DOI: 10.29302/Pangeea 18.06

THE RIVER BASIN OF IARA, CONSIDERATIONS ON THE ENERGY AND HORIZONTAL FRAGMENTATION OF THE LANDFORMS

Prof. ALEXANDRU SIMUTheological High School “Sfântul Vasile cel Mare”, Blaj, Romania

Prof. LIVIA MUREŞAN , Naţional High School “I. M. Clain”, Blaj, Romania

ABSTRACT: Geographic information systems allow mapping and various and complexanalyses of geographic components. The quantitative and qualitative results of depth anddensity analysis of fragmentation find their use in a wide range of areas, from road and railsystems building, to forest and land developments.

Key words: Iara Basin; energy; fragmentation; density of drainage; Landform energy;

Introduction

This study presents the results of theanalysis of two very important morphometricindicators, specific to the quantitativegeomorphology. Quantitative data obtainedcan be used in qualitative and hydrologicalgeomorphological studies on thespatio-temporal evolution of leakageparameters.

The area for which this analysis of thedensity of fragmentation and landformenergy is carried out overlaps the basin of theIara valley, a tributary of Aries to the leftside.

According to Horton-Strahler classi-fication, this basin has the V order and it issituated on the eastern flank of theGilău-Muntele Mare Mountain (Figure 1).

The geological composition of the area is

Fig. 1. Geographical position

46 Alexandru Simu, Livia Mureşan

due to the predominance of the hard rocks(granite, andesites, amphibolites, subshrubs,paragnaises, micashistes) characteristic ofthe Great Mountain area and less of softrocks (conglomerates, clays, etc.) whichcharacterizes the Iara Depression (Figure 2).

In fact, as we will highlight in this study,

the petrography of the area is the decisivefactor in the spatial evolution of the densityand energy of fragmentation.

The altitudinal range of the hydrographicbasin falls in values that oscillate between1825.8m (Mount Mare) and approx. 350-400m in the area of the Iara Depression.

As it can be seen from the hypsometricmap, more than two thirds of the basinsurface overlaps over the mountainous area,a fact that is particularly important in spatialand temporal evolution of differentgeomorphological, hydrological orbio-pedo-climatic processes (Fig.3).

Problem Description

The density of the horizontalfragmentation of the landform (Grigore,1979, Ungureanu, 1989) or the drainagedensity is the ratio of the hydrographic /drainage network length to the surface unit

(generally km²), expressing the degree ofhorizontal fragmentation of the landform;and the landform energy highlights therelationship between the geologicalcomposition, the basic local level, on the onehand, and the degree of deepening / erosionof the hydrographic network, on the otherhand.

The lithological, tectonic andlong-lasting development have underpinnedthe present aspect of the landform, imposingspecial morphological, hypsometric features,which in turn represent the support of thedrainage network organization.

Fig. 2. Geological map

47The River Basin of Iara, considerations on the energy and horizontal fragmentation of the landforms

Obtained results

A) Density of drainageThe morphometric studies of river basins

differentiate this parameter as follows:drainage density and hydrographic networkdensity. The first quantitative parameterrefers to the totality of permanent andtemporary watercourses, and the secondrefers only to the segments of permanentwatercourses. In order to obtain thequantitative information necessary todetermine the quantitative values of thehydrographic network density (length /number of segments) it is necessary to vectorall the permanent segments of thehydrographic network using large and verylarge scale maps, and for the determinationof the drainage density values, it is necessaryto map out on the field all organizeddrainage systems starting from the smallest(gullies, holes) and to the torrential ones.

This parameter specific to thequantitative geomorphology reveals thedegree of fragmentation of the relief imposed

by the lithological, tectonic substrate, thevariety of landforms and the types of specificgeomorphological processes. For the Iarahydrograph ic ba s i n , we r ecor dmorphologically and lithologically theexistence of some areas specific to themountainous area with a massive youngmassif with deep, young valleys and highdensity at altitudes between 1200 m and1600 m where the density values oscillatebetween 1 , 5 km / km2 and over 2.5 km /km2 (Figure 4).

Within these perimeters, thehydrographic network achieves both strongfragmentation and strong vertical erosionimposed by the low local base leveldetermined by the relatively low altitude ofthe Iara Depression.

At altitudes above 1600 m, the lowdensity values (<1.0 km / km2) are specificto the higher leveling platformFârcaş-Cârligata, at the bottom of which Iaraand its tributaries have their sources. Thearea of the Iara Depression records on alarge part of its surface, low densities of the

Fig. 3. Hypsographic an hypsometric map

48 Alexandru Simu, Livia Mureşan

permanent hydrographic network, withvalues ranging from 0.5 km / km2 to 1 km /km2. On the other hand, one can notice ahigh-density area of over 2 km / km2, whichrepresents a real "water gathering market"corresponding to the confluence zone of theIara valley with the tributaries Almăşeni,Capra, Făget, Agriş, Cacova etc., a graftedarea almost central to the Iara Depression.

