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 gravel as aggregate for concrete became widespread, and gravel from the Tama River was also utilized. Especially after the Great Kanto Earthquake in 1923, the demand for reconstruction caused a rapid increase in river gravel production. Around this time, the center of gravel mining in the Tama River was the middle reaches from Tachikawa to Inagi. This was because the lower reaches had already been exhausted. From the late Taisho era, large excavators and dredging vessels began to be used, enabling integrated operations from gravel extraction to sorting and washing, which advanced the mechanization and rationalization of the gravel industry.

Construction of Gravel Railways

Gravel extraction was closely related to the construction of railways. The railways laid around the Inagi area for the purpose of gravel extraction and transportation are listed as follows.
The Tamagawa Gravel Railway, established in 1920 and opened between Kawasaki and Omaru in 1927 (later the Nambu Line); the Keio Electric Railway’s Tamagawara Line, which began operations between Chofu and Tamagawara in 1916 (later the Keio Line); the Tama Railway, which opened from Musashisakai to Koremasa on the Chuo Line in 1922 (later the Seibu Tamagawa Line); and the Tokyo Gravel Railway, which started operations between Kokubunji and Shimogawara in 1910 (the Japan National Railways Shimogawara Line). Looking at the construction periods, all were built within a short span of less than 20 years from the late Meiji period to the early Showa period, and these railways were already completed by 1929. The locations of these railways show that the Nambu Line, Keio Line, and Chuo Line served as main axes, with branch lines extending like fishhooks toward the Tama River.

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, during the 1940s, postwar reconstruction gradually progressed, and gravel extraction from the Tama River began to regain the prewar vitality. However, due to the advancement of gravel pollution caused by indiscriminate excavation, an agreement concerning the regulation of gravel collection from the Tama River downstream of Hino Bridge was concluded in 1952, leading to strengthened regulations. Entering the 1960s, regulations were further tightened, and in 1964, commercial extraction up to Mannen Bridge in Ome City was completely banned. The following year, in 1965, a complete ban on gravel extraction was imposed throughout the entire Tama River, bringing the history of gravel mining to a close.

Reference Literature: "Inagi City History, Volume II"
"Folklore of Inagi City (IV)" and "Inagi Things and Life 3"