Torrential Floods and Town and Country Planning in Serbia

Nat. Hazards Earth Syst. Sci., 12, 23–35, 2012 www.nat-hazards-earth-syst-sci.net/12/23/2012/ Natural Hazards doi:10.5194/nhess-12-23-2012 and Earth © Author(s) 2012. CC Attribution 3.0 License. System Sciences

Torrential ﬂoods and town and country planning in Serbia

R. Ristic´1, S. Kostadinov1, B. Abolmasov2, S. Dragicevi´ c´3, G. Trivan4, B. Radic´1, M. Trifunovic´5, and Z. Radosavljevic´6 1University of Belgrade Faculty of Forestry, Department for Ecological Engineering in Protection of Soil and Water Resources Kneza Višeslava 1, 11030 Belgrade, Serbia 2University of Belgrade Faculty of Mining and Geology, Belgrade, Serbia 3University of Belgrade Faculty of Geography, Belgrade, Serbia 4Secretariat for Environmental Protection of Belgrade City, Belgrade, Serbia 5Institute of Transport and Trafﬁc Engineering-Center for Research and Designing, Belgrade, Serbia 6Republic Agency for Spatial Planning, Belgrade, Serbia

Correspondence to: R. Ristic´ ([email protected]) Received: 12 August 2011 – Revised: 8 November 2011 – Accepted: 14 November 2011 – Published: 2 January 2012

Abstract. Torrential floods are the most frequent natu- pogenic extreme phenomena all around the world makes us ral catastrophic events in Serbia, causing the loss of hu- pay more attention to their environmental and economic im- man lives and huge material damage, both in urban and ru- pacts (Guzzetti et al., 2005; Schmidt et al., 2006; Lerner, ral areas. The analysis of the intra-annual distribution of 2007). Floods, in all their various forms, are the most fre- maximal discharges aided in noticing that torrential floods quent natural catastrophic events that occur throughout the have a seasonal character. The erosion and torrent control world (Berz et al., 2001; Barredo, 2007). Among natural works (ETCWs) in Serbia began at the end of the 19th cen- hazards with serious risks for people and their activities, tor- tury. Effective protection from torrential floods encompasses rential (flash) floods are the most common hazard in Serbia biotechnical works on the slopes in the watershed and techni- (Ristic´ and Nikic,´ 2007) and the most significant regarding cal works on the torrent beds, within a precisely defined ad- huge material damage and loss of human lives. The fre- ministrative and spatial framework in order to achieve maxi- quency of these events, their intensity and diffusion in the mal safety for people and their property. Cooperation to over- whole country (Fig. 1) make them a permanent threat with come the conflicts between the sectors of the water resources severe consequences to environmental, economic and social management, forestry, agriculture, energetics, environmen- spheres. The representative examples are the torrential floods tal protection and local economic development groups is in- that occurred in the watersheds of the main tributaries of the dispensable at the following levels: policy, spatial planning, following rivers in the past 15 yr: the Kolubara (June of 1996; practice, investments and education. The lowest and most May of 2011), the Great Morava (July of 1999), the Kolubara effective level is through the Plans for Announcement of and the Drina (June of 2001), the South Morava (November Erosive Regions (PAERs) and the Plans for Protection from of 2007), the West Morava, the Drina and the Lim (Novem- Torrential Floods (PPTFs), with Hazard Zones (HZs) and ber of 2009), the Great Timok (February of 2010), the Pèinja Threatened Areas (TAs) mapping on the basis of the hydro- (May of 2010), and the Drina (December of 2010). logic, hydraulic and spatial analysis of the factors that are Serbia has not been included in the most recent studies that important for the formation of torrential floods. Solutions have examined flood hazards within the territory of Europe defined through PAERs and PPTFs have to be integrated into and globally (Barredo, 2007; Mosquera-Machado and Dilley, Spatial Plans at local and regional levels. 2009). This paper presents the most significant aspects of the phenomenon of torrential floods as the most common natural hazard in Serbia. The first part of this paper presents a map 1 Introduction with the spatial disposition of the most destructive torrential floods in the last 60 yr, including the results of the analysis Natural or anthropogenic calamities may cause huge mate- of the characteristics of the maximal discharges and some rial damage and, unfortunately, the loss of human lives (Toya interesting cases of historic torrential floods reconstructed and Skidmore, 2007). The occurrence of natural and anthro- by the “hydraulic flood traces” method. The second part of

Published by Copernicus Publications on behalf of the European Geosciences Union. 24 R. Ristic´ et al.: Torrential floods and town and country planning in Serbia this paper is concerned with a brief history of the Erosion and the air and water capacity of the soil (Ristic´ et al., 2001; and Torrent Control Works (ETCWs) in Serbia, in the period Nondedeu et al., 2006; Nondedeu and Bédécarrats, 2007; from 1907 to 2006, along with a review of the legislation Szendreine-Koren and Nemeskeri, 2007). pertaining to the issues of erosion and torrent control. The The climate, along with the specific characteristics of the third part of the paper refers to the issues of town and coun- relief, distinctions of the soil and vegetation cover, severe try planning as a tool for mitigating the harmful effects of erosion processes and social-economic conditions result in erosion and torrential floods. the frequent occurrence of torrential floods. Erosion pro- The main objectives of this paper are to present the inte- cesses of different categories of destruction are present in gral notion of the problem of torrential floods in Serbia while 76 355 km2 (86.4 % territory of Serbia) in Serbia. The aver- highlighting some possible improvements to the process of age annual production of erosive material in the territory of town and country planning as a useful means for more effec- Serbia is 37.25×106 m3, in other words, 487.85 m3× km−2, tive torrential watershed management. which is 4.88 times more than the geological (natural) erosion. The average rate of soil formation on the slopes in 1.1 Torrential floods and erosion Serbia is 0.1 mm yr−1. Geological (natural) erosion is the action of wind, water, ice and gravity in wearing away the soil Torrential (flash) flood represents a sudden appearance of at a rate smaller than 0.1 mm yr−1 (≤ 100 m3× km −2 yr−1). maximal discharge in a torrent bed with a high concentra- It is a relatively slow, continuous process unlike acceler- tion of sediment. In extreme cases, the two-phase fluid flows ated erosion, which produces a rate of soil loss higher than out from the torrent bed with enormous destructive energy. 0.1 mm yr−1 (>100 m3× km −2 yr−1) due to human activi- The two-phase fluid (water and sediment) can contain frac- ties (Kostadinov, 2008). tions (60 % of total volume) with different granulations rang- Severe and excessive erosion processes cover 35 % of the ing from clay particles to rock fragments, diameters of up to territory of Serbia (IWRMJC,` 2001). With local economic 5.0 m and a total mass of over 200 tons (Jevtic,´ 1978). development, soil erosion becomes more frequent and severe Torrential watershed is a hydrographic entity that in- (Ananda and Herath, 2003; Bakker et al., 2005). The con- volves the beds of the mainstream and its tributaries, and the struction of roads and residential areas and the inappropri- gravitating surfaces with erosion processes at a certain level ate use of agricultural and forest land contribute to the con- of intensity. The attribute “torrential” refers to any water- centration of fast surface runoff, as well as sediment trans- shed with a sudden appearance of maximal discharge with portation from the gravitating surfaces to the channel net- a high concentration of sediment, regardless of the size and work. The roads interact positively with clear cutting. They category of the stream (Ristic´ and Maloševic,´ 2011a). A to- modify the hill slope flow paths and cause faster delivery of tal of 9260 torrential watersheds were registered in Serbia on the water to the channels during storm events with the con- the basis of an investigation carried out from 1930 to 1974 version of the subsurface flow into surface flow (Jones and (Gavrilovic,´ 1975). Grant, 1996). Such flows contribute 20 to 60 times more sed- Torrential floods that once occurred rarely during the pre- iment (unsealed roads) than undisturbed forest surfaces and development period have now become more frequent and de- about 10 times more sediment than harvested areas (Motha et structive due to the transformation of the land usage in the al., 2003). Clear cutting and removal of the vegetation influ- watersheds from rural to urban land usage (Kusky, 2010). ence the water balance by affecting evapotranspiration and The decrease of surfaces covered with forest vegetation, possibly snow accumulation and melt. These activities in- along with urbanization and inadequate agricultural mea- crease the peak discharge by as much as 50 % in small basins sures, are some of the negative aspects of human activities and 100 % in large basins (Jones and Post, 2004). Timber that cause torrential floods. Due to these activities, former harvesting has the potential to increase the total flow and discharges with a 100-yr recurrence interval have become lengthen the duration of larger flows while enabling sedi- events with a 20-year recurrence interval (Ristic´ et al., 2006). ment movement (Troendle and Olsen, 1994). Steep terrains Along with the watershed development, there are changes in without vegetation are particularly prone to increased surface its hydrological regime that increase the torrential flood vol- runoff and erosion (Wipf et al., 2005), like ski runs with de- ume. The soil and vegetation cover directly affects the inten- creased surface roughness and increased velocity of runoff sity of the surface runoff by creating “losses” of precipitation and sediment yield (Fattorini, 2001; Freppaz et al., 2002; through the processes of interception, evaporation, transpira- Ristic´ et al., 2011b). tion and infiltration (Ristic´ and Macan, 1997a, 2002). The eroded soil becomes compacted with an insufficient amount of nutrients and organic matter. The infiltration rates and water-storage capacity of the soil profile are reduced, which, in turn, increases the overland flow and erosion. The amount of surface runoff depends on the total precipitation, the type of land usage, and the characteristics of the vegetation cover

