River-based political geography of the Ainu–Wajin trade

During the first two centuries of Tokugawa shogunate's reign, the trade between the Matsumae Domain and Ainu communities reinforced the centrality of rivers in local territorial arrangements in Ezochi (“Ezochi” will be used when referring to the area in the Tokugawa period, switching to “Hokkaido” in the modern era). With approval to manage trade in Ezochi, Matsumae began extending its network by establishing trading posts along the southeastern coast. This expansion triggered significant changes in existing social structures, political alliances, residency patterns, and economic practices of the Ainu communities, integrating local systems of natural resource procurement into the broader economy of the Tokugawa shogunate (Walker Reference Walker2001). In eastern Ezochi, the Kushiro River emerged as a vital route inland to resource-rich areas, empowering the headman residing at the trading post by the river mouth, further shaping the dynamics of territorial influence in the region.

Scholars have noted the significance of rivers in Ainu societies for territorial claims, resource governance, and social organization. Anthropologist Hitoshi Watanabe's study of oral histories and residential patterns of Ainu communities in the Tokachi region during the 1950s revealed that “river groups” under a patrilineal headman asserted exclusive rights over resources in a river basin. These groups, connected by kinship as well as subsistence activities and ritual practice, claimed autochthony and defended their resources with surveillance and arms. Venturing beyond one's group's territory required a visit to the headman, gift payment, and the approval of the local gods (Watanabe Reference Watanabe1972, pp. 16–17, 67–68, 77–78). Irimoto Takashi added to Watanabe's claims by exploring the connection between territoriality and trade. Comparing river groups in the Tokachi region, Irimoto argued that trade strengthened territorial exclusivity, centralized authority, and deepened social stratification. This process also led to a more elaborate and exclusive “system management” that involved permission and punishment for trespassing and entry fees to catch game, ultimately resulting in “a territoriality that is area-oriented with a permanent basis” (Irimoto Reference Irimoto1992, p. 78).

These works highlight the historical importance of river-based trade in this region's territorial practices and institutions. For these local communities, rivers provided subsistence resources, both directly as habitat for riverine biomass such as salmon, and indirectly as a key component of local ecosystem dynamics that support other fauna and flora. Rivers also served as a transportation and communication route, connecting riverine settlements that formed governance units. Residences, religious structures, and military outposts also appeared along rivers (Utagawa Reference Utagawa1981, pp. 127–182). The physical contours of a river also shaped these units, which also served as organizing metaphors that anchored their community in both the physical landscape and their cosmological worldview. The tree-like hierarchy of tributaries and parent streams gave shape to local political hierarchies, while many charismatic species drawn to rivers and wetlands, such as bears, cranes, and owls, were incorporated into belief systems and institutional arrangements (Kaiho Reference Kaiho1996, p. 157). In sum, rivers facilitated the local territorialization of these local, subsistence-based communities.

In eastern Ezochi, this river-centered, subsistence-based territoriality either originated in or was reinforced by the Ainu–Wajin trade of the Tokugawa period (1603–1868). Local groups were engaged in long-distance maritime trade as early as the tenth century (Segawa Reference Segawa2007, p. 253), and by the Tokugawa period (1603–1868), the island's northern region served as a gateway for goods moving between the Amur River and Sakhalin Island, while island's eastern region was linked to Kamchatka via the Kuril Islands (Kaiho Reference Kaiho1987; Minoshima Reference Minoshima2015; Segawa Reference Segawa2007). Matsumae Domain, following the Shakushain's War (1669–1672), began appointing vassals to trading posts. Transactions involved Wajin items such as iron and bronze weapons, lacquerware, rice, sake, and silk, which were exchanged with Ainu products such as herring, kelp, and salmon, as well as medicinal products such as bear galls and components for arms manufacturing, such as raptor feathers for helmets and arrows. By the end of the 1700s, over sixty posts had been established throughout Ezochi and many posts began to function as administrative centers (Howell Reference Howell1995, p. 31; Kaiho Reference Kaiho1978; Segawa Reference Segawa2007, pp. 45–47; Walker Reference Walker2001, pp. 38–39). This trade system spurred greater integration of Ainu communities into the trade network and fostered dependence on goods from the mainland for their subsistence.

