GEOGRAPHICAL STUDIES AND ENVIRONMENT PROTECTION RESEARCH
No. 9
2010
Editorial Board
Editor:
Zvi Yehoshua OFFER, Ben-Gurion University, Israel Mary RÉDEI, Eötvös Loránd University, Hungary
Scientific secretary:
Alina VLĂDUŢ, University of Craiova, Romania Liliana POPESCU, University of Craiova, Romania
Editorial Advisory Board:
Lucian BADEA, The Institute of Geography, The Romanian Academy, Romania Dan BĂLTEANU, The Institute of Geography, The Romanian Academy, Romania Léon BRENIG, University of Brussels, Belgium
Pompei COCEAN, University of Babeş-Bolyai, Romania Slavoljub DRAGIĆEVIĆ, Belgrade University, Serbia Recep EFE, Balikesir University, Turkey
George ERDELI, University of Bucharest, Romania Robert FOVELL, University of California, USA Ioan IANOȘ, University of Bucharest, Romania
Nina NIKOLOVA, St. Kliment Ohridsky University of Sofia, Bulgaria Maria PĂTROESCU, University of Bucharest, Romania
Viorica TOMESCU, University of Craiova, Romania Magdy TORAB, Alexandria University, Egypt
Editor-in-Chief: Sandu BOENGIU, University of Craiova, Romania Members:
Sorin AVRAM (University of Craiova), Amalia BĂDIȚĂ (University of Craiova), Gheorghe CURCAN (University of Craiova), Cornel GOLEA (University of Craiova), Oana IONUȘ (University of Craiova), Mihaela LICURICI (University of Craiova), Cristina MARA (University of Craiova), Emil MARINESCU (University of Craiova), Ioan MARINESCU (University of Craiova), Ștefan NEGREANU (University of Craiova), Vasile PLENICEANU (University of Craiova, Romania), Mihaela VIERU (Carleton, University, Canada), Cristiana VÎLCEA (University of Craiova, Romania).
Site administrator: Vîlcea Cristiana
Cover by: Şoşea Cristina
Photo by: N. Cruceru (Băluţa gorge, Mehedinţi county, Romania) Editorial correspodence should be addressed to:
University of Craiova, Geography Department, 13, Al. I. Cuza Street, Craiova, România,
Tel: 0251416574 int. 4110, Fax: 0251418515, E-mail: [email protected] web: http://forumgeografic.ro The jurnal is indexed in international databases:
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ISSN – 1583-1523 ISSN – 2067-4635 (on line)
GEOMORPHOLOGY, PEDOLOGY
Lucian BADEA - The Ancient City of Callatis and the Neotectonic Movements ……….. 5 Sandu BOENGIU, Emil MARINESCU, Oana IONUȘ, Mihaela LICURICI – The Analysis of the
Relief Fragmentation Features within the Bălăciţa Piedmont ……… 9 Nicolae CRUCERU, Gheorghe HERIŞANU – The Dynamics of the Present Processes within the
Sărăţel Catchment Area ……… 17
Dan LESENCIUC – Endokarstic Relief within the Natural Reserve Area of “Repedea Hill Fossil
Site” ……… 31
Prakriti BISTA, Rajan GHIMIRE, Shree Chandra SHAH, Keshab Raj PANDE – Assessment of Soil Fertility Management Practices and their Constraints in Different Geographic Locations
of Nepal ………. 41
CLIMATOLOGY, HIDROLOGY
Alina VLĂDUŢ – Ecoclimatic Indexes Within The Oltenia Plain ………. 49 Ion MARINICĂ, Iulica VĂDUVA – Comparison between the Oltenia Plain and the Southern
Dobroudja Plateau in Terms of Pluviometric Deficit……… 57 Gheorghe ROMANESCU, Cristian STOLERIU, Cristina DINU – The Determination of the
Degree of Trophicity of the Lacustrine Wetlands in the Eastern Carpathians (Romania) .. 65
ENVIRONMENT GEOGRAPHY
Peter VANDERSTRAETEN, Olivier BRASSEUR, Michaël FORTON, Anne CHEYMOL, Marianne SQUILBIN – Particulate Matter and Nitrogen Dioxide in the Brussels Ambient Air. To What Extent Local Emission Reductions Need to Be Drastic to Enable Compliance
with the EU Limit Values ……….. 75
Eli ZAADY, Leon BRENIG, Daniele CARATI, Annick MEURRENS, Yves LÉNELLE, Peter VANDERSTRAETEN, Zvi Y. OFFER – Heavy Metals Identified in Airborne Particles During Weekend Periods in Brussels Urban Environment ……… 87 Sandrine BLADT, Yves LENELLE, Catherine BOULAND, Camille CHASSEUR – Index of
Indoor Air Chemical Pollution in Brussels Habitat ………. 93 Maria PĂTROESCU, Cristian IOJĂ, Laurențiu ROZYLOWICZ, Mihai NIȚĂ, Annemarie
IOJĂ, Gabriel VÂNAU, Diana ONOSE – Indoor Air Quality in Bucharest Housings in the Framework of Present Environmental Changes ……….. 97 Maria PĂTROESCU, Mihăiţă- Iulian NICULAE – The Rurality between the Ramnicul Sarat and
the Buzau Valleys – Definitive Component of the Subcarpathian Landscapes Dynamics … 107 Gabriela OSACI-COSTACHE, Marian ENE – The Analysis of Forest Dynamics within the Contact
Area between the Carpathians and the Subcarpathians by Using Historical Cartography Approach and Open Source GIS Software. Case Study: The Limpedea Catchment (Romania) 115 Florin VARTOLOMEI, Iuliana-ARMAS – The Intensification of the Antropic Pressure Through the
Expansion of the Constructed Area in the Subcarpathian Sector of the Prahova Valley/ Romania
Ileana PĂTRU–STUPARIU, Mihai-Sorin STUPARIU, Alina HUZUI – Mathematical Models Used for Visual Assessment of the Landscape in Situ – Case Study Sinaia Town……… 133 Răzvan OPREA, Alexandru NEDELEA, Gheorghe CURCAN – The Landscapes Differentiations
in the Area of Prahovean Bucegi Mountains ……….. 139 Attila SÜTŐ, Géza SALAMIN, Pál SZABÓ – Issues of Territoriality and Territorial Cohesion in the
Revision of the TSP and the Territorial Agenda – A Sort of Connection between Geography
and Regional Policy ……… 145
Alina SATMARI – The Subsidence Caused by the Waste-Coal Self-Ignition Process in the Anina Town (Romania). Preliminary Study ………. 155
HUMAN GEOGRAPHY
Ioan IANOŞ, Cristian TĂLÂNGĂ, Cristian BRAGHINĂ, Cătălina Andra GHEORGHE – Characteristics of the Industrialisation Process Around the Moment of Collapse of a Centralised Political System. Romania as a Case Study ………. 161 Marcel TÖRÖK, Mircea VOICULESCU, Mircea ARDELEAN, Florentina POPESCU – The Use
of the Digital Terrain Model in Analyzing the Natural Potential of the Muntele Mic - Poiana Mărului - Ţarcu Mountains Tourist Area to Extend and Plan the Ski Domain…….. ………. 173 Mihaela LICURICI, Oana IONUŞ, Cristiana VÎLCEA – Social Vulnerability and Risks Associated
to the Balkan Endemic Nephropathy in Mehedinţi County ……….. 181 Dávid LÓRÁNT, Tünde AMBRUS – Responsible Tourism and Tourism Ecology ……….. 191
THE ANCIENT CITY OF CALLATIS AND THE NEOTECTONIC MOVEMENTS
Lucian BADEA1
1 Institute of Geography, Romanian Academy, Address: 12 Dimitrie Racoviţă, Bucharest, ROMANIA
Abstract
Southeastwards of Mangalia, 6 - 7 meters under the sea level, on a surface of about two hectares, there were discovered vestiges of the ancient fortress of Callatis. The settlement known since the 4th century B.C. had almost a millenary existence, but it is not known when it ceased to exist and what causes triggered it. Different suppositions were made and, among them, the telluric causes are plausible. The Southern Dobroudja Platform is penetrated by mobile faults and the compartment of Mangalia is affected by a negative neotectonic movement that gets accentuated towards southeast, where the epicentres of earthquakes with repeated manifestation have been observed. The negative movement rate is 3 - 4 mm/year and, cumulated during the 15 centuries that passed since the disappearance of the city of Callatis, it could explain the depth at which the vestiges of the settlement are presently located.
