Оригинален научен труд Original Scientific Article

GIS AIDED EROSION RISK ANALYSES ON THE VODNO MOUNTAIN

Ivan BLINKOV1, Ivan MINCEV2 & Bozin Trendafilov2

1 Faculty of Forestry – Skopje, Institute of Forestry – Dept. of Land and Water - , bul. „Alexandar Makedonski“ bb. 1000 Skopje, Republic of Macedonia 2 Mediterranean Agronomic Institute of Chania, Crete, Greece, MSc student, Department of Environmental Management

ABSTRACT

Blinkov I., Mincev I. & Trendafilov .B (2008): GIS aided erosion risk analyses on the Vodno mountain. Proceedings of the III Congress of Ecologists of the Republic of Macedonia with International Participation, 06- 09.10.2007, Struga. Special issues of Macedonian Ecological Society, Vol. 8, Skopje. Erosion has been an on-going problem for millennia. Forecasted climate changes will cause increase of ero- sion intensity because of the increase of the temperatures contribute to forest die-back, wild fires and soil degrada- tion but increase of intensive rainfall frequency will dramatically intensify the soil erosion. In this paper there are presented hypothetical scenarios for intensifying the erosion processes in case of change of land cover i.e. loss of forest cover. The research was carried out on the Vodno Mountain. In the past, the city of Skopje was permanent- ly endangered by the torrents from Vodno. The erosion control works (plantations, hydraulic structures..) started in 1952 enabling protection of the city. So the main goal of this paper is to implement GIS (Geographic Information Systems) in the existing meth- odologies of Gavrilovic for assessing soil erosion parameters. There have been used several standardized datasets for development of the GIS model (Land cover map, Erosion map of R.Macedonia, geological map, DEM, climat- ic data). Erosion GIS model has been created assessing the current situation and the hypothetical situations where the land cover was radically changed because of erratic conditions. Also the impact of the environment and the ur- ban areas were assessed.

Key words: erosion, risk assessment, Vodno, GIS

ИЗВОД

Блинков Иван, Минчев Иван, Трендафилов Божин. (2008): Анализа на ризиците од ерозија на планината Водно базирано на ГИС. Зборник на трудови од III Конгрес на еколозите на Македонија со меѓу- народно учество, 06-09.10.2007, Струга. Посебни изданија на Македонското еколошко друштво, Кн. 8, Ско- пје. Ерозијата претставува проблем со милениуми. Прогнозираните климатски промени ќе предизвикаат зголемување на ерозивните процеси бидејќи порастот на температурите води кон сушење на шумите, шум- ски пожари и деградација на почвата, а пак порастот на фреквенцијата на интензивни врнежи драматично ја интензивира ерозијата. Во овој труд се презентирани хипотетички сценарија за интензивирање на ерозив- ните процеси во случај на промена на користењето на земјиштето поточно губиток на шумскиот покров. Ис- тражувањата се реализирани на планината Водно. Во минатото градот Скопје перманентно бил под закана на Водњанските порои. Противерозивните работи (пошумувања, хидротехнички објекти и др.) кои почнаа во 1951 овозможија заштита на градот. Така главна цел на трудот е да се имплементира ГИС во постојната методологија на Гаврилович - пресметување на ерозивните елементи. Употребен е стандарден сет на податоци за развој на ГИС модел (користење на земјиштето, карта на ерозија, геолошка карта, ДЕМ, климатски податоци). ГИС моделот на ерозијата е креиран преку процена на сегашната ситуација и хипотетичка ситуација во случај на радикална промена на земјишниот покров поради променливите услови. Исто така и влијанието врз животната среди- на и урбаното подрачје е земено во предвид.