As this trade network grew, so did the power of the headmen and their territorial claims over the river basin. Often residing in the trade post area, trade strengthened the authority of headmen, who typically headed a household with wives and slaves and were responsible for defending territory from rival clans, punishing criminals, managing labor, adjudicating conflicts, presiding over religious ceremonies, and administering common resources. This shift coincided with the use of Wajin goods as talismans of political authority (Segawa Reference Segawa2007, pp. 52–92). Headmen who gained prominence through trade displayed goods such as swords, silk, and lacquerware, as symbols of authority and prestige. Accruing symbolic power, these Wajin goods were incorporated into ceremonial practices such the bear sacrificial rite, which would feature ceremonial arms, lacquerware to store offerings, and sake (Utagawa Reference Utagawa1992). Headmen and their lieges also began to wear imported swords as emblems of power. These goods were associated with the Wajin trade and used in trade meetings, during which these objects were displayed as signs of authority and exchanged as pledges of agreement and subjugation (Howell Reference Howell1994; Walker Reference Walker2001, pp. 204–226). Ainu leaders began to use these objects to pay debt, seal contracts, and help resolve conflicts (Iwasaki Reference Iwasaki1998, pp. 139–167). In turn, these objects, as tokens of what may be described as fiduciary agreements with Matsumae vassals, enabled the headmen to claim control over rivers. Trade converted the surplus value from resource extraction into talismanic items of Wajin origin that symbolized power, wealth, and alliance.

Trade, however, depended on the ability of local communities to extract river resources and convert them into tradable goods. Salmon was one such trade item, with an oversized impact on Ainu territoriality. Local communities took advantage of the species' instinct to return to their natal rivers to spawn in fall. Winter camps were built upstream to catch and dry salmon, as the species tends to spawn near river sources with a gravel riverbed habitat and sufficient groundwater flow – conditions that are found more upstream (Ito and Watanabe Reference Ito and Watanabe2020). Thus, in eastern Ezochi, Ainu migrated seasonally along rivers: in the warmer seasons, they moved coastward for marine species, such as cod, ray, and herring in the spring, and sea cucumbers and kelp in the summer, while in the colder months they relocated upstream for salmon and game hunting such as deer, eagles, and bear, as well as repairing boats and knitting nets and ropes, in preparation for warmer months (Ashikaga Reference Ashikaga1968, pp. 42–43). Trade records from the early 1800s, for example, report the following:

This record tracks the seasonal and gendered relocation from the coast to the upstream forests of Nishibetsu in the winter.

The Kushiro River, due to its length and access to the inland headwaters of other streams, was particularly suited for the salmon trade. Archaeologist Segawa Takuro argues that salmon trade in Ezochi only existed along longer rivers, since the only type of salmon suitable for drying and trading were the lean salmon that expended their fat to travel upstream for spawning (Segawa Reference Segawa2007, pp. 123–129).Footnote ¹ These upstream winter camps served as workshops for salmon catching and drying. Although they may have resembled the facilities for processing herring and other marine goods associated with coastal trading posts, they were locally managed with little oversight from Wajin merchants. The impact of salmon trade can also be seen in residential patterns. According to travelogues from the 1850s, an Ainu community of seventy-two households was located near the Kushiro trading post. Several salmon fishing camps were located upstream, and that the Kushiro headman had territorial claims over the headwaters of the Nishibetsu and Abashiri rivers – both renowned salmon rivers (Ashikaga Reference Ashikaga1968, pp. 60–63). Control over longer rivers or areas with many river sources gave greater economic leverage and political power to the Kushiro river group.

