ACTUAL WATER EROSION RISK IN POLAND BASED UPON CORINE LAND COVER 2006

Rafał Wawer, Eugeniusz Nowocień, Bogusław Podolski
Department of Soil Science Erosion Control and Land Protection, The Institute of Soil Science and Plant Cultivation - State Research Institute, Pulawy, Poland

ABSTRACT

Erosion risk in Poland is generally well recognized. The first country wide map in mid-scale map of potential water erosion risk was produced in '80 according to the qualitative method of potential water erosion risk (PWER) indicator, developed by Anna and Czeslaw Jozefaciuk. The potential erosion risk indicator corresponds to an erosion thread for the soil without any plant cover. It bases on relatively static factors of slope, soil texture and average annual rainfall, distinguishing five grades of erosion intensity. The indicator provides no information on the real and actual state of erosion risk,  which depends mostly from the kind of land use. Anna and Czesław Józefaciuk from the Pulawy Erosion Research Center, located in the Institute of Soil Science and Plant Cultivation – State Research Institute, developed methodology for the qualitative indicator of actual water erosion risk (AWER), which includes a land use factor, as well as the factor for erosion prevention techniques.
The work includes the production of an actual water erosion map, based on the digitized map of potential water erosion at a scale of 1:300.000 and CORINE Land Cover 2006. The results show relative high actual erosion risk in highest intensities – up to 1.7% of Poland under the very strong erosion, up tp 0.9% under strong erosion and up to 4.4% under medium erosion. Compared to potential water erosion, where the same grades cover 17.6% of country's area, the erosion risk at high grades decreased by 10.6%. The values are almost identical to the results of AWER assessment performed basing upon CORINE CLC2000 (10), however the general trend is decreasing for the erosion risk grades: 0, 1, 2 and 4; while grades 3 and 5 very slightly increased. According to the land use structure derived from CLC2006, up to 2.18 million hectares (compared to 2.23 million in 2000) remain under the risk of water erosion in high erosion intensity grades and requires erosion control measures.

Key words: soil erosion, water erosion risk, erosion risk indicator, erosion risk map.

INTRODUCTION

According to hitherto estimations the share of land surface potentially threaded with water erosion in Poland is estimated to 30%, while the erosion intensities in grades from average to very strong have the share of ca 17% of the country's area [5]. The average annual soil loss due to water surface erosion in Poland is estimated to 76Mg·km^-2 according to Jozefaciuk [6], while the extremes oscillate between 2.7 to 280 Mgkm^-2, according to Maruszczak [9].

Poland has a country-wide map of potential water erosion indicator (PWER) in scale of 1:300.000, made in the '80 by the Pulawy Erosion Research Center, supervised by Czeslaw Józefaciuk [6,7]. The map was produced in result of generalization of source paper materials:  1:25000 slope maps derived from topographical maps and 1:300.000 soil maps; and it has been positively validated in detailed studies at a scale of 1:5000. The potential water erosion risk (PWER) indicator distinguishes five grades of water erosion intensity, although the developed PWER map was generalized to three grades:

1. Low erosion risk, grades 1 and 2 from the 5-grade system;

2. Madium erosion risk, grade 3 from the 5-grade system;

3. High erosion risk, grades 4 and 5 from the 5-grade system.

The potential water erosion risk presents a static type of indicator, utilizing factors of soil texture, slope and average annual rainfall, relatively stable in time. The indicator of actual water erosion risk (AWER), developed also by Anna and Czeslaw Józefaciuk [7] introduces the dynamic factor of land use and agrotechnique, which strongly influence the intensity of surface water erosion.

The lack of country-wide spatial land use information for Poland limited the application of actual water erosion risk indicator to detailed local, small area studies [8,10,11], based mostly on satellite scenes, aerial orthophoto maps and high resolution DEMs. The results of these detailed studies, compared to the results of physical modeling revealed good representation of Józefaciuks' qualitative indicators regard to the physics of water erosion processes [10].

Thanks to the regular and increasingly frequent publication of the CORINE Land Cover [1,2,3,], allow country-wide assessments of actual water erosion risk. CORINE CLC is a reliable source of land use information, produced from LANDSAT imagery using remote sensing techniques. For the area of Poland three time series of the CLC dataset are available: 1990, 2000 and 2006, both in vector (reference scale 1:100.000) and raster (resolution of 100m and 250m).