Клучни зборови: ерозија, анализа на ризик, Водно, ГИС

573 Ivan BLINKOV et al.

Introduction Aims and objectives

In the last years there has been a huge de- The aim of this study is to create GIS-mod- velopment in the spatial representation and analy- el for assessment erosion and torrential risk based on sis of the data. The GIS (Geographical Informa- the methodologies of Gavrilovic. tion Systems) is an integral part of the new develop- Erosion Risk was assessed as: ments and it represents a big leap towards better un- a. Actual risk (based on present situation) derstanding of the spatial extent of the environmen- b. Potential risk (was created scenario for tal problems. The GIS represents set of tools which hypothetic situation) can make the life easier to the user. GIS modeling Risk of torrents was assessed on the similar presents an opportunity to automatise the process of way but in this assessment was estimated the risk for production of output with standardized input and al- the urban area ready set parameters. The objectives of this study are: The future of the solving of the environmen- a. To recognize erosion and torrent risk tal problems is to perceive the problems globally and b. To create basic numerical and graphical to produce spatial data which will be available to the (GIS) dataset broad scientific community. c. To assess the on site erosion risk using Risk is a concept that denotes a potential neg- GIS ative impact to an asset or some characteristic of val- d. To assess the torrential risk ue that may arise from some present process or fu- ture event. In everyday usage, risk is often used syn- Methodology onymously with the probability of a known loss. Usually, the probability of that event and some as- The issue of soil erosion and torrent control sessment of its expected harm must be combined in- has very crucial spatial extent. GIS systems encom- to a believable scenario (an outcome), which com- pass all the important tools for this purpose. bines the set of risk, regret and reward probabilities First activity was collecting of basic dataset: into an expected value for that outcome. Paradoxi- maps, tabular data etc. After all maps were scanned, cally, a probable loss can be uncertain and relative digitized and georeferenced. Then field activities in an individual event while having a certainty in the were carried out. Field activities consisted of: rec- aggregate of multiple events. ognition of the terrain with comparison to the pre- Risk management is the human activity viously prepared maps, GPS surveying, photo inter- which integrates: risk recognition, risk assessment, pretation, surveying of the elements of the hydrau- developing strategies to manage it, mitigation of risk lic structures. using managerial resources. After that data from terrain was transferred to The strategies include transferring the risk to PC and implemented into the basic GIS-model. another party, avoiding the risk, reducing the nega- For estimation of the needed parameters, part tive effect of the risk, and accepting some or all of of the basic data was reclassified according to the the consequences of a particular risk. methodology requirements. Regarding erosion risk analyses, it should be The mostly used methodologies related to separate: actual erosion risk and potential erosion erosion and torrents in the R. Macedonia are by risk. Erosion damages could be on -site: soil loss- Gavrilovic. In this case study two main methods es; water loss, landscape deterioration and off-site: have been tested for applied GIS use: torrential flash floods >> damages on houses and in- a) Estimation of maximal water discharge - frastructure, filling up reservoirs, mechanical and Qmax; (by Gavrilovic) chemical pollution of the water. b) Estimation of erosion coefficient – Z - In recent time there have been several at- and transported sediment - G; (Erosion tempts to implement the already established scien- Potential Model by Gavrilovic) tific models into the GIS environment. There have c) Estimation of hydraulic conditions of the been several developed software packages which present drainage channel using Shaesy implement these algorithms into the spatio-digi- model for V and the present. tal environment (HEC-RAS, WEPP, ARC-INFO, Estimation were carried out in actual and hy- USLE, KINEROS…..). pothetic situation The main idea of this study is to use the ex- For estimation of maximal water discharge isting national datasets which are with standardized was used the following formula: quality and to implement them in the existing devel- 0,5 Qmax = A S1 S2 W (2gDF) oped methodologies, like the one of Gavrilovic. A – catchment shape coefficient A=0.195 * S/ L S – catchment perimeter; L – water course

574 Зборник на трудови од III Конгрес на еколозите од Македонија GIS aided erosion risk analyses on the Vodno mountain

length D – average height difference D=Naverage -

The catchment and the water course were Nmin digitized from the topographic maps and these pa- F – catchment area rameters were extracted automatically with the GIS For Estimation of transported sediment was software. used the following formula 1.5 S1 – permeability coefficient of the area; G = T Han π Z F Rn where This parameter shows from what kind of par- T – temperature coefficient; T=(t / 10 + 0.1); ent rock is the area conceived. This parameter was t – annual average temperature; extracted from the existing geological map. The per- Han – annual average sum of rainfall ; These meability is subdivided into three categories: low, parameters were taken from the climatic dataset. medium and high permeability. The existing geo- π = 3.14 logical classes were converted into the three cate- Z - Average erosion coefficient in the catch- gories. ment

S2 – vegetation cover coefficient The erosion coefficient was taken from The vegetation cover is also subdivided into the existing digital erosion map of the country three classes: 1. forested areas, 2. transitional wood- as average value extracted from the GIS layer. land and clear pasture areas, and 3. clear agriculture Rn - retention coefficient of the catchment areas without vegetation cover and bare-land. These Rn = ( S * D )0.5 / ( 0.25 * ( L + 10 )) classes were extracted from the existing CORINE For estimation of the erosion coefficient Z land cover map with conversion of the classes. was used the following formula W – retention of discharge in case of inten- Z = γ xa (ϕ + Jsr0,5) sive rainfall or snow meltdown γ - reciprocity value of the resistant coeffi- 0.5 W = h (15 – 22h – 0.3 L ) cient to erosion h – amount of intensive rainfall, average of xa - soil protection by natural or man made the rainfall above 30mm cover This parameter was taken from previous stud- ϕ - coeff. of visible erosion processes ies (Blinkov et al,1997). Jsr - mean inclination of the catchment 0.5 (2gDF) – energetic potential of the torren- For estimation of channel hydraulic capaci- tial waters during intensive rainfall ties were used the following formulas: Q = F * V -2 g – gravitational constant 9.81 (m·s ) F – cross profile area – 2m

Study area

Fig. 1. Location of the study area – Gornovodnjanski Poroj Сл. 1. Локација на Горноводњански Порој

Proceedings of the III Congress of Ecologists of Macedonia 575 Ivan BLINKOV et al.

