Seite - 1441 - in Book of Full Papers - Symposium Hydro Engineering

 The lack of resources for technical maintenance of the dams and their structures brought some dam owners to the necessity either to keep the corresponding reservoir permanently empty or to cut the dam body and thus to prevent any further impounding. So, they also prevented any flood risks for the downstream residents. Such destruction is usually performed without any technical design and compliance with the related legal requirements. Of course, the result is devastating for the materials of the dam body, too.  The lack of resources (i.e. finances, qualified personnel, equipment etc.) for technical maintenance of the small dams and their facilities including for carrying out reparatory works sets many municipalities as dam owners between the hammer of the legal requirements and the anvil of resources.  The emphasis on environmental friendliness has led recently to some curious legal requirements. For example, every new dam must have a fish pass according to the Act for Fishery and Aquacultures. In the process of legislation development, such examples of nonsense should be cleared. 3.2. PERFORMANCE PROBLEMS DUE TO THE LACK OF TECHNICAL MAINTENANCE The following issues due to the lack or even absence of technical maintenance can be formulated with respect to the performance of the small dams and to the related findings in [3, 4, 5] as well:  In general, often there has been no technical maintenance of the dams and their facilities. There is no monitoring system, no measurements and analyses of the technical conditions are carried out. Usually, there is no technical documentation including drawings left from the design and construction.  Settlement of the embankment at the central part of the dam. Thus, the dam crest level has sunk below the maximum water level in the reservoir, and the risk of crest overflow during flood conditions strongly increases with all negative consequences of such event.  The legal requirement for cleaning the river bed 500 m downstream of the dam is in general not held by the dam owner.  Many small dams have suffered some damages over the years of operation without proper maintenance. They need a serious and urgent repair for restoring their full operational functionality. Otherwise, subsequent load impacts and floods could lead to heavy damages of the dam body with possibly uncontrolled release of the impounded water. Independantly how small this volume might be, the resulting flood wave could certainly have severe consequences.  Erosion of the streambed downstream of the spillway. In some cases, the structure of the spillway itself is in a good condition. However, the following spillway race and the stilling basin (if available) have been for 1441