes within the hydrological regime zone was also achieved.
Small streams in the Central European agricultural landscape represents significant potential for the improvement of the hydromorphological river status, because its restoration is not limited by high costs and several realization difficulties as it is for the main rivers.
The main precondition of successful restoration is allowing for the natural development of the channel course without stabilization of the banks. It is important to mention that the result of the restoration is also influenced by the riparian zone, the flood plain and land cover in the whole watershed.