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 laid for the purpose of gravel extraction and transportation in the areas surrounding Inagi.
Established in 1920 (Taisho 9), the Tamagawa Gravel Railway (later known as the Nambu Line) opened the Kawasaki-Omaru section in 1927 (Showa 2). The Keio Electric Railway (later known as the Keio Line) began operations between Chofu and Tamagawahara in 1916 (Taisho 5). The Tamate Railway (later known as the Seibu Tamagawa Line) opened the section from Musashisakai to Kosei in 1922 (Taisho 11). The Tokyo Gravel Railway (National Railways Shimokawahara Line) began operations between Kokubunji and Shimokawahara in 1910 (Meiji 43). Looking at the periods of construction, all of these railways were built within a short span of less than 20 years, from the late Meiji era to the early Showa era, and by 1929 (Showa 4), these railways were already completed. The locations of the constructed railways show that the Nambu Line, Keio Line, and Chuo Line serve as the main lines, with branches extending towards the Tamagawa River in a fishhook shape.

Impact of Gravel Mining

With the mechanization of gravel extraction and the realization of large-scale transportation through railway construction, gravel extraction from the Tama River reached its peak 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, since the 9th year of the Showa era, gravel extraction has been prohibited in the high water area upstream of the Futako Bridge and downstream of the Hino Bridge, with only low water area extraction being permitted.
After the war, in the 1950s, post-war reconstruction gradually progressed, and the gravel extraction from the Tama River began to regain the pre-war vitality. However, due to the pollution caused by reckless extraction, an agreement regarding the regulation of gravel collection from the Tama River downstream of Hino Bridge was concluded in 1952, leading to strengthened regulations. As we entered the 1960s, the regulations were further tightened, and in 1964, commercial extraction was completely banned up to Mannen Bridge in Ome City. In the following year, 1965, a complete ban was implemented across the entire Tama River, marking the end of the history of gravel extraction.

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