Nat. Hazards Earth Syst. Sci., 12, 23–35, 2012 www.nat-hazards-earth-syst-sci.net/12/23/2012/ R. Ristic´ et al.: Torrential ﬂoods and town and country planning in Serbia 25

Fig. 1. Spatial disposition of the most destructive100 torrential floods(● - material in Serbia damage from100 and 1950 lossto of2010 human( (● lives; –- materialmaterial ● - material damage damage);damage and loss ■ – ofandcontrol human loss profiles lives; of from human the lives; ● - material damage); ■ – control profiles from the 100100 (●( ●- materialmaterial damage damage and and loss loss of human of human lives; lives; ● - material ● –- materialmaterial damage); damage); damage); ■ –– controlcontrol ■ – profiles control profiles from 101profiles thefrom RHMOSRHMOS the from observation observation the system;system;101 ▼-profile– profileRHMOS Orć Oruša,cuša,´ the observation Plavska the Plavska River River (refers system; (refers to Fig. to2); ▼ Fig.1-7-profile locations 2); of Orthe ćuša, the Plavska River (refers to Fig. 2); 1-7 locations of the 101 RHMOS observation system; ▼-profile Orćuša, the Plavska1–7 locations River of (refers the profiles to (refersFig. to2); Fig. 1-7 4). locations102 of the profiles (refers to Fig. 4) 101 RHMOS observation system; ▼-profile Orćuša, the Plavska River (refers to Fig. 2);103 1-7 locations of the102 profiles (refers to Fig. 4) 102 profiles (refers to Fig. 4) 104 102 profiles (refers to Fig. 4) 103 103 105 The climate, along with the specific characteristics of the relief, distinctions of the soil and vegetation 103 2 Torrential floods in Serbia 106 cover, severe erosiontomatic 104processes water-level and social-economic recorders conditions (Ristic´ et resulted al., 2011c). in the frequent The ob- occurrence of 104 107 torrential floods. Erosionservation processes system of wasdifferent under categories the supervision of destruction of theare Republicpresent in 76,355 km2 104 108 (86.4% territory of Serbia)105 in Serbia.The The averageclimate, annua lalong production with of erosive the material specific in the territorycharacteristics of of the relief, distinctions of the soil and vegetation 105 The climate, along with the specific characteristics of 2.1the relief, Characteristics distinctions of maximal of the discharges soil and in vegetation Serbian 6Hydro3 Meteorological Office3 -2 of Serbia (RHMOS). At most 105 The climate, along with the specific characteristics of the relief, distinctions of the109 soilSerbia and is 37.25·10vegetation m , in other words, 487.85 m ·km , which is 4.88 times more than the geological torrential watersheds 110 (natural) erosion. Theprofiles average106 measurements rate cover,of soil formation severe started on the inerosion slopes 1953, in withSerbia processes a isfew 0.1 mm profiles .yearand- 1. Geologicalsocial-economic conditions resulted in the frequent occurrence of 106 cover, severe erosion processes and social-economic conditions resulted in the frequent occurrence of 2 106 cover, severe erosion processes and social-economic conditions resulted in the frequent111 (natural) occurrence erosion2 isstarting the 107 actionof in of 1946, wind,torrential water, and our ice investigationandfloods. gravity inErosion wearing confined away processes to the the soil mea- at a rate of smaller different categories of destruction are present in 76,355 km 107 torrential floods. Erosion processes of different categories of destruction are present in112 76,355 than 0.1 km mm.year -1surements (≤ 1002 m3·km of-2. upyear to-1). 2007.It is a relatively The study slow, area continuous (66 873 process km2) unlikecov- accelerated 107 torrential floods. Erosion processes of different Thecategories characteristics of destruction of the maximal are discharges present in in Serbian 76,355 km108 . -1 3 -2. -1 108 (86.4% territory of Serbia) in Serbia. The average annual production of erosive material in the113 territoryerosion, which of producesers the a rate central of soil(86.4% partloss higher of territory Serbia, than 0.1 south mm ofyear ofSerbia) the(> 100 rivers m in·km SavaSerbia.year and) due The to human average annual production of erosive material in the territory of 108 (86.4% territory6 of 3Serbia) in Serbia. The average3 annua-2torrentiall production watersheds were of erosive studied by material data114 processing inactivities the with (Kostadinov,territory 109 2008).of Serbia is 37.25·106 m3, in other words, 487.85 m3·km-2, which is 4.88 times more than the geological 109 Serbia is 37.25·10 m6 , in3 other words, 487.85 m ·km 3, which-2 is 4.88 times more than the115 geological Danube (Fig. 1). The ranges of values of the main physical 128 control profiles (Fig. 1), which were. equipped- 1 with au- . - 1 110109 (natural)Serbia erosion.is 37.25·10 The averagem , in rateother of words,soil formation 487.85 onm the·km slopes, which in Serbia is 4.88 is 0.1 times mm moreyear116 .than GeologicalSevere the and geological excessive erosion110 processes(natural) cover 35% erosion. of the territory The of Serbia average (IWRMJ rateČ, 2001). of Withsoil local formation on the slopes in Serbia is 0.1 mm year . Geological 110 (natural) erosion. The average rate of soil formation on the slopes in Serbia is 0.1 mm117 .yeareconomic- 1. Geologicaldevelopment, soil erosion becomes more frequent and severe (Ananda and Herath, 2003; 111 (natural) erosion is the action of wind, water, ice and gravity in wearing away the soil at 118a rateBakker smaller et al., 2005). 111The construction(natural) of roads erosion and residential is the areas action and the ofinappropriate wind, usewater, of ice and gravity in wearing away the soil at a rate smaller . -1 3 -2. -1 www.nat-hazards-earth-syst-sci.net/12/23/2012/ Nat. Hazards Earth. Syst.-1 Sci., 12, 23–335, 2012-2. -1 112111 than(natural) 0.1 mm erosionyear (is≤ the100 actionm ·km ofyear wind,). Itwater, is a relatively ice and gravityslow, continuous in wearing process away unlikethe 119soil accelerated agriculturalat a rate and smaller forest 112land contributethan to the0.1 concentr mmationyear of fast (≤ surface 100 runoff, m ·km as wellyear as sediment). It is a relatively slow, continuous process unlike accelerated . -1 3 -2. -1 . -1 3 -2. -1 120 transportation from the gravitating surfaces to the channel network. The roads interact positively with . -1 3 -2. -1 113112 erosion,than 0.1 which mm producesyear (≤ a 100rate mof ·kmsoil lossyear higher). It than is a 0.1relatively mm year slow, (> 100 continuous m ·km year process) 121due unlike toclear human cutting. accelerated They modify113 the hill erosion,slope flow paths which and cause produces faster delivery a ofrate the waterof soil to the losschannels higher than 0.1 mm year (> 100 m ·km year ) due to human . -1 3 -2. -1 114113 activitieserosion, (Kostadinov, which produces 2008). a rate of soil loss higher than 0.1 mm year (> 100 m ·km 122year during) due storm to events human with the conversion of the subsurface flow into surface flow (Jones and Grant, 1996). 123 Such flows contribute 20114 to 60 timesactivities more sediment (Kostadinov, (unsealed roads) than 2008). undisturbed forest surfaces and 115114 activities (Kostadinov, 2008). 124 about 10 times more sediment115 than harvested areas (Motha et al., 2003). Clear cutting and removal of the 116115 Severe and excessive erosion processes cover 35% of the territory of Serbia (IWRMJČ, 2001).125 Withvegetation local influence the water balance by affecting evapotranspiration and possibly snow accumulation 126 and melt. These activities116 increase Severe the peak discharge and excessive by as much as erosion 50% in small processes basins and 100% cover in 35% of the territory of Serbia (IWRMJČ, 2001). With local 117116 economicSevere and development, excessive erosionsoil erosion processes becomes cover more 35% frequent of the territoryand severe of Serbia(Ananda (IWRMJ and Herath,127Č , 2001).large 2003;basins With (Jones localand117 Post, 2004).economic Timber harvesting development, has the potential tosoil increase erosion the total flowbecomes and more frequent and severe (Ananda and Herath, 2003; 118 Bakker et al., 2005). The construction of roads and residential areas and the inappropriate128 lengthen use theof duration of larger flows while enabling sediment movement (Troendle and Olsen, 1994). 117 economic development, soil erosion becomes more frequent and severe (Ananda129 andSteep Herath, terrains without 2003; 118vegetation areBakker particularly et prone al., to increased2005). surface The runoff construction and erosion (Wipf of et roads and residential areas and the inappropriate use of 119 agricultural and forest land contribute to the concentration of fast surface runoff, as well as sediment 118 Bakker et al., 2005). The construction of roads and residential areas and the 130inappropriate al., 2005), like skiuse runs 119 ofwith decreasedagricultural surface roughness and and forest increased landvelocity contribute of runoff and sediment to the concentration of fast surface runoff, as well as sediment 120 transportation from the gravitating surfaces to the channel network. The roads interact positively131 yield (Fattorini, with 2001; Freppaz et al., 2002; Ristić et al, 2011b). 119 agricultural and forest land contribute to the concentration of fast surface runoff,132 as well as sediment120 transportation from the gravitating surfaces to the channel network. The roads interact positively with 121 clear cutting. They modify the hill slope flow paths and cause faster delivery of the water to the channels 120 transportation from the gravitating surfaces to the channel network. The roads interact133 2. TORRENTIALpositively FLOODSwith IN SERBIA 122 during storm events with the conversion of the subsurface flow into surface flow (Jones and134 Grant, 1996). 