Thus, headmen's influence over the length of rivers and their adjacent lands enabled them to act as a mediator between Wajin merchants and riverine communities. The headmen oversaw the procurement and transportation of trade items that moved through settlements and down along the river, where they were gathered and sold at trading posts in exchange for goods, such as rice and sake, which were then distributed back to local settlements. Trading posts became the entry point for market and state forces, disrupting existing social hierarchies and exerting greater pressure on the local ecosystem. Over time, headmen's dependence on trade led to the increased exploitation of rivers, and ultimately, to an inter-watershed dispute.

A dispute over a salmon river

In 1853, the same year that Matthew Perry's US Navy fleet arrived in Tokyo Bay, a conflict ensued between two Ainu river groups in eastern Ezochi. The dispute arose when Ainu contractors trading at the Nemuro post set a salmon net at the mouth of the Nishibetsu River, whose forested headwaters were accessible via the Kushiro River and was a key hunting and fishing area for the Kushiro river group. Although the economic volatility during this time likely triggered this dispute, its underlying cause was the local leaderships' dependency on the Ainu–Wajin trade and the depletion of resources due to rapacious exploitation. This local conflict, occurring at the fraying edges of Pax Tokugawa, was not an isolated event. It reflected the shogunate's effort to fortify its position in Ezochi against the perceived threat of foreign invasion. The shogunate sought to strategically link the river to the vast network of roads, rivers, and maritime routes, with post stations and highways linking navigable waterways.

Wajin administrators' efforts to gain greater control over these regions were prompted by two late-eighteenth-century developments in eastern Ezochi: an Ainu rebellion against Wajin proprietors and the encroachment of Russians. First, a local insurrection disrupted trade and raised fears of widespread insurgency. The Menashi–Kunashir Rebellion of 1789, led by Ainu workers on Kunashir Island and resulted in seventy-one Wajin deaths, signaled potential trouble in a region with weak administrative oversight (Iwasaki Reference Iwasaki1998; Tanimoto Reference Tanimoto2020). Until this time, Ainu–Wajin trade in eastern Ezochi was primarily handled by merchants paying trading rights from Matsumae administrators. Many merchants, aside from engaging in trade, also operated fisheries and processing facilities for which they introduced new technologies, such as large fishnets, and adopted new ways to procure labor, such as debt servitude and peonage. Increasing dependence on commercial fisheries contributed to instances of intimidation and violence against Ainu workers (Hirano Reference Hirano2015; Howell Reference Howell1995).

The specter of Ainu unrest grew larger with the arrival of foreign envoys on northern shores. Backed by Imperial Russia, envoys such as Adam Laxman (1766–1806) reached Nemuro in 1792 with two Japanese castaways to request a fur trade agreement (Azuma Reference Azuma2017; Koller Reference Koller2004). Habuto Masayasu (1752–1817), one of the three shogunal magistrate assigned to Ezochi, reported that “Russians approached Kamchatka, encroached upon and renamed dozens of islands, and established offices there.” He further documented a series of Russian arrivals on the northern shores, starting with one such encroachment in 1765 (Habuto Reference Habuto1985, p. 32). For the shogunate, these Russian incursions heightened the urgency for cultivating ties with local Ainu communities.

These two problems pushed the shogunate to seek greater territorial control by strengthening the existing trade system and establishing Wajin settlements.Footnote ² In the years to follow, shogunate officials seized control over eastern Ezochi. A 1799 decree appointed officers to Hakodate, Matsumae's administrative center that was also used by the shogunate's magistrate, and called for “guarding the border with foreign countries” and to “further investigate the land […], educate the barbarians to change their customs, ways of trading, and gain their obedience in opening the land.”Footnote ³ Recognizing Ezochi as the domain of Ainu “barbarians,” the magistrate envisioned a colonization plan that included the expansion of the existing trade network. Trading posts were recast as not only centers of economic activity but also hubs of administrative control, where the vassals sought to promote Japanese language usage, farming, and the use of money, while also banning practices such as polygamy, thus aligning with Habuto's vision that “in 100 years all of Ezochi will be transformed into a land similar to that of our country” (Habuto, p. 38). To achieve this goal, the magistrate supported the establishment of Wajin settlements and the construction of a transportation network.

