1. RESULTS AND DISCUSSION
THE IMPACT OF A PORT ON THE SURROUNDING SEASHORES BASED ON THE 13-YEAR MONITORING RESULTS
Hannes Tõnisson1 Kaarel Orivku1 and Are Kont1
1Institute of Ecology at Tallinn University. Uus-Sadama 5, Tallinn, Estonia,
Acknowledgements: This study was supported by Estonian Science Foundation grants: 8549, 9191, IUT18-9 and the BONUS project BaltCoast.
INTRODUCTION
The study was carried out in the vicinity of Sillamäe town and industrial port, located on the north-eastern coast of Estonia. Sillamäe was one of the most serious threats for the whole Baltic Sea environment. The town was founded together with the construction of a chemical and metallurgy plant in 1946, where fuel rods and nuclear materials for the Soviet nuclear power plants and weapons were produced. The current study is focusing on the shore processes and the coastal sea fronting Sillamäe. The town is located east of the port. It is the region with the highest potential impact of the port. Until the town was founded and the factory with its nuclear waste depository was constructed, the shores near the town were in a good natural balance. Construction of the port, waste depository, etc. and additionally climate warming has taken place since then. The shores in front of the nuclear waste depository are well protected today. However, the rapidly expanding port is the major obstacle of the longshore sediment transport since The aim of the study is to analyze the impact of the port to the changes in coastal evolution and sediment budget in the vicinity of the port based on the regular monitoring results.
RESULTS AND DISCUSSION
We have noticed no clear trends in shoreline changes in the Sillamäe study site. The shoreline position is changing from year to year due to some major storms. These changes are mostly temporary and less than 5 m or caused by sea-level fluctuations. The length of the studied area is approximately 3,300 m. Only 450 m of it has experienced some erosion while the rest of shoreline is mostly stable or slowly advancing towards the sea. We have found that some of the profiles have a volume of only over 20 m3/m of shoreline. These profiles (5, 6, 8, 9) are measured from the locations where unstable shorelines/scarp edges are recorded and occasional erosion is reported. The profile No. 9 is the only steadily receding profile here, which has lost over 6 m3 (ca 20 %) of its initial volume of sediments during the study period. The healthiest profiles had about 70–80 m3 of sediments in the active zone (profiles 1, 1a, 2, 7). Gradual accumulation is reported in each of these locations. Based on the photos taken from the study area, we can conclude that there are no visible changes in the shoreline position. Changes on the backshore are clearly visible in the western part of the study area. However, these changes are mostly resulted from extreme storm events and cannot be associated with the harbour constructions. a) b)
E S T O N I A
Sillamäe c) a) b) c)
Profile 2
Profile 6
Profile 9
Figure 3. a) healthy profile, gradual accumulation, temporary erosion may appear after strong storms, b) unhealthy profile, occasional erosion from the scarp, coastal slope is more or less stable, c) unhealthy profile, gradual erosion and shore retreat.
Figure 1. a) location of Estonia, b) gray box - the location of study area, c) study area with studied profiles on 2014 orthophoto.
METHODOLOGY
The dynamics of the seashores was assessed using remote methods and in situ measurements. Remote methods included the analyses of shoreline changes and changes in scarp positions in space and time using orthophotos. The study is also based on the measurements of scarp edges, shorelines and shore profiles conducted in 2004–2016. The measurements were carried out using Leica GS09 RTK-GPS and Leica level. The volume of sediments in the active zone of each profile was calculated. The active zone was defined as the zone from the mean shoreline to the elevation where storm waves were still able to influence the shore processes. Finally, photographs from different years but taken from exactly the same locations on the study area were also used.
CONCLUSIONS
The results suggest that either a stable geomorphic state or a slow accumulation has prevailed along major part of the studied coast. After stronger storms, occasional erosion events were registered in several sections of the study site. However, these changes were mostly temporary and a stable state was usually restored soon after the erosion event. There are two exceptions on profiles 1 and 9. The first of them has experienced a gradual increase in the volume of sediments (the most distant from the port) while the second one has gradually lost the sediments (the closest to the port). The reason of the loss is directly attributable to the unsuitable hard defence measures established during the Soviet period but still influencing the shore processes. Finally, we can conclude that the monitoring of shore processes from 2004–2016 has not registered major changes on the shores directly influenced from the new harbour. Most of the changes on the shores are temporary and caused by natural extreme events. a) b)
c1)
c2)
Profile 1
b1)
b2) a)
2013
2007
2013
2006
Figure 2. a) RTK-GPS measurements from 1.7 m depth until the stable land (not influenced by waves), b) Profile nr 1, based on RTK-GPS measurements and levelling survey c) photographs from exactly the same location (central part of the study area) from 2007 (c1) and 2013 (c2) – nearly no visible changes.
Figure 4. a) the volumes (in m3, y-axis) of the profiles from different locations from , b) recession of the backshore, western part of the study area. The pipes of heating water have been removed by the local authorities to avoid collapse into the sea.