Soil erosion risk assessment in the fire-affected area Penteli-Neos Voutzas-Mati

Postgraduate Thesis uoadl:2864819 249 Read counter

Unit:
Κατεύθυνση Στρατηγικές Διαχείρισης Περιβάλλοντος
Library of the School of Science
Deposit date:
2019-03-04
Year:
2019
Author:
Roussos Orfeas
Supervisors info:
Δρ. Βαρβάρα Αντωνίου, Δρ. Γεωλόγος, Ε.Δ.Ι.Π. Τμήμα Γεωλογίας και Γεωπεριβάλλοντος, ΕΚΠΑ
Δρ. Εμμανουήλ Σκούρτσος, Δρ. Γεωλόγος, Ε.Δ.Ι.Π. Τμήμα Γεωλογίας και Γεωπεριβάλλοντος, ΕΚΠΑ
Δρ. Στυλιανός Λόζιος, Επικ. Καθηγ. Τμήμα Γεωλογίας και Γεωπεριβάλλοντος, ΕΚΠΑ
Original Title:
Εκτίμηση του κινδύνου διάβρωσης του εδάφους στην πυρόπληκτη περιοχή Πεντέλης-Νέου Βουτζά-Ματίου
Languages:
Greek
Translated title:
Soil erosion risk assessment in the fire-affected area Penteli-Neos Voutzas-Mati
Summary:
The area of Penteli – Neos Voutzas – Mati in Eastern Attica was hit by a severe wildfire on the 23rd of July, 2018, which resulted in heavy damages and loss of human lives. The fire is also expected to have heavy environmental impacts, not only in the short but also in the long term. An increase in soil erosion, which is anyway an important problem in the Mediterranean countries, is one of them. The main objective of the present thesis was to carry out a quantitative estimation of the soil erosion hazard in this area. The result should act as a basis for determining the impacts of the fire on soil erosion and also for identifying the high risk areas within the burned area.
In order to achieve these aims, the first step was to examine the subject of soil erosion, particularly focusing on its relationship to wildfires. A comparative analysis of the various soil erosion assessment models was carried out, giving an emphasis on the ones that were already applied in similar cases of post-fire soil erosion hazard in the Mediterranean countries: USLE/RUSLE, PESERA, EPM-Gavrilović, MMF.The specific characteristics of the burned area and its surroundings, which could be relevant to the soil erosion hazard (geology, hydrogeology, geomorphology, climate, soil properties, land use and cover, the characteristics of the specific fire and management of the post-fire situation) were also closely examined, in order to assist in the selection of the most appropriate method and the steps of its implementation. It is important to note that a big part of the area can be treated as a Wildland–Urban Interface, which is particularly vulnerable to wildfires.
On the basis of the above, the Revised Universal Soil Loss Equation RUSLE was selected as being the most appropriate for our case, based mainly on its simplicity and the comparability of its results, since there are plenty of examples of application of this method in Greece and other Mediterranean countries, including cases of post-fire erosion risk research. The available data (geological map, DEM, Landsat 8 satellite images, climate data, orthophotomap etc) was processed using GIS. The calculation was carried out not only on the burned area, but on the entire river basin, to which the burned area belongs. This approach was preferred, not only because of the interconnections between the burned and the non-burned part of the same catchment, but also because the results in the non-burned part can act as a useful comparison to the ones in the burned area.
As a result, two maps of soil loss were produced: one representing the pre-fire and one the post-fire soil erosion hazard on the entire river basin. A third map representing the change in soil loss as a percentage was also produced. The results indicated that there is a significant increase in soil erosion hazard in the burned area, in contrast to the rest of the catchment, in which a slight decrease was observed. However, comparing our results with the results of similar studies in Greece and other Mediterranean countries, the average increase was found to be relatively low. The difference can be attributed to the special characteristics of the burned area, i.e. the high percentage of built-up area, in which the soil is sealed, and of already highly degraded areas with low vegetation cover. In these areas, the change in vegetation cover was not very significant and does not cause a great increase in soil erosion risk. There was also a comparatively small change in agricultural areas, since they were not greatly affected by the fire.
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Contrary to the above, the soil erosion hazard increased greatly in areas previously covered by relatively dense vegetation (pine forests, narrow torrent valleys). The increase often exceeded 60% and in extreme cases even reached 187%. In some parts of the burned area, where this increase coincides with pre-existing conditions favoring soil erosion (e.g. high soil erodibility, steep slope), the soil erosion hazard can be significantly high, partly exceeding 100 t/ha per year. Due to the relatively high population density of the burned area, the soil erosion hazard is also associated with a high vulnerability to other related natural disasters, like floods. The proximity of (often poorly planned) urbanized built-up areas to semi-natural wildland, as it is typical in Eastern Attica, is a factor, which additionally increases the natural disaster hazard. It should also be noted, that although the first months after the fire have passed, this is no reason for assuming that the soil erosion hazard will be low from now on, since it’s not rare for burned areas in Mediterranean countries to exhibit a greater soil loss in the second, third or even fifth year after a fire.
When interpreting the results, we must always have in mind that their quantitative accuracy is limited, as demonstrated by the significant deviations in the amount of soil loss estimated in similar studies in Greece and other Mediterranean countries. We should also be aware of the fact, that RUSLE was designed for calculating only sheet and rill erosion, and does not take account of gully and tunnel erosion, let alone other forms like wind and tillage erosion. However, the application of RUSLE in the burned area of Penteli – Neos Voutzas – Mati indicates that it can still be useful in supporting post-fire environmental management. Besides proving that there is a significant post-fire soil erosion hazard compared to the prefire situation, it also assists in identifying the parts of the burned area, in which the soil erosion hazard is especially high and in which erosion control and especially soil stabilization measures are probably most urgently needed.
Main subject category:
Science
Keywords:
soil erosion, RUSLE, wildfires, Attica, Wildland–Urban Interface
Index:
Yes
Number of index pages:
2
Contains images:
Yes
Number of references:
79
Number of pages:
110
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