Can new beaches be built sustainably?.
In Zagreb, on October 6, 2022, the second workshop was held as part of the Beachex project, entitled Sustainable construction of beaches – construction of new and increasing the capacity of existing beaches (BEACHEX 2019-2023). At the workshop, new knowledge and results of the Beachex project on beach replenishment were presented, as well as the experiences of various experts in the field of construction, geology, and biology, as well as the experiences of designing and managing beaches.
On behalf of the Argonauts association, member Mirta Mudronja took part in it, and she tells us the main parts:
“The workshop was a series of lectures. The lecturers presented the purpose of the project, presented the example of Great Britain on the subject, presented some methods they use in their work, and presented examples of bad and good practices in Croatia.
Some data collected so far:
- 1904 beaches in HR with a total length of 6373 km (average 370 m) make up 6% of the coast of that number, 355 beaches are replenished (filled), but compared to Italy or Spain with extremely small amount of material on average (0.19 m3/m vs. ITA 6.5 m3/m vs. ŠPA 42 m3/m).
- 25% of beaches are estimated to be artificial
- The trend is around 10 new beaches per year.
Great Britain has a multidisciplinary approach, a developed national plan, and cooperation with local communities, which is not exactly to be compared with Croatia, considering the extreme conditions and risks suffered by their coast, as well as the wealth that that country has and can invest.
Data on beach geology were presented at the workshop:
- The age of the beaches (young formations, they are only about 6500 years old)
- Sources of material (coastal rocks, rivers, sea)
- Particle size (gravel > 2 mm, sand, silt < 0.063 mm); the most common sediment is sand
- The beaches in HR are mainly carbonate pebbles.
When replenishing the beach, you should pay attention to:
- grain size (speed of wear; also very small particles can cover and destroy living organisms in the seabed – the disappearance of habitats and biodiversity (pina nobilis, Posidonia oceanica…); small particles below 0.063 mm in the filling material should be max. 5% ( it can be more, but then a barrier made of solid material must be placed in front).
- grain shape (affects material movement).
- mineral composition (can affect, for example, soil temperature, indirectly and, for example, the sex of turtles on those beaches!) quartz (river pebbles) vs. carbonate (tucanik).
- there should be no organic material because then the sea blooms.
- tourist requirements should also be met (assess the required capacity).
In addition to the type of soil, the orientation of the beach in the micro-location, the direction and intensity of the winds, climate changes (sea level), etc. are important.
In testing these conditions, the following are used:
- long-term video monitoring (like web-cam on the beach) for at least 1 year (the longer the period, the more reliable the data).
- filming with a drone.
- classic geodetic recording from the field.
- numerical models (computer projections).
Influence of the human factor:
- the problem of poor backfilling material such as ordinary earth (organic material of very small particles is fatal for the seabed).
- the unresolved issue of disposal of construction waste.
- untreated sewage.
- mariculture (fish farms are excluded from the Natura 2000 area).
In the lecture on beach design, the importance of the secondary beach – coastal promenade and vegetation behind the sunbathing area (primary beach) were discussed, as well as the existing condition, use of the beach, needs for amenities and reception capacity (5-6 m2 per sunbed for optimal comfort), dispersion users towards unorganized natural beaches by simply arranging the access roads.
At the workshop, the practice of the city of Vodice was praised, where the material is returned to the coast in the fall so that the sea does not carry it away in the winter, and in the spring they level the ground again and prepare it for the season. In this way, they save up to 70% of the material. And they are also testing a new type of backfill material that may not migrate as much, which will reduce the need for backfilling.
The worst example in the Republic of Croatia is the devastation of the coast by the former government from Podgora, and the positive efforts of the new young government to correct that mistake, to make the local population and future generations aware of the importance of preserving coastal beach resources.
This topic is extremely important to local communities, including Murter, to be able to harmonize the needs for tourist facilities, without destroying this very branch which is their main source of income, along with other branches such as fishing, etc. Beach designers must also become familiar with the mentioned topics, because unfortunately the environmental impact studies are done according to general data, without taking into account the micro-location.”
The high frequency of replenishment, the increase in costs, and the lack of a coastal area development strategy point to the sustainability of the current practice of replenishment of beaches.
The Argonauts Association will monitor the project and inform the local governments on the island and in the immediate vicinity about the conclusions of this project and the guidelines that will follow from it.