METHOD

The analysis was performed on the base of Actual Water Erosion Risk (AWER) method, developed by Anna and Czeslaw Józefaciuk [7], which introduces five grades of water erosion risk and erosion intensity related to the risk classes:

1. very low erosion risk (weak erosion);

2. low erosion risk (moderate erosion);

3. medium erosion risk (average erosion);

4. high erosion risk (strong erosion);

5. very high erosion risk (very strong erosion).

The water erosion risk classes are distinguished by an overlay operation of spatial layers representing: soil texture, slope, average annual rainfall and land use type. The decision rule for the AWER indicator is shown in Table 1.

As the potential erosion risk indicator (PWER) (Table 2) can be interpreted as an erosion intensity on slope-along plowed land in black fallow the decision rule for actual water erosion (AWER) indicator can be transformed to a set of reduction factors, diminishing the potential erosion intensity [7]. The values of the reduction factor, assumed for particular Corine Land Cover land use classes are given in Table 3. As CLC data carries limited quantity of information we have simplified the original decision rule, assuming all land use types mentioned in the method are maintained with no erosion control measures.

Table 1. Decision rule for the estimation of actual water erosion indicator [7]

Soil groups according to their susceptibility to water erosion. Texture classes according to Polish PTG classification.	Slope inclinaton	Small-area fields						Orchards		Permanent grasslands
		Conventional tillage with plowind direction:			Conservational tillage with plow direction:			On terraces and sod	In sod belts perpendicular to slope
		Slope-along	Perpendicluar to slope	terraces	Slope-along	Perpendicluar to slope	terraces
Very high susceptibility Loess and loess-like, silts	< 3° 3–6° 6–10° 10–15° >15°	1 2 3 4 5	0 0 1 2 3	0 0 1 2 3	0 1 2 3 4	0 0 0 1 2	0 0 0 1 2	0 0 0 1 2	0 0 1 2 3	0 0 0 1 2
High susceptibility Loose sands, rendzinas	< 3° 3–6° 6–10° 10–15° >15°	1 1.2 2.3 3.4 5	0 0 1 1.2 3	0 0 0.1 1.2 3	0 0.1 1.2 2.3 4	0 0 0 0.1 2	0 0 0 0.1 2	0 0 0 0.1 2	0 0 0.1 1.2 2	0 0 0 0.1 2
Average susceptibility low-loamy sands, loamy sands, gravels, old rendzinas	< 3° 3–6° 6–10° 10–15° >15°	0.1 1.2 2.3 3.4 4.5	0 0 0.1 1.2 2.3	0 0 0.1 1.2 2.3	0 0.1 1.2 2.3 3.4	0 0 0 0.1 1.2	0 0 0 0.1 1.2	0 0 0 0.1 1.2	0 0 0.1 1.2 2.3	0 0 0 0.1 1.2
Low susceptibility Light loams, average loams, calcarous loams.	< 3° 3–6° 6–10° 10–15° >15°	0 0 0 3 4.5	0 0 0 1 2.3	0 0 1 1 2.3	0 0 0 2 3.4	0 0 0 0 1.2	0 0 0 0 1.2	0 0 0 0 1.2	0 0 0 0 2.3	0 0 0 0 1.2
Very low susceptibility Heavy loams, clays, rocky soils, heavy soils with non-calcarous skeleton, peats.	< 3° 3–6° 6–10° 10–15° >15°	0 0.1 1.2 2.3 3.4	0 0 0 0.1 1.2	0 0 0 0.1 1.2	0 0 0.1 1.2 2.3	0 0 0 0 0.1	0 0 0 0 0.1	0 0 0 0 0.1	0 0 0 0.1 1.2	0 0 0 0 0.1

Table 2. Decision rule for the estimation of potential water erosion indicator [7]

Soil groups according to their susceptibility to water erosion Texture classes according to Polish PTG classification	Slope inclinations [%]
	0–6	6–10	10–18	18–27	>27
	Degree of erosion thread
Very high susceptibility Loess and less-like, silts	1	2	3	4	5
High susceptibility Loose sands, rendzinas	1	1; 2	2; 3	3; 4	5
Average susceptibility Low-loamy sands, loamy sands, gravels, old rendzinas	1	1; 2	2; 3	3; 4	4; 5
Low susceptibility Light loams, average loams, calcarous loams.	0	1	2	3	4; 5
Very low susceptibility Heavy loams, clays, rocky soils, heavy soils with non-calcarous skeleton, peats.	0	1	1; 2	2; 3	3; 4; 5