The percent density values are shown inFIG. no. 4. Thus we find a predominance ofhigh density areas of between 1.0 and 2.0 km/ km2. These geographic areas, where thesehigh values of the parameter are recorded,account for 47% of the total river basin.

In fact, the analysis of the 1:25 000topographical map highlights that an intensefragmentation of the territory is directlyproportional to the density of the riversegments. From a morphometric point ofview, there has been ascertained a closeconnection between the density of thehydrographic network and the frequency ofthe water courses on a certain territory, thephysical-geographic characteristics.

For the Iara river basin, thephysico-geographic conditions imposed by

the lithology of Muntele Mare Massif(Massif granite, Granodiorites, subshrubs,Paragnaises) and the soft deposits of the IaraDepression, determined a variation in thevalues of water courses frequency. Thus, themountainous area has specific high values,while the depression corresponds to lowvalues. In brief, the use of thisgeomorphological parameter helps to expressthe degree of dissection in the horizontalplane of the morphological surfaces within aterritory, as a result of the modeling of thelandform and its partitioning by the action ofthe exogenous factors.

B) Landform energyThe result of the investigation of this

parameter is the landforms energy map(Figure 5). In this way we obtain valuablequantitative data showing the peculiarities ofthe deformation, in close correlation with theintensity of current geodynamic processes,with visible effects in the degree of evolutionof the landforms.

For the water catchment area of the Iaravalley, there has been found the existence ofvalues ranging from 30 to over 500 m / km2.

Fig. 4. Density map

49The River Basin of Iara, considerations on the energy and horizontal fragmentation of the landforms

These values are determined by thegeological composition of the Muntele-MareMassif and the contact area with the ColinarDepression of Transylvania, which includesthe Iara Depression.

Thus, in the mountainous area, one cannotice the predominance of the low andmedium values, specific to theMăguri-Mărişel erosion platform, where theerosion speed is slowed by the hardness ofthe geological substratum made of granite,granodiorite, subshrubs, paragneisses etc.

Also, values below 100 m / km2predominate in the Iara Depression, wherethe substratum is predominantly made up ofthe soft structures specific to the Plateau ofTransylvania. The maximum values of350-450 m / km2 are recorded in the middleof the basin, , where the local base levelspecific to the depression zone imposed anerosion and thus a strong deepening of theriver so that the minor bed is locatedopposite the main interfluvial peak, ataltitudes of 800-900 m; this peak separatesValea Ierii from the tributaries that havetheir springs on the eastern slope of theGreat Mountain. At the same time in the

confluence area with Arieşul, the values ofthe parameter are large because the Iara riverhas grafted its bed over a narrow area wherea crystalline massif emerges and stands outthrough great energy and geodesy and forthis reason Iara created an impressive gorge(figure 6).

In percentage terms, most over 60%values are specific to areas/fragments withdepth of fragmentation exceeding values of100 to 200 meters. Thus, more than 75% ofthe water catchment area is very fragmented(Figure 7), because it overlaps the mountainridge of the eastern area of theGilău-Muntele Mare Mountains. The lowestvalues of fragmentation depth are found inthe area of the Iara Depression, where thesoft rocks did not impose such great energy.

The second area with reduced landformenergy is found on the interfluvial peakseparating the upper course of the IaraValley from the area of the sources of thetributaries on the left (Huza, Săvuleşti, Iartaetc.), where the Magi-Mărişel levelingsurface occupies an appreciable extent , andthe predominance of granites andgranodiorites imposed a massive, heavyaspect.

Fig. 5. Energy map

50 Alexandru Simu, Livia Mureşan

Conclusions

This study is a short study of appliedgeomorphology which aims to presentaspects of hypsometry determined by GIStechnology. The quantitative analysis of thehorizontal and vertical fragmentation of thelandforms, the practical issues addressed,hopefully will make this work a practicaltool and a database of real use for the localand regional authorities in order to achievea sustainable arrangement of thisgeographical space, by taking concrete and

effective measures.In fact, the water catchment area of the

Iara valley is of great importance from thetourist point of view due to the climaticresort and the numerous hostels located inthe proximity of Cluj-Napoca, which canlead the local authorities to modernize theroad and public infrastructure so that alongwith the physical-geographic features ofmountain and depression area, it shouldbecome a true oasis of relaxation, whether inthe hibernation or the summer season.

Fig. 7. Percentage of fragmentation

Fig. 6. Valea Ierii gorge

51The River Basin of Iara, considerations on the energy and horizontal fragmentation of the landforms

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