Προσομοίωση υδρολογικής απόκρισης πριν και μετά από πυρκαγιά στην πειραματική λεκάνη Αγίου Νικολάου Ευρυτανίας

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dc.contributor.author Βαρσάμη, Γεωργία Α. el
dc.contributor.author Varsami, Georgia A. en
dc.date.accessioned 2015-04-01T10:15:19Z
dc.date.available 2015-04-01T10:15:19Z
dc.date.issued 2015-04-01
dc.identifier.uri http://dspace.lib.ntua.gr/handle/123456789/40507
dc.description Εθνικό Μετσόβιο Πολυτεχνείο--Μεταπτυχιακή Εργασία. Διεπιστημονικό-Διατμηματικό Πρόγραμμα Μεταπτυχιακών Σπουδών (Δ.Π.Μ.Σ.) “Επιστήμη και Τεχνολογία Υδατικών Πόρων” el
dc.rights Αναφορά Δημιουργού-Μη Εμπορική Χρήση-Όχι Παράγωγα Έργα 3.0 Ελλάδα *
dc.rights Αναφορά Δημιουργού-Μη Εμπορική Χρήση-Όχι Παράγωγα Έργα 3.0 Ελλάδα *
dc.rights Αναφορά Δημιουργού-Μη Εμπορική Χρήση-Όχι Παράγωγα Έργα 3.0 Ελλάδα *
dc.rights.uri http://creativecommons.org/licenses/by-nc-nd/3.0/gr/ *
dc.subject Υδρολογική προσομοίωση el
dc.subject Άγιος Νικόλαος (Ευρυτανία) el
dc.subject HEC-HMS el
dc.subject Ορεινή δασική λεκάνη el
dc.subject Σενάριο πυρκαγιάς el
dc.subject Hydrologic simulation en
dc.subject Agios Nikolaos (Evrytania) en
dc.subject HEC-HMS en
dc.subject Mountainous forest watershed en
dc.subject Fire scenario en
dc.title Προσομοίωση υδρολογικής απόκρισης πριν και μετά από πυρκαγιά στην πειραματική λεκάνη Αγίου Νικολάου Ευρυτανίας el
dc.contributor.department Τομέας Υδατικών Πόρων και Περιβάλλοντος el
heal.type masterThesis
heal.classification ΔΙΑΧΕΙΡΙΣΗ ΥΔΑΤΙΚΩΝ ΠΟΡΩΝ el
heal.classification WATER RESOURCES MANAGEMENT en
heal.classificationURI http://localhost:8080/healp/data/8/8/10
heal.classificationURI http://localhost:8080/healp/data/8/8/10
heal.language el
heal.access free
heal.recordProvider ntua el
heal.publicationDate 2014-10-14
heal.abstract Αντικείμενο της παρούσας μεταπτυχιακής εργασίας αποτελεί η υδρολογική προσομοίωση ορεινής δασικής λεκάνης απορροής με χρήση του προγράμματος HEC-HMS και η εκτίμηση της μεταβολής της υδρολογικής απόκρισης μετά από ενδεχόμενη πυρκαγιά. Η περιοχή μελέτης οριοθετείται στο ελατοδάσος Αγίου Νικολάου Ευρυτανίας και έχει έκταση 1,45 km2. Αποτελεί μία από τις τρεις πειραματικές λεκάνες του Ινστιτούτου Μεσογειακών Δασικών Οικοσυστημάτων και Τεχνολογίας Δασικών Προϊόντων (ΙΜΔΟ&ΤΔΠ), από το οποίο και παραχωρήθηκαν τα βροχομετρικά και σταθμηγραφικά δεδομένα. Η εφαρμογή του μοντέλου προσομοίωσης έγινε σε επίπεδο επεισοδίου βροχής με στόχο την εκτίμηση των πλημμυρικών μεγεθών. Η ανάλυση των γεωμορφολογικών και υδρολογικών χαρακτηριστικών της εξεταζόμενης περιοχής πραγματοποιήθηκε σε περιβάλλον GIS, μέσω της πρόσθετης εργαλειοθήκης HEC-GeoHMS, που επιτρέπει τη δημιουργία αρχείων εισόδου σε λογισμικά υδρολογικών μοντέλων. Για την προσομοίωση των επιμέρους συνιστωσών του υδρολογικού κύκλου έγινε επιλογή των κατάλληλων μεθόδων από ένα σύνολο δυνατοτήτων που διαθέτει το πρόγραμμα HEC-HMS. Τα αρχικά ελλείμματα εκτιμήθηκαν με εφαρμογή της μεθόδου του αριθμού καμπύλης της Soil Conservation Service - SCS (πλέον Natural Resources Conservation Service - NRCS), η άμεση απορροή με τη μέθοδο του Μοναδιαίου Υδρογραφήματος της SCS και η βασική απορροή με το πρότυπο εκθετικής μείωσης. Επιπλέον, λόγω του δασικού χαρακτήρα της λεκάνης ενσωματώθηκε στο μοντέλο και πρότυπο για την εκτίμηση των απωλειών παρεμπόδισης. Η υδρολογική προσομοίωση υλοποιήθηκε σε δύο μεμονωμένα γεγονότα βροχής (1/7/2001 και 29/8/2002), όπου και υπολογίστηκαν τα υδρογραφήματα εξόδου για κάθε επεισόδιο. Ακολούθησε η διαδικασία της βαθμονόμησης, χρησιμοποιώντας ως μέτρο προσαρμογής το δείκτη Nash-Sutcliffe, και η επαλήθευση του υδρολογικού μοντέλου με ένα τρίτο επεισόδιο βροχόπτωσης (24/10/2003). Τελικό στάδιο της εργασίας αποτέλεσε η διερεύνηση της υδρολογικής συμπεριφοράς της υπό μελέτη λεκάνης με την κατασκευή ενός σεναρίου πυρκαγιάς, ώστε να ελεγχθεί η μεταβολή της πλημμυρικής απορροής μετά τη φωτιά σε μία κατ΄εξοχήν δασική έκταση. Για την ανάλυση των επιδράσεων της μελετώμενης πυρκαγιάς θεωρήθηκε αναγκαίος ο επαναπροσδιορισμός των παραμέτρων του μοντέλου, με βάση αντίστοιχα αποτελέσματα μελετών της διεθνούς βιβλιογραφίας, λαμβάνοντας παράλληλα υπόψη τις συνθήκες που επικρατούν στη συγκεκριμένη περιοχή. el
