Journal of Environmental Science and Engineering B 1 (2012) 918-921
Formerly part of Journal of Environmental Science and Engineering, ISSN 1934-8932
Asssment of Soil Erosion in Mountain Watershed Ecosystems in Tirana-Region
史东鹏Entela Çobani and Oltion Marko
Department of Environmental Engineering, Faculty of Civil Engineering, Polytechnic University of Tirana, Tirana 355, Albania Received: May 21, 2012 / Accepted: June 5, 2012 / Published: July 20, 2012.
Abstract: Land erosion is an increasing problem that is riously affecting our country in recent years. In many areas of our country, mountainous and hilly territories suffer major erosion in both surface and depth, where the solids are deposited in the flat parts of the country, thus leading to a higher content of gravel in agricultural land and filling of the wage networks. The phenomenon of erosion is greater in the vicinity of residential areas where damages are larger and more nsitive. One of the most vulnerable in our country in terms of soil erosion is the district of Tirana. This study had the main goal to define and categori of erosion rates in natural environments of the forest economies of the Tirana,
the rate of recovery of vegetation, slope and rainfall index, which will rve as information and guidance on the land u by farmers, communes and the state regulatory officials, depending on the ownership of the woodland surfaces.
Key words: Erosion, ecosystem, soil, slope, land cover, vegetation.
1. Introduction
Soil erosion reprents one of the most destructive phenomena of the earth, by both surface and depth erosion. The relatively significant activity of water erosion that is obrved in our country is favoured by many factors such as landscape, geological structure, slope, soil, climate, etc.. The incread intensity of erosion is cloly linked with high rate of destruction of vegetation cover. The degradation of vegetation or its complete destruction is determined by many factors, especially by the socio-economic system of each country [1]. This is also obrved in Tirana, where as a result of negative impacts caud by mankind on the natural environment, the erosion phenomenon is becoming more and more problematic, especially during periods of inten precipitation.
情人节 英语This phenomenon is also significantly affecting on massive slides which are already evident in many areas of the country, causing considerable damage to the
Corresponding author: Oltion Marko, Ph.D., rearch fields: soil erosion, forest, waste treatment technology, environment.E-mail:***********************.environment, and in the economy. A crucial role in preventing this phenomenon belongs to vegetation, especially the forest [2]. But the role of vegetation is not immediately en after its installation.
2. Materials and Methods
Tirana area is one of the most typical areas of our country regarding the development of erosion.
The study and analyzing of the factors that influence the development of erosion is bad on a methodology which is ud to asss the risk of erosion also in other areas of our country, where data are collected according to the division of forest economies [2]. Regarding the paration of the vegetation coverage rate, it is done according to this grouping: up to 0.3;
0.4-0.7 and > 0.70 [3, 4].
Asssment of the risk of erosion as per the slope is grouped as follows:
0°-5°: little risk of erosion;
6°-15°: moderated risk of erosion;
16°-30°: average risk of erosion;
31°-45°:
major risk of erosion;
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Asssment of Soil Erosion in Mountain Watershed Ecosystems in Tirana-Region
919
> 45°: strong risk of erosion.
Soil erosion rate is determined by comparing the open profile of land with the standard profile in terms of soil erosion at four levels as follows [5]:
Class 1: up to 25% of a horizon in most of the surface; Class 2: from 25%-75% of a horizon in most of the surface;
Class 3: over 75% of the horizon and generally also a part of B horizon;
Class 4: deeply eroded soil, in such a way which prents a network streams with average depth or deep depth.
To express the degree of aggressiveness of the climate factor, the combination of the product of the amount of multi-annual mean precipitation with the sum of precipitation during the critical period, for each 100 m elevation above a level is ud, according to Eq. (1) [6]:
000
.10k v
r R R I ⋅= (1) I r —rainfall indicator;
R v —sum of multi-annual mean rainfall in mm; R k —sum of multi-annual mean rainfall during the critical period in mm;
mbr是什么10.000—coefficient of converting the results into reduced productive values.