Keywords: Podisul Dobrogei, vestigii submerse, miscari neotectonice, seisme, cicluri de sedimentare, retea de falii
Rezumat
Vechiul oraș Callatis și mișcările neotectonice. La sud-est de Mangalia, sub nivelul mării, la o adâncime de 6 - 7 m, pe o suprafaţă de aproximativ 2 ha, au fost descoperite vestigii ale cetăţii antice Callatis. Cunoscută din secolul al IV-lea î.e.n., a avut o existenţă de aproape un mileniu, dar nu se ştie când anume şi-a încetat existenţa şi mai ales din ce cauze. S-au făcut diferite presupuneri şi, dintre acestea, cauzele telurice sunt cele plauzibile.
Platforma Dobrogei de Sud este străpunsă de falii mobile, iar compartimentul Mangaliei este afectat de o mişcare neotectonică negativă care se accentuează spre sud-est, acolo unde s-au constatat epicentrele unor seisme cu manifestări repetate. Rata mişcărilor negative de 3 - 4 mm/an, cumulată timp de 15 secole de la dispariţia oraşului Callatis, ar putea explica adâncimea la care se află în prezent vestigiile oraşului.
Cuvinte-cheie: Dobrudja Tableland, submerged vestiges, neotectonic movements, earthquakes, sedimentation cycles, fault network
SUBMERGED VESTIGES
By the middle of the year 2009, in the daily press there appeared 2 - 3 articles of the type of those destined for curiosities and somewhat sensational, concerning the presence of the vestiges of the antique Callatis fortress at 6 or 7 meters under the sea water level. After brief investigations, a team of autonomous divers, eager of submerged archaeological research, assessed that numerous remains of the renowned disappeared settlement are to be found on a surface of about two hectares, in the sand and ooze on the bottom of the sea. The fact is extremely inciting for those who wish to investigate the unknown, but also for any person who knows about the temporarily prosperous settlement that existed more that 20 centuries ago, the present location of its vestiges being under the sea water.
There is no doubt that when such a discovery is made many questions arise and numerous hypotheses may appear, some of them even being the product of a rich fantasy, but still, the phenomenon must have a correct, verifiable explanation. The archaeological remains of Callatis fortress certify its existence from the 4th century
B.C., but there are certain references that appear in written documents dated two centuries before. We are more interested in the moment of the disappearance of the fortress than in that of its foundation by the Greeks, on the place of a Getae settlement.
During its about one millennium long existence, the fortress had prosperity and decline periods, being known the fact that the decay registered at the beginning of our era was followed by a flourishing period, which probably lasted for a few centuries.
The exact duration, as well as the moment and precise causes of the disappearance of the fortress are not known. Different suppositions have been made in connection with this phenomenon, the most plausible causes being the telluric ones, especially since the vestiges of the fortress are under the sea water.
One of the hypotheses argues that the disappearance was provoked by a strong earthquake that led to the submersion of an important part of the settlement. Another one pleads for the progression of the sea (an ingression), which would have destroyed the settlement through inundation and the action of the waves (abrasion). Without
taking into account other probable social-economic and historic causes that would have led to the desertion of the settlement, the main cause is still the one related to natural phenomena of tectonic nature, the one that changed the relations between sea and land in a relatively short period.
The tectonic signals have always been noticeable, even in 2009, when a shallow depth earthquake, having the epicentre at approximately 15 kilometres distance of Mangalia town, shook the region.
Although the earthquake registered only 5.1 degrees on the Richter scale, it was felt on a large area and it did not cause prejudices. Nevertheless, there occurred other more severe earthquakes, with important effects on the seaside and on Dobroudja region, firstly affecting the settlements. Among these events, it is important to mention the earthquake that took place on March 31st, 1901, when there were registered 7.2 degrees on the Richter scale; the earthquake occurred at a depth of 15 kilometres in the Black Sea, had the epicentre eastwards of the Caliacra Cape and it led to the formation of a tsunami wave that flooded the settlement of Mangalia and important seashore surfaces.
STRUCTURE OF THE REGION
From the structural viewpoint, the region belongs to the South-Dobroudja Platform (Eoproterozoic unit), being bordered northwards by the main (crustal) fault Palazu (Capidava - Ovidiu). Towards south and south-west, it is limited by Fierbinţi fault, which crosses the entire Moesic domain. From the morphological point of view, it represents the entire Southern Dobroudja Tableland, in the southeastern part of which there is located the Mangalia Tableland.This unit is made of old formations and its base, constituted of granitic gneiss and mesometamorphic crystalline schists (Palazu crystalline), deepens southwards. The above sedimentary formations accumulated during several sedimentary cycles, very probably starting with the Lower Paleozoic (Vendian - Cambrian), the presence of which was registered in the drills realized at Palazu Mare, Cumpăna, and around Mangalia (V. Mutihac et al, 2004, p. 30). The next cycle, taking place from the Middle Jurassic to the Cretaceous, mainly marked the deposition of the carbonaceous rocks.
The Jurassic deposits do not crop out, while the Cretaceous ones are open in the valleys from the western part of the Tableland, which are directed towards the Danube, and especially along the Carasu Valley. When the Danube - the Black Sea Canal was dug along the Carasu Valley, the formations of the Cretaceous cycle got to be known in detail and they prove that in the second half of
the Cretaceous the region underwent certain tipping movements that led to the appearance of sedimentation discontinuities.
The following sedimentation cycle - the Paleogene one - led to the accumulation of predominantly calcareous (Eocene) and disodilic bituminous (Oligocene) formations, which are preserved on limited surfaces. After a stratigraphic gap up to the Badenian, there followed the last sedimentation cycle, the Mio- Pliocene one, which started with sandy Badenian depositions that only appear discontinuously. They are discordantly covered by Sarmatian organogenic limestones, giving the general characteristic of the Southern Dobroudja Tableland. They appear in all valleys directed towards the Danube, but also on the seaside, in the sector located southwards of Eforie.
This last sedimentation cycle ends with the deposition of certain clayey Pliocene sands that are present at the surface of the tableland only towards the Danube.
The entire ensemble of rocks appeared during the last sedimentation cycles is covered by a relatively thick layer made up of loess and loessial deposits, hiding the character induced by the Sarmatian calcareous formations.