heal.abstract Floods and forest fires are considered to be two of the most common natural disasters, causing many times irreversible impacts to the environment. In the last decades, both disasters present an upward tendency and are ranked especially high in the agenda of the European Environment Agency. Large scale fire events affect the hydrological behavior of natural catchments by altering their land cover. This phenomenon is very common in the Mediterranean areas, which are more vulnerable to such hazards. Forested areas that have suffered from fire events are even more prone to floods, as drastic changes occur in the hydrologic, hydraulic and geomorphologic characteristics of drainage basins. The aim of this postgraduate thesis is the simulation of the hydrological response of a small mountainous forest watershed before and after a possible fire, through the use of the HEC-HMS software package. The study area is located in the Agios Nikolaos fir forest, which belongs administratively to the Municipality of Karpenisi in the Prefecture of Sterea Ellada. It is one of the three experimental watersheds of the Institute of Mediterranean Forest Ecosystems and Forest Products Technology (FRIA) and covers an area of 1,45 km2. The streams that cross the study area flow into River Vroussos, which is one of the main tributaries of River Karpenisiotis, the main river. The studied watershed is of great hydrological research interest, due to its mountainous and forest nature among other elements. HEC-GeoHMS (Geospatial Hydrologic Modeling Extension), as developed by the Hydrologic Engineering Center (HEC) of the US Army Corps of Engineers (USACE), is used to analyze the geomorphological and hydrological characteristics of the study area and also to create the basin model. It is an extension toolbox to ESRI's ArcGIS software that allows users to produce the background support files which are necessary for the hydrologic model. The program also has the tools to demonstrate spatial characteristics, such as the river shape and the subbasin's attributes. The Digital Elevation Model (DEM) of the study area is a prerequisite for developing the basin model, though in this case it was not available before the beginning of the study. Hence, we have created a raw DEM from maps (1:5000) provided by the Hellenic Military Geographical Service. The required tasks in order to extract the necessary data for HEC-HMS were: 1)DEM preprocessing 2)Basin processing and extracting hydrological and geomorhological characteristics 3)Selection of models to estimate the hydrological parameters and the development of HEC- HMS input files. The final outcome of the study area model shows the three (3) subbasins that were developed. The Hydrologic Engineering Center-Hydrologic Modeling System (HEC-HMS) has been applied to simulate the precipitation-runoff processes. HEC-HMS was designed and developed by the US Army Corps of Engineers' Hydrologic Engineering Center and is a software platform that provides a range of model options to simulate different parts of the hydrological cycle. HEC-HMS can support both long term hydrological year and event based modeling. The developed HEC-HMS model was an event-based simulation that run for two rainfall events (1/7/2001 & 29/8/2002). All the necessary rainfall and runoff data have been acquired by the FRIA, through measuring tapes. The observed flow data were collected from a flow measuring station, located in the outlet of the studied basin, while rainfall measures were received by a rain gauge located 70 m away from the basin. The representation of watershed hydrologic processes was based in the formulation of models for the computation of rainfall losses, direct runoff and baseflow. There are many methods to compute the different models. The selection of methods was mainly determined by the shortage of reliable data of the region. Consequently, the SCS (now NRCS) Curve Number method was applied for the estimation of rainfall losses, the SCS Dimensionless Unit Hydrograph for the estimation of direct runoff and the recession baseflow method to approximate the typical behavior observed in the watershed when channel flow recedes exponentially after an event. Moreover, the simple canopy method was integrated in the model, due to its ability to represent the presence of plants in the landscape. The total output of the aforementioned procedure was the hydrograph in the outlet of the basin. It has to be noted that, compared to the initial assumptions, there were discrepancies among the simulation results and the observed flood hydrographs as well as and an under-evaluation of all hydrological values. Model calibration is the process of modifying the input parameters to a simulation model until the output from the model matches to the maximum extent possible with the observed runoff data. The model parameters that were calibrated are the curve number (CN) and the Ia/S ratio of the SCS loss method, the lag time of the SCS unit hydrograph and the ratio to peak in baseflow method. The initial