Supervisors info:
Δρ. Ευθύμιος Λέκκας, Καθηγητής Τμήμα Γεωλογίας και Γωπεριβάλλοντος ΕΚΠΑ
Δρ. Στυλιανός Λόζιος», Αναπλ. Καθηγητής Τμήμα Γεωπεριβάλλοντος Ε.Κ.Π.Α
Κωνσταντίνος Σούκης», Ε.ΔΙ.Π Τμήμα Γεωλογίας και Γεωπεριβάλλοντος Ε.Κ.Π.Α
Δρ Μιχαήλ Διακάκης
Summary:
The «Manning roughness coefficient» is a key parameter in the calculation of flow within open conductors [open channel flow]. The coefficient’s contribution to flood runoff calculation makes it an important factor in hydro-meteorological disaster research, which in recent years has seen an increase due to climate change. The estimation [computation] of this coefficient is done empirically by the use of special manuals, a process that involves particularly high levels of uncertainty. Currently, it creates significant problems to scientists researching natural disasters, floods, climate change etc, such as geologists. This paper examines whether it is possible to determine (calculate) the Manning coefficient using unmanned aerial vehicles (UAV) or drones and photometry techniques within the river bed, in combination with the application of special algorithms of the Matlab software. Specifically, this coefficient is calculated by the formula: n = (n0 + n1 + n2 + n3 + n4) * m [the process is analyzed in the following chapters]. When the coefficient “n” is established, the equation Q=(1.486/n)AR2/6Se1/2 is used, to calculate the discharge of an open conductor, which in our case are two rivers. The decisive factor in the results accuracy is the factor n0 given by the equation n0=0.0926R1/6/0.35+2log(R/d50). In addition, we present the process through which, by using photometry and a Matlab software application, the d50 can be determined [i.e. the average diameter corresponding to the 50% of the grains within a riverbed]. In this study, the Manning coefficient for two rivers is calculated. These are located within the area of Mandra, Attica and are the “Agia Aikaterini” and “Soures” rivers. They caused the catastrophic floods on November 15, 2017, after the intense and sudden rain that struck the area. We present in detail the way of determining [calculating] the coefficient as well as the way of using the BaseGrain program. Then we compare the obtained result with the one that has been calculated with the traditional, empirical method [i.e. compare the Manning coefficients calculated with the two different methods]. In conclusion, reference will be made to the pros and cons of the method used.
Keywords:
Manning Roughness Coefficient, Photogrammetry, Matlab, BaiseGrain, Natural disasters, climate change, Floods, Mandra Attica, Greece