A geological cross-section with general south - north direction along the seaside, going from the border to north of Palazu, points out a structure that is pierced by numerous faults, the compartments located north of Mangalia showing a lowering tendency towards south and southeast. Besides the old Paleozoic and Mesozoic formations, the faults also influence the Paleogene and Miocene sedimentary layer. Although this layer is less affected in vertical plan than the older formations, its compartments are involved in the same general lowering movement towards southeast, which corresponds to the general direction of the faults (Fig. 1).
TECTONIC MOBILITY
During its very long evolution and on its structural completion in the time of the last sedimentation cycle and after it, the Southern Dobroudja Tableland underwent certain tipping movements and, at the same time, a breaking process determined by a network of faults that cross this structural edifice on its entire depth, touching all formations, from the Proterozoic fundament to the Mio-Pliocene layers.
The faults - especially the main ones and those that structurally delimitate the Southern Dobroudja Tableland - will always be reactivated, defining this tableland as a horst, in relation with the neighbouring units from the north towards the south. Another important element is that the faults within this unit delimitate compartments that are characterized by
different vertical movement tendencies and some of them are very active.
Fig. 1 Geological cross-section along the seaside, between Vama Veche and Siutghiol (after V. Mutihac et al. 2009)
In other words, the Southern Dobroudja Platform is not a rigid structural unit. Besides the main faults that delimitate it, the base plate was affected by secondary faults, the mobility of which is pointed out by the neotectonic movements and by the earthquakes.
North of Mangalia (approximately on the Cobadir - Topraisar - Costineşti alignment) there is located an important fault that delimitate the compartment of Mangalia, bordered southwards by another important, active fault: Sabla - north Caliacra. The earthquakes with the epicentres located southeastwards of Mangalia - such as the one that took place on March 31st 1901 (7.2 degrees – it led to the formation of a big wave that flooded the seashore) and the one that occurred on August 5th 2009 - depend on this fault.
The above-mentioned compartment descends towards southeast and it is permanently affected by present movements that are not uniform from viewpoints of sense or intensity.
On the Map of the Recent Vertical Crustal Movements (work of M. Visarion, M. Săndulescu, I. Drăgoescu, M. Drăghici, I. Cornea, M. Popescu, printed at the Institute of Geology and Geophysics, 1977), the western and southwestern parts of the Southern Dobroudja Tableland are shown as an area caught in a positive movement of more than 1.5 mm/year. As we approach the seaside, the positive movement decreases, then is inverted and the
negative character of the movement becomes more and more accentuated up to the shore line.
On the map that is annexed to the article published in 1998 by D. Zugrăvescu et al., in the southeastern sector there is delineated an area in which the negative movements reach 3 - 4 mm/year.
This area slightly broadens towards the sea, the town of Mangalia - the place of the ancient fortress Callatis - being located in its central part.
The eastern side of the Dobroudja Tableland is generally affected by a light negative present neotectonic movement, but the research conducted during the last 50 - 60 years underlined the most important subsidence in the area located around Mangalia (Fig. 2). The recurring earthquakes, which register or even surpass 7 degrees, represent the most obvious proof of the instability of the structure crossed by an active fault. To the subsidence movements characterized by intensities of 3 - 4 mm/year during the earthquakes, there were associated plungings (falls) of the soil, which explains clearly enough the alteration and relatively rapid disappearance of the city of Callatis.
Usually, on long term, the intensity of the movements is variable and their value can decrease down to the cessation or even reversal of the movement. On the other hand, on short periods, the assessment made at a given moment can be considered as such.
The rate of 3 - 4 mm/year, which was recorded by the researches conducted during the last hundred years, can be taken into consideration for the almost 15 centuries past since the disappearance of the city of Callatis under the seawater.
The remains of the fortress are to be found at a depth of 6 - 7 meters, which generally corresponds
to the subsidence process characterized by values of 0.3 – 0.4 m/century and confirms the hypothesis of the disappearance of the settlement as a consequence of the neotectonic process that affects the seaside in the Mangalia – Vama Veche sector.
Fig. 2 The present crustal movements within the Dobroudja Tableland (after D. Zugrăvescu et al. 1998)
REFERENCES
Badea, L., (1996), Neotectonic movements and their effects on Romania’s landform, Rev. Roum.
Géographie, 40, pp. 13 - 18.
Cornea, I., Drăgoescu, I., Popescu, M., Visarion, M.
(1978), Monografia mişcărilor crustale verticale recente în Republica Socialistă România, Inst.
Cerc. Fiz. Seismol., Bucureşti.
Mutihac, V., Stratulat, Maria Iuliana, Fechet ,Roxana Magdalena, (2004), Geologia României, Edit.
Didactică şi Pedagogică, R. A. Bucureşti.
Săndulescu, M., (1984), Geotectonica României, Edit. Tehnică, Bucureşti.
Zugrăvescu, D., Polonic, Gabriela, Horomnea, M., Dragomir, V., (1998), Recent vertical crustal movements on the Romanian territory, major tectonic components and their relative dynamics, Rev. Roum. Géophis, 42, pp. 3 – 14.
THE ANALYSIS OF THE RELIEF FRAGMENTATION FEATURES WITHIN THE BĂLĂCIŢA PIEDMONT
Sandu BOENGIU1, Emil MARINESCU1, Oana IONUŞ1, Mihaela LICURICI1
1 University of Craiova, Geography Department, 13, A.I. Cuza Street, Craiova, Romania, e-mail: [email protected]
Abstract
Within the Bălăciţa Piedmont there are to be distinguished two areas with specific features, which correspond to the Danube catchment and to the Jiu drainage area. Both in the case of the drainage density, as well as in that of the relief energy, the distribution of the value classes correlated with the two catchments underlines major differences, but also certain resemblances, situation which is explained by the evolution time, the base level, the flow direction in relation with the structure and the lithological and climatic homogeneity.
The analysis of the data enabled the quantification of the relief energy and of the drainage density within the Bălăciţa Piedmont, as well as the correlation of the two parameters in report to the main catchments. The computation and representation methods for the two indicators of the relief fragmentation (i.e. the depth and the density) allowed for a quantitative interpretation (the identification of five value classes), as well as for a spatial interpretation (the grouping of the values depending on the two collecting rivers: the Danube and the Jiu). The aggregation of the influence factors on the two main drainage areas is mostly due to the fact that the Danube catchment extended its area in the detriment of the Jiu catchment, the three more important tributaries (the Blahniţa, the Drincea and the Desnăţui) catching sectors within the upper course of the tributaries of the Jiu.
The analysis of the relief fragmentation within the Bălăciţa Piedmont shows that this unit is on different evolution stages.
The complexity of the fragmentation is closely connected to the maturity degree of the valleys and to the morphogenetic complexes imposed by the paleogeographical evolution.
Keywords: catchment, relief energy, drainage density, correlation coefficient, the Bălăciţa Piedmont
Rezumat
Analiza particularităţilor fragmentării reliefului în PiemontulBălăciţei. În Piemontul Bălăciţei se disting două areale cu particularităţi diferite, aferente bazinului hidrografic al Dunării şi bazinului Jiului. Distribuţia claselor de valori corespunzătoare celor două arii de drenaj, atât în cazul densităţii, cât şi în cel al adâncimii fragmentării, reliefează diferenţe majore, dar şi unele similitudini, fapt datorat timpului de evoluţie, nivelului de bază, direcţiei de scurgere faţă de structură şi omogenităţii litologice şi climatice.
