Estimation of the Areas with Accelerated Surface Runoff in the Upper Prahova Watershed (Romanian Carpathians)

Liliana Zaharia1, Gabriel Minea1, Gabriela Ioana-Toroimac1, Ruth Barbu2, Ioan Sârbu1

1University of Bucharest – Faculty of Geography, Department of Meteorology and Hydrology, Bucharest, 2University of Bucharest, Faculty of Geography, “Simion Mehedinţi – Nature and Sustainable Development” Doctoral School, Bucharest, Romania

 E-mail: [email protected], [email protected], [email protected]

Abstract This paper aims to identify the areas prone to rapid surface runoff and, consequently, with high potential for flood occurrence. In order to reach this goal we relied on the Flash Flood Potential Index (FFPI), which integrates those physical parameters of the watershed that control the surface flow: rock permeability, soil texture, slope gradient, curvature profile and land use. The integration of these parameters was accomplished in a GIS environment, through multiple operations that included digitization, interpolation, cropping, conversion, classification, reclassification and cartographic algebra. The size of the grid cell was set to 20 (hence, the area of a pixel/cell was 400 m2). Depending on the favorability/restrictiveness of each flow control factor, five classes, numbered from 1 to 5, were established. By adding the specific values of each class with the investigated parameters, we obtained a new grid, called FFPI. This was further reclassified into four classes: very low, low, medium and high. The study area overlaps the Upper Prahova watershed, a region with significant socio-economic importance (especially for the road and railroad transportation, as well as for tourist activities), where floods and other associated phenomena (inundations, landslides) are frequent and may lead to serious damage. The preliminary results of the investigation point out the prevalence of the areas with medium and low FFPI; the values of the FFPI are high especially within the urban areas, where good conditions for accelerated flow exist, which explains why these areas are so much prone to flooding and slope processes.

Keywords: accelerated surface runoff, flash flood potential index (FFPI), physiographical features, Upper Prahova Watershed

1. Introduction Surface runoff is the resultant of the interaction between the specific natural and anthropogenic factors in a given area (Pişota & Zaharia, 2002). While climatic factor (and especially precipitation) is the main control of surface runoff, under similar pluviometric input, hydrological response is very different, depending on the features of the area affected by the flow. Thus, part of the meteoric water may be retained by the vegetation canopy (especially the forest) or by the forest litter (Arghiriade, 1977; Gaspar, 2006). Depending on the characteristics of the bedrock and soil (porosity, permeability, texture, water saturation etc.), another fraction of precipitation percolates the substratum, thus contributing to the ground-water runoff (Scrădeanu & Alexandru, 2007). In urban areas, the highly impervious substratum favors the surface flow and water accumulation in the low-lying areas. Terrain morphological features and morphometric attributes control water concentration and water velocity along the slopes. These factors are variable in space and time (because of the phenological phases, soil humidity, changes in land use and land occupation), and that’s why their influence on runoff increases or diminishes accordingly. The combination of all the factors that encourage accelerated overland flow increases the susceptibility of flood occurrence, especially within the medium and small watersheds in the mountain areas (Stănescu & Drobot, 2002). Within this context, the present paper aims, by integrating the main physical factors controlling the surface flow, to estimate the areas prone to accelerated runoff, and therefore with high potential for flood occurrence. The integration was accomplished in GIS environment and it materialized in the computation of a synthetic index, called Flash Flood Potential Index (FFPI). Depending on its values, four classes reflecting the flood ocurrence potential were established (very low, low, medium and high). FFPI method was initiated by Smith (2003) and applied for case studies in the United States (Abeyta 2009; Brewster, 2010; Kruzdlo & Ceru, 2010). In Romania, it was employed and adapted by Mătreaţă & Mătreaţă (2010), Teodor & Mătreaţă (2011) and Minea (2011), who used it in order to estimate the flash flood potential on small

BALWOIS 2012 - Ohrid, Republic of Macedonia - 28 May, 2 June 2012 1 and medium watersheds. Borcan & Achim (2011) applied the method on a larger basin (the Ialomiţa’s). The study deals with the upper (mountain) watershed of the Prahova River (about 340 km2), a region that, because of its specific socio-economic activities (especially transportation and tourism), is vulnerable to the risks induced on the one hand by the slope runoff, and on the other hand by the floods. The obtained results were partly validated by field observations. These data may be turned into useful spatial information, which can support the planning efforts aimed at curbing, or at least at diminishing, the risks induced by floods and accelerated flow down the slopes.

