Gravel Mining in the Tamagawa River

Gravel extraction in the Tama River basin has been carried out since the Edo period, and records show that gravel was sold as a tax to the shogunate. However, it became more prominent from the mid-Meiji period, when river gravel was gathered using a shovel, transported with a gravel scoop, and sorted with a gold pan before being shipped to Tokyo. This was before large excavation and sorting machines were introduced, and all gravel extraction was done manually, giving rise to the term 'Tama River gravel sorting.' Additionally, gravel collected in the lower reaches was transported to Rokugo using wooden sailboats and was then transferred for shipment to the city of Tokyo. During the Meiji period, the primary use of river gravel was for ballast for roads and railways, and it seems that larger gravel sizes were in demand. In the villages along the Tama River, gravel sorting became a significant source of cash income for farmers.

Gravel Mining Since the Taisho Era

During the Taisho era, the use of concrete aggregates became widespread, and gravel from the Tamagawa River was also utilized. Especially after the Great Kanto Earthquake in Taisho 12 (1923), the production of river gravel surged due to reconstruction demands. At that time, the center of gravel extraction from the Tamagawa River was in the middle reaches around Tachikawa to Inagi. This was because the lower reaches had already been depleted. From the late Taisho period, large excavators and mechanical boats began to be used, allowing for a consistent process from gravel extraction to sorting and washing, leading to the mechanization and rationalization of the gravel industry.

Construction of Gravel Railways

The extraction of gravel was closely related to the construction of railways. The following is a list of railways that were established for the purpose of gravel extraction and transportation in the Inagi area.
The Tamagawa Gravel Railway, established in 1920 and opened between Kawasaki and Omaru in 1927 (later known as the Nambu Line), the Keio Electric Railway's Tamagawara Line, which began operations between Chofu and Tamagawara in 1916 (later known as the Keio Line), the Tamate Railway, which opened from Musashisakai to Kosei in 1922 (later known as the Seibu Tamagawa Line), and the Tokyo Gravel Railway, which began operations between Kokubunji and Shimokawara in 1910 (later known as the National Railways Shimokawara Line), among others. Looking at the periods of establishment, all of these were constructed within a short span of just under 20 years from the late Meiji era to the early Showa era, and by 1929, these railways were already completed. The positions of the established railways show that the Nambu Line, Keio Line, and Chuo Line served as the main axes, with branches extending towards the Tamagawa in a hook shape.

Impact of Gravel Mining

The mechanization of gravel extraction and the realization of large-scale transportation through railway construction led to the peak of gravel extraction from the Tama River from the late Taisho era to the early Showa era. However, large-scale gravel extraction has various negative impacts on the Tama River itself. These include the destruction of riverbank levees, difficulties in water intake for agricultural use due to the lowering of the riverbed, and adverse effects on fisheries due to water pollution. In response to this, from Showa 9 onwards, gravel extraction in the high water area upstream of the Futako Bridge and downstream of the Hino Bridge was prohibited, allowing only extraction in the low water area.
After the war, in the 20s of the Showa era, post-war reconstruction gradually progressed, and gravel extraction from the Tama River began to regain its pre-war vitality. However, due to gravel pollution caused by indiscriminate extraction, the "Agreement on the Regulation of Gravel Extraction from the Tama River" was concluded in Showa 27 for the Tama River downstream of the Hino Bridge, leading to strengthened regulations. As we entered the 30s of the Showa era, regulations were further tightened, and in Showa 39, commercial extraction up to the Mannen Bridge in Ome City was completely banned. In the following Showa 40, a complete ban was imposed across the entire Tama River, marking the end of the history of gravel extraction.

Reference materials. "History of Inagi City Volume 2"
"Folklore of Inagi City (4)" "Inagi Things and Life 3"