Efficient sediment management at the entrance of an ancient harbour

Elpidoforos Repousis, Athanasios Ziros, Michalis Chondros, Constantine Memos

Thursday 2 july 2015

17:54 - 17:57h at Amazon (level 1)

Themes: (T) Water engineering, (ST) River and coastal engineering, Poster pitches

Parallel session: Poster pitches: 13B. River Engineering

In this study, an investigation was carried out of the ancient harbour of Lechaion (Peloponnese, Greece), including submerged groynes, regarding its associated coastal sedimentation features. Continuous small steep alluvial fans mainly form the shoreline profile. Significant ongoing geotectonic up-lift of the area, affecting rivers by gradually minimizing their hydraulic gradient along with present human pressure have produced a deltaic environment lacking adequate inland deposits. As for the range of possible applicability of the examined design, and beyond the north coastline of Peloponnese characterized nowadays by a drastic recession, there are many examples of similar conditions produced by dams slowing down river flow. Today, certain harbour facilities are still visible. Two outer jetties, positioned on the edge of a geotechnical work separating from an inner basin are included. What is to be closely examined is the submerged character of these jetties. The entrance of the channel leading to the inner harbour basin can also be seen with the remains of two smaller jetties one on each side also positioned in order to control siltation. Herein the evaluation of both the efficiency of this ancient harbor design using submerged elements and simultaneous adjacent shore protection, was carried out through the computational model MIKE 21 (2007, DHI). A direct by-product of this study was the assessment on how the ancient engineer faced siltation at the entrance of the harbour by simultaneously minimizing downstream erosion. Investigation revealed a harbour layout with submerged groynes and breakwaters capable in reducing downstream shore erosion and this as an answer to the conventional groynes used today, along with avoiding sediment trapping at the port entrance on the upstream of the entrance of an internal-basin harbour facility introduced in a deltaic environment lacking of continuous river sediment supply.