The Influence of the Roughness Coefficient on Flood Phenomena - Machico's Watershed, Madeira Island, Portugal

Flood phenomena, intensified by regional and global climate change, are increasingly recurrent and devastating events. Extreme cases such as those in 2010 and 2013 on the island of Madeira corroborate this indicator. The regions most affected are those with the highest urban index and the most significant soil waterproofing, such as Machico. Therefore, based on the recent history of floods in the city of Machico and the aid of georeferencing tools such as ArcGIS, the geomorphological and hydrological analysis of the hydrographic basin of the Machico stream was carried out in order to verify the expected flow rate for a recurrence period of 100 years, through the Gumbel Probabilistic Distribution. Subsequently, the river mouth's flow capacity was analyzed using the Manning-Strickler equation, where the minimum roughness coefficient necessary to allow the flow of the expected high peak flow will be evaluated. Finally, the results suggest that the river's mouth does not have the capacity to drain the precipitated flow, requiring changes in the bed roughness coefficient.