The Kushiro River was central to these efforts because the waterway, aside from offering access to rich inland resources, connected to Shari Pass, a road that reached the Sea of Okhotsk. This shortcut, a footpath that was already well-trodden by locals, became a part of the shogunate's extensive transport network (Vaporis Reference Vaporis1995) when Wajin settlers built a road that connected the Kushiro and Shari rivers (Tanimoto Reference Tanimoto and Murakami1988). In 1800, the shogunate's Hachiōji Office, near Edo, sent fifty samurai-farmers with thirty-five rifles to settle in Shiranuka, near the mouth of the Kushiro River (Kushiro shi 1931, p. 197). The group's leader, Hara Hanzaemon Taneatsu (1749–1827), proposed that in addition to defending the north, his unit would “open the land to the ways of farming” (Habuto, p. 65). Made up of samurai families who had experience serving as security officers and tenant farmers in the outskirts of Edo, they arrived in 1800 and constructed Shari Pass, which began in Shibecha, a settlement along the Kushiro River, and continued to Shari, a trading post that was part of western Ezochi and therefore gave access to the trading post in Soya, the northernmost settlement on the island. This new road thereby bridged the far corners of eastern and western Ezochi, thus closing the circle of control around the island and shortening the voyage from Soya to Hakodate.

For Shari Pass to be a viable shortcut to the Sea of Okhotsk, however, a safe passage via the Kushiro River was essential. In the first recorded instance, Habuto traveled from Hakodate along the island's southern coast, rounded Cape Nosappu in the east, around Kunashir Island, and then trekked from Shibetsu along the Shibetsu River, through Nishibetsu, to Shibecha (Fukui Reference Fukui1961). The expedition then traveled downstream along the Kushiro River by foot and midway embarked on a boat to travel to Kushiro Port. A month later, Matsudaira Tadaaki, the aforementioned shogunal magistrate, circumnavigated most of the island via the Kushiro River (Isoya Reference Isoya1961). In this 1801 mission, Matsudaira's group, which included Isoya Norikichi, who left a record of this trip, a porter, and two Ainu guides, traveled clockwise from Hakodate, cutting northward from Yufutsu to Ishikari to the Sea of Japan, then rounding Cape Soya to the Sea of Okhotsk. On June 13th, they left Shari, located west of Shiretoko Peninsula, to travel upstream on Shari River by boat. Midway up the river, the group disembarked to hike on the newly constructed Shari Pass. Isoya noted that they “traveled on the newly opened mountain road, marching through a thick forest with a swarm of mosquitoes and horseflies” (Isoya Reference Isoya1961, p. 57). Along the path was “a makeshift shack built by the Hachiōji soldier-farmers,” where they stayed the night, and arrived in Shibecha on the 15th. On the 16th, they traveled down the Kushiro River, during which a sword was lost when the ship capsized. Our scribe mentions several tributaries and a lake, until they arrived in the Kushiro trading post, where some 200 Ainu households resided.

Similar survey expeditions occurred after 1802. For example, accounts of travels and trading were recorded by Arai Heibei (1770–1830), a shogunate vassal assigned to Hakodate in 1807 who later became the key financial officer of Ezochi. His account, dated 1809, tells of a shipment from Kushiro that included kombu from Nishibetsu, which probably meant that the kombu originated from a post on the Okhotsk via the Shari Pass–Kushiro River route. Other items, such as raptor feathers and sturgeon, from the far end of the Shari Pass (Arai Reference Arai1961, p. 77),Footnote ⁴ are also noted to have come through Nishibetsu's “raptor feather store” (ibid., p. 84). There were also Wajin-led efforts to introduce agriculture to locally produce tradable goods. For example, Arai mentions a time when “millet yield was insufficient” and therefore the Wajin merchants were “unable to pay the barbarians” (ibid., p. 81). One such group of farm plots, “2 ri (8 km) upstream [from Kushiro] constructed by the Shiranuka settlers” (ibid., p. 81), produced crops such as daikon, millet, beans, and burdock, which the farmers would sell at the post. In exchange, the farmers purchased “rice from Edo,” as well as sake made locally in Kushiro or shipped from Echigo, or present-day Niigata (ibid., p. 70). Arai's account tells of the importance of Nishibetsu, an area that was connected to the Tokugawa transportation network via the Shari Pass and the Kushiro River.