2. Study area The study area overlaps, as mentioned previously, the upper watershed of the Prahova River (area 337 km2; river length 35 km), lying in the Carpathian Mountains, at the contact between their Eastern and Southern branches. More specifically, it belongs on the west to the Bucegi Mts., on the east to the Baiu Mts. and on the north to the Timişului Mts. (Fig. 1), which are predominantly made up of Lower Cretaceous sedimentary formations, represented by calcareous sandstones, calcareous schists and sandy schists. Because of the lithology, fault systems and neotectonic processes, in the Curvature Carpathians region uplifting processes are extremely active: in the study area the lifting rates are “as high as +5 mm/yr” (Zugrăvescu et al., 1998).

Figure 1. Upper Prahova Catchment and location of gauging and weather stations. Gauging stations: 1. on Azuga River. 2. Buşteni on Valea Cerbului River, 3. Buşteni on Prahova River. Weather stations: a – , b – Omu Peak, c – 1500 Source data: information processed from topographic maps, scale 1:25,000; geo-spatial.org, 2011

BALWOIS 2012 - Ohrid, Republic of Macedonia - 28 May, 2 June 2012 2 The valleys are narrow, with breaks of slopes in their long profile. The mean altitude of the watershed (determined through GIS techniques), based on the topographic maps of Romania (edition 1980), is 1286 m. Maximum elevation reaches 2505 m a.s.l. in the Omu Peak, while the minimum altitude of 571 m a.s.l. is found within the Prahova channel, at the point where it leaves the investigated territory (Fig. 1). The mean gradient of the watershed is 23.1°; gradients between 30° and 81.1° can be observed on 23.03% of the study area, and especially in the Bucegi Mts., on the “Bucegi Eastern Scarp” (Mihai et al., 2009). The cliff has a structural origin, inasmuch as it represents the flank of a syncline (Micalevich - Velcea, 1961). In the Upper Prahova watershed, precipitation is the main flood control. The mean amount of recorded precipitation at the weather stations in the area is 941.7 mm at Predeal (1090 m a.s.l. altitude), 999.1 mm at Omu Peak (2505 m a.s.l.), and 1025,7 mm at Sinaia (1510 m a.s.l.) (according to Administraţia Naţională de Meteorologie – ANM, 2008, and to the data obtained from the National Meteorological Administration – NMA, for the period 1961 – 2000). Most precipitation falls during the May – August interval (over 120 mm/month in June and July); they have a prevailing torrential character and generate floods (Fig. 2a). The maximum precipitation fallen in 24 hours has reached 122.1 mm at Predeal (on June), 102.4 mm at Omu Peak (on June), and 106 mm at Sinaia (on July) (Fig. 2b).

150 a 150 b Predeal w.s. Predeal w.s. Omu Peak w.s. Omu Peak w.s. Sinaia w..s. 120 120 Sinaia w.s.

90 90

60 60 Precipitation (mm) Precipitation Precipitation (mm) Precipitation 30 30

0 0 I II III IV V VI VII VIII IX X XI XII I II III IV V VI VII VIII IX X XI XII Time Time Figure 2. Mean (a) and maximum in 24 h (b) precipitations in Upper Prahova Catchment (1961 – 2000) (charts based on data from ANM)

Referring to the meteorological conditions, Stăncălie et al. (2010) and Zoccatelli et al. (2010), pointed out that the effect induced by the Carpathians is characterized by „a high frequency of organized thunderstorm systems” and the hydrological response consists in „flood frequency in the summer season (late June, July and August)”. The Upper Prahova Watershed is drained by a dense network of torrential streams, channels and valleys. The basic morphometric characteristics of the Upper Prahova watershed and its main sub-basins are synthetically shown in Table 1. One can note not only the high gradients of the river thalwegs and the high mean altitudes of the watersheds, but also the small size of the basins. All these conditions encourage water concentration, accelerated overland runoff and flash flood events.

