Sensitivity analysis of parameters in hydrology behavior of a drainage basin after a fire - Application in the area of ​​the watershed of the stream Picrodafni

The subject of this diploma thesis is the investigation of the hydrological response of this study’s catchment area based on the interaction of the recovery period and the characteristics of the fire, with soil moisture conditions before and after the fire. In addition, through sensitivity analysis, the quantitative effect of various parameters on post-fire hydrological response is investigated. First, a reference is made regarding the sensitivity of a burned area to increased runoff after the fire, with the condition being more unfavorable when the affected area is peri-urban. Then, both the direct and indirect effects of fire on the hydrological response of a watershed are described, as well as the quantitative conclusions drawn about them by the scientific community. The application of the study was carried out in a peri-urban area of the Picrodafni catchment, in the folds of the Ymittos mountain, which was affected by a fire in July 2015. At its exit point, it meets the urban fabric of the municipality of Ilioupoli. Following, the methods that will be used in this thesis are presented. These are: the rational method, for calculating the peak discharges before and after the fire and the Papathanasiou and Goodrich methods, for calculating the post-fire quantities. The methodology followed for the Monte Carlo sensitivity analysis is also presented. Then, pre-fire and post-fire soil conditions scenarios are formulated for application to the study area. Based on these, the changes in discharges and flow rates are derived for four different classes of fire intensity according to the Papathanasiou method, and for three different recovery periods. The same is repeated for the Goodrich method. Evaluating and comparing the results for the application in the study area, the changes in the magnitudes according to the Papathanasiou method, show that the more favorable the scenario in terms of soil moisture conditions before and after the fire and the lower the intensity of precipitation after the fire, the more intense the effect of fire intensity on the response will be. In addition, the changes in the flow rates for the unfavorable scenarios in terms of soil moisture conditions according to Goodrich, have a greater relationship with the values according to Papathanasiou for the case of very strong fire intensity, while for the more favorable scenarios the changes in the flow depth resulting from Goodrich are closer to Papathanasiou values for the case of low fire intensity. Finally, according to the Monte Carlo results, the sensitivity of the discharge one month after the fire, in terms of most parameters, decreases as the values of the input parameters increase. Only for two parameters, discharge shows a stable behavior regardless of their values