Land use change for flood protection: A prospective study for the restoration of the river Jelasnica watershed

Abstract

Serbia?s hilly-mountainous regions are extremely vulnerable to flooding as a consequence of their natural characteristics and human impacts. Land mismanagement influences the development of erosion processes, and causes soil degradation that significantly reduces the land?s capacity to infiltrate and retain rainwater. Inappropriate land use as well as development activities replace permeable with impervious surfaces in the watershed. This leads to more rapid runoff generation and the more frequent appearance of torrential floods and bed-load deposits on downstream sections. Environmental degradation creates economicsocial problems within local societies which is often followed by depopulation. Restoring watersheds to their optimal hydrologic state would reduce flood discharge and by increasing groundwater recharge would increase both low-flow and average discharges in springs and streams. Best management practices could be developed through the application of specific combinations of biotechnical, technical and administrative measures, and by using the concept of ?natural reservoirs?. The design of such practices is explored through a case study of the watershed of the river Jelasnica, southeastern Serbia. Realization of these planned restoration works should help decrease the annual yields of erosive material by 44.1% and the specific annual transport of sediment through hydrographic network by 43.6%. Representative value of the coefficient of erosion will be reduced from Z=0.555 to Z=0.379. The value of maximal discharge Qmax-AMCIII (1%)=54.17 m3?s-1, before restoration, is decreased to Qmax-AMCIII (1%)=41.22 m3?s-1 after restoration, indicating the improvement of hydrological conditions, as a direct consequence of land use changes. Administrative measures are applied through ?Plans for announcement of erosive regions and protection from torrential floods in the territory of Leskovac municipality?.Brdsko-planinska podrucja Srbije izlozena su destruktivnom dejstvu poplava, sto je posledica njihovih prirodnih karakteristika i uticaja ljudskog faktora. Neodgovarajuce koriscenje zemljista utice na razvoj erozionih procesa usled cega dolazi do degradacije, smanjenja infiltraciono- retencionog kapaciteta, odnosno, povecavaju se nepropusne i slabo propusne na racun propusnih povrsina. Na taj nacin se stvaraju uslovi za cescu pojavu bujicnih poplava i deponovanje vucenog nanosa na nizvodnim deonicama. Degradacija zivotne sredine stvara ekonomsko-socijalne probleme u okviru lokalnih zajednica sto cesto prati depopulacija. Restauracija slivova, do njihovog optimalnog hidroloskog stanja, bi smanjila poplavni proticaj i poboljsala obnavljanje rezervi podzemnih voda, uz povecanje malog i srednjeg proticaja na izvorima i potocima. Prakse najboljeg upravljanja bi se mogle razraditi primenom specificnih kombinacija biotehnickih, tehnickih i administrativnih mera i koncepta ?prirodnih rezervoara?. Kreiranje takve prakse upravljanja je istrazeno u studiji slucaja sliva reke Jelasnice u jugoistocnoj Srbiji. Realizacija planiranih restauracionih zahvata bi trebalo da dovede do smanjenja godisnje produkcije erozionog materijala za 44.1% i specificnog godisnjeg pronosa nanosa kroz hidrografsku mrezu za 43.6%. Reprezentativna vrednost koeficijenta erozije bice redukovana sa Z=0,555 na Z=0,379. Vrednost maksimalnog proticaja Qmax-AMCIII (1%)=54,17 m3?s-1, pre restauracije smanjena je na Qmax-AMCIII (1%)=41,22 m3?s-1 posle restauracije, sto ukazuje na poboljsanje hidroloskih uslova kao direktnu posledicu promene nacina koriscenja zemljista. Administrativne mere se primenjuju kroz ?Planove za proglasenje erozionih podrucja i zastitu od bujicnih poplava na teritoriji opstine Leskovac?. PR Projekat Ministarstva nauke Republike Srbije, br. 43007