Analiza datelor a permis cuantificarea energiei reliefului şi a densităţii fragmentării reliefului din Piemontului Bălăciţei şi corelarea celor doi parametrii în funcţie de bazinele hidrografice principale. Metodele de calcul şi reprezentare a celor doi indicatori ai fragmentării reliefului au permis atât o interpretare cantitativă (identificarea a cinci clase de valori), cât şi una spaţială (gruparea valorilor în funcţie de cele două râuri colectoare: Jiu şi Dunăre). Gruparea factorilor de influenţă, pe cele două bazine hidrografice principale se datorează în principal faptului că bazinul Dunării s-a extins în detrimentul bazinului Jiului, cei trei afluenti mai importanti - Blahniţa, Drincea şi Desnăţuiul captând sectoare din cursul superior al afluenţilor Jiului.
Din analiza fragmentării reliefului Piemontului Bălăciţei rezultă că acesta se află în diferite stadii de evoluţie, complexitatea fragmentării fiind strâns legată de gradul de maturitate a văilor şi de complexele morfogenetice impuse de evoluţia paleogeografică.
Cuvinte-cheie: bazin hidrografic, adâncimea fragmentării, densitatea fragmentării, coeficient de corelaţie, Piemontul Bălăciţei
INTRODUCTION
The Bălăciţa Piedmont represented the study object for both geographers and geologists and, thus, a series of information was recorded in papers that were particularly dedicated to this sub-unit of the Getic Piedmont, or in works that referred to more extended regions. Among these authors, we mention Roşu Al.
(1959), Ghenea C. et al. (1963), Badea L. (1970) Badea L. et al. (1974, 1976), Posea Gr. et al. (1974), Cucu V. et al. (1980), Stroe R. et al. (1980, 1983).
The study of this region is minutely resumed in 1992, in the work entitled Geografia României, volume IV, where the natural background, the human geography elements concerning the population and the settlements, as well as the economic potential of
the Bălăciţa Piedmont are analysed. Within this study, the denomination used for the researched area is “Bălăciţa Piedmont” (Rom. “Piemontul Bălăciţei”), as a component of the Getic Piedmont.
The most recent studies that deal with this geographical unit belong to Stroe R. (2003), Enciu P.
(2007), Enache C. (2008) and Boengiu S. (2008).
The river network in the Bălăciţa Piedmont is distributed on two drainage basins: of the Danube and of the Jiu. The interfluve between the two catchments divides the piedmont into two parts that are approximately equal and symmetrical in form. The geological conditions, although apparently simple, the generally divergent character, the dominance of the autochthonous rivers, except for the Motru and the Jiu, give the original note in the organization and the
evolution of the hydrographical network within the Bălăciţa Piedmont (Boengiu S. 2002).
The hydrographical network that is tributary to the Jiu has west – east orientation, the main tributaries being on the right; towards the springs, the slope of the thalweg ascends rapidly – in the area of origin being 3 – 6 gullies that come together to form the main watercourse. The valleys are asymmetrical, the slopes on the left (the north) being much steeper and more linear, while those in the right (the south) are generally convex and show gentler slopes. At the same time, the rivers are quite long, 20 – 70 kilometres, showing narrow valleys in the upper sector, but also wide floodplains at least on half of the distance covered.
All these characteristics show the fact that the watercourses situated north of the watershed between the catchments of the Jiu and of the Danube appeared on the initial surface that was cut by the rivers that regressively advanced from the Jiu towards the west, as the Jiu deepened its riverbed, but they were also influenced by the structure of the fundament in which the strata incline towards north-east, making easier the appearance of the right side tributaries. The main factor that led to the configuration described above and to the slopes of the valleys, which are steeper towards north, is represented by the general inclination of the piedmont that, as shown by the maximum heights on the interfluves, descends from the north-west (330 – 350 meters) towards the south- east (150 – 200 meters).
The watercourses that head from the Piedmont towards the Danube show a west – east or north- west – south-east orientation in the upper sector, they gradually gravitate towards south and, before leaving the piedmont or at its limit, they bend towards west. There can be noticed a resemblance between the course of the Danube, which firstly bends towards west at Ostrovul Corbului, and its tributaries, fact which underlines the dependency of these watercourses on the route followed by the Danube (Boengiu S. 2002).
The analysis of the cross-sections and the hypsometrical map shows the permanent movement of the Blahniţa and of the Drincea towards east, the western slope being less inclined than the eastern one, which is steep, forming the scarp of a cuesta.
All the tributaries are consequent to the geological structure and come from the west, on the eastern slope in the upper and middle sector being only much younger gullies.
MATERIALS AND METHODS
The map of the relief drainage density and that of
topographical maps, scale 1:25,000, through the method of the cartograms; a geographical database was realised by using the ArcGIS 9.2 software and the entire hydrographical network was vectorised, starting with the 1st order in the Horton-Strahler system. Taking into account the significant leaps within the series of values and the morphometrical aspects of the study area, there were chosen five classes. The repartition of the surfaces and the share of the value classes were graphically represented and, in order to realise a unitary, comparative analysis, the classes of the drainage density and relief energy were also computed and represented in intervals with entire values.
Methods specific to the statistical analysis allowed for the observance of the parameters of the drainage density, relief energy, as well as the correlation between the two parameters.
The field observations were conducted in order to clarify or to add certain elements that did not appear on the maps.
DISCUSSIONS AND RESULTS
The relief of the Bălăciţa Piedmont is characterised by the existence of three areas that display specific features (Boengiu S., 2008), i.e. the catchments of the Blahniţa and of the Drincea, that of the Desnăţui and the Jiu catchment area.
The drainage areas of the Blahniţa and of the Drincea (Boengiu S. et. al, 2003) are characterised by rivers with subsequent valleys, which deeply cut a monocline structure with north-west – south-east orientation, made up of deposits of soft, predominantly sandy rocks; thus, they reduced much of the initial piedmont surface, which was maintained only on the narrow interfluves. The catchment of the Desnăţui is completely different, the interfluves are broad, tabular, the deepening of the hydrographical network being much diminished. The drainage area of the Jiu river is characterised by the parallelism of the main valleys and the consequent watercourse of the Jiu tributaries, while the interfluves are narrow, sometimes made up of intersection hills and the valleys keep a relatively important width.
The previous analyses (Stroe R., 2003; Boengiu S., 2005, 2008; Boengiu S. & Avram S., 2009) were conducted for the entire piedmont or for each catchment area within the piedmont, while the present study follows a comparative analysis between the area corresponding to the Danube catchment and that connected to the Jiu river catchment.
The drainage density
The map of the drainage density (Fig. 1) displays values comprised between 0 km/sq km
and 6.6 km/sq km. The density that accounts for the highest share (Table 1), representing more than half of the territory (54.11 percent) is given by the values of up to 3 km/sq km; this class of values is mostly distributed in the catchment of the Desnăţui, where the interfluves present the aspect of genuine high plains.There follows the class with density values comprised between 3 and 4 km/sq km, with a share of 19.35 percent, which underlines the fact that higher densities (4 – 6.6 km/sq km) represent exceptions from the general rule (6.47 percent). The
distribution of the value classes corresponding to the two basins (Graph 1) points out to major differences, but also to certain similarities. Thus, the repartition of the surfaces and the share of the drainage density classes display lower values within the area related to the Danube (2 - 3 km/sq km – 15.37 percent, 3 - 4 km/sq km – 8.16 percent and 4 – 6.6 km/sq km – 2.49 percent) than within the one corresponding to the Jiu river (2 - 3 km/sq km – 17.36 percent, 3 - 4 km/sq km – 11.19 percent and 4 – 6.6 km/sq km – 2.98 percent) for the classes comprising values above 2 km/sq km.