Table 1. Morphometrical features of watercourses in the Upper Prahova River Watershed Data about Watercourse Watershed Watercourse L H (m) Ir Cs A Hm 2 (km) source confluence (‰) (km ) (m) Azuga* 23 1600 938 29 1.96 88 1360 Valea Cerbului* 7 1400 861 77 1.14 26 1536 Zamora* 7 1720 837 126 1.27 10 1311 Valea Rea* 7 1800 808 141 1.22 15 1337 Peleş* 6 1980 808 195 1.25 6 1415 Izvoru Dorului* 16 2140 753 87 1.50 33 1446 Valea Fetei* 5 1400 882 103 1.12 10 1324** Prahova** 35 1200 517 19 1,26 337 1286

L = river length, H = altitude, Ir = river slope, Cs = sinuosity coefficient, A = watershed area, Hm = watershed mean altitude. * - According to data from Aquaproiect, 1992; ** - Results obtained through GIS techniques based on the topographic maps of Romania, scale 1: 25,000, edition 1980.

BALWOIS 2012 - Ohrid, Republic of Macedonia - 28 May, 2 June 2012 3 The mean pluriannual discharges recorded in the Upper Prahova watershed are small and do not exceed 3.02 m3/s (Table 2). The maximum discharges and floods are specific for late spring and summer. More than 50% of the maximum discharges of the Prahova and Valea Cerbului rivers and 41% of those of the Azuga River occur during June – August interval (52% and 59% respectively) (according to Zaharia, 2004, for the period 1961 – 2000). During the flood events, maximum discharge may be 50 to 130 times higher than the mean pluriannual discharge. The largest floods recorded at the gauging stations lying on the rivers belonging to the Upper Prahova watershed were the following: on the Azuga, at the homonymous gauging station, 94 m3/s (July 2, 1975), 92.4 m3/s (November 11, 2001) and 81.5 m3/s (March 23, 2007); on the Valea Cerbului, at Buşteni I, 62.3 m3/s (June 19, 2001), 54.2 m3/s (July 17, 1988) and 24.7 m3/s (August 13, 1999); on the Prahova, at Buşteni I (formerly called Poiana Ţapului), 165 m3/s (July 2, 1971), 154 m3/s (July 18, 1969) and 153 m3/s (July 19, 1981) (according to the data provided by the National Institute of Hydrology and Water Management – NIHWM).

Table 2. Physico-geographical and hydrological features of the catchments corresponding to the gauging stations in the Upper Prahova River Watershed 1 1 1 1 1 2 2 1 Gauging station/ A ALT P F URB Qm Qmax Pan No. 2 3 3 Q /Q watercourse (km ) (m) (°) (%) (%) (m /s) (m /s) max mod (mm) 1. Azuga/Azuga 90 1334 5.8 72 4 1.83 94 51.3 921 Buşteni (Poiana 2. 25 1429 9.9 66 1 0.48 62.3 130.4 836 Ţapului/ValeaCerbului 3. Buşteni/Prahova 208 1282 6.1 66 5 3.02 165 54.6 914

A = catchment area; ALT = catchment mean altitude; P = catchment mean slope; F = forest rate; URB = urbanization rate, Qm = mean pluriannual discharge; Qmax = maximum discharge; Pan= mean annual rainfall. Considered periods: for Qm: Azuga/Azuga (1960 – 2010), Buşteni/Valea Cerbului (1958 – 2010) and Buşteni (Poiana Ţapului)/Prahova (1966-2010); for Qmax: Azuga/Azuga (1960 – 2008), Buşteni/Valea Cerbului (1958 – 2008), and Buşteni (Poiana Ţapului)/Prahova (1956-2008). Data sources: 1) Zaharia, 2004; 2) Administraţia Bazinală de Apă Buzău - Ialomiţa, 2011.

The concern for this study area is determined by its socio-economic importance and by the fact that it is highly prone to accelerated surface flow and inundations. Thus, the is a major Transcarpathian axis, which facilitates the connection between the southern and central parts of the country. It is paralleled by the national (DN1) or European (E60) road and by the railroad 300 (a stretch of the 4th Pan-European Corridor) (Dobre et al., 2011). Along the Prahova River valley, there are a number of settlements (Posada, Sinaia, Poiana Ţapului, Buşteni, Azuga, Predeal) with industrial and tourist functions (mountain trips, winter sports, climbing) belonging to the urban system „Sinaia – Azuga – Buşteni – Predeal – Râşnov – Braşov” (Cocean et al., 2009). The built up area of the settlements in the investigated area totals about 9 km2 and is inhabited by approximately 27,000 people (according to data from The National Institute of Statistics, 2012).