From the literature indicator I r (indicator of rainfall) is classified as follows:
I r < 50: erosion risk of first category;
51 ≤ I r ≤ 80: erosion risk of cond category; 81 ≤ I r ≤ 150: erosion risk of third category; 151 ≤ I r ≤ 275: erosion risk of fourth category; I r > 275: erosion risk of fifth category.
sunt3. Results and Discussion
The total area of forest economies (the studied area) is 83.840 ha, divided according to the forest economies and the vegetation coverage rate which is as follows: As it can be en from the data in Table 1, most of the forest area of Tirana district take part in the interval of 0.3 with 55%, then in the range of 0.4-0.7 with 27.5% and in the interval of 0.7 with 17.5%.
Table 1 Forest area according to coverage rate.
Area according to coverage rate (ha)
Up to 0.3 0.4-0.7 > 0.7 44,501.8 26,974.25 12,363.95
This shows that the forest vegetation in the economies is deteriorated, which directly affects the dynamics and development of soil erosion.
Field study of soil is made on the basis of expeditions carried on during the period of 2003-2006, and ongoing consultation with studies previously conducted in the economies.
For each main profile considered in the field, the relevant files were completed and for each horizon the morphological description was done where samples were taken from 500-1,000 g which were labelled and restudied in a subquent stage.
From the analysis made in this area it resulted to have the land types and subtypes:
(1) Brown mountain lands which lie in the belt of oak forests ranging from 400 m to 1,400 m above a level in height. This type of land is located in the form of two subtypes, according to the FAO classification Eutric Cambisols (CMe) and Rhochic Nitosol (NTr); (2) Fulvous forest lands which lie on land formations above the area mountain brown lands, at the height ranging of 1,200-1,800 m above the a level. This type of land is found in the form of two subtypes, Humic Camisols (CMu Humic Nitosols (NTu));
(3) Brown meadows lands, or Haplic Phaeazems (CME).
The slope gradient is one of the main elements of landscape that has an impact on soil erosion. Given the fact that in this area the vegetation is degraded, the influence of inclination of the slopes will be greater. According to the management plans and inventories of forest economies and topographic maps, the categorization of slope was done as follows:
As en from Table 2, the slope of the mountain in this area is from moderate to large. Soil erosion rate is determined by comparing the considered profile with the standard one, and in terms of soil erosion it is
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Asssment of Soil Erosion in Mountain Watershed Ecosystems in Tirana-Region 920
Table 2 The area according to the slope.
Area (ha) according to the slope
0°-5° 6°-15° 16°-30°
31°-45°
>
华浦教育45° 4,104 4,117 66,761 8,364 494 classified in four class:
Class 1 (E1): Up to 25% of the first horizon (A) in most of the surface;
Class 2 (E2): From 25%-75% of the first horizon (A) in most of the surface;
Class 3 (E3): Over 75% of the first horizon, and generally, part of the horizon (B);indies
monet>ticklingClass 4 (E4): Deeply eroded soil.
In a more detailed way, the erosion rate is prented in Table 3.
As en from Table 3, erosion in forested areas of Tirana district is quite large, where around 41% of the surface area takes part in the third and fourth grades of erosion.
Erosion by the vegetation coverage rate is made after determining the class of coverage of forest vegetation, where by the surfaces with coverage rate (0.1-0.3, 0.4-0.7 and > 0.7), profiles were opened, in the same way as for determining the degree of erosion. In Table 4, it prents the distribution of erosion risk class in function of the degree of coverage by vegetation.
As en from Table 1, surfaces with coverage of 0.1-0.3 are the most affected by erosion, as a result of degradation of vegetation, while in areas with large scale of coverage (> 0.7) no erosion of class E4 is found. Table 5 prents the distribution of erosion risk class according to the slope which characterize the area, where grouping according to the slope is done at five levels (0°-5°, 6°-15°, 16°-30°, 31°-45°, > 45°).
As en from Table 5, the surface with small scale slope (0°-5°), no erosion of fourth class is found, while in areas of steep slope (>45°), only erosion of third and fourth class is found. This shows the influence of slope in the development of soil erosion process. While erosion under rainfall index is done by calculating the average annual rainfall for 100 m above a level, and the critical period is October-March. Results for this indicator are given in Table 6. Regarding the precipitation indicator, territories up to 100 m above a level are classified in the first category, by 200-500 in the cond category, by 600-1,100 in the third category, by 1,200-1,700 in the fourth category and for altitudes > 1,700 m above a level in the fifth category.