121 clear cutting. They modify the hill slope flow paths and cause faster delivery of the water to the channels 121 clear cutting. They modify the hill slope flow paths and cause faster delivery of the 135water 2.1. to Characteristics the channels of maximal discharges in Serbian torrential watersheds 123 Such flows contribute 20 to 60 times more sediment (unsealed roads) than undisturbed forest surfaces and 122 during storm events with the conversion of the subsurface flow into surface flow (Jones and Grant, 1996). 122 during storm events with the conversion of the subsurface flow into surface flow (Jones136 and Grant, 1996). 124 about 10 times more sediment than harvested areas (Motha et al., 2003). Clear cutting and removal137 The characteristicsof the of 123the maximal Such discharges flows in Serb contributeian torrential 20watersheds to 60 were times studied more by data sediment (unsealed roads) than undisturbed forest surfaces and 123 Such flows contribute 20 to 60 times more sediment (unsealed roads) than undisturbed138 forestprocessing surfaces with 128 andcontrol profiles (Fig. 1), that were equipped with automatic water-level recorders 125 vegetation influence the water balance by affecting evapotranspiration and possibly snow 139accumulation (Ristić et al., 2011c).124 The observationabout system 10 timeswas under more the supervisionsediment of thanthe Republic harvested Hydro areas (Motha et al., 2003). Clear cutting and removal of the 126124 andabout melt. 10 These times activities more sediment increase than the peakharvested discharge areas by (Motha as much et al.,as 50% 2003). in smallClear basinscutting140 and and Meteorological100% removal in Office of the125of Serbia (RHMOS).vegetation At most influence profiles measurements the water started inbalance 1953, with bya few affectin g evapotranspiration and possibly snow accumulation 141 profiles starting in 1946, and our investigation is confined to the measurements of up to 2007. The study 127125 largevegetation basins (Jonesinfluence and thePost, water 2004). balance Timber by harvesting affecting hasevapotranspiration the potential to increaseand possibly the total142 snow areaflow (66,873accumulation and km 2) covers126 the centraland part melt. of Serbia, These south of activitiesthe rivers Sava increase and Danube the(Fig. 1).peak The discharge by as much as 50% in small basins and 100% in 128126 lengthenand melt. the Theseduration activities of larger increase flows whilethe peak enab dischargeling sediment by asmovement much as (Troendle 50% in smalland 143Olsen, basins ranges 1994). and of values 100% of the127 mainin physicallarge characteristics basins of (Jonesthe investigated and watersheds Post, 2004).are presented Timber in table harvesting has the potential to increase the total flow and 144 1. The recorded maximal discharges were the consequence of the fast surface runoff generated in the 129127 Steeplarge terrains basins without(Jones vegetationand Post, are2004). particularly Timber proneharvesting to increased has the surface potential runoff to andincrease erosion145 the following(Wipf total ways: etflow short and 128intensive rain,lengthen long less intensiv the eduration rain and snow of melt larger and the coincidenceflows while of rain enabling sediment movement (Troendle and Olsen, 1994). 130128 al.,lengthen 2005), likethe skiduration runs with of largerdecreased flows surface while roughness enabling and sediment increased movement velocity of(Troendle runoff146 and and andsediment snowOlsen, melt. The1994). torrential floods in Serbia can be caused in all the above mentioned ways, but it is 147 possible to recognize 129the dominantSteep way interrains certain watersheds. without The vegetation number of extreme are particularlyevents in prone to increased surface runoff and erosion (Wipf et 131129 yieldSteep (Fattorini, terrains 2001; without Freppaz vegetation et al., 2002; are particularly Ristić et al, prone2011b). to increased surface runoff 148and individualerosion months (Wipf (maximal130 et dischargeal., 2005),Qmax over likethe referential ski runs threshold with Q maxsrdecreased, Qmax> Qmaxsr surface) was roughness and increased velocity of runoff and sediment 132130 149 analyzed for all the observed years. The average maximal discharge Qmaxsr was determined as the mean al., 2005), like ski runs with decreased surface roughness and increased velocity of150 runoff value andof all thesediment recorded131 annual maximalyield discharges (Fattorini, Qmaxi in the2001; observed Freppaz years N. et al., 2002; Ristić et al, 2011b). 133131 2.yield TORRENTIAL (Fattorini, 2001; FLOODS Freppaz IN SERBIA et al., 2002; Ristić et al, 2011b). 151 132 134 N 132 ∑Qmaxi 133 2. TORRENTIAL FLOODS IN SERBIA 135 2.1. Characteristics of maximal discharges in Serbian torrential watersheds 152 Q = i=1 133 2. TORRENTIAL FLOODS IN SERBIA max sr N 134 136 134 153 Qmaxsr – the mean value135 of all the recorded2.1. Characteristicsmaximal discharges Qmaxi inof the maximal observed years dischar N ges in Serbian torrential watersheds 137 The characteristics of the maximal discharges in Serbian torrential watersheds were studied by data 135 2.1. Characteristics of maximal discharges in Serbian torrential watersheds 136 138 processing with 128 control profiles (Fig. 1), that were equipped with automatic water-level recorders 4 136 139 (Ristić et al., 2011c). The observation system was under the supervision of the Republic Hydro 137 The characteristics of the maximal discharges in Serbian torrential watersheds were studied by data 140137 MeteorologicalThe characteristics Office of Serbiathe maximal (RHMOS). discharges At most inprofiles Serb ianmeasurements torrential watershedsstarted in 1953, were with studied a few by data138 processing with 128 control profiles (Fig. 1), that were equipped with automatic water-level recorders 141138 profilesprocessing starting with in 1946,128 control and our profilesinvestigation (Fig. is 1), conf thatined we tore the equipped measurements with automaticof up to 2007. water-level The study recorders 139 (Ristić et al., 2011c). The observation system was under the supervision of the Republic Hydro 142139 area(Risti (66,873ć et al.,km2 )2011c). covers theThe central observation part of Serbia,system south was of under the rivers the Savasupervision and Danube of the(Fig. Republic 1). The Hydro140 Meteorological Office of Serbia (RHMOS). At most profiles measurements started in 1953, with a few 143140 rangesMeteorological of values of Office the main of physicalSerbia (RHMOS). characteristics At ofmost the investigatedprofiles measurements watersheds arestarted presented in 1953, in table with a few141 profiles starting in 1946, and our investigation is confined to the measurements of up to 2007. The study 2 144141 1.profiles The recorded starting maximal in 1946, discharges and our investigationwere the conseque is confnceined of tothe the fast measurements surface runoff of generated up to 2007. in the The study142 area (66,873 km ) covers the central part of Serbia, south of the rivers Sava and Danube (Fig. 1). The 2 145142 followingarea (66,873 ways: km short) coversintensive the rain, central long partless ofintensiv Serbia,e rain south and ofsnow the meltrivers and Sava the coincidenceand Danube of (Fig. rain 1). The143 ranges of values of the main physical characteristics of the investigated watersheds are presented in table 146143 andranges snow of melt. values The of torrential the main floods physical in Serbia characteristics can be caused of the in investigatedall the above watersheds mentioned ways,are presented but it is in table144 1. The recorded maximal discharges were the consequence of the fast surface runoff generated in the 147144 possible1. The torecorded recognize maximal the dominant discharges way were in certain the conseque watersheds.nce ofThe the number fast surface of extreme runoff eventsgenerated in in the145 following ways: short intensive rain, long less intensive rain and snow melt and the coincidence of rain 148145 individualfollowing months ways: short(maximal intensive discharge rain, Qlongmax overless intensivthe referentiale rain andthreshold snow meltQmaxsr and, Qmax the> coincidenceQmaxsr) was of rain146 and snow melt. The torrential floods in Serbia can be caused in all the above mentioned ways, but it is 149146 analyzedand snow for melt.all the The observed torrential years. floods The averagein Serbia maximal can be discharge caused in Q allmaxsr the was above determined mentioned as the ways, mean but it147 is possible to recognize the dominant way in certain watersheds. The number of extreme events in 150 value of all the recorded annual maximal discharges Qmaxi in the observed years N. 147 possible to recognize the dominant way in certain watersheds. The number of extreme events 148in individual months (maximal discharge Qmax over the referential threshold Qmaxsr, Qmax> Qmaxsr) was 151 148 individual months (maximal discharge Qmax over the referential threshold Qmaxsr, Qmax> Qmaxsr) was149 analyzed for all the observed years. The average maximal discharge Qmaxsr was determined as the mean N 149 analyzed forQ all the observed years. The average maximal discharge Qmaxsr was determined as the mean150 value of all the recorded annual maximal discharges Qmaxi in the observed years N. 150 value of∑ all themax irecorded annual maximal discharges Q in the observed years N. 151 152 Q = i=1 maxi 151 max sr N N N Q 153 Qmaxsr – the mean value of all the recorded maximal discharges Qmaxi in the observed years N ∑ maxi Q i=1 ∑ maxi 152 Qmax sr = i=1 N 152 Qmax sr = 4 N 153 Qmaxsr – the mean value of all the recorded maximal discharges Qmaxi in the observed years N 153 Qmaxsr – the mean value of all the recorded maximal discharges Qmaxi in the observed years N 4 4 5 500 [m3.s-1] Number of extreme events (Qmax>Qmaxsr) 450 Qmaxa

