979 Developments in Maritime Transportation and Exploitation of Sea Resources – Guedes Soares & López Peña (eds) © 2014 Taylor & Francis Group, London, ISBN 978-1-138-00124-4 Modelling the effect of wave current interaction at the mouth of the Danube river Eugen Rusu & C. Guedes Soares Centre for Marine Technology and Engineering (CENTEC), Instituto Superior Técnico, Technical University of Lisbon, Lisbon, Portugal ABSTRACT: The objective of the present work is to evaluate the effects of the wave-current interactions at the mouths of the Danube river in the Black Sea, area usually subjected to intense navigation. A SWAN based modelling system is applied to the target area and numerical simulations are performed in a high resolution computational domain for the main environmental patterns characteristic to this part of the sea, considering the situations without and with the current fields included. A field experiment was also carried out and its results confirm in general the output provided by the model simulations. The results show that the currents induce relevant enhancements in terms of significant wave heights. Moreover, the higher values of the Benjamin Feir Index, resulted in the case when the current fields are considered in the modelling process, indicate also an elevated risk of rogue wave occurrences in the target area. This is because here high energetic wave conditions are usual and the currents induced by the Danube outflow make this coastal area representative from the point of view of the relevance of the wave– current interaction process. A visual representa- tion that gives a first idea on the impact of these interactions between waves and opposite currents 1 INTRODUCTION The coastal sector at the mouths of the Danube River can be considered as very significant for coastal navigation because it is the main south- ern gate for the Rhine–Main–Danube Canal that is part of a trans-European waterway from Rotterdam on the North Sea to Sulina on the Black Sea (3500 km). Hence the navigation in this area represents a key issue in the development of the logistic chain related to the inland navigation in Europe and the links of the harbors from the Black and the Mediterranean seas with those from the northern part of Europe. Since the Sulina channel represents the main entrance to the seventh Pan European transport corridor, this coastal area is usually subjected to high navigation traffic. On the other hand, the environmental conditions, which are often quite hard in this part of the sea, especially in winter time, raise elevated risks to the navigation in this coastal sector. For this reason, several accidents and incidents took place in the last years close to Sulina channel and as an illustrative example only in December 2009, two sea ships, under Georgian flag, JUPITER and TURGUT’S, grounded at the entrance on the Sulina channel, due to the bad weather conditions. Images from these two accidents, which fortunately had not very important negative consequences, are shown in Figure 1. Moreover, the most sensitive problems occur exactly at the entrance of the Sulina channel. Figure 1. Recent accidents close to the Danube mouths (December 2009): a) Jupiter ship, which grounded south of Sulina beach; b) Turgut S ship, which grounded north of Sulina Channel.