3. Data and methods In order to reach the proposed objective we devised a physiographic method known as Flash Flood Potential Index (FFPI). As mentioned previously, this was proposed by Smith (2003) and applied in the United States (Abeyta 2009; Brewster, 2010; Kruzdlo & Ceru, 2010). In Romania, it was adapted by Mătreaţă & Mătreaţă (2011), Teodor & Mătreaţă (2011) and Minea (2011). The method consists in estimating a synthetic index (FFPI), which integrates the main geographical factors that control the flow: rock permeability, slope gradient, curvature profile, soil texture, land use and land cover. This index provides information at grid level (pixel) about the accelerated or decelerated character of the overland flow and, consequently, about the potential of flood occurrence. Integration is achieved by intersecting in GIS environment the corresponding grids for the considered geographical features. The main contribution of the present study is the introduction of rock permeability as a new parameter for computing FFPI. We deem this factor is important for our investigated territory, inasmuch as we deal here with a mountainous topography in which soil is generally weakly developed and the rocks are bare on relatively large areas, especially on the eastern scarp of the Bucegi Mts. All the analyzed parameters are integrated as spatial data in GIS software (e.g. ArcGis). In order to apply this method, we run a sequence of operations that can be separated into three stages: I. The collection of the necessary data (vector and raster) and their geographical referencing in the same projection system. For this purpose, we used geological maps of scale 1:50,000; pedological maps of scale 1:200,000; and the Digital Elevation Model – with a grid cell of 20 (20 x 20 = 400 m2) obtained through the manual digitization of the topographical maps of Romania, scale 1:25,000 (using Bilaşco’s recommendations, 2009) – as well as the data

BALWOIS 2012 - Ohrid, Republic of Macedonia - 28 May, 2 June 2012 4 derived from it (gradient, profile curvature). Likewise, we used spatial data derived from Corinne Land Cover (2006), corroborated with aerial photographs (ANCPI, 2005). The cartographic and vector materials were georeferenced in the Stereographic Projection 1970. II. Conversions of vector layers (polygon topology) into raster, and classification/reclassification of raster layers. Based on the existing literature (Chendeş, 2007; Drobot & Chendeş, 2008), we established for each investigated parameter five unit classes, with values from 1(minimum) to 5 (maximum), corresponding to their hydrological response and adapted to the local features. Class 1 signifies a low participation in the flow formation, while class 5 corresponds to a high participation (Table 3). The establishment of these classes also depends on terrain characteristics, for which this method doesn’t have a general validity. For instance, we assume that the sediments and colluvial deposits are permeable and hence, they hinder the flow, while the flysch made up of sandstones and calcareous schists is much less pervious and therefore it plays a very important part in flow formation. Sandy texture encourages percolation, while loamy and, especially, clayey textures are almost impervious when become wet (Chendeş, 2007). From the hydrological standpoint, the negative profile curvature (convex slopes) encourages accelerated flow (Constantinescu, 2006), while the positive one (concave slopes), associated with low gradients is specific for decelerated flow. Likewise, the forests are deemed to retain part of the water, thus hindering the flow, while urban areas, with impervious ground, have the opposite effect. III. The summation through cartographic algebra of the raster layers. The summation is a methodological contribution of the present study, inasmuch as previous works opted for either for the mediation (Smith, 2003; Minea, 2011) or for the weighted average (Mătreaţă & Mătreaţă, 2011; Teodor & Mătreaţă, 2011) of the spatial data provided by the different raster layers taken into account. The option for summing was justified by the fact that the final results obtained through this method reflected better the situation in the field, in comparison with the results obtained only through average mediation (simple and weighted). Depending on the extreme values, the FFPI grid was reclassified into four classes: (i) very low – FFPI < 10 – associated to decelerated flow; (ii) low – 10 < FFPI < 15; (iii) medium – 15 < FFPI < 20; and (iv) high – FFPI > 20 – associated to accelerated flow (Table 3). The method assumes that both precipitation and the antecedent moisture index are uniformly distributed over the investigated territory.