0 2 4 6 8 10
0.00 0.39 0.78 1.16 1.55 1.94 2.33 2.72 3.11 3.49 3.88 4.27 4.66 5.05 5.44 5.82 6.21 More
Drainage density (km/sq km) Frequency
(100%) The JiuThe Danube
Graph 1. The frequency of the value classes of drainage density on the sectors corresponding to the Danube and to the Jiu When the values between 0 and 2 km/sq km are
taken into account, the share is favourable to the area that corresponds to the Danube (0 - 1 km/sq km – 9.27 percent, 1 - 2 km/sq km – 17.90 percent), as compared to the area that corresponds to the Jiu (0 - 1 km/sq km – 1.64 percent, 1 - 2 km/sq km – 12.57 percent). The most important difference of the drainage density between the two areas is to be noticed in connection with the 0 - 1 km/sq km class – with 7.63 percent, followed by the 1 - 2 km/sq km class – with 5.33 percent, while at the upper classes the difference is attenuated, being under 3 percent.
The relief energy
The map of the relief energy (Fig. 2) displays values comprised between 0 and 157 meters. The highest share in the relief energy (Table 2), representing almost half of the territory (45.52 percent) is given by the values of up to 30 meters, which are mainly distributed in the north and the west of the piedmont.
They are followed by the 30 - 60 meters and 60 - 90 meters value classes, which account for 31.93 percent, respectively 32.01 percent of the surface; the less extended surfaces are occupied by the values comprised between 90 and 120 meters (8.50 percent) and above 120 meters (only 1.45 percent).
The distribution of the values corresponding to the two catchment areas (Graph 2) underlines a total lack of synchronization related to the repartition of the surfaces and of the share of the relief energy classes. Thus, the most numerous population of values within the catchment corresponding to the Danube is registered at the level of the 0 – 30 meters class (21.5 percent), while in the drainage area corresponding to the Jiu, it registers only 4.02 percent and the highest share for the surface corresponding to the Jiu is given by the 60 – 90 meters class (21.47 percent), while within the area corresponding to the Danube, it owns only 10.54 percent of the values.
0 1 2 3 4 5 6 7 8 9
4 13 22 31 40 49 58 67 76 85 94 103 112 121 130 139 148 More
Relief energy (m) Frequency
(100%) The Jiu
The Danube
Graph 2. The frequency of the value classes of relief energy on the sectors corresponding to the Danube and to the Jiu Table 1
Quantitative data on the drainage density
Table 2
Quantitative data on the relief energy
Values
(km/sq km) Number
of values Relative frequency (percent) The Jiu The Danube The Jiu The Danube The Jiu The Danube
0.00 0.00 2 44 0.16 3.17 0.19 0.15 1 21 0.08 1.51 0.39 0.30 1 20 0.08 1.44 0.58 0.45 5 30 0.41 2.16 0.78 0.61 14 47 1.15 3.39 0.97 0.76 20 42 1.64 3.03 1.16 0.91 41 38 3.36 2.74 1.36 1.06 62 60 5.08 4.32 1.55 1.21 68 63 5.57 4.54 1.75 1.36 68 48 5.57 3.46 1.94 1.52 89 70 7.30 5.04 2.14 1.67 109 67 8.93 4.83 2.33 1.82 79 73 6.48 5.26 2.52 1.97 107 86 8.77 6.20 2.72 2.12 83 73 6.80 5.26 2.91 2.27 75 72 6.15 5.19 3.11 2.43 78 62 6.39 4.47 3.30 2.58 69 62 5.66 4.47 3.49 2.73 52 60 4.26 4.32 3.69 2.88 49 72 4.02 5.19 3.88 3.03 44 44 3.61 3.17 4.08 3.18 29 32 2.38 2.31 4.27 3.34 22 38 1.80 2.74 4.46 3.49 12 29 0.98 2.09 4.66 3.64 8 24 0.66 1.73 4.85 3.79 6 20 0.49 1.44 5.05 3.94 12 26 0.98 1.87 5.24 4.09 6 9 0.49 0.65 5.44 4.25 2 14 0.16 1.01 5.63 4.40 3 21 0.25 1.51 5.82 4.55 0 7 0.00 0.50 6.02 4.70 1 3 0.08 0.22 6.21 4.85 0 1 0.00 0.07 6.41 5.00 1 3 0.08 0.22 More 5.16 2 2 0.16 0.14 - 5.31 - 1 - 0.07 - 5.46 - 1 - 0.07
Values
(meters) Number
of values Relative frequency (percent) The Jiu The Danube The Jiu The Danube The Jiu The Danube
4 4.00 1 8 0.08 0.58 8.5 7.70 8 67 0.66 4.83
13 11.41 20 155 1.64 11.17 17.5 15.11 21 98 1.72 7.06
22 18.81 29 54 2.38 3.89 26.5 22.51 26 60 2.13 4.32 31 26.22 38 58 3.11 4.18 35.5 29.92 29 49 2.38 3.53 40 33.62 40 67 3.28 4.83 44.5 37.32 41 82 3.36 5.91 49 41.03 69 53 5.66 3.82 53.5 44.73 65 51 5.33 3.67 58 48.43 79 60 6.48 4.32 62.5 52.14 60 54 4.92 3.89 67 55.84 100 52 8.20 3.75 71.5 59.54 85 79 6.97 5.69 76 63.24 85 65 6.97 4.68 80.5 66.95 93 40 7.62 2.88 85 70.65 82 48 6.72 3.46 89.5 74.35 55 36 4.51 2.59 94 78.05 52 31 4.26 2.23 98.5 81.76 30 21 2.46 1.51 103 85.46 33 18 2.70 1.30 107.5 89.16 21 16 1.72 1.15 112 92.86 18 17 1.48 1.22 116.5 96.57 10 15 0.82 1.08 121 100.27 5 9 0.41 0.65 125.5 103.97 8 5 0.66 0.36 130 107.68 6 4 0.49 0.29 134.5 111.38 2 5 0.16 0.36 139 115.08 5 1 0.41 0.07 143.5 118.78 1 2 0.08 0.14 148 122.49 1 0 0.08 0.00 152.5 126.19 0 1 0.00 0.07 More 129.89 2 2 0.16 0.14 - 133.59 - 1 - 0.07 - 137.30 - 3 - 0.22
Fig. 1. The map of the drainage density in the Bălăciţa Piedmont
Fig. 2. The map of the relief energy in the Bălăciţa Piedmont
The correlation between the drainage density and relief energy
The representation in rectangular system (Graph 3) of the 2,608 values (1,388 for the area corresponding to the Jiu catchment and 1,220 for that within the Danube catchment) led to a correlation coefficient (r) of 0.202. The signification of this value was achieved through the application of the Student t=10.528 and Fischer z=0.327 control tests, as well as through the computation of the standard deviation or of the square average error of the size Sz, Sz=0.019.