4 400 26 R. Ristic´ et al.: Torrential ﬂoods and town and country planning in Serbia Profile: Orćuša 350 River: Plavska 2 53 A=252 km 500300 N=61 3. -1 [m s ] Number of extreme events (Qmax>Qmaxsr) 3. -1 Qmaxsr=50.87 m s 450250 3. -1 Qmaxa Qmaxa=380.0 m s 42 400200 Maximal discharge QmaxII Q V maxProfile: Orćuša 350150 Number of extreme events QmaxXII QmaxI River: Plavska 2 31 A=252 km 300100 N=61 QmaxVI 3. -1 Qmaxsr=50.87 m s 25050 3. -1 Qmaxa=380.0 m s 20 2000 I II III IV V VI VII VIII IX X XI XII Maximal discharge QmaxII QmaxVMonth 150 Number of extreme events 171 Q I QmaxXII 172 Fig. 2. Themax Orćuša Profile, the Plavska River; the number of extreme events (Q >Q ) per month; 1 max maxsr 100

173 monthly maximal discharges andQmax VIabsolute maximal discharge 174 (the profile location is presented in Fig. 1) 50 175 176 0 0 177 I II III IV V VI VII VIII IX X XI XII 178 Month 171179 The relationship between the maximal discharges is represented by a power function (Fig. 3): 172180 Fig. 2. The Orćuša Profile, the Plavska River; the number of extreme events (Qmax>Qmaxsr ) per month; Fig. 2. The173 Or cuša´ Proﬁle, the Plavskamonthly River; the maximal number discharges of extreme and events absolute (Qmax maximal>Qmax discharge sr) per month; monthly maximal discharges and 181 Q = 3.143 ⋅ Q 1.031 absolute maximal174 dischargemax a (the proﬁlemax sr location is(the presented profile location in Fig. 1). is presented in Fig. 1) 175182 176 177 10000 Q [m3.s-1] 178 maxa 179 The relationship between the maximal discharges is represented by a power function (Fig. 3): 180 1000 1.031 181 Qmax a = 3.143 ⋅ Qmax sr 182

10000 3. -1 Qmaxa [m s ] 100

Qmaxa=3.143Q 1.031 1000 maxsr R=0.886

Absolute maximal discharge 10

W.Morava Ibar G.Morava Vardar Drina

100 Kolubara Struma S.Morava Dunav W.Drim 3. -1 Qmaxsr [m s ] 1 1.031 1 10 100Qmaxa=3.143Qmaxsr 1000 Average maximal discharge R=0.886

183 Absolute maximal discharge 10 184 Fig. 3. Relation Qmaxa=f(Qmaxsr) Fig. 3. Relation Qmax a = f(QmaxW.Morava sr). Ibar G.Morava Vardar Drina 6 Kolubara Struma S.Morava Dunav W.Drim 3. -1 Qmaxsr [m s ] characteristics of the investigated1 watersheds are presented threshold Qmax sr,Qmax > Qmax sr) was analyzed for all the 1 10 100 1000 in Table 1. The recorded maximal discharges were the con- observed years. The average maximal discharge Qmax sr was Average maximal discharge sequence183 of the fast surface runoff generated in the following determined as the mean value of all the recorded annual max- ways: short184 intensive rain, long less intensive rainFig. and 3. snowRelation Qmaxaimal=f(Q dischargesmaxsr) Qmax i in the observed years N. melt, and the coincidence of rain and snow melt. The torren- N 6 tial ﬂoods in Serbia can be caused in all the above mentioned P Qmax i ways, but it is possible to recognize the dominant way in i=1 Q = certain watersheds. The number of extreme events in indi- max sr N vidual months (maximal discharge Qmax over the referential

Nat. Hazards Earth Syst. Sci., 12, 23–35, 2012 www.nat-hazards-earth-syst-sci.net/12/23/2012/ R. Ristic´ et al.: Torrential ﬂoods and town and country planning in Serbia 27

Table 1. The ranges of values of the main physical characteristics of the investigated watersheds.

Parameter Min. value Max. value A-drainage area [km2] 10 1268 L-the length of main channel [km] 6.4 93.2 Pp-peak point [m.a.s.l] 452 2017 Cp-conﬂuence point [m.a.s.l] 87 986 Sa-main channel slope [%] 0.76 7.84 Sw-weighted slope of main channel [%] 0.26 4.66 Sm-mean watershed slope [%] 8.98 45.70 Lc-the shortest distance from conﬂuence point to watershed centroid [km] 3.4 46.5 Wm-mean width of the watershed [km] 1.32 19.40

Table 2. Basic characteristics of the reconstructed torrential ﬂoods.

