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Modeling Soil Erosion Using RUSLE and GIS – A Case Study of Korifla Sub-Watershed (Central Morocco)

Eddefli Fatimazahra, Ouakil Abdelhadi, Khaddari Achraf, Tayebi Mohamed

Ecological Engineering & Environmental Technology

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2023

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Vol. 24, iss. 4

128--137

EN

Soil loss is a problem that contributes to land degradation in many countries and Morocco is no exception. Our study focuses on water erosion in Korifla, a sub-basin of the Bouregreg watershed in northern Morocco. The objective is to quantify erosion using the RUSLE method which is based on five factors: Runoff erosivity, soil erodibility, cover factor, topography and conservation practices. These are processed by remote sensing and a geographic information system. The soil loss map shows that on an area of 1838 km2, erosion is estimated to be between 0.00 t/ha/year and 27.61 t/ha/year. The cumulative effect of the factors R, K, LS, C, and P are both the origin of this erosion and its spatial distribution.

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Selekcja i przetwarzanie wzmocnionych przestrzennie obrazów wielospektralnych Landsat TM – porównanie wyników opartych o dane scalone i dane źródłowe

Pirowski T, Szczasiuk G.

Archiwum Fotogrametrii, Kartografii i Teledetekcji

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2013

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Vol. 25

155--167

EN

The paper presents results of merging lower-resolution spectral data (Landsat, 30m) with panchromatic images of higher spatial resolution (IRS 5.8m). During the first stage of the research, thirty methods of merging satellite data (including their variants) have been tested. The first assessment was based on statistical measures covering spectral distortion and spatial enhancement of pansharpened images. The second assessment was based on the color composite factors essential for photo interpretation. Comparing both obtained ranks of methods revealed substantial differences in their assessed spectral distortion. On the other hand, there appeared similarities in the obtained values for the spatial enhancement of pansharpened images. The reasons of such discrepancies were defined. The research allowed appointing the HPF (High Pass Filter) and LCM (Local Correlation Modeling) methods as the best according to the tested factors. In the second part of the research, the applicability of the selected methods was tested. Information content of color composites was analyzed as well as tresholding and band ratioing. In the tests there were used images fused through five merging methods: HPF, LCM, IHS (Intensity, Hue, Saturation), PCA (Principal Components Analysis) and WMK (based on band ratioing and having specific photo interpretation features). The findings of the research suggest that none of the merging algorithms provide universal solution. Depending on the data processing technique used, the best results are based on images obtained from various integration methods. It means that the method ranks do not correspond with method applicability. Methods appointed as the best ones obtain poor results in some tests and methods which came low in the rank received high rank in some tests. If this conclusion becomes confirmed, it might be necessary to revise the assessment methods of merged images.

PL

W publikacji przedstawiono wyniki badań związanych z integracją danych spektralnych (Landsat) z obrazami panchromatycznymi o wyższej rozdzielczości przestrzennej (IRS). W pierwszym etapie porównano zgodność - przedstawionych we wcześniejszych publikacjach rankingów metod integracji: formalnej (Pirowski, 2009) i wizualnej (Pirowski, 2010). Zestawienie wykazało duże różnice w ocenie stopnia zniekształcenia informacji spektralnej generowanej przez poszczególne metody integracji. Natomiast potwierdziła się zgodność rankingów w aspektach związanych z oceną stopnia wzmocnienia przestrzennego syntetycznych obrazów. Za najlepsze metody, uzyskujące w obu rankingach wysokie noty, uznano HPF i LCM.. Wybranych pięć metod integracji - HPF, LCM, IHS, PCA i WMK - poddano testom praktycznym: analizie potencjału informacyjnego kompozycji barwnych, progowaniu oraz wagowaniu międzykanałowemu. Wstępne badania wskazują, iż żaden z algorytmów scalania nie daje produktu uniwersalnego. W zależności od zastosowanej techniki przetwarzania danych optymalne wyniki uzyskuje się bazując na obrazach pochodzących z różnych metod integracji. Pośrednio oznacza to, że opracowane rankingi nie przekładają się na aspekty praktyczne – metody, wskazane w nich jako najlepsze, wypadają w niektórych testach relatywnie słabo, i odwrotnie. Jeśli ta wstępna konkluzja się potwierdzi, oznaczać to będzie konieczność zrewidowania metod oceny scalonych obrazów.

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Wykorzystanie zdjęć LANDSAT w badaniu struktury sieci osadniczej w wybranych krajach pozaeuropejskich

Grzegorczyk A.

Teledetekcja Środowiska

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2009

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T. 41

37--50

EN

The main aim of the article is to assess the usage of the following methods for the settlement structure analysis: satellite images interpretation, Zipf rule and nearest neighbour index. This assessment is carried out during the analysis of the relationship between socio-economic development level and the diversification and complexity of settlement Settlement network development was especially investigated in the 1950. and 1960. R. B. Potter (1999) summarising heretofore research stated that the balanced and hierarchised settlement network does not develop in LEDCs. Therefore it was interesting to check if such a statement is not exaggerated. The analytical data were obtained from LANDSAT ETM+ images interpretation. Due to it, the coefficients of variation for particular countries were calculated to investigate settlement network diversification. The diversification was presented also on choropleth maps. Afterwards it was analysed if the Zipf rules (classic, using population number data and modified, using built-up areas values obtained from satellite images) describe the settlement network complexity in countries under investigation. The nearest neighbour index was used to check spatial complexity of the networks. By the networks diversification analysis, it was proved that there was a relationship between socio-economic level and networks diversity in the countries under investigation, although there are also other processes influencing this relationship. There is intense spatial dynamism in core regions and neighbouring peripheries in the countries with the most diverse networks (the most developed counties). In the least diverse countries there is the low spatial dynamism or there were significant decentralisation forces in the past. By the networks complexity analysis, the development level and networks complexity relationship was revealed. In the relatively less developed countries the settlement networks were far from equilibrium (primate city pattern) and built-up areas dispersed. In more developed countries settlement networks were close to equilibrium and concentrated, so compact urbanised areas were present. Changes in networks complexity take place in the most developed areas, however, peripheries are spread across the overwhelming part of the countries, which is irrespective to the level of their development. Hence, networks’ structures enhancement and their dispersion occur only in some parts of the countries. Therefore R. B. Potter’s and others statements seem to underestimate the LEDCs’ processes. The visual satellite images interpretation allowed the analysis of the data rarely used in settlement structure researches. This enabled the analysis with lack of population statistical data limitations, e.g. unreliable data not covering the whole population within the city or town, data not comparable between different countries (problem of different city definitions), from different years for each country. The comparison of modified and classic Zipf rules showed that the modification was correct. The data availability for modified rule was also much greater. This method occurred useful in LEDCs as spatial urbanised areas expansion is characteristic for the urbanisation process there (Cohen, 2006). The nearest neighbour index NNI analysis was also much more precise and due to the greater data availability, statistically significant. The conclusions of the methodological aim can be extrapolated, providing for the limitations described, for other countries not being covered by the research.

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Wykorzystanie zdjęć Landsat MSS i TM do tworzenia satelitarnych map obrazowych

Lewiński S.

Archiwum Fotogrametrii, Kartografii i Teledetekcji

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1998

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Vol. 8

2-1--2-4