For the drainage density – relief energy correlation there was computed the determination
coefficient CD=4.07, which means that 4.07 percent of the values of the relief energy are determined by the drainage density (the unexplained variation showing the value of 95.93 percent).
The analysis conducted on the basis of the applied tests and of the graphical representation led to the conclusion that the repartition of the fragmentation density and depth determinations that were obtained do not enter a Gauss curve, being dependent on certain other factors. The significant spreading of the data into the intervals of values of relief energy of 0 - 20 meters and 60 - 70 meters demonstrates the grouping of the influence factors on the two main catchments (of the Danube and of the Jiu).
Graph 3. The correlation between drainage density and relief energy
a – the interval of points concentration within the area corresponding to the Danube catchment;
b – the interval of points concentration within the area corresponding to the Jiu catchment
CONCLUSION
The highest values of the fragmentation are registered in the western and the northern parts, while the south and the east display the lowest values.
The analysis of the relief fragmentation within the Bălăciţa Piedmont shows that this unit is on different evolution stages, the complexity of the fragmentation being closely connected to the maturity degree of the valleys and to the morphogenetic complexes imposed by the paleogeographical evolution (Boengiu, 2005). The sector corresponding to the Danube, which
comprises the catchments of the Blahniţa and of the Drincea, as well as the Danube slope between Şimian and Batoţi settlements, is characterized by erosion in the most advanced stage, the initial piedmont surface being almost totally destroyed.
The sector that comprises the Desnăţui drainage area is characterised by much more reduced fragmentation densities and depths than the rest of the unit, the piedmont surface forming interfluves.
The sector corresponding to the catchments of the Jiu and of the Motru rivers is characterized by a less advanced evolution stage, the piedmont surface
0,00 1,00 2,00 3,00 4,00 5,00 6,00 7,00
0 20 40 60 80 100 120 140 160
Relief intensity (m) Drainage density
(km/sqkm) Jiu Dunare
The Jiu The Danube
a b
forming relatively rounded and very narrow surfaces on the interfluves.
The resemblances concerning the fragmentation parameters between the two areas are due to the lithological and climatic homogeneity, while the differences are a consequence of the evolution time depending on a certain base level and of the flow direction in report to the structure.
The grouping of the influence factors on the two main catchments (of the Danube and of the Jiu) is mainly due to the fact that the Danube catchment extended its surface in the detriment of the Jiu drainage area, the three more important tributaries, i.e. the Blahniţa, the Drincea and the Desnăţui capturing sectors from the upper course of the tributaries of the Jiu river.
ACKNOWLEDGEMENTS
The authors would like to kindly acknowledge all persons and institutions that supported this research by means of their knowledge, equipment or financial funds.
We mention that this study benefited by material and logistic support from the project Vulnerability of slopes and landslides in the Bălăciţa Piedmont.
The use of G.I.S. and the achievement of digital maps of vulnerability, CNCSIS code 2005/2008.
Special gratitude goes towards the researchers that previously studied this piedmont unit and to the useful suggestions offered by the reviewers.
REFERENCES
Badea, L., (1970), Terasele fluviatile din Oltenia, SC GGG, Seria Geografie, t. XVII, nr. 1, Bucureşti.
Badea, L., Ghenovici, Alexandra, (1974), Judeţul Dolj, Edit. Academiei. Bucureşti.
Badea, L., Niculescu, Gh., Sencu, V., (1976), Harta geomorfologică a României, sc. 1:1000000, Atlasul Naţional al R.S.R., pl. III-1, Edit.
Academiei, Bucureşti.
Boengiu, S., (2002), Observaţii hidrogeografice în Piemontul Bălăciţei. Revista Geografică T. VIII –2000, Institutul de Geografie, Academia Română, Bucureşti.
Boengiu, S., Curcan, Gh., Marinescu, E., (2003), Relief aspects within the hydrological basin of
the Drincea river, Analele Universităţii de Vest din Timişoara, Seria Geografie, vol. XIII.
Boengiu, S., (2005), Caracteristici morfometrice ale versanţilor din Piemontul Bălăciţei, Edit.
Universităţii din Bucureşti, Revista de Geomorfologie, vol. 4-5 / 2002-2003, Bucureşti.
Boengiu, S., Torok-Oance, M., (2005), Features of the fragmentation, within the Blahniţa basins.
The piedmont sector, Forum Geografic – SCGPM, nr. 4, Edit. Universitaria, Craiova.
Boengiu, S., (2008), Piemontul Bălăciţei. Studiu de geografie, Edit. Universitaria, Craiova.
Boengiu, S., Avram, S., (2009), Bălăciţa piedmont. A model of formation and evolution, Zeitschrift fur Geomorphologie, suppl. 2, nr. 53, Stuttgart–Berlin.
Coteţ , P., (1957), Câmpia Olteniei, Edit. Ştiinţifică, Bucureşti.
Cucu, V., Popova-Cucu, Ana, (1980), Judeţul Mehedinţi, Edit. Academiei, Bucureşti.
Enache, C., (2008), Geologia Olteniei, Edit.
Universitaria, Craiova.
Enciu, P., (2007), Pliocenului şi Cuaternarului din vestul Bazinului Dacic, Edit. Academiei Române, Bucureşti.
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Seria E, nr. 6, Bucureşti.
Posea, Gr., Popescu, N., Ielenicz, M., (1974) Relieful României, Edit. Didactică şi Pedagocică, Bucureşti.
Roşu, Al., (1959), Câteva observaţii fizico- geografice în Câmpia înaltă a Bălăciţei, Probleme de geografie, vol. VI, Bucureşti.
Stroe, R., (1983), Harta geomorfologică a Piemontului Bălăciţei, Lucr. Seminar. Geogr.
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Stroe, R., (2003), Piemontul Bălăciţei. Studiu geomorfologic, Edit. MondoRo, Bucureşti.
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Academiei Române, Bucureşti.
THE DYNAMICS OF THE PRESENT PROCESSES WITHIN THE SĂRĂŢEL CATCHMENT AREA
Nicolae CRUCERU1, Gheorghe HERIŞANU1
1 Spiru Haret University, Faculty of Geography, Bucharest, e-mail: [email protected], [email protected]
Abstract
The Sărăţel catchment displays a territory mostly located in the molasse area of the Buzău Subcarpathians. The physical-geographical characteristics, as well as the social-human impact, created a complete geomorphologic system, in which the present geomorphologic processes register accentuated dynamics. Starting with the year 2002 until 2008 there were monitored areas with significant impact on the landscape, among the most important processes under study being the landslides, the torrents, the ravines and the creep.
Keywords: present geomorphologic processes, landslides, torrents, ravines, creep
Rezumat
Dinamica proceselor actuale din bazinul hidrografic Sărăţel. Bazinul Sărăţel prezintă un teritoriu localizat în cea mai mare parte în arealul molasic al Subcarpaţilor Buzăului. Caracteristicile fizico-geografice, la care se adaugă impactul socio-uman, au creat un sistem geomorfologic integral, în cadrul căruia se manifestă o dinamică accentuată a proceselor geomorfologice actuale. Începând din anul 2002 şi până în 2008 au fost monitorizate areale cu impact însemnat asupra peisajului, dintre care se remarcă alunecările de teren, torenţii, ravenele şi creepul.