Explanations to table 1 and 2 In case of two erosion grades occurring simultaneously in one record, the lower value is taken for areas with average annual rainfall below 600mm, while the highest for remaining areas. In case of some cells in Table 2, the third erosion risk grade is applied to areas with average annual precipitation exceeding 800mm. The grades of the intensity of surface water erosion: 0. no erosion:  does not occur on given area; 1. weak erosion: causes only small surface soil losses; 2. moderate erosion: causes visible wash-off of humus horizon and worsening of soil properties. The full regeneration of soil is not always possible through conventional tillage. 3. average erosion: may lead to total reduction of humus horizon and development of soils with typologically un-formed profiles. The terrain dismemberment is starting. Considerable debris flow into surface waters. 4. strong erosion: can cause total destruction of soil profile, including the parent rock. This results in large fragmentation of terrain's relief and deformation of hydrology. 5. very strong erosion: effects similar to grade 4, but more intensive, driving into permanent degradation of ecosystems.

Table 3. The erosion risk reduction factor values for Corine CLC2006 land use classes [12]

Corine Land Cover land use classes				Reduction factor
No	Label Level1	Label Level2	Label Level3
111	Artificial surfaces	Urban fabric	Continuous urban fabric	4
112			Discontinuous urban fabric	4
121		Industrial, commercial and transport units	Industrial or commercial units	5
122
			Road and rail networks and associated land	5
123
124
			Port areas	3
131
			Airports	5
132
		Mine, dump and construction sites	Mineral extraction sites	1
133
			Dump sites	5
141
			Construction sites	0
142
		Artificial, non-agricultural vegetated areas	Green urban areas	3
			Sport and leisure facilities	2
211	Agricultural areas	Arable land	Non-irrigated arable land	0
222		Permanent crops	Fruit trees and berry plantations	2
231
		Pastures	Pastures	3
242
		Heterogeneous agricultural areas	Complex cultivation patterns	1
243
			Land principally occupied by agriculture, with significant areas of natural vegetation	1
311	Forest and semi natural areas	Forests	Broad-leaved forest	5
312			Coniferous forest	5
313			Mixed forest	5
321		Scrub and/or herbaceous vegetation associations	Natural grasslands	3
322			Moors and heathland	3
324			Transitional woodland-shrub	3
331		Open spaces with little or no vegetation	Beaches, dunes, sands	5
332			Bare rocks	5
333			Sparsely vegetated areas	0
334			Burnt areas	0
411 -523	Wetlands and inlad waters			5

Since original map of potential water erosion presents a generalization of source 1:25000 maps, reclassified from 5- to 3-grade erosion risk we had to reverse the process of generalization to achieve 5-grade erosion intensity as in original method. To adopt the three-class map of potential water erosion to original decision rule for AWER indicator, we have assumed two approaches, considering the highest and the lowest erosion risk grade within 3- grade classification (Table 4). The results are considered as maximal and minimal actual water erosion risks.

Table 4. Potential water erosion risk in Poland [2,13]

Erosion grade 5 classes	Erosion grade 3 classes	Explanation	Potential water erosion
			Number of polygons	Area
				ha	%
0		no erosion		20967844	67.1
1	1	weak erosion	5212	4775015	15.3
2		moderate erosion
3	2	medium erosion	3730	3693926	11.8
4	3	strong erosion	752	1479384	4.7
5
3-5	2-3	average to very strong erosion	4482	5173310	16.5
Sum			11303	31252987	100

The source PWER dataset was transformed to Polish PUW 1992 projection. CLC database has been reclassified to adopt it to decision rule, as described in Table 3. The actual erosion map has then been produced by overlaying the vector dataset of potential water erosion map with reclassified CLC2006 vector data set (Table 4) and performing database operations subtracting reduction factors from potential erosion risk classes. The zero and negative AWER values were classified in a "no erosion" category. The results are considered as maximal and minimal actual water erosion risks.

