The positions of the Chinda (Odaki) Falls have been recorded in historical documents and paintings since the late 15th century. This study aimed to estimate the recession rates of the Chinda Falls by tracing the history of its retreat.

The earliest painting of the Chinda Falls by Sesshu in 1476 indicates that the Odaki Falls was located downstream within 333 m of its present position. A regional geography of Bungo province completed in 1803 mentioned that the Odaki Falls in 1799 was lowered 114-223 m from the current location. In 1909, a dam was constructed 60-70 m above the Odaki Falls for hydroelectric power generation. Subsequently, Odaki Falls continued its recession, approaching within 20 m of the dam in 1952, and has been controlled by artificial reinforcement since then to prevent damaging the dam by waterfall retreat. The present Odaki Falls is located 17.5 m downstream from the dam.

The average recession rate of the Odaki Falls was less than 0.7 m/year in the last 500 years. Additionally, the following variations in recession rates of the Odaki Falls were observed during this period. The calculated recession rate from 1476 to 1799 was less than 0.7 m/year, while that from 1799 to 1909 was 0.6-1.6 m/year, and that from 1909 to 1952 was 0.9-1.2 m/year. The results show that the recession rate of the Odaki Falls has varied three times at most during the last 500 years. The estimated recession rate after the deposition of Aso-4 welded ignimbrite (90 ka B.P.) was 0.36 m/year.

From the above, the recession rate of the Odaki Falls possibly increased during the 19th century. However, the number of recorded natural disasters represented by floods, earthquakes, and volcanic eruptions did not increase in the same period. These results indicate that the century-scale environmental changes around the Odaki Falls barely increased or decreased the recession rate of that waterfall.

In recent years, floods with sediment have occurred often in Japan, causing serious channel changes and bed deformation in mountainous rivers. In this study, we investigated a flood event caused by heavy rainfall due to Typhoon Hagibis in 2019, which produced tremendous damage to the Uchikawa River basin in Miyagi prefecture, and determined the characteristics of the flood event and processes of active landform deformation by focusing on the sediment transport capacities of the channels. The flood mainly occurred in the transition zone between the mountains and the alluvial plain in the lower Uchikawa River basin. The flood flowed down the back marsh and former channel along the Uchikawa and Gofukuya Rivers, which resulted in massive sediment deposition with longitudinal sediment sorting. The sediment transport capacities of the main channels were calculated based on the sediment transport by floodwaters. The results showed that the flooding occurred due to a decrease in the sediment transport capacity, and each event of flooding along the Uchikawa River and other main channels occurred separately. We also calculated the sediment transport capacities of the Sozu, Tenchi, and Oyaokawa Rivers, which flooded due to the 2018 torrential rainfall in the western part of Japan. With these additional cases, we confirmed that the sediment transport capacity can be an indicator to explain the process of sediment transport and deposition, and detect areas that are likely to be affected by active landform deformation.

Childcare workers acquire qualifications and search for employment at childcare training schools. These include vocational schools, junior colleges, and universities. This study aimed to clarify childcare workers’ decision-making process in selecting a training school and their first career post. It focused on daycare nurseries in the city of Chiba, Chiba prefecture, with specific reference to newly graduated childcare workers and labor supply.

An interview survey revealed that many childcare workers were employed where they received practical training or were introduced to the nursery by teachers. The social welfare corporations surveyed have an organized recruitment network with training schools, and this network supplies newly graduated labor to nurseries in the vicinity of training schools. Focusing on childcare workers’ decision-making process, most interviewees wanted to be employed within commuting distance of their parents’ homes. This is related to the structural aspects of the employment search and regional issues in the childcare labor market. Students in training schools searching for employment tend to rely on local listings collected from the schools, and recently the number of training schools has increased in the Tokyo metropolitan area due to growing demand for nursery facilities. As a result, information on recruitment at training schools reflects the growth in local employment.

In this study, childcare workers were mainly from the suburbs of the Tokyo metropolitan area and were able to find local employment. However, this suggests that it is more difficult to be employed locally in rural areas where there is less demand for childcare services. The labor supply of childcare workers is dependent on the regional unevenness of demand for their services.