Cuvinte-cheie: procese geomorfologice actuale, alunecări de teren, torenţi, ravene, creep
INTRODUCTION
The dynamics of the present processes represents a segment of global interest because of the always more extended altered surfaces and of the intensities that sometimes affect the human society, even if occasionally the location, the amplitude and the intensity are (irreversibly or not) generated by man. The geomorphologic research passed from the descriptive studies conducted at the beginning of the last century to a monitoring and highly accurate analysis based on the technologies and the methodologies in use. The present studies can facilitate the explanation, the stage and the dynamics of certain geomorphologic processes and this is why the field familiarity with the area under analysis constitutes a requirement.
In the Romanian Subcarpathian area, the modelling processes represented the subject or constituted chapters of the numerous PhD theses or scientific papers bearing the title „study of geomorphology”. Among the published theses we mention those edited after 1967, in which the dynamic morphology is highly important - Roşu Al.
(1967), Badea L. (1967), Grumăzescu H. (1973), Brânduş C. (1981), Bălteanu D. (1983), Armaş Iuliana (1999), Dinu Mihaela (1999), Ene M. (2004)
and so on; there are to be added other PhD theses defended but not yet published (Micu M., Cruceru N.
and so on). Furthermore, the palpable results of the present processes monitoring were presented in scientific papers that are well supported by field data.
We shall limit the area to that in the Buzău Subcarpathians, where we quote the studies related to the dynamics of the processes, which were conducted by Mihăilescu V. (1951), Posea Gr., Badea L.
(1953), Alexandru Medelaine, Dragomirescu Ş., Şeitan Octavia (1964), Posea Gr., Ielenicz M. (1970), Popescu Dida (1971), Posea Gr. (1969, 1972), Badea L. (1972, 1973), Iancu Silvia (1974), Ielenicz M.
(1978, 1986), Bălteanu D. (1979), Niculescu Gh.
(1986), Cruceru N. (2004, 2005), Vespremeanu- Stroe A., Micu M., Cruceru N. (2007) and so on.
The present study aimed at achieving detailed mathematical data related to the present morphology and to the dynamics of certain processes (landslides, torrentiality, ravination and creep). Through the time monitoring of the main geomorphologic processes, we aim at quantifying and extending the monitored area.
Study area
The morpho-hydrographical catchment of the Sărăţel river is located at the exterior of the
Carpathian Bend, in the Buzău Mountains group and in the Buzău Subcarpathians sub-group.
From the mathematical viewpoint, it is located within the following coordinates:
- North – 45°28’40” N and 26°30’52” E;
- South – 45°17’10” N and 26°40’38” E;
- East – 45°24’21” N and 26°43’46” E;
- West – 45°25’12” N and 26°31’56” E.
From the hydrographical viewpoint, it is a left tributary of the Buzău river, the confluence being located near the settlement of Berca, Buzău County.
The limit of the Sărăţel is represented by the watershed between the river with its tributaries and the conterminous catchments: the Slănicul de Buzău valley in the northeast and the east; the Murătoarea valley in the east (southwards of the mud volcanoes plateau); the Bălăneasa valley in the west.
From the altitudinal point of view, in the northern part, the Sărăţel catchment reaches 935.4 meters in the Ivăneţu Ridge and the altitudes descend near the confluence with the Buzău to only 141.6 meters.
The catchment area covers a total surface of 189.54 square kilometres, representing one of the smallest catchments that are tributary to the Buzău.
At national level, it enters the category of small catchments.
The river is 34.21 kilometres long and it is characterised by an average multi-annual flow around 1 cubic meter/second.
From the geological viewpoint, the catchment area is located in the south of the Paleogene flysch and within the Mio-Pliocene molasse, with friable rocks, affected by present modelling processes.
There appear rocks such as the sandstones, the limestone, the conglomerates, the gypsum, the salt, the marls, the clays, the sands, included in the folded and faulted structures. The impact of the external agents generated a special landscape, dominated by landslides and torrential organisms.
The altitudes descend from the north to the south, from 900 meters in the Leordeţu Hill, 885 meters in the Pietrişului Peak, 821 meters in the Bocu Peak, 802 meters in the Piţigoiului Peak and so on, to altitudes under 150 meters in the lower sector of the Sărăţel floodplain.
Within the catchment area there are dominant the narrow interfluvial ridges, the main ones respecting the morpho-tectonic influence, while the secondary ones are perpendicular on the former. The structural relief, with numerous cuesta escarpments, creates a special note within the landscape. In the saliferous areas, there was formed a spectacular specific karst relief with accentuated dynamics.
The hydrography is represented by a poor phreatic nappe, with scanty flows. The surface water shows
important seasonal and annual variations.
Nevertheless, there are to be noticed the sulphurous, chlorinated, salty etc. springs located in the areas of Căneşti, Păcuri, Negoşina, Gonţeşti settlements.
From the climatic viewpoint, the Sărăţel catchment area is comprised between the 6 and 10°
C isotherm, with an average pluvial value of about 700 millimetres/year.
METHODOLOGY
Besides the classical methods that imply the use of maps and the field mapping with traditional means (compass, theodolite, steel measuring tape etc.), we used new instruments and methodologies in the detriment of the geographical science.
The maps or other finalities of the system impose two types of structures/models: raster and vector. The raster model uses a network of cells with regular distribution and an element belonging to this network is called pixel, being distributed row after row (from top to bottom) and column after column (from left to right). The raster data are presented under the form of points, lines and areas.
The raster model answers the requirement of representing an object in a more precise image (closer to the truth), results through numerous geometrical data, such as the position, the shape and their dimensions in space. The data analysis and the combination of strata (data or maps) are based on complex algorithms and imply an ideal topology, which imposes the elimination of the errors from the beginning.
The topographical elevation surveys were conducted during many field campaigns:
- for the landslides: August 2002, August 2005 and September 2008;
- for the torrents: June 2007;
- for the ravines: August 2002, August 2005 and August 2008;
- for the creep, depending on the depth: July 2003 – July 2007.
During the topographical measurements/
elevation surveys, the theodolite was used in 2002, afterwards the total topographical station (Sokkia 610), the Garmin GPS (GPSmap 60Csx) for the landslides (the contour and the markers implanted in the slid mass), torrents (the contour), ravines (the length and the contour), the creep (the location). For the creep, we drew upon the “pillar test” method mentioned by A. Young (1960, 1972), quoted by N.
Rădoane, 2002 and which consists in the introduction of plastic rodlets (5 millimetres in diameter and up to 5 centimetres long) in the profile of the materials; this method offers the possibility to
of the phenomenon but not the differentiation of the movement speed of the material in depth. For this purpose, we used another method inspired by the examples emitted by N. Rădoane in 2002, with small changes. Thus, on two of the sample-plots (Plopeasa and Scoroşeşti) we used, instead of the plastic rodlets and wooden stakes (numerically marked with paint), red brick powder perpendicularly introduced (in 2003) on the topographical surface down to the depth of 50 centimetres, with the help of certain metallic tubes (3 centimetres in diameter), disposed at about 10 meters distance. Within these plots, the depth observations were conducted during 4 years, only at the beginning and at the end of the monitoring.
As database, there were used:
- The Topographical Maps scale 1:25,000, editions of 1979, 1981, 1982 (scanned and georeferenced);
- The Geological Maps scale 1:200,000, Covasna sheet (29 – L-35-XXI; year 1968) and Ploieşti sheet (36 – L-35-XXVII; year 1967) (scanned and georeferenced);
- The Satellite Images LANDSAT TM in seven bands, with 30 meters resolution;
- The Aerial Images or Aerial Photographs overlapped on the Digital Terrain Model (DTM), based on the above-mentioned topographical material.