Despite the effort to oversee the area, the interiors of eastern Ezochi remained primarily in control of Ainu river groups, as Wajin merchants relied on local leaders to procure and deliver inland resources. The Nishibetsu River dispute sheds light on this political geography. In this incident, river rights were central to this territorial dispute. In 1853, an Ainu contractor in Nemuro cast a net at the Nishibetsu River's mouth to catch salmon. This angered Menkakushi (Japanese name: Sei'ichirō), the Ainu headman from Kushiro, who petitioned that his group had rights to the Nishibetsu River's headwaters, which was accessible via the Shari Pass. Between 1856 and 1860, despite episodes of sabotage and destruction of property, the two river groups resolved their differences through negotiations mediated by Wajin trading post officials. In an 1857 report, Menkakushi claimed that his grandfather, Bekerenishi, sent a sword and sheath, along with six silver cups, to the grandfather of his Nemuro counterpart Ikashunte, in exchange for “overseeing the river from the mouth to the headwater” (Akiba Reference Akiba1989, p. 406). The Nemuro leader, while admitting possession of these “treasures,” denied knowledge of the agreement they represented. The magistrate at Akkeshi, a nearby trading port, ruled in favor of the Kushiro group and imposed a ban on rigging nets across the river.

Of note is the Wajin intervention and how Wajin items served as evidence for territorial claims. Although the exchange of river rights with trade items is not strictly a purchase, it indicates that high-value ritual objects, when underwritten by oral narratives that recount past contractual ceremonies, functioned as pledges for the transfer of rights. The trade-driven system of politics, ritual, and territoriality persisted due to the consistently high market value of local fauna as items of luxury and refinement throughout the shogunate (Iwasaki Reference Iwasaki1998, p. 175; Segawa Reference Segawa2007). However, the disputing river groups also served as subcontracted bosses for the respective trade posts of Kushiro and Nemuro. Post officials were likely concerned about the halted flow of goods due to the stalled negotiations and the destruction of processing workshops. Still, a crucial factor for the ruling in favor of the Kushiro group may have been that Kushiro's port was accessible year-round, while Nemuro's port would be icebound and therefore inaccessible during winter.

This dispute may have also been influenced by the instability of the Tokugawa monetary system, triggered by the demand by foreign powers to begin trading internationally (Crawcour and Yamamura Reference Crawcour, Yamamura and Smitka2012). In 1854, the shogunate reassumed control over Ezochi, while Hakodate was granted permission for international trade. The new magistrate also sent surveyors to explore the land, including Enomoto Takeaki (1836–1908), who later to become a naval commander of the shogunate forces, and Matsuura Takeshiro (1818–1888), a scholar-monk turned explorer who coined the name “Hokkaido” as the modern designation of the island. What enabled these surveys, and thus rendered the land legible to the emerging state institutions, was the trade network that connected Hakodate through eastern Ezochi and reaching to the Kuril Islands. On this eastward route, the Kushiro River provided access to inland regions and the island's northern coast (Kushiro sōsho henshū iinkai 1994, pp. 16–18). In the modern era, the river's function as a transportation route intensified, as it was enlisted in the efforts to build the Japanese Empire.

River, dispossessed by design

In 1868, the new Meiji government declared itself a new nation based on democracy and science, while also launching the modern colonization of Ezochi, subsequently annexed and renamed “Hokkaido.” The Hokkaido Colonization Commission (hereafter “the Commission”) was established in 1869 through a series of decrees that mandated it to build infrastructure, establish settlements, and develop industries in the newly claimed territories. Colonization necessitated the transformation of Ezochi into a legible territory, involving the parceling and conversion of land into transferrable plots and the introduction of policies to spur migration from the mainland. During this transitional phase, the Kushiro River continued to facilitate the hauling of goods