Investigating the interaction of waves and river discharge during compound flooding at Breede Estuary, South Africa [post]

Sunna Kupfer, Sara Santamaria-Aguilar, Lara van Niekerk, Melanie Lück-Vogel, Athanasios Vafeidis
2021 unpublished
Abstract. Recent studies have drawn special attention to the significant dependencies between flood drivers and the occurrence of compound flood events in coastal areas. This study investigates compound flooding from tides, river discharge (Q) and specifically waves using a hydrodynamic model at Breede Estuary, South Africa. We quantify vertical and horizontal differences in flood characteristics caused by driver interaction, and assess the contribution of waves. Therefore, we compare flood
more » ... acteristics resulting from compound flood scenarios to those in which single drivers are omitted. We find that flood characteristics are more sensitive to Q than to waves, particularly when the latter only coincide with high spring tides. When interacting with Q, however, the contribution of waves is high, causing 10–12 % larger flood extents and 45–85 cm higher water depths, as waves caused backwater effects and raised water levels inside the lower reaches of the estuary. With higher wave intensity, the first flooding began up to 12 hours earlier. Our findings provide insights on compound flooding in terms of flood magnitude and timing at a South African estuary and demonstrate the need to account for the effects of compound events, including waves, in future flood impact assessments of open South African estuaries.
doi:10.5194/nhess-2021-220 fatcat:bhqhlx3mjrbufnylu63ugqtpem