RESULTS
The Sărăţel catchment lies on a complex fundament from the geological-structural and lithological points of view, represented by tight folds and faults and a diverse lithology dominated by Mio- Pliocene formations, poorly resistant at erosion and favourable to the present modelling processes. There are to be added the frequency and intensity of the downpours, the temperature variations, the energy and the fragmentation density of the relief and the land use, which lead to a great complexity and variety of the present geomorphologic processes. The present study deals with the complex of slope processes, such as the landslides, the torrentiality, the ravination and the creep.
The landslides
Numerous landslides with a great complexity of types are present within the Sărăţel catchment area. A total number of 338 plots with landslides were inventoried (2006-2007), covering an affected surface of more than 100 square meters (both the active and the stabilised ones). As case studies, we present two landslides monitored between 2002 and 2008.
Căneşti 1 Landslide
The landslide is located on the southern slopes of the Bocu hill, the slope ”towards Păcuri”, on an old, relatively stabilised glacis. The deposits belong to the Bedanian and they are dominated by marls and clays, tuffs and gypsums. The landslide is located within Căneşti settlement, in the concave bank of the former meander of the Sărăţel river.
After the construction of the communal road, the water of the Sărăţel was deviated 80 meters towards the south. From the mathematical viewpoint, the landslide has the following coordinates: in the south 45°23’46’’ N and 26°36’41’’ E, in the north 45°23’51’’ N and 26°23’36’’ E, in the east 45°23’48’’ N and 26°36’39’’ E and in the west 45°23’49’’ N and 26°36’43’’ E.
This is a landslide tongue with average depth and it is located on a slope with relatively small inclination, of up to 27°. The movement of the clayey mass does not take into account the geological structure (asequent landslide). The study area is crossed by a drainage that is only maintained during the rains that supply the clayey matrix with water. The area affected by the landslide extends on about 5,000 square meters, 4,020 of which are comprised between the detachment scarps and only 3,224 square meters represent the body of the landslide (September 2008) (Table 1).
Table 1 Morphometrical characteristics of the Căneşti 1 Landslide
The sector of the slope that is strictly affected by the landslide extends on a maximum length of 166 meters and a maximum width of 37.5 meters, having a maximum thickness of 5.3 meters in the narrowing sector from the terminal part. The detachment scarp has an almost circular shape, being fragmented by ravines that favour the withdrawal of the cornice. It is 0.5 – 3 meters deep and it is affected by gullies and ravines. The slid mass shows a wavy micro- morphology, with steps comprised between 0.30 and 0.70 meters. There are also present small steps that are perpendicular on the flowing direction and are characterised by dimensions under 0.8 meters (Fig. 1).
Morphometrical features in meters
L (average length) 158
l (average width) 22.6
h (average thickness of the mass)
2.4 S (surface of the slid mass) 3224 square meters V (volume of the slid mass) 8569.92 cubic meters Average movement speed (per
year)
2.2
Fig. 1 Căneşti 1 Landslide The slid mass has a volume of 8,569.92 cubic
meters. The landslide toe is located on a quasi- horizontal surface, having the shape of a spreading cone and, at the terminal part, it takes the form of a wave that slightly surpasses one meter. The movement speed of the slid mass is realised differently. The monitoring period of the markers was relatively short (only three years)
During this interval, the movement speed of the markers varied from 2.1 meters to 11.3 meters (during 3 years, from August 2005 until September 2008) (Table 2). The data acquired in the field support the fact that the most intense movements took place in 2005, both in spring, after the sudden snow melting, and at the end of the summer, after a downpour. After this period, the movement was
There developed a drainage network that crosses the body of the landslide on its central part, sometimes leading to a strong moistening of the nearby material and imposing it a more rapid movement speed than to the other stripes.
It is a semi-stabilised landslide, being invaded by a vegetation of small bushes.
Nevertheless, it remains a geomorphologic process with important impact on the landscape and it represents a risk factor because of the nearby social-economic activities. The terrain on which the landslide is located belongs to the common pasture. In the eastern part, the residences are situated at only 30 meters of the lateral detachment scarp, while the courtyard and the orchard are located on the upper part of the respective cornice. In the western part, the residences are to be found starting with 63 meters. From the landslide toe to the communal road there is only a distance of 16.35 meters, this portion presenting a prolonged spring moistening.
Table 2 Distance covered by the markers within the Căneşti 1 Landslide
Şuchea Landslide
The landslide is located on the northern slopes of the Pietricica Suchii hill, on the slope called
”Strâmbu Şuchii cu Pini”, which has been stabilised through pine tree plantations starting with the ’60s.
The deposits belong to the Badenian and to the Helvetian, being dominated by marls, clays and gypsums. The landslide is located within Şuchea settlement, near the Strâmbu Şuchii riverbed, which is a tributary of the Sărăţel on the right. From the mathematical point of view, the landslide has the following coordinates: in the south 45°24’06’’ N and 26°35’01’’ E, in the north 45°24’30’’ N and 26°34’58’’ E, in the east 45°24’26’’ N and 26°35’02’’ E and in the west 45°24’25’’ N and 26°34’60’’ E.
It is a landslide tongue with average depth and it is located on a slope with relatively small inclination, of up to 28°. The movement of the mass is realised on a dominantly clayey slope and it does not consider the geological structure (asequent landslide). The landslide under study developed as a typical mudflow, but without having a clear supply area. Initially, the landslide appeared at the end of the 60’s under the form of a ravine that evolved regressively both upstream and laterally. In the 90’s, it became a real mudflow that reached the riverbed, the materials being subsequently taken by the Strâmbu Şuchii stream. The lateral slopes mainly supplied the materials. Once the slope gets milder, the flow becomes a landslide, having a slower and periodical movement.
The area affected by the landslide extends on almost 3,300 square meters, 2,120 of which are comprised between the detachment scarps and only 1,943 square meters represent the body of the landslide (September 2008) (Table 3). The slope that is strictly affected by the landslide extends on a maximum length of 202 meters, a maximum width of 46.7 meters near the toe (the spreading cone) and a minimum one of 5.3 meters, having a maximum thickness of 6.9 meters in the narrowing sector from the terminal part. The detachment scarp has an ovoid shape and it is fragmented by ravines that favour the withdrawal of the cornice. Its depth varies between 0.5 and 0.8 meters and it is affected by gullies and ravines. The slid mass shows a wavy micro-morphology, with steps comprised between a minimum of 0.30 meters and up to 0.80 meters.
There are also present small steps perpendicularly disposed on the flow direction, their dimensions being less than 1.8 meters (Table 4 and Fig. 2). The volume of the slid mass is of about 7,469.28 cubic meters. The landslide toe is located on a quasi- horizontal surface, a floodplain terrace, and it takes Markers
No.
Distance covered between August 2005 and September 2008 (meters)
1. 2.1
2. 4.8
3. 4
4. 3.8
5. -
6. 5.1
7. 5.3
8. 7.7
9. 5.1
10. 6.2
11. 6.8
12. -
13. -
14. -
15. 10.1
16. 6.2
17. 10.2
18. -
19. -
20. 6.3
21. 8.2
22. 11.3
23. -
24. 6.2
25. 8.9
26. -
Average speed = 6.6 meters
