Summary:

The aim of river and valley restoration is re-establishment of natural or close to natural state in which the river channel and valley were before regulation works. River and valley were losing their natural state due to various factors. Mostly, it was connected with the radical changes as the result of the regulation works, i.e. river bed straightening , river gradient increase, standardization of size and shape of river cross section , liquidation of banks and channel bed irregularities, ecotones destruction, cutting off links between old river-bed and main river channel, reduktion in overbank flooding and floodplain storage. Increasing of water pollution in the past it was also chemical factor which changed natural state of rivers. Restoration is usually long-lived process which consists of different technical measures and induced by them ecological changes of water body and surroundings areas accomplished by nature. The full re-establishment of natural state is not possible in practice. By the time the restoration works begin the hydrological, hydraulic and environmental conditions should be recognized. The restoration works may be placed in the river bed, bank zone, along river valley and in tributaries or in the catchment area. The process of restoration encounters many and varied difficulties and limitations from which the most important are abillity to serve economic functions, technical limitations and ownership conditions. As the result of river restoration the state, which previously led to particular regulation works, can be created. In many European countries comprehensive actions have been made to re-establish the natural state of the river. Nationwide and local programmes for river restoration were established. In Poland mainly minor actions have been taken, i.e. connecting an old river-bed to the main (regulated) river bed, old waters treatment, re-establishement of forest wet biotope. In the near future more such actions are planned, especially in the area of Biebrza National Park.