Foto: Vojta Herout, www.nafotime.cz
Nature-friendly Flood Control Measures in Písečná
At least 12 houses in the village of Písečná u Žamberka were regularly threatened by flooding and the increased water level of the local Potočnice river which had been inappropriately straightened in the past. The modifications resulted in the reduced capacity of the riverbed during floods and a low ability to retain water during the dry season. In addition, it was not possible to change the profile of this river directly. Based on models, the hydrologists proposed the construction of a relief channel, which, in the event of a flood, would serve as a natural by-pass. The first flood has already verified that this solution works. Thanks to the new riverbed, ponds and planting of greenery, a pleasant green area has also been created in the village, where people like to meet.
The Adaptation Journey
The positive impact
They needed to deal with two manifestations of climate change on the Potočnice river in Písečná u Žamberka - excessive drought and floods. The aim was, therefore, to propose such changes for the river that would retain water during dry periods and help the original riverbed to cope during floods.
How does it work?
Along the Potočnice stream, two right-hand relief channels were built because the project designers evaluated that two sections of the Potočnice river were critical. The new relief channels are in a close-to-nature form. They have a compound (gradually sloping) profile and the narrowest deepened part, at the bottom of the riverbed, is meandering.
At a normal flow rate, the relief channels are saturated only by the nameless tributaries of the Potočnice river. Habitat and sedimentation ponds, culverts, which ensure the correct distribution of water, and anti-flooding walls were created there.
A raised ford, in the form of a stone wall, was created on a spot where cars or agricultural machinery needed to cross. Creating a bridge would have been expensive, so the authors chose a raised ford, which was created as a more economical and simpler solution to something that was needed. In addition, the place looks nice and fits nicely into the landscape.
In addition, modifications in the vicinity of the original riverbed and planting of trees and shrubs have succeeded in improving the appearance of the public space.
The local community of the village of Písečná has long struggled with problems of increased water level in the Potočnice river. In the past, the riverbed was inappropriately modified, and, at high flows, the riverbed did not have enough capacity. The biggest problems were caused by two sections between river kilometres 4,508 to 4,972 and 5,771 to 6,034. Altogether, it was more than 700 meters of the stream that threatened 12 local houses with fifty inhabitants. In addition, the designers of the measures had to deal with the fact that it was not possible to intervene in the original riverbed to improve the condition.
Operation and maintenance
Maintenance costs are expected to be around 20,000 crowns per year. It mainly involves the operational maintenance of the area and the necessary mowing of the riverbed, without which the riverbed would overgrow with grass and not fulfil its function.
Obstacles and challenges
Floods or torrential rains at the time of the construction could have caused major problems. Fortunately, the flood only came after the necessary adjustments had been completed. As a result, it was immediately discovered that everything worked as expected.
Operation and maintenance
Shortly after the work was completed, the project was tested by a flood. It immediately showed that the measures were effective.
The modifications made to the stream protected the houses in the village. In addition, the quality of the previously degraded habitats has increased and so has the aesthetic and recreational value of the area. By retaining water in the habitat ponds, the soil water balance of the floodplain has improved and the sedimentation ponds have reduced the inflow of sediments from the surrounding areas into the stream.
How much did it cost?
The costs reached 9.5 million crowns.
The majority of the amount, 8.1 million crowns, was provided by the Operational Program Environment. The remaining part of project was funded by the municipality of Písečná.
With proper maintenance the service life of the project is unlimited.
Thanks to this project, flood damage has been eliminated during each major flood. It is difficult to estimate the savings. However, it is clear that the potential flood damage would have been, in any case, higher than the total cost of the project.
Revitalization of water elements Flood control measures Floods and torrential rainfall