Table 3. The classification and indexing of the physiographic factors necessary for the computation of the FFPI values in the Upper Prahova Watershed Parameter Slope Profile FFPI Lithology Score gradient* curvature Soil texture* Land use** (class) (permeability) given (°) (radian/m) Sediments Broadleaf and colluvial forests, very low deposits 0 – 5 – Loamy – clayey coniferous 1 (< 10) and mixed forests low Loamy – clayey, loamy, - 5 – 10 – – 2 (10 – varying textures 15) - Grasslands, Loamy, glades, medium 10 – 20 1 – 2,99 loamy – clayey, pastures, 3 (15 – loamy sandy agricultural 20) lands Calcareous Loamy, clayey, 20 – 30 0 – 0,99 – 4 flysch Loamy – clayey high Sandstone- (> 20) > 30 -1,99 – 0 Clayey Urban areas 5 shale flysch * - according to the hierarchical system proposed by Mătreaţă & Mătreaţă, 2011; ** - data obtained by processing the ortophotoplans ANCPI, 2005 and CLC, 2006; FFPI = Flash Flood Potential Index.

4. Results and discussions By using the described methodology, we estimated the FFPI values at the scale of the upper watershed of the Prahova River and consequently we were able to come up with a regionalization

BALWOIS 2012 - Ohrid, Republic of Macedonia - 28 May, 2 June 2012 5 map. As shown in Figure 3, FFPI takes values from 7 to 25. The high values correspond to the areas with high gradients, to the concave slopes, to the areas with loamy or clayey textures, and to the areas with bare rocks. Such areas are found especially on the eastern scarp of the Bucegi Mts., on the eastern slope of the Baiu Mts. (between Poiana Ţapului and Sinaia), and on the gorges stretch lying upstream of Posada. Likewise, they are specific for urban areas. Considering the FFPI classes established according to the criteria mentioned in the Data and methods section, we made a preliminary assessment of the situation at the level of the entire investigated territory. Based on our findings, we were able to notice the prevalence of the areas with medium (54.07%) and low (44.86) values of FFPI index, while the class of high values accounts for only 1.02% of the study area. The latter, generally corresponds to the urban areas (Azuga, Buşteni, Poiana Ţapului, Sinaia), where, because the impervious surfaces prevail, water cannot percolate the ground and so it concentrates into channels and flows rapidly down the slope. This favorability for accelerated flow is further enhanced by the fact that higher up on the slopes there are areas with medium values of FFPI.

Figure 3. The distribution of FFPI in the Upper Prahova Watershed

The results obtained show that the settlements developed along the Prahova River at the foot of the Bucegi and Baiu Mts., experience a high vulnerability to the risk induced on the one hand by the accelerated overflow and on the other hand by the flash floods occurring on the rivers dissecting the

BALWOIS 2012 - Ohrid, Republic of Macedonia - 28 May, 2 June 2012 6 slopes. The results were partly validated by the field investigations carried out in the perimeter of the Buşteni town, and in Poiana Ţapului, which is one of its neighborhoods. These investigations confirmed the existence of good conditions for accelerated flow and flash flood formation. The areas with high values of FFPI overlap both part of the densely built-up areas and the transport infrastructure, thus making them extremely vulnerable. A major element of vulnerability is the road and railroad transport infrastructure (of national and European rank), inasmuch as many sections of it lie within the Prahova’s floodplain, near the valley sides, and in the areas highly prone to inundations, caused either by the river overflowings or by the waters running down the slopes (Fig. 4. a). In order to lessen the flood risk generated by the rapid concentration of meteoric waters along the steep slopes, most watercourses were improved through hydrotechnical structures. Thus, thresholds were created across the thalwegs and channels were dug in order to divert the waters that menace the adjacent buildings and the various elements of infrastructure (Fig. 4.b).

300 railroad DN1/E60 road

Prahova River road a b Figure 4. a. The railroad and the DN1/E60 road lying in the Prahova’s floodplain (photo: Gabriela Ioana -Toroimac); b. The improvement works on the Urlătoarea Valley, in the Poiana Ţapului neighborhood Buşteni town (photo: Liliana Zaharia). Focusing our analysis to the Valea Cerbului sub-basin (the only one on the right bank of the Prahova having a gauging station), we notice that the map of FFPI distribution indicates that the highest percentages (57.01%) are held by the medium class (15-20), followed by the low class (10- 15), which accounts for 42.74%. The lowest shares (0.02%) of the areas correspond to very low class (<10). As far as the high class (>20) is concerned, it accounts for only 0.23% of the entire area and is found both in the upper part of the watershed (corresponding to the Bucegi Eastern Scarp) and in the lower one (Fig. 5).