RESULTS

The analysis results show the area undergoing most devastative erosion grades (between 3 and 5) covers about 7.0% of country's area. These grades are mostly located on uplands, mountains and post-glacial lake districts i.e. on the terrains with diverse terrain's relief. The total area of land under water erosion risk covers between 16.3% and 17.9% of Poland. The detailed results are shown in Table 5.

Comparing the potential (Fig. 1, Table 4) and the actual (Fig. 2 and 3, Table 5) water erosion risk maps for Poland a significant reduction of areas undergoing the most destructible erosion grades (i.e. grades form 3 to 5) is clearly visible.

Table 5. Actual water erosion risk in Poland, based upon CLC2006

Erosion grade	Explanation	Minimal actual water erosion			Maximal actual water erosion
		Number of polygons	Area		Number of polygons	Area
			ha	%		ha	%
0	no erosion	207523	26170956	83.7	190758	25655177	82.1
1	weak erosion	13341	2517739	8.1	17064	532586	1.7
2	moderate erosion	11421	380345	1.2	24334	2875028	9.2
3	medium erosion	14150	1652453	5.3	8675	1371516	4.4
4	strong erosion	3325	530921	1.7	5604	287187	0.9
5	very strong erosion	0	0	0.0	3325	530921	1.7
3-5	medium to very strong erosion	17475	2183373	7,0	17604	2189623	7.0
Sum		249760	31252415	100	249760	31252415	100

Fig. 1. The map of potential water erosion risk in Poland (PWER) [2,13]

Fig. 2. The map of minimal actual erosion risk in Poland, based on Corine Land Cover 2006

Fig. 3. The map of maximal actual erosion risk in Poland based on Corine Land Cover 2006

DISSCUSION

The most important factor – the share of the areas under medium to very strong erosion grades [6,7] equaled to 16,5% in potential erosion map and to 7.0% in both: maximal and minimal; actual erosion maps. The results indicate that round 7% of Poland's terrestrial landscape should undergo erosion control measures (meliorations), i.e. kept under permanent crop cover.

Compared with the result of AWER assessment, performed basing on CORINE CLC2000, current results for CORINE CLC2006 do not differ considerably (Table. 6).

Table 6. Differences between AWER assessments based upon CORINE CLC2000 [12] and CORINE CLC2006

Erosion grade	Explanation	Minimal actual water erosion		Maximal actual water erosion
		Area		Area
		ha	%	ha	%
0	no erosion	92487	0.297	148809.0	0.477
1	weak erosion	-9411	-0.030	-46211.0	-0.148
2	moderate erosion	-41409	-0.132	-64780.0	-0.207
3	medium erosion	-44565	-0.143	-9027.0	-0.029
4	strong erosion	2534	0.008	-31688.0	-0.101
5	very strong erosion	0	0.000	2534.0	0.008
3-5	medium to very strong erosion	-42031	-0.134	-38181.0	-0.122
Sum		-362	0.000	-362.0	0.000

The highest changes are observed in the increase of the area with no erosion risk, while the areas under the risk grades from 3 to 5 decreased by 0.12% to 0.13% with a slight increase of the most severe erosion class.

The small difference in the total area under investigation is a remnant of area calculation and generalization from square meters to hectares.

Since the smallest scale of source data used in the analysis equals to 1:300.000, the maps of actual water erosion risk should be considered at the same level of detail quality.

Again, analogically to the assessment for the year 2000 [12], the results show far higher actual water erosion risk in Poland than those obtained by European erosion risk assessments. The difference come both from the data quality as well as form different methodologies [12].

CORINE Land Cover data remain the best available georeferenced country-wide land use data for Poland, however its present resolution corresponding to the scale 1:100.000, where linear elements smaller then 100m are not visible, cannot reflect the real state of land use structure in satisfactory manner. Especially in the central, eastern and southern part of Poland, characterized with small farms and dense structure of plots – so-called "chessboard of plots", where plots often have width lesser then 10m and are divided by a dense net of balks and afforestations, the current still CLC introduces large amount of uncertainty in the classification of land use.

Presented AWER indicator should be considered as an indicator of state as defined by Gobin et al. [4]. Its relatively detailed resolution and good source data of potential erosion map and CORINE CLC2006 [3] provides good information for general policies at regional level supplementing hitherto widely used map of potential erosion risk. However it is not suitable for detailed studies on farm level or geodetic zone, which in Poland is equal to an extent of a village.