Table 3 Rate of erosion.
Rate of erosion
E1 E2 E3 E4 ha % ha % ha % ha %
19,441 23 29,808 36 18,646 22 12,945 19 Table 4 Determination of the erosion rate according to the coverage rate.
Class
Area in (ha) divided according to coverage rate
Total (ha) 0.1-0.3 0.4-0.7
>
0.7
E1 2,745.60 7,467.6 9,228.25 19,441.45 E2 13,633.55 13,935.9 2,238.80 29,808.25 E3 18,703.80 2,044.95 896.90 21,645.65 E4 9,418.85 3,525.80 - 12,944.65
Table 5 Determination of the erosion rate according to the slope.
Class
Area in (ha) divided according to the slope
0°-5° 6°-15° 16°-30° 31°-45° >
45°
E1 E2 E3 E4 3,115.3
824.4
164.9
1,438.1
2,058.9
494.1
126.5
14,181.8
25,159.4
18,411.1
9,009.1
706.2
1,765.5
2,471.7
3,420.8
-
-
103.8
389.2
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Asssment of Soil Erosion in Mountain Watershed Ecosystems in Tirana-Region 921 Table 6 Calculation of rainfall indicator.
Altitude above a level (m) Rainfall最新大学排行榜
indicator I r
Erosion
risk category
100 86.4
I 200 99.3
II 300 113.0 II 400 127.5 II 500 143.0 II 600 159.3 III 700 176.8 III 800 195.0 III 900 214.1 III 1,000 234.0 III
1,100 254.8 III
1,200 276.4 IV 1,300 299.5 IV 1,400 322.5 IV 1,500 347.7 IV 1,600 373.0 IV 1,700 398.7 IV 1,800 426.2 V
1,900 454.1 V
2,000 483.0 V 4. Conclusion
From the study and analysis of arch results, it will arrive at some preliminary conclusions of the study: The study area lies on three land types. Brown mountain lands lie in the belt of oak forests ranging from 400 m above a level to 1,400 m. This type of land is located in the form of two subtypes. The study of vegetation shows that interventions with negative effects on the forest environment from anthropogenic factors em to be quite large.
The current rate of erosion turns out to be quite critical. It is divided into four class: first class includes 19,441.45 (ha) or 23% of the total area, the cond class 29,808.25 (ha) or 36%, the third class 18,645.65 (ha) or 22% and the fourth class 12,944.65 (ha) or 19%.
According to the classification made by grouping class of erosion according to vegetation cover rates, it shows that the surfaces of small scale coverage have more erosion of third and fourth class.
Bad on the results of rainfall indices the erosion risk is distributed in five categories, from I to V.
In areas that are eroded and that prent the risk of slippage or landslips it should be intervened by biological works, where the works should be made on tho surfaces which have degraded vegetation.
In the upper parts of water catchment areas, where the amount of liquid and solid flow is less, protective fences with wood material must be constructed, as well as dikes with dry stone masonry with concrete.
In risk areas risk of slippage or landslips, hydro-technical works should be built with gabions, as they are more flexible.
In the main bed flow hydro-technical works must be constructed with cement mortar stone walls dimensioned according to given methods, taking into account the permeability of the terrain to be placed.
References
[1]O. Marko, Land Erosion and Measures of Restoration,
SHPLU Tirana, Tirana, 2010, pp. 10-35.
[2]O. Marko, Risk evaluation of masive forests erosion in
Vithkuqi area district of Korca, Ph.D. Thesis, Agriculture
University of Tirana, Tirana, 2006.qq名字英文
[3] D.B.C. Beasley, L.F. Huggins, E.J. Monke, ANSWERS:
A model for watershed planning, Transactions of ASAE
23 (1980) 938-944.
[4]Management of Land Cover in Watershed, FAO, Italy,
1977, pp. 55-80.
[5]O. Marko, Asssment of Soil Erosion Risk in Mountains
Watershed, DDS Tirana, Tirana, 2010, pp. 94-100.
[6]H.M.J. Arnoldus, An approximation of rainfall factor in
the universal soil loss equation, in: M. De Boodt, D.
Gabriels (Eds.), Asssment of Erosion, Record No.
198****4087,1980,pp.115-170.
.
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