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V magistrskem delu smo obravnavali problematiko zapadlega in plavnega lesa v vodotokih in obvodnem prostoru ter njegov vpliv na naravne procese. Najpogosteje se lesno plavje preučuje z vidika sovplivanja na poplavno ogroženost, v novejšem času pa se raziskuje tudi geomorfološke in ekološke vplive na vodotoke. Problematika plavnega lesa je izpostavljena v vodotokih z gozdnim zaledjem in na območjih erozijskih žarišč. Zaradi zapadlega in plavnega lesa v vodotoku se spreminjajo pretočne razmere, povečata se poplavna ogroženost in odlaganje sedimentov, pojavlja se nenadzorovano širjenje struge, dvigne se niveleta dna, prihaja do zamašitev premostitev in prepustov ter posledično do njihovih poškodb in rušitve, zmanjšuje se uporabna prostornina zadrževalnikov in akumulacij hidroelektrarn … Upravljanje s plavnim lesom temelji na poznavanju vzrokov nastanka, virov, dinamike, količine, premeščanja in odlaganja. Za izračun dinamike se uporabljajo empirične enačbe, razvite z laboratorijskimi poskusi in nadgrajene z opazovanji v naravi. Tveganja zaradi zapadlega in plavnega lesa v vodotokih preventivno zmanjšamo s skladno namensko rabo prostora, z ustreznim gospodarjenjem z gozdovi, s pravilnim umeščanjem in dimenzioniranjem javne infrastrukture, ozaveščanjem javnosti ter z gradnjo zadrževalnih objektov, preusmerjanjem in odstranjevanjem plavnega lesa. Plavni les ima tudi nekatere ekološke funkcije (ugoden vpliv na stabilnost struge zaradi zmanjševanja hitrosti in strižnih sil vode, nastajanje tolmunov), kar izboljšuje razmere za vodne in obvodne organizme. Ugotavljamo, da je potrebno ob vse pogostejših vremenskih ujmah problematiko plavnega in zapadlega lesa enakovredno uvrstiti v upravljanje vodotokov. Za zmanjševanje ogroženosti zaradi lesnega plavja sta potrebna interdisciplinarni pristop in sodelovanje pri poglabljanju znanja, načrtovalskih in izvedbenih aktivnostih. The master's thesis deals with the issue of woody debris and driftwood in streams and riparian areas and their effect on natural processes. Driftwood is commonly studied in terms of its effect on the flood risk while recent studies also cover the geomorphological and ecological impacts of driftwood on streams. Floating woody debris is a serious issue in streams in forested lands or erosion hotspots. Driftwood and floating woody debris in streams lead to changes in the streamflow, increase the flood risk and accumulation of sediment, cause uncontrolled widening of stream channels, raise stream bed levels and jam bridging structures and culverts, eventually damaging and destroying them and causing reductions in useful capacity of reservoirs and hydroelectric plants' accumulation pools. Driftwood management is based on profound understanding and knowledge of driftwood causes, sources, dynamics, quantities, transfers and deposition. Driftwood dynamics is calculated using empirical equations, which are developed on the basis of laboratory tests and upgraded with nature observations. The risk of driftwood and floating woody debris can be mitigated by harmonised land use, appropriate forest management, proper siting and dimensioning of public infrastructure, awareness-raising, construction of detention structures, diversion and removal of driftwood. Floating woody debris has certain ecological functions (favourable impact on the stability of the stream bed due to reduction of flow speed and shear forces of water, formation of stream pools), which improves the conditions for aquatic and riparian organisms. It has been established that in the light of increasing frequency of natural disasters the issue of driftwood and floating woody debris needs to be included in the scope of water source management. Reduction of the drift risk will require an interdisciplinary approach and cooperation in the acquisition of knowledge as well as with regard to planning and implementation activities.