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Lakes or natural reservoirs are usually formed by the water supplied by torrents runoff. Furthermore, runoff, according to the torrential environment that forms the watershed (climate, geology, vegetation and relief) is usually associated with debris flow. As a result, many lakes and reservoirs are undergoing an alluviation process which leads to an important reduction of their total capacity. In fact, long-term process of torrents may threaten their existence. Lakes and reservoirs have an important role since the impounding water is used for multi purposes such as municipal supply, irrigation and recreation. Often, lakes form wetlands that are really important and are protected by national or international treaties. In this paper, the methodology we use involve the analysis of torrential environment (potential) of the lake Volvi watershed. Moreover, the mean annual sediment yield calculated according to Gavrilovic method so as to assess the risk of alluviation. Also, Kronfellner–Kraus method used in order to take under consideration the sediment that can flow into the lake after an extraordinary flood event. Finally, flood control works proposed so as minimize the threat of alluviation. The present study shows that the torrential environment (potential) is rather moderate, although during intense rainfalls great volume of water and debris discharge are produced so the only solution against alluviation is the construction of flood control works.
alluviation, flood control works, torrentional environment, watershed
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