Water course Proﬁle Date of A Qmax qmax sp Precipitation duration appearance [km2] [m3×s−1] [m3×s−1×km−2] / Mean intensity 1–Lještarska Vladicin` Han 25.07.1982 2.64 16.16 6.12 90 min; 1.17 mm min −1 2–Kalimanska Vladicin` Han summer 1929 16.04 149.0 9.30 / 3–Sejanicka` Grdelica 02.07.1983 12.51 62.75 5.02 90 min; 1.01 mm min −1 4–Manastirica Breždje 13.06.1996 29.5 154.9 5.25 180 min; 0.75 mm min −1 5–Ribnica Paštric´ 13.06.1996 104 418.08 4.02 180 min; 0.75 mm min −1 6–Kamišna Mokra Gora 27.05.2007 26.94 76.3 2.83 120 min; 0.83 mm min −1 7–Vlasina Vlasotince 26.06.1988 972 780 0.80 240 min; 0.34 mm min −1

– Qmax sr – the mean value of all the recorded maximal Morava River, the West Morava River, the Ibar River, the discharges Qmax i in the observed years N, Kolubara River, the White Drim River, the Vardar River and the Struma River). In this period, the high water levels were the result of intensive rainfall of a few-hours duration. The – Q – the recorded maximal discharge in the observed max i daily and monthly maximums of precipitation were recorded year (annual maximum), at almost all the rain-gauge stations in Serbia in the period from May to June. The period from February to the first – N – the number of observed years, half of March was noted as the secondary maximum. The absolute maximal values of discharge Qmax a were recorded in the periods with frequent extreme events at most profiles. – Qmax a – the absolute recorded maximal discharge, and However, the values of Qmax a were also recorded in the periods with rare extreme events at some profiles, as a conse-

– QmaxI-XII – the recorded maximal discharges in certain quence of specific climate and hydrological conditions in- months. cluding: a sudden rise in air temperature during the winter that caused snow melt and often coincided with a long The analysis of the intra-annual distribution of maximal dis- low intensity rain; snow precipitation at the end of winter charge allowed the indication of critical parts of the year followed by a sudden rise in air temperature and fast melt- with frequent appearances of extreme events. According to ing; along with a few sequential rain events during the sum- this analysis, the appearance of maximal discharges in tor- mer that caused a reduction of infiltration and water stor- rential watersheds has a seasonal character. In other words, age capacity of the soil. The intra-annual distribution of the number of extreme events is larger in certain parts of the maximal discharges combined with the number of ex- the year. The critical periods are the end of spring (from treme events are presented in diagrammatic form (Fig. 2). May to the first half of June) and the end of winter (from Each diagram contains: the names of the profile and the February to the first half of March). The period from May river, the size of the watershed A, the number of observation to the first half of June was marked as the primary maxi- years N, the average maximal discharge Qmax sr, the absolute mum in most watersheds (the Great Morava River, the South www.nat-hazards-earth-syst-sci.net/12/23/2012/ Nat. Hazards Earth Syst. Sci., 12, 23–35, 2012 28 R. Ristic´ et al.: Torrential floods and town and country planning in Serbia

2 maximal discharge Qmax a and the number of extreme events the watersheds ranging from A = 1 to A = 10 km , with the (y axes in Fig. 2) in individual months. Also, the recorded remit of reconstruction of extreme hydrologic events using maximal discharges QmaxI-XII in individual months are the “hydraulics flood traces” method. presented (e.g. Fig. 2: the recorded maximal discharge 3 −1 3 1 was QmaxI = 60.5 m s in January, QmaxII = 123 m s- in 3 −1 3 −1 February, QmaxV = 97.9 m s in May, QmaxVI=52.9 m s 3 State of the art in the erosion and torrent control 3. −1 in June and QmaxXII = 60.5 m s in December). All the in Serbia 3 1 monthly maximums overpass Qmax sr=50.87 m s- . The largest number of extreme events Qmax >Qmax sr, i.e. 4 oc- 3.1 Erosion and torrent control works currences, were recorded in May; and the absolute maximal 3 −1 discharge Qmax a of 380 m s was recorded in November. The erosion and torrent control works (ETCWs) in Europe The relationship between the maximal discharges is repre- started around the middle of the 19th century. They started sented by a power function (Fig. 3): at the end of 19th century in Serbia but began as an orga- nized activity in 1907. In the period from 1907 to 2006, sig- Qmax a = 3.143×Qmax sr (1) nificant scope of works were performed (Kostadinov, 2007), including technical works (1 501 656 m3-check dams, bank 2.2 Historical cases of torrential floods reconstructed by protective structures, torrent training) and biotechnical works the “hydraulics flood traces” method (120 987 ha-afforestation, forest protective belts, silt-filtering strips, grassing, terracing and contour farming). Some of the more interesting events of historic torrential In the period from 1961 to 1988, there was the greatest floods are presented in Table 2, showing their basic charac- scope of the ETCWs. The average amount of funds allocated teristics. The sizes of the investigated watersheds range from for that purpose was 9.68×106 Cper yr. The dynamics of the A = 2.64 km2 to A = 972 km2. The discharges per unit area works performed from 1994 to 2000 was accompanied by a are presented in a diagram (Fig. 4). The main characteristics large drop of funding (on average 0.248×106 Cper yr), as a of the presented events are: the steepness of the torrent beds, result of the weakening of the economy, the falling apart of with a main Sa=5.74–13.45 % channel slope; huge parts of the former Yugoslavia and the war. From 2002 to 2007, the the watersheds occupied by bare lands, degraded forests and amount of money invested in ETCWs was 1.045×106 Cper agricultural land; shallow, skeletal soil with a low infiltra- yr (Ristic´ and Nikic,´ 2007). According to the Basic Plan of tion capacity; excessive erosion processes; the duration of Water Resources Management of Serbia (IWRMJC,` 2001), rain events that range from 90 to 240 min; and the inten- it is necessary to perform ETCWs on an area of 43 700 ha sity that has a range of I = 0.34 to I = 1.17 mm × min−1 (340– and technical works on a volume of 344 314 m3 in the next 1170 m3× km−2). The consequence of these characteristics 20 yr. By 2050, biotechnical works are planned on an area was the sudden appearance of torrential floods and a high of 160 100 ha and the volume of planned technical works content of sediment and destructivity. reaches 1 357 700 m3. This requires an investment of about The value of the maximal discharge is the basic input 18.7×106 Cper yr. The priority is the protection of settle- data for the design of protective structures in torrential beds ments and road networks from torrential floods and erosion (check-dams, overflows, regulations). The determination of control in watersheds of water supply system reservoirs. the maximal discharge in a torrential watershed requires a The most significant investor in erosion and torrent con- careful approach as we must bear in mind some specific control in Serbia is the State-owned company “Serbian Waters”. ditions, including the steepness of the slopes of the terrain There are no developed concepts in the field of agriculture and the torrent bed, the fast concentration of runoff and the for sustainable use of land on slopes with an erosion con- transport of huge quantities of sediment. Hydrologic prac- trol function. The State-owned company “Serbian Forests” titioners in Serbia use a control model known as “curves of performs afforestation, but not with the emphasis on erosion maximal discharges per unit area” for the calculated values and torrent control. The Directorate for Forests (within the of the maximal discharges in watersheds ranging from 10 to Ministry of Agriculture, Forests and Water Resources Man- 100 000 km2 (Jankovic´ and Maloševic,´ 1989). The model is agement) treats the problem of erosion control as a minor based on statistical processing of the recorded data on max- issue. The State-owned company “Serbian Waters” has ju- imal discharges observed for more than 30 yr. However, the risdiction over all water streams in a territory of 55 953 km2 interval for watersheds A < 10 km2 has not been defined due and “Serbian Forests” manage 19 083 km2(9057 km2 of state to the lack of control profiles in small watersheds within the forests and 10 026 km2 of private forests). However, there RHMOS observation system. Because they are created by are no examples of joint activity in the protection from ero- graphic interpolation, the curves of maximal discharges per sion and torrential floods. Paradoxically, although the above unit area (Fig. 4) are not reliable for the A = 1–10 km2 in- three areas belong to the same ministry, there is no cooper- terval. This served as the source of our motivation to start ation among them on a horizontal level. Even though large collecting the data on maximal discharges per unit area in hydropower systems are highly vulnerable to the deposition

Nat. Hazards Earth Syst. Sci., 12, 23–35, 2012 www.nat-hazards-earth-syst-sci.net/12/23/2012/ 185 186 2.2. Historical cases of torrential floods reconstructed by the „hydraulics flood traces“ method 187 188 Some of the more interesting events of historic torrential floods are presented in table 2, showing their 189 basic characteristics. The sizes of the investigated watersheds range from A=2.64 km2 to A=972 km2. The 190 discharges per unit area are presented in a diagram (Fig. 4). The main characteristics of the presented 191 events are: the steepness of the torrent beds, with a main Sa=5.74-13.45% channel slope; huge parts of the 192 watersheds occupied by bare lands, degraded forests and agricultural land; shallow, skeletal soil with a 193 low infiltration capacity; excessive erosion processes; the duration of rain events that range from 90 to 194 240 minutes and the intensity that has a range of I=0.34 to I=1.17 mm·min-1 (340-1170 m3·km-2). The 195 consequence of these characteristics was the sudden appearance of torrential floods and a high content of 196 sediment and destructivity. 197 198 The value of the maximal discharge is the basic input data for the design of protective structures in 199 torrential beds (check-dams, overflows, regulations). The determination of the maximal discharge in a 200 torrential watershed requires a careful approach as we must bear in mind some specific conditions, 201 including the steepness of the slopes of the terrain and the torrent bed, the fast concentration of runoff and 202 the transport of huge quantities of sediment. Hydrologic practitioners in Serbia use a control model 203 known as “curves of maximal discharges per unit area” for the calculated values of the maximal 204 discharges in watersheds ranging from 10 to 100,000 km2 (Janković and Malošević, 1989). The model is 205 based on statistical processing of the recorded data on maximal discharges observed for more than 30 206 years. However, the interval for watersheds A<10 km2 has not been defined due to the lack of control 207 profiles in small watersheds within the RHMOS observation system. Because they are created by graphic 208 interpolation, the curves of maximal discharges per unit area (Fig. 4) are not reliable for the A=1-10 km2 209 interval. This served as the source of our motivation to start collecting the data on maximal discharges per 210 unit area in the watersheds ranging from A=1 to A=10 km2 with the remit of reconstruction of extreme R. Risti211c´ et al.:hydrologic Torrential events ﬂoods using and the town„hydraulics and countryflood traces” planning method. in Serbia 29 212 100 ]

-2 Tr=50 years

km Tr=100 years -1.

s Tr=1000 years 3. Tr=10000 years q [m 2 10

1 3 4 5 6

1 7 Maximal discharge per unit area

A [km2] 0.1 1 10 100 1000 10000 Size of the watershed 213 214 Fig. 4. Maximal discharges per unit area for some extreme events (1-The Lještarska River; 2-The Fig. 4. 215Maximal dischargesKalimanska per River; unit area 3-The for Sejani someč extremeka River; events 4-The (1–The Manastirica Lještarska River; River; 5-The 2–The Ribnica Kalimanska River; 6-The River; 3–The Sejanickaˇ River; 4–The216 ManastiricaKamišna River; 5–The River; Ribnica 7-The River;Vlasina 6–The River);The Kamišna locations River; 7–The of profiles Vlasina are River).presented The in locations Fig. 1 of profiles are presented in Fig. 1217 218 . 219 of eroded material during torrential floods, the Ministry of “The Forest Law”, 1974; “The Railway Law”, 1975; “The Infrastructure and Energetics does not recognize the need for Law on Security in Railway Traffic”, 1977; and7 “The Min- erosion and torrent control. ing Law”, 1978. “The Water Law” passed in 1975 was the most complete legal regulation regarding erosion and torrent 3.2 Serbian and Yugoslav legislation in the field of control. Some of its particularly interesting provisions stipu- erosion and torrent control lated that any works of a large scale (dams, roads, etc.) could not be performed without previous projects and special funds Until 1930, in the Kingdom of Yugoslavia there were no provided for erosion and torrent control (by “self-managing regulations or legislation in the field of erosion and torrent communities of interest”, following the principles of solidar- control. However, ECTWs were performed during that pe- ity and mutual assistance). The structures for erosion and riod on the basis of the existing regulations from the period torrent control were classified as protective structures and put of Austria-Hungary, the Kingdom of Serbia and the King- in line with other water management structures, i.e. classified dom of Montenegro (Kostadinov et al., 1999). The “Law as water management activities of special social interest. of Torrent Control” was passed in 1930. It was the first Erosion and torrent control problems were dealt with in law which provided the definitions of torrent and watershed, later Water Laws passed in 1989 and 1991 (OG-The Offi- as well as some system resolutions of torrential control fi- cial Gazette of the Republic of Serbia, No. 46/1991) and nancing. The first regulation after the Second World War 2010 (OG, No. 30/2010). It can be argued that, in com- was passed in 1952 named “The Law on the protection of parison with the previous Water Laws, the latest Laws, es- soil from leaching and rockslides in the region of Grdelickaˇ pecially “The Water Law” passed in 2010, represent a step Gorge and Vranjska Valley”. A step further was “The Law backwards. Namely, the issues of erosion and torrent control on Erosion and Torrent Control” that was passed in 1954, are mentioned in only a few Articles. The regulations of the which enabled the performing of erosion control works on Law regarding erosion and torrent control are enforced and the land threatened by erosion, irrespective of the ownership applied by municipal authorities, which often have no orga- of the land. nizational or financial capabilities to execute the Law. In the period 1965–1978, no specific laws regarding the issues of Erosion and Torrent Control were brought, and any issues were partially regulated by other laws, including “The Water Law”, 1967, 1975; “The Law on Agricultural Land Use”, 1965, 1974; “The Law on Capital Construction”, 1973; www.nat-hazards-earth-syst-sci.net/12/23/2012/ Nat. Hazards Earth Syst. Sci., 12, 23–35, 2012 30 R. Ristic´ et al.: Torrential floods and town and country planning in Serbia

4 Town and country planning as a tool for mitigation of characteristically with steep downhill, influences the devel- the impacts of torrential floods opment of infrastructure and residential areas in the proximity of streams and exposes them to the destructiveness of Water resource planning in Serbia is one of the most im- torrential floods. Municipalities are required to make PAERs portant aspects of spatial planning, especially in the fields and PPTFs, applying methodology prescribed by the Min- of flood protection and environmental protection. The har- istry of Agriculture, Forestry and Water Resources Manage- monization of the national legislation with European Union ment (1998). PAERs enable implementation of erosion con- directives introduced the obligation to produce flood haz- trol measures to the level of cadastre parcels in order to re- ard maps, flood risk maps and flood risk management plans strain further soil degradation caused by inadequate land use. within “The Water Law” passed in 2010. However, more de- The technical basis for determination of HZs on a municipal tailed methodological recommendations for developing such territory are identified and declared “erosion zones” (soil sur- plans were not defined by this law. Although the latest Ser- face overtaken by apparent processes of erosion or without bian Water Law accepted the basic principles of the “Direc- apparent erosion, which might occur due to a change in land tive 2007/60/EC on the assessment and management of flood use). Land owners or users are obliged to apply the following risks” (Official Journal of the European Union, 6 Novem- measures: administrative restrictions (straight row farming ber 2007), its shortcoming is the lack of a classification of down the slope, clear cuttings on slopes, grazing on eroded various flood types. The Serbian Water Law identifies only surfaces) and mandatory practices (contour or terrace farm- river floods, whereas the Directive 2007/60/EC lists several ing, conversion of crop fields into grass fields, reclamation types of floods, including river floods, flash floods, urban of degraded pastures, afforestation of bare land, conversion floods and sea floods in coastal areas (pg. 28, paragraph 10). of annual to perennial crops, limited and controlled cutting). Flood protection in the Republic of Serbia is at a satisfac- PPTFs enable the determination of a flood extent and endan- tory level on big rivers (the Danube, the Sava, the Drina, the gered sections in riparian zones, maximal discharge and wa- Great Morava, etc), with 29 large surface reservoirs, more ter depth. Also, PPTFs oblige municipal authorities to make than 3550 km of embankments and numerous river regula- appropriate action plans with precisely defined responsible tions (Republic Agency for Spatial Planning, 2010). How- persons, other participants and activities if a torrential flood ever, a large number of settlements, infrastructure systems, occurs. PPTFs prescribe a ban on the construction of resi- industrial plants as well as huge surfaces of agricultural land dential and infrastructure objects in flood zones. are endangered by torrents, so it is very important to create The design of such practices is explored through a case legal, spatial planning and technical documents in order to study of the experimental watershed of the Manastirica River, predict hazards and provide adequate protection measures. which experienced a catastrophic torrential flood in June Effective torrential watershed management (ETWM) is l996. This investigation is also concerned with the analysis evaluated by maximum safety, avoidance or mitigation of of impacts (erosion and torrential floods) under the actual and damages, environmental protection and support of local sus- planned conditions of the watershed (after restoration). The tainable economic development. One of the most important planned restoration works involve biotechnical (reforestation segments of ETWM is watershed restoration to its optimal of eroded or abandoned arable land, forest protective belts, hydrologic state in order to reduce flood discharge and enrich silt filtering strips, contour farming and terracing), technical both low flow and average discharges in springs and streams (check dams and torrent training works) and administrative by increasing groundwater recharge. Restoration of torren- measures prescribed through PAERs and PPTFs. The con- tial watersheds involves biotechnical works on slopes and sequences of land use changes were analyzed on the basis technical works in the channel network, coordinated within a of field investigations, usage of aerial and satellite photo im- precisely defined administrative and spatial framework. Co- ages, topographic, geological and soil maps. The land use operation and overcoming of conflicts between the sectors of classification was made on the basis of the CORINE method- water resources management, forestry, agriculture, energet- ology (EEA, 1994). Area sediment yields and the inten- ics, environmental protection and local economic develop- sity of erosion processes were estimated on the basis of the ment are indispensable at the following levels: policy, spatial “Erosion Potential Method” (EPM). This method was cre- planning, practice, investments and education. ated, developed and calibrated in Serbia (Gavrilovic,´ 1972) The lowest and the most effective level of planning and it is still in use in all the countries that originated from is through Plans for Announcement of Erosive Regions the former Yugoslavia. The historical maximal discharge (PAERs) and the Plans for Protection from Torrential Floods (Qmaxh) was reconstructed by the “hydraulics flood traces” (PPTFs), with Hazard Zones (HZs) and Threatened Areas method (Ristic´ et al., 1997b). The determination of maximal (TAs) mapping. HZs are sources of impacts (fast surface discharge (Qmax c), under hydrological conditions after the runoff and sediment) and TAs are locations under the in- restoration of the watershed, was performed using a synthetic fluence of impacts. TAs in most torrential watersheds in unit hydrograph theory and Soil Conservation Service (SCS) Serbia are located in the downstream sections within set- methodology (SCS, 1979; Chang, 2003). This is the most tlement zones. The morphology of narrow torrent valleys, frequently used procedure in Serbia for the computation of

Nat. Hazards Earth Syst. Sci., 12, 23–35, 2012 www.nat-hazards-earth-syst-sci.net/12/23/2012/ R. Ristic´ et al.: Torrential ﬂoods and town and country planning in Serbia 31

Fig. 5. HZ (Hazard Zones), TA (Threatened Areas) and LU (Land use) in the watershed of the Manastirica River: 1 – Discontinuous urban fabric; 2 – Broad-leaved forest; 3 – Coniferous forests; 7 – Natural grasslands; 8 – Complex cultivation patterns; 9 – Pastures; 10 – Land principally occupied by agriculture, with significant areas of natural vegetation (location of the watershed is presented in Fig.1-point 4). maximal discharges at small, ungauged watersheds, enriched road system. The TA of the Manastirica River watershed is by a regional analysis of lag time (Ristic,´ 2003), internal positioned on the downstream section, at the watershed out- daily distribution of precipitation (Jankovic,´ 1994) and clas- let, in the zone of the village of Breždje (Fig. 5). The tor- sification of soil hydrologic classes (Djorovic,´ 1984). The rent valley is narrow (on average 200 m), with a steep slope data on the maximal daily precipitation was provided by the downhill (about 35 %) and more than 200 houses, roads and RHMOS observation system (1945–2010). infrastructure systems (water supply, electric power supply and sewer) in the proximity of the Manastirica River (some HZs on the Manastirica River watershed (Fig. 5) occupy houses are just 15–20 m away from the torrent bed). The vil- 32.68 % of the total area (9.78 km2), while the TA occupies lage of Breždje was flooded in June l996, after heavy rain 1.34 % of the total area (0.4 km2). HZs involve settlements, of 135 mm, which lasted for 3 h. Almost 130 hectares of access roads, degraded pastures and arable land on slopes land and 37 buildings were flooded (out of which 15 were (surfaces marked 1, 8, 9, 10; on Fig. 5) as the most signif- severely damaged), 14 km of roads were damaged or blocked icant sources of sediment and fast surface runoff. The soil and 140 inhabitants were evacuated. The discharge into the in HZs is eroded, compacted and characterized by a reduced Manastirica River increased 815 times, from Q = 0.19 m3 s−1 3 −1 water storage capacity. The construction of roads and houses to QmaxhMan−1996 = 154.9 m s . The water level increased in settlements, inappropriate use of agricultural land (straight from 30–40 cm to 6.2 m (Ristic´ et al., 1997b). raw farming, overgrazing) and forestry activities (clear cutting, removal of timber) enforce the intensity of erosion pro- The realization of restoration works will help cesses, fast surface runoff and sediment transport. The trans- decrease annual yields of erosive material from 3 3 −2 3 fer of impacts from HZs occurs on steep slopes and through Wa=24 357 m (825.7 m ×km ) to Wa=16 198 m the torrent beds of the Manastirica River and its tributaries, (549.1 m3× km−2). The effects of hydrological changes with the following effects: development of erosion (sheet were estimated through the comparison of the histor- erosion, furrows, gullies, etc.), transport of sediment, fast ical maximal discharge and the computed maximal concentration of surface runoff, flood wave formation, flood- discharge (under the conditions after the planned restora- ing of riparian zones, demolishing of houses and bridges, fill- tion). The value of the historical maximal discharge 3 −1 ing of road culverts with sediment, and destruction of the (QmaxhMan = 154.9 m × s ) is significantly decreased after www.nat-hazards-earth-syst-sci.net/12/23/2012/ Nat. Hazards Earth Syst. Sci., 12, 23–35, 2012 364 Conservation Service (SCS) methodology (SCS, 1979; Chang, 2003). This is the most frequently used 365 procedure in Serbia for the computation of maximal discharges at small, ungauged watersheds, enriched 366 by a regional analysis of lag time (Ristić, 2003), internal daily distribution of precipitation (Janković, 32367 1994) and classification of soil hydrologic R. Ristic´ classes et al.: (Djorovi Torrentialć, 1984). floods The and data townon the and maximal country dailyplanning in Serbia 368 precipitation was provided by the RHMOS observation system (1945-2010). 369 180 ] -1

s 3. -1

3. Q =154.9 m s 160 maxhMan-1996

Q [m QmaxhMan-1996 140 QmaxcMan

120

3. -1 QmaxcMan=84.5 m s 100

80 Discharge

t [h] 0 0 1 2 3 4 5 6 7 8 9 10111213141516171819 Time 370 371 Fig. 6. Historical (QmaxhMan-1996) and computed (QmaxcMan) hydrographs of maximal discharges on the Fig. 6. Historical372 (QmaxhMan−1996) and computed (QmaxcManManastirica) hydrographs River of maximal discharges on the Manastirica River. 373 374 HZs on the Manastirica River watershed (Fig. 5) occupy 32.68% of the total area (9.78 km2), while the 2 375 TA occupies 1.34%3× − of1 the total area (0.4 km ). HZs involve settlements, access roads, degraded pastures restoration (Q376max cManand =84.5arable land m ons slopes), which (surfaces indicates marked 1, an 8, 9, 10;ation on Fig. of inappropriate5) as the most significant perceptions sources of of the risks, which can improvement377 in thesediment hydrological and fast surface conditions runoff. The as soil a directin HZs is eroded,have compacted fatal consequences. and characterized An by extension a reduced of the observation consequence378 of erosionwater storage and torrent capacity. control The construction works (Fig. of 6).roads andsystem, houses especially in settlements, over inappropriate small watersheds use of (A < 10 km2), with At the same379 time, agricultural other significant land (straight parameters raw farm suching, overgrazing) as the andlonger forestry periods activities of (clear observation, cutting, removal improved of equipment (auto- 380 timber) enforce the intensity of erosion processes, fast surface runoff and sediment transport. The transfer main physical381 characteristicsof impacts from of HZs the occurs watershed on steep slopes and totaland throughmatic the torrent water beds level of the recorders Manastirica and River rain-gauges and its and calibrated precipitation382 remain tributaries, the same. with the following effects: development ofweather erosion radars(sheet erosion, connected furrows, to one gullies, information etc.), center), as well 383 transport of sediment, fast concentration of surface runoff,as data flood collection wave formation, regarding flooding historical of riparian torrential floods (by 384 zones, demolishing of houses and bridges, filling of road culverts with sediment and destruction of the the “hydraulic flood traces” method), all would combine to 5 Final consideration385 road system. The TA of the Manastirica River watershed is positioned on the downstream section, at the 386 watershed outlet, in the zone of the village of Brežđe (Fig.form 5). a The relevant torrent datavalley baseis narrow that (on would average improve the decision 387 200 m), with a steep slope downhill (about 35%) and makingmore than process 200 houses, and representroads and infrastructure a precious source for estimat- Natural hazards388 cannotsystems be (water prevented, supply, butelectric better power understand- supply and sewer)ing in the possible proximity catastrophic of the Manastirica events. River The (some forecast and simulation 389 houses are just 15-20 m away from the torrent bed). The village of Brežđe was flooded in June l996, after ing of the processes and scientific methodologies for predic- of torrential floods are essential for early flood warnings and tion can help390 mitigate heavy their rain impactof 135 mm, (Alcantara, which lasted 2002). for 3 hours. Au- Almost 130 hectares of land and 37 buildings were 391 flooded (out of which 15 were severely damaged), 14 planningkm of roads of were rescue dama operations.ged or blocked Particular and 140 attention needs to thorities in some392 Europeaninhabitants were countries evacuated. have The recognized discharge into the the Manastirica River increased 815 times, from Q=0.19 3. -1 3. -1 be paid to the characteristics of torrential flood waves, in- need to warn393 the publicm s toabout QmaxhMan-1996 the threats=154.9 m ofs flooding. The water and level increasedcluding from their 30-40 sudden cm appearance,to 6.2 m (Risti destructivity,ć et al., short duration 394 1997b). highlight the need to use watersheds wisely (Pottier et al. and seasonal character. 2005), whilst395 considering environmental protection and flood 396 The realization of restoration works will help decrease annual yields of erosive material from Wа=24,357 3 3 -2 3 3 -2 management397 as factorsm (825.7 of a similarm ·km ) importance to Wа=16,198 and m the (549.1 opti- m ·km ).Torrential The effects floods of hydrological need serious changes attention, were with the follow- mum flood control398 estimated system asthrough a compromise the comparison between of the thesehistorical maximaling activities: discharge identification and the computed of HZs maximal and TAs (whole water- two competing399 objectives discharge (Plate, (under 2002).the conditions after the planned restoration).sheds or certainThe value parts), of the short historical term maximal protection strategies, long In most cases, torrential floods are caused by natural oc- term protection strategies, strictly controlled11 land use, risk currences (such as the climatic, morphologic and hydro- management systems, along with public education and media graphic particularities of the watersheds), but human factors coverage. The importance of PAERs and PPTFs is illustrated contribute significantly to the effects of the disasters (the mis- by the example of the Serbian capital, the city of Belgrade, management of forest and agricultural surfaces, uncontrolled with a territory of 3500 km2 and 190 torrents in both rural urbanization, and the absence of erosion control and flood and highly urbanized areas. The Master Urbanistic plan of protection structures). Torrential floods are the most frequent Belgrade was finished in 2002, but some solutions were not catastrophic events that occur in Serbia in both urban and applicable because certain areas for residential and infras- rural areas, with serious risks to people and their activities. tructure construction were located in torrential flood zones or These natural hazards have caused the death of more than on landslides. This was evident during the heavy rain events 70 people in the last 60 yr and material damage estimated at and floods in 2003 and 2004. The authorities of the city more than 8 billion euros. of Belgrade decided to produce PAERs and PPTFs. These The lack of a representative data base for determining the plans were finished during 2005 (The Faculty of Forestry potential catastrophic maximal discharges influences the cre- and IWRMJC,ˇ 2005) and their solutions were implemented

Nat. Hazards Earth Syst. Sci., 12, 23–35, 2012 www.nat-hazards-earth-syst-sci.net/12/23/2012/ R. Ristic´ et al.: Torrential floods and town and country planning in Serbia 33 in the Master Urbanistic Plan in order to eliminate the short- vious Water Law (OG, 1991) defined that local authorities comings of its former version. That served as the motivation were obliged to make PAERs and PPTFs, but the funding for for other municipalities in Serbia to start making PAERs and the intended solutions had to be provided by State authorities PPTFs. So far, 30 municipalities have produced the above (The Directorate for Waters and the State-owned company mentioned plans, which cover about 22 % of the territory of “Serbian Waters”). The latest Water Law (OG, 2010) defines Serbia. that the production and financing of PAERs and PPTFs, as Development of HZs and TAs mapping and detailed risk well as the implementation of the intended solutions, have to assessment support a readiness for these disasters. HZs and be met at the local level. This is not a suitable solution if we TAs maps provide the basis for torrential flood prevention take into consideration that local authorities, with negligible and mitigation by identifying “source” zones of impacts (fast exceptions, do not have the financial and human resources surface runoff and sediment) and areas that are potentially (experts) needed for the application of ETCWs. Obviously, exposed to flooding, which threatens the safety of human some changes of the existing Serbian Water Law are a neces- lives and property. These maps then guide the local au- sity. thorities in adopting torrential flood management programs There is a Serbian tradition in the realization of ETCWs (through PAERs and PPTFs), including restoration measures, of longer than 100 yr, which has produced significant results. prevention, education and preparedness. Short term protec- However, the existing level of investment (1.045×106 Cper tion comprises of all measures that can be relatively promptly yr) is not at a satisfactory level. Future financing has to be realized (in a period ranging from one month to one year), based on a much larger share of the Republic and regional including good maintenance of regulated and natural torrent funds and partly on the municipal funds , in order to reach the beds, administrative bans (on construction in flood zones and planned level of investments (18.7×106 Cper yr) in erosion clear forest cutting on degraded slopes) and mandatory prac- and torrent control. tices (controlled urbanization, contour or terrace farming). Serbian society is changing towards the acceptance of Eu- Long term protection includes: forming of reservoirs and ropean standards in all areas of public activity, and a part of retentions for the reception of torrential flood waves, dis- this change is harmonization of legislation and practices in location of residential and infrastructure objects from flood the field of flood prevention, with an emphasis on protection zones, and effective erosion and torrent control of water- from torrential floods as the most common natural hazard in sheds. The risk of fast surface runoff can be significantly Serbia. Some European countries (Italy, Austria, Switzer- decreased by changes in land use (afforestation of bare land, land, France and Spain) have extensive experience in torren- reclamation of degraded forests, meadows and pastures, silt- tial watershed management. The application of certain posi- filtering strips, contour farming and terracing) in order to tive experiences from these countries can improve torrential reduce erosive material production and meliorate water in- watershed management in Serbia. On the other hand, Serbia filtration and water storage capacity of the soil. It is very has achieved great success in the areas of erosion and tor- important to inform and educate all stakeholders about these rent control with certain original solutions that might be of planned activities, provide subsidies for implementation and interest to the European scientists and professionals in this media support. field. This paper is the first step in presenting the Serbian Integral planning and management at local and regional experience related to the issues of erosion and torrent control levels is very important in order to overcome the collapse and a step towards the exchange of technical and scientific of strategic thinking in Serbia in the past 20 yr, which has information between European countries and Serbia. been reflected in many ways, especially in the domain of natural hazards prevention (Vujoševic,´ 2010). All levels of Acknowledgements. This study was supported by the Ministry of planning (spatial, urbanistic, regulation) have to consider all Education and Science of the Republic of Serbia within project the dominant factors for the initiation of erosion processes 43007 (“Studying climate change and its influence on the environment: impacts, adaptation and mitigation-subproject: Frequency of and fast surface runoff formation. Problems of erosion pro- torrential floods and degradation of soil and water as a consequence cesses and protection from torrential floods in Serbia have of global changes”). been integrated into the spatial planning documents in the last few years. However, we need at least five years to im- Edited by: F. Luino prove that process, in accordance with the solutions from the Reviewed by: two anonymous referees latest “Draft of the Spatial Plan of the Republic of Serbia” (Republic Agency for Spatial Planning, 2010). Effective protection from torrential floods requires coordinated work in the fields of water resources management, forestry, agriculture, energetic, environmental protection and local economic development. PAERs and PPTFs should be integrated into Spatial Plans in order to improve the process of planning and aid in the establishment of sustainable solutions. The pre- www.nat-hazards-earth-syst-sci.net/12/23/2012/ Nat. Hazards Earth Syst. Sci., 12, 23–35, 2012 34 R. Ristic´ et al.: Torrential floods and town and country planning in Serbia

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