Karel Mulder’s observations and experiences during his secondment-visit in Rome

We have a beautiful Dutch showpiece: the sand engine, a great solution for strengthening endangered parts of the coast and creating new coastal nature with only a modest intervention. A wonderful solution for other erosive beach lines you would say. This coastal erosion is partly a natural process, sand simply moves along the coast and that is why many Wadden islands grow on the east side. But that sand comes from other places where it can’t always be missed. Moreover, a higher water level and more storms as a result of climate change accelerate that process. That is why it is a good idea to build something like the sand motor in targeted areas. But in the Mediterranean, coastal erosion has often been a problem for much longer. The deltas of the Nile, Ebro and Tiber have expanded greatly in history, but have been retreating for much longer. The Tiber delta coastline continued to grow until the early 20th century. As a result, the classic port of ancient Rome, Ostia, is now about 4 kilometres from the current coastline.

No sand motor

How did this happen, this shift of the coastline? Sand and clay on the coast come from rivers: mountains and agricultural land erodes and ends up in the sea via rivers. Many large rivers enter the sea in the Netherlands/ Belgium/ North Germany. The North Sea bed therefore mainly consists of sand and clay, and that material also supplements the coast. Tiber, Ebro and Nile also drain sand and clay, but this has decreased drastically in the past century. This is due to several reasons. For example, the water discharge from rivers has decreased due to much greater water use in agriculture. Many dams have also been built: to feed hydroelectric power stations and to have enough water for agriculture, industry and cities. But those dams barely let sand and clay through, so that material accumulates in the water reservoirs. Result: Silt accumulates behind the dams, but sand and silt are no longer supplied on the beach, and that coastline is affected in many places around the Mediterranean Sea. Then a sand motor at the mouth of the Tiber? Where would that sand come from? The southern part of the North Sea is about 40-50 meters deep and sand can be extracted there in many places. The Tyrrhenian Sea (between mainland Italy, Sardinia and Sicily) is often hundreds of meters deep at about twenty kilometres from the coast, and has virtually no sand; a sand motor is therefore not just an option. In that case, the sand supply by rivers must therefore be restored in order to preserve the coastline. Because the beaches of Lazio are a tourist attraction, and they protect a few hundred thousand inhabitants and the Roman airport Fiumicino. But that just doesn’t happen. The sand that has accumulated in the water reservoirs is often extremely polluted. So it cannot just be thrown over the dam into the river. In addition, of course, the erosion of agricultural land must also be limited, so as not to endanger agricultural productivity. And those dams also produce sustainable electricity, so they combat climate change and cannot be missed! And finally, river management in Italy is characterized by fragmented decision-making and an enormous amount of interests. Ultimately, there will be little more to it than some careful restoration of the sand and silt discharge of the Tiber, and the prevention of coastal erosion by all kinds of measures such as the construction of breakwaters (which will drain sand along the coast against), planting of extra dune vegetation and regulating beach use. A complicated task not only for the Tiber estuary and other areas of deltas in the Mediterranean but also for many other areas, e.g. in West Africa, where similar problems arise.