The PWER and AWER maps do not cover the buffer of 1km from the Poland's border. The border areas of Poland were classified and not included in civil mapping for national security reasons.

ACKNOWLEDGMENTS

The unit responsible for the realization of the CLC2006 project in Poland remains general Inspectorate of Environment Protection, acting as the National Contact Point for cooperation with EEA. The work was performed by the Institute of Geodesy and Cartography. The financial resources for the realization of the CLC2006 project came from European Environmental Agency as well as from the National Found for Enviornment Protectiona and Water Managemet.

REFERENCES

1. Bittner G., Feranec J., Jaffrain G., 2002. Corine land cover update 2000: Technical guidelines, EEA Technical report No 82.

2. Duer I., Fotyma M., 1999. Polski kodeks dobrej praktyki rolniczej [Polish code of good agricultural practice]. Wyd. IUNG, Puławy, 74 [in Polish].

3. EEA, 2007. CLC2006 technical guidelines. EEA technical report No 17/2007, 70.

4. Gobin A., Govers G., Jones R., Kirkby M., Kosmas C., 2003. Assessment and reporting on soil erosion. Background and workshop report. EEA technical report 92, 103.

5. Jadczyszyn J., Stuczynski T, Szabelak P, Wawer R., Zielinski M., 2003. History and current status of research and policies regarding soil erosion in Poland. In Agricultural Impacts on Soil Erosion and Soil Biodiversity: Developing Indicators for Policy Analysis. Proceedings from an OECD Export Meeting Rome, Italy, March 2003, 201–209.

6. Józefaciuk Cz., Józefaciuk A., 1995. Erozja Agroekosystemów [Erosion of agroecosytems]. Biblioteka Monitoringu Środowiska, 168 [in Polish].

7. Józefaciuk Cz, Józefaciuk A., 1996. Mechanizmy i wskażówki metodyczne badania procesów erozji [The erosion mechanisms and methodological indicators for the research on erosion]. Biblioteka Monitoringu Środowiska, 148 [in Polish].

8. Józefaciuk Cz., Józefaciuk A., Nowocień E., Wawer R., 2002. Przeciwerozyjne zagospodarowanie zlewni wyżynnej potoku Grodarz z uwzględnieniem ograniczania powodzi [The anti-erosion management of Grodarz stream watershed with consideration of flood risk mitigation]. Monografie i Rozprawy Naukowe. Wyd. IUNG, 4, 69, [in Polish].

9. Maruszczak H., 1991. Denudacja chemiczna [Chemical denudation]. In: Geografia Polski, Środowisko Przyrodnicze, PWN [in Polish].

10. Nowocień E., Wawer R., 2002. Porównanie jakościowych metod analitycznych i fizycznego modelowania cyfrowego w badaniach erozji wodnej powierzchniowej [The comparison of qualitative analytical methods and physical modeling in water erosion investigations]. Zeszyty Problemowe Nauk Rolniczych, 487, 69–76 [in Polish].

11. Wawer R., 2004. Digital Watershed Model as a basis for projecting anti-erosional meliorations in rural watersheds. Acta Agrophysica, 115, 201–210.

12. Wawer R., Nowocień E., 2006. Digital map of actual water erosion risk in Poland. A qualitative, vector based approach. Polish Journal of Environmental Studies. 16, 5, 763–772.

13. Zaliwski A., Stuczyński T., 1999. Zintegrowany system informajci o rolnictwie [Integrated information system on agriculture]. Nowe Rolnictwo, 12, 38 [in Polish].

 

Accepted for print: 19.05.2010

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Rafał Wawer
Department of Soil Science Erosion Control and Land Protection,
The Institute of Soil Science and Plant Cultivation - State Research Institute, Pulawy, Poland
Czartoryskich 8, 24-100 Pulawy, Poland

Eugeniusz Nowocień
Department of Soil Science Erosion Control and Land Protection,
The Institute of Soil Science and Plant Cultivation - State Research Institute, Pulawy, Poland
Czartoryskich 8, 24-100 Pulawy, Poland

Bogusław Podolski
Department of Soil Science Erosion Control and Land Protection,
The Institute of Soil Science and Plant Cultivation - State Research Institute, Pulawy, Poland
Czartoryskich 8, 24-100 Pulawy, Poland

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