The route of sediment
Here we are on the bank of the Esino River; we will then head to Marina di Montemarciano and then down to Porto Sant’Elpidio, passing by the incredible “artificial” beach of San Michele in Sirolo. A journey from the river to the sea to discover the delicate balance between these two natural elements and the solutions put in place by the Marche Region to safeguard rivers, ecosystems and coastlines.
River or stream?
We are standing on the bank of the Esino river – if one can still call it a river: there is very little water here. This watercourse, the second most important after the Metauro in terms of catchment area and average annual flow in the entire Marche Region, stretches for about 90 km before flowing with a wide discharge into the Adriatic. But this route, forged by nature centuries ago, today encounters some difficulties.
A troubled journey
In this area, various human activities, including the construction of a hydroelectric plant, have caused profound changes in the riverbed over time. Added to these negative developments, there have also been the impacts of climate change, specifically the change in rainfall patterns. Precipitations now occur less frequently, are more concentrated in time, and more powerful. The sum of these changes has contributed to a severe variation in the river water regime:its currents now lack the strength to carry sediment and gravel to the estuary. The end result of the lack of sediment is an exposed coastline that is vulnerable to the force of the sea, thus creating a powerful phenomenon of coastal erosion.
… And if it rains?
Sediments that remain trapped in the riverbed due to the scarce water flow caused in part by man and in part by low rainfall, accumulate more and more and eventually create a layer that raises the bedrock level, sometimes to the point of surfacing above the water level. Under these conditions, even an “ordinary flood”, caused by average rainfalls, can have quite serious impacts. In the quarry area on the banks of the Esino River we have a clear example of this phenomenon, called overflooding: an old bridge, now collapsed, which was once high enough to allow the passage of military vehicles below it, is now almost submerged by water.
The beach nourishment
As we have seen, one of the many solutions put in place by the Marche Region in the northern area of Marina di Montemarciano is extensive beach nourishment to replenish the beach, which currently no longer exists. And where do they get gravel and sediment from? Precisely from the Esino river where sediments are stranded due to changes in the water regime: indeed, studies confirm that on a lithological, granulometric and morphological level, the gravel trapped in the Esino is exactly the same as the gravel that is now missing in the areas most prone to erosion.
The risks faced by river ecosystems
During the operation of removing gravel from the riverbed, which in itself is very simple, the delicate ecosystems that thrive within the riverbed are necessarily affected. To minimize the impacts associated with the removal, the Region conducted an impact assessment that resulted in some concrete actions: firstly, with respect to the four designated drawdown areas in the river, only two will be activated per year; secondly, the drawdowns will be carried out away from the reproductive periods of the ichthyofauna and avifauna (thus between March and September); and finally, the drawdown will be carried out avoiding to affect the low water bed, i.e., the area where the river passes most frequently and where the most complex ecosystems live.
Different solutions for different areas
How to choose the right solution for each area? As David Piccinini explains, 782 transects (small spatial delimitations) have been created along the 180 km of coastline of the Marche Region, which allow to carry out annual topographic surveys to check the advancement or regression of the shoreline; these data have been collected since 2005, and thanks to them experts are now able to choose the ideal interventions to be put in place for each homogeneous stretch of coastline (“physiographic unit”), also taking into account the natural, ecosystemic and touristic value of the various areas.
An “artificial” beach: San Michele in Sirolo
In 2009, before data and studies clearly related the surplus of sediment stranded along the Esino river to the deficit on the coast, nourishment of this now eroded beach was carried out by taking 156,000 cubic meters of alluvial gravel from a quarry. Today, after many years, the sea has smoothed out the originally lithologically and morphologically diverse sediments, thus making the shoreline homogeneous. The 2009 beach nourishment would be defined “structural”: that is, it affected both the emerged and the submerged beach to ensure greater stability also in view of the fact that this shore is one of the most beautiful and popular on the Marche coast.
“The beach of San Michele in Sirolo is a coastal
protection work.”
David Piccinini
Porto Sant'Elpidio: breakwaters to protect both coast and homes
We are now in Porto Sant’Elpidio, the last stop on our journey that started from the Esino river and led us to the various areas of the Marche coast, getting to know their peculiarities and the defense measures put in place to safeguard them. Sant’Elpidio is a urban and touristic area, and therefore needs a solution that dissipates waves energy as much as possible. It was therefore decided to build a set of breakwaters. In order to further increase their effectiveness, especially in view of the scenarios of rising mean sea level predicted for the coming decades, the height of boulders was set at two meters above the actual mean sea level. This level, which has never been reached before, makes us realise the extent of the changes we will have to get used to and adapt to, and how important it is that local administrations take them into account when planning and designing coastal protection works.