As a consequence of increased urbanisation, floods threaten inhabitants of various cities in Japan. Although a conventional way of treating urban flooding is to construct sewage systems, alternative approaches have to be developed because of their expense in the context of the current financial crisis. Rain gardens have recently been recommended as a best management practice for the treatment of stormwater runoff in Northern European countries, the USA, etc. While demand for rain gardens has been increasing in Japan, there is a lack of knowledge about policy planning for the development of rain gardens. This present study aims to 1) visualise a possibility for the development of rain gardens as a map and evaluate its effect in terms of storm water management in most urbanised area “Delta Zone” in Hiroshima-City, Japan, 2) discuss a method for policy planning for mainstreaming rain gardens as a kind of green infrastructure. By use of GIS technology, the areas under the conditions (elevation < 5.0 m, slope angle < 1.1 degrees and GWL < -2.0 m) were selected as potential areas for rain garden installation. Next, 1) green spaces, 2) sandy spaces, 3) car parks on the potential areas were identified because those spaces are easier to install rain gardens than building and road areas. As s result, it was indicated that “Delta Zone” could obtain a rainwater infiltration function to treat 20 mm/h stormwater event if only 10 % of those spaces turn into rain gardens. In addition, a practical scenario to mainstream rain gardens in Japan was discussed.

We tested and verified topographic changes in a landslide area caused by the Hokkaido Eastern Iburi Earthquake in 2018. We accomplished this using real-time kinematic unmanned aerial vehicles (RTK-UAV) and structure-from-motion multi-view stereo (SfM-MVS) photogrammetry. To verify our measurement accuracy, the position coordinates of 11 validation points in the 4-ha assessment area were obtained using a ZED-F9P, dual frequency RTK global navigation satellite system (GNSS) on March 12^th, 2019. The maximum height difference between verification points was approximately 28 m. We moreover extracted position coordinates of validation points from a digital surface model (DSM), and an orthomosaic image was created from aerial images obtained by the RTK-UAV. Subsequently the position coordinates of validation points obtained by the two methods were compared. The analysis of topographic changes was performed on two DSMs created from the aerial images acquired on March 12^th and April 23^th, 2019. The average position between each validation point and the model was 0.060 m ∼ 0.064 m in both horizontal and vertical directions. The maximum vertical error was 0.108m. Knowing this error is important for monitoring the dynamics and stability of surface soil during plant growth. The analysis of topographical changes indicates a change of -0.1 m to +0.1 m in 86.86 % of the total assessment area. A change of -0.5 m to -0.1 m was the most frequent at 11.36%. In particular, the erosion area was confirmed at the boundary area between the forest and the landslide area. These results demonstrate that using RTK-UAV, topographic changes area measurable within an error range of 0.1 m even in sloped forests, where it is difficult to set ground control points.

Coastal pine forest is one of the important green infrastructures, which provides several ecosystem services such as disaster prevention and beautiful scenery. Most of the coastal pine forests in Japan, however, has been unmanaged and changing to different types of forests through natural succession. In addition, the structure has been declining due to pine wilt disease. In this situation, coastal pine forest in Fukutsu City, Fukuoka Prefecture, has been restored by autonomic activities of local people. Enthusiasm come from people's memory of the past such as beautiful landscape of the pine forest and thought of recovering it. Local council, which was established under the policy of Fukutsu City, took a roll to share people's memories, recognize challenges and establish a goal in the local area. The council has act as the platform for public involvement and the motivation for the activities. Fukutsu City has transferred authority and fiscal resources to the local council according to the policy on promoting local governance. Thus it has successfully brought the governance-based solution to ecosystem management for keeping the functions of green infrastructure.