abstractions (Ia) were overrated compared to the common values (Ia=0,2S), according to the SCS methodology. According to Hawkins et al. (2002), a Ia/S value of about 0.05 is more accurate and adapts better to the models. In addition, the calibrated values of the lag time showed significant variation compared to the initial smaller values as obtained from the empirical relationship of the SCS. Therefore, the best results were accomplished by reducing the initial abstractions of the model and increasing the lag time of each subbasin. Goodness-of-fit of the calibrated model was evaluated using the Nash-Sutcliffe efficiency coefficient. Model validation is a process of demonstrating a model's ability to simulate observed data with acceptable accuracy, for different time periods (mainly after calibration). During this process, the parameter values of the calibrated model were being kept constant. The validation of the model was performed with the rainfall event of the 24th of October 2003. In this task, the input validation data was an average value of the hydrologic parameters calibrated for the rainfall events in 1/7/2001 and 29/8/2002. The model performance was evaluated quantitatively again, using the Nash-Sutcliffe criterion. The watershed's response to rainfall events, after a fire, is governed by many factors interacting with each other, such as fire intensity, vegetation cover, soil properties, soil moisture content, rainfall intensity and time interval between the burning and the meteoric event. In addition, it must be considered that fire can change soil properties, inducing the formation of a water repellent layer at or near the soil surface, reducing soil infiltration capacity, increasing overland flow and accelerating surface erosion (Letey, 2001). A scenario of a wildfire event was formulated, in order to assess the hydrological response in the watershed follows the impact of the fire. Considering that Greek forest areas are quite vulnerable to fires due to the weather conditions during summer and the fact that the study area is covered by Mediterranean conifer forests - which are among the most flammable and prone to forest fires - the basin planned to be completely burned and thus have a 0% forest coverage after the fire. Therefore we have investigated the behavior of a burnt afforested catchment. In this study a systematic literature review has been conducted in order to explore the hydrological parameters after the fire effect: curve number, initial abstractions and lag time. The values of the curve numbers were defined in proportion with the land use and hydrology soil group, in accordance with Goodrich's results and the initial abstraction, according to the new curve numbers' values. The value of lag time was defined based on literature review and was reduced by 40% compared with its pre-fire values. The analysis of the hydrological response was based on the event on 24/10/2003. The presented hydrological response of the basin had crucial changes after the fire event. Significant changes are observed in all hydrologic values; a tenfold increase appears in the peak flow discharge and in the total outflow volume, while the peak flow occurrence time is reduced by 45 min. To sum up, data availability of hydrologic parameters in the study area makes the simulation procedure better and more accurate, while also decreases the possible uncertainties of the hydrologic response. Further research on the studied subject could explore alternative methods for the computation of losses, direct runoff and baseflow, as provided by the HEC-HMS and conclusions could be drawn on the basis of their suitability. Other potential research subjects could examine in depth the model's calibration and validation procedure through the study of more rainfall events, which would improve the performance of the model as well as reduce uncertainty. Moreover, the baseflow mechanism of the model could be further explored in order to perform a more integrated analysis of the study area hydrologic regime. The suggested methodology, regarding the fire scenario, should be implemented and further enhanced with data of similar watersheds in order to confirm its robustness and increase its accuracy and universality. en
heal.advisorName Μπαλτάς, Ευάγγελος el
heal.committeeMemberName Γιακουμάκης, Σπυρίδων el
heal.committeeMemberName Παναγούλια, Διονυσία el
heal.academicPublisher Εθνικό Μετσόβιο Πολυτεχνείο. Σχολή Πολιτικών Μηχανικών el
heal.academicPublisherID ntua
heal.numberOfPages 113 σ.
heal.fullTextAvailability true

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