4:00 PM - 6:00 PM
[HDS08-P03] Multi-functional Evaluation of Coastal Sand Dunes as Green Infrastructure
Keywords:Green Infrastructure, Coastal sand dunes, wind-blown sand
In recent decades, the impact of wind-blown sand carried by strong ocean winds on agricultural and residential areas, caused by coastal development, has become a problem in many parts of Japan. At Kawashimo Beach in Ishikari City, Hokkaido, Japan, the beach has been developed by removing coastal sand dunes for recreational use, but in recent years the problem of wind-blown sand and its maintenance cost has become an issue. Most of the beaches were developed as bathing beaches, but some natural coastal dunes were left at the northern end of the beaches. There were also artificial coastal dunes at the southern end of the beach, which had been restored to protect the hinterland from wind-blown sand. In these dunes, coastal vegetation was established and no sand deposition on the sand fence behind was observed. Therefore, the coastal dunes were considered to be effective as green infrastructure for the conservation of the unique ecosystem of sandy beach as well as for the prevention of wind-blown sand damage. This study aimed to evaluate the multifunctionality of coastal sand dunes as green infrastructure by quantifying the biological community (vegetation, invertebrate community) and the amount of sedimentation in the natural dune area, the beach area, and the artificial dune area at Kawashimo Beach.
We set two survey lines named A and B in the natural dune area, and four survey lines named C, D, E, and F in the beach area at intervals of about 20 m. We also set a line named G in the artificial dune area. Each line was set to be perpendicular to the shoreline with the fence as the reference point. The amount of the deposition, vegetation and invertebrates on coastal dune were surveyed for each line. The amount of the deposition was calculated as the seasonal change in elevation of the topographic section obtained by aerial photogrammetry. The area from 0.5 m to 10 m from the fence was set as the calculation range, and the amount of the deposition near the fence was compared from May 2021 to October 2021. For the vegetation survey, we recorded species presence and coverage (%) of each species by belt transects on May 2021. We placed plots of 2 m×2 m at intervals of 2 m from the fence to the vegetation limit. For the invertebrates surveys, we collected invertebrates by pitfall traps on July 2021. We set traps at intervals of 8 m from 5 m from the fence to the shoreline. Then, we compared the number of species, diversity index, and species composition of each line by the survey data of vegetation and invertebrates. Cluster analysis was used to compare the species composition of vegetation. DCA was used to compare the species composition of invertebrate community.
The amount of the deposition near the fence from May 2021 to October 2021 was the largest in the beach area, and almost none in the natural dune area. Vegetation coverage was not observed in the beach area. In the artificial dune area, more alien species appeared and vegetation coverage tended to be lower than in the natural dune area, but vegetation was established. The species composition of invertebrate community was divided into two types: the beach area and the others. The beach area mainly consists of widely distributed species. The natural dune and artificial dune areas contain not only widely distributed species but also species living on coastal vegetation dependently.
In result, the beach area tended to be different from the natural dune area in terms of the amount of the deposition and biological community. On the other hand, the artificial dune area showed many similarities with the natural dune area in terms of that. It was found that the rehabilitation of coastal dunes is an effective method with multifunctionality as green infrastructure, including measures against wind-blown sand and restoration of ecosystems.
We set two survey lines named A and B in the natural dune area, and four survey lines named C, D, E, and F in the beach area at intervals of about 20 m. We also set a line named G in the artificial dune area. Each line was set to be perpendicular to the shoreline with the fence as the reference point. The amount of the deposition, vegetation and invertebrates on coastal dune were surveyed for each line. The amount of the deposition was calculated as the seasonal change in elevation of the topographic section obtained by aerial photogrammetry. The area from 0.5 m to 10 m from the fence was set as the calculation range, and the amount of the deposition near the fence was compared from May 2021 to October 2021. For the vegetation survey, we recorded species presence and coverage (%) of each species by belt transects on May 2021. We placed plots of 2 m×2 m at intervals of 2 m from the fence to the vegetation limit. For the invertebrates surveys, we collected invertebrates by pitfall traps on July 2021. We set traps at intervals of 8 m from 5 m from the fence to the shoreline. Then, we compared the number of species, diversity index, and species composition of each line by the survey data of vegetation and invertebrates. Cluster analysis was used to compare the species composition of vegetation. DCA was used to compare the species composition of invertebrate community.
The amount of the deposition near the fence from May 2021 to October 2021 was the largest in the beach area, and almost none in the natural dune area. Vegetation coverage was not observed in the beach area. In the artificial dune area, more alien species appeared and vegetation coverage tended to be lower than in the natural dune area, but vegetation was established. The species composition of invertebrate community was divided into two types: the beach area and the others. The beach area mainly consists of widely distributed species. The natural dune and artificial dune areas contain not only widely distributed species but also species living on coastal vegetation dependently.
In result, the beach area tended to be different from the natural dune area in terms of the amount of the deposition and biological community. On the other hand, the artificial dune area showed many similarities with the natural dune area in terms of that. It was found that the rehabilitation of coastal dunes is an effective method with multifunctionality as green infrastructure, including measures against wind-blown sand and restoration of ecosystems.