Figure 5. The distribution of FFPI in the Upper Prahova Watershed (1. Buşteni gauging station on Valea Cerbului River)

BALWOIS 2012 - Ohrid, Republic of Macedonia - 28 May, 2 June 2012 7 The latter has a high vulnerability to floods and slope runoff, inasmuch as many buildings and elements of transport infrastructure are concentrated within this area (Fig. 6.a and b). Otherwise, this territory is frequently affected by the inundations brought about by slope runoff and the flood events occurring on the Valea Cerbului. As mentioned previously, the largest floods occurred in July 1988 (54.2 m3/s), June 2001 (62.3 m3/s) and August 1999 (24.7 m3/s) (according to NIHWM). In order to lessen the damage produced by the floods and inundations affecting the lower stretch of the Valea Cerbului, several hydrotechnical engineering works have been accomplished (river bank reinforcements, channelization). Although we consider the results of FFPI method as appropriate, as long as they were validated by field observations, we must necessarily be aware of some limitations and possible errors. These may derive from the following: the resolution at which the various investigated parameters are spatialized; the basic hypotheses regarding the uniform distribution of precipitation and antecedent moisture; the type, density and phenological stage of forest vegetation etc. The establishment of qualitative classes for FFPI is subjective, depending on the values determined for the study area, which are valid only for this particular territory.

a b

arrangements partially degraded

Figure 6. a. DN1/E60 road crossing the Valea Cerbului River in Buşteni town; b. Buildings and road in close proximity of the Valea Cerbului River in Buşteni town (arrangements of river banks, partially degraded are remarkable) (photos: Ruth Barbu)

5. Conclusions and perspectives The estimation of the areas with accelerated surface runoff allows the identification of the areas prone to flash flood and inundations. A method that can be used in this respect relies on the determination of the FFPI, a synthetic index that integrates the main controls of surface flow. The present study applied the FFPI method on the Upper Prahova watershed, an important region from the socio-economic point of view, which shows a high degree of vulnerability to the risks associated with slope runoff and floods. In order to determine the FFPI values, several parameters were integrated in GIS environment, as follows: rock permeability, slope gradient, profile curvature, soil texture, land use and land cover. The final results point out that in the Upper Prahova Watershed, FFPI has values ranging from 7 to 25. More than half of the study area (54.07%) corresponds to the medium class, with FFPI values between 15 and 20. The high values class (over 20) accounts for only 1.02% of the territory. Such values are specific especially for the urban areas (Azuga, Buşteni, Sinaia), which makes them extremely vulnerable to accelerated overland runoff down the slopes and to flash floods. In perspective we intend to improve the results of the FFPI method using, if possible, a finer spatial resolution. We also intend to extend the validation of the results in other areas and to estimate the vulnerability to rapid overland runoff and flood of area identified as exposed to such processes. Even though the method may contain some uncertainties and possible errors, it allows the identification of the areas prone to accelerated runoff and floods, thus meeting the requirements of preliminary flood risk assessment as they are stipulated in the EU Directive on the assessment and management of flood risks (2007). The spatializing of the perimeters favorable to accelerated flow with the help of the FFPI may prove to be very helpful, especially for the local communities, which try to introduce structural and non-

BALWOIS 2012 - Ohrid, Republic of Macedonia - 28 May, 2 June 2012 8 structural measures for diminishing the negative consequences of this phenomenon. In our opinion, in the urbanized perimeters, an important part in this respect should be played by the development and proper maintenance of the drainage network, which is aimed at evacuating the pluvial waters. At the slope level, it is necessary to accomplish hydrotechnical engineering works, in order to reduce flow velocity. Periodical rehabilitation of the existing improvement structures is compulsory, because the high frequency and the force of the flash floods contribute to their deterioration in a relatively short time, thus reducing their efficiency.

Acknowledgment We wish to thank the National Institute of Hydrology and Water Management and National Administration of Meteorology Bucharest for their kindness to put at our disposal hydrological and climatic data. Furthermore we wish to express our gratitude to PhD. Octavian COCOŞ, who assisted us with the translation of the paper.

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