V – mean water velocity m/s V = K C (R mountain Vodno to fulfil all their needs for tree (fu- J )^0,5 el wood, constructive wood …). It was extremely on K – torrential coefficient the north slopes of the mountain. As a result of over C – velocity coefficient ; R – hydraulic radius cutting, irregular agricultural activities and over- R = F / O ; J – bad slope grazing, mountains Vodno became bareland. Re- Greater part of the parameters were automat- sults of these were increasing of erosion processes, ically extracted from the digitized layers with statis- torrential flows, loss of biodiversity etc. tical tools. After the II world war, exactly after the big- gest flash flood in the XXth century caused of torrents Study area and dataset from Vodno, erosion control activities on the moun- tain Vodno started. The last “big one” happened in Background 1951, when there was 1 dead, a lot of injured, but A few centuries B.C., the Vodno Mountain material cost was considerable. On the part near the had been covered with good forest. The valley of the foot of the mountain, as a result of intensive erosion Vardar at Skopje was populated by the Illyric tribe of processes and transport power of the water from the Dardani whose capitol was Skupi (ancient Skopje). Gornovodnjanski Poroj, there was about 25000 m3 Not until the reign of Justinian was a new sediment in the city. town erected on the site, a settlement which devel- A lot of bareland was afforested. Almost all oped rapidly in the 9th and 10th centuries and be- torrents were regulated with hydraulic structures. came an important Byzantine centre. After that Sko- Few acts or sub act regulative were proclaimed. Ed- pje was a centre of the Serbian Kingdom (king Du- ucative measures contribute to present situation. san – 14th century). Skopje was a great trade centre Beside other, all above activities enabled migration of the Ottoman Empire (XV-XX century).All former of the greater part of the city on the right side of the cities have been located on the left side of the riv- river Vardar. er Vardar. Now, Vodno is “the lungs of Skopje”, the There are a lot of reasons for this. A part of most important green part in the city of Skopje and the area along the river on its right side has been per- its neighbourhood, so the Macedonian government manent affected by Vardar floods. Torrential floods proclaimed part of the mountain as a park-forest. have affected the other part, located on the foot of Maintenance of the present forest cover (sil- the Vodno hillside. The bigger part of the right side vicultural activities, protection from: fires, pests, was unsuitable for living. disease from illegal cut, from illegal construction During the history, people who lived in Sko- and afforestation of the existing barelands) are nec- pje (and previous settlements) cut forest from the essary for the improvement of the quality of life and

Fig. 2. Part of the basic dataset for the park-forest Vodno – developed GIS layers Сл. 2. Дел од основниот датасет за парк-шумата Водно – изработени ГИС карти

576 Зборник на трудови од III Конгрес на еколозите од Македонија GIS aided erosion risk analyses on the Vodno mountain safety of the citizens of Skopje and the settlements ta etc. Basic data was prepared for the whole moun- from the southern side. tain but detail researches were carried out for one Because of the importance of the torrent: catchment – Gornovodnjanski poroj (Fig. 2, 3, 4). Gornovodnjanski poroj it was selected for detail analysis (Fig. 1). Results and discussion The dataset was comprised of: 1:25,000 topographic maps; Land cover/use map, vector The main hydrographical characteristics ex- (1:50,000); Geology map, vector (1:100,000); Soil tracted from the GIS –layers are as follows: map; Torrential map; Drainage map; DEM (Digital - catchment area - F = 3.27 km2, Elevation Model), raster; Climatic data; tabular da- - Highest altitude - Niz = 1066 m. a.s.l.,

Fig. 3. Part of the dataset used for reclassification according to the Gavrilovic methodology needs Сл. 3. Дел од картите користени за рекласификација според пристапот во методологијата на Гавриловиќ

Fig. 4. Examples of actual (current situation (photo 2007) and hypothetic situation (photo 1920) on the Vodno Сл. 4. Изглед на актуелната (2007 година) и хипотетичката ситуација (1920 година) на планината Водно

Proceedings of the III Congress of Ecologists of Macedonia 577 Ivan BLINKOV et al.

Tab. 1. Erosion risk analysis Tab. 1. Analiza na rizicite od erozija Z Rn E W Gsp G m3/km2.y m3/y m3/km2.y m3/y actual 0.21 0.47 167.07 552.86 78.79 267.63 potential 0.94 0.47 1601.15 5235.75 746.13 2439.86 Legend: Z – erosion coefficient by Gavrilovic E – total annual erosion production G – total annual transported sediment Z – 4.5 times higher risk W, G – 9.5 times larger quantities of sediment

Fig. 5. Erosion risk map of the Gornovodnjanski Poroj catchment – actual and potential Сл. 5. Карта на ризик од ерозија на Горноводњански порој - актуелна и потенцијална

Tab. 2. Water discharge estimation – current and hypothetic situation Tab. 2. Presmetuvawe na protek na voda vo postojna i hipoteti~ka situacija

Probability (%) 2 10 5 4 2 1 0.5 0.1 return period (years) 5 10 20 25 50 100 500 1000 h 0.052 0.052 0.052 0.052 0.052 0.052 0.052 0.052 K 0.4 0.5 0.67 0.75 0.85 1 1.5 1.7 hn 0.021 0.026 0.035 0.039 0.044 0.052 0.078 0.088 W 0.291 0.361 0.477 0.531 0.597 0.693 0.995 1.107 A 0.47 0.47 0.47 0.47 0.47 0.47 0.47 0.47 S1 0.64 0.64 0.64 0.64 0.64 0.64 0.64 0.64 2gDF 140 140 140 140 140 140 140 140 S2 0.66 0.66 0.66 0.66 0.66 0.66 0.66 0.66 Q – current 8.10 10.04 13.27 14.75 16.58 19.26 27.65 30.77 S2 – hyp. 0.94 0.94 0.94 0.94 0.94 0.94 0.94 0.94 Q – hypothetic 11.54 14.30 18.90 21.01 23.61 27.43 39.38 43.83

578 Зборник на трудови од III Конгрес на еколозите од Македонија GIS aided erosion risk analyses on the Vodno mountain

Fig. 6. Sheme of hydraulic structures (channel, thresholds, cascades) in the Gornovodnjanski Poroj bad Сл. 6. Шема на хидротехничките објекти (канал, прагови, прегради) во коритото на Горноводњански порој

- Profile altitude – Nvl = 295 m.a.s.l., Conclusions - Mean catchment altitude – Nsr = 604 masl. - Current erosion risk is low - Z=0.21 - stream length - L = 3.137 km, - Current estimated erosion intensity is W=552 - catchment perimeter - O (S) = m3, out of them quantities of sediments are very 7.621km, low G =257 m3 - Mean bed inclination - Isr = 6.2%. - Potential erosion risk is high Z = 0.94 For the climatic data there were used some - Estimated erosion intensity according to the previously defined values for the period 1951-2000 scenario is W = 5235 m3 and transported sedi- where average values were t = 12.1oC ; H (P) = ments G = 2439 m3, or 9.5 times higher. 488 mm. This data was transformed according to the - Estimation of water discharge and estimated ca- mean catchment altitude. pacities of the channels show that in normal sit- For estimating water discharge with differ- uation channels can accept even discharge with ent probability there were used previously estimated 1-2% probability by the hypothetic scenario values for extreme precipitation with different dura- - Solid waste and legal and illegal construction tion and probability for HMS Skopje – Zajcev Rid could cause flow resistance so the channels (Blinkov 1993). Duration of effective precipitation wouldn’t accept discharge with probability over (Tk = 66’) was estimated by the time of concentra- 5-10% (current situation) or 20% (hypothetic tion (Tc) based on stream length and bed slope. Ac- situation). cording to it extreme precipitations with this dura- tion and probability of 1% (estimated using Gumbel distribution) is 52 mm.

Proceedings of the III Congress of Ecologists of Macedonia 579 Ivan BLINKOV et al.

Recommendation Минчев, И. (2004). Примена на ГПС и ГИС ме- тодологијата во шумарството - дипломска We are obliged to : Protect the forest; Clean работа up the channels; Extract illegal bans Трендафилов, Б. (2007). Креирање ГИС-база на Potential Erosion risk is high and we are ob- парк-шумата Водно - дипломска работа ligated to protect the environment and citizens of Blinkov, И., et al.: Risk-Disaster management Skopje and prevention against natural hazards in mountaneous/forested region, INTERREG References IIIb Cadses project, on-going project

Блинков, И. (2001). Заштита на земјиштето од ерозија

Note : This paper is part of researches and analysis carried out until now through the project RIMADI- MA Risk-Disaster management and prevention against natural hazards in mountaneous/forested region, IN- TERREG IIIb Cadses project - ID nro 5D102, carried out by Faculty of Forestry-Skopje, Parks and greenery - Skopje and 10 foreign partners, supported by European Union

580 Зборник на трудови од III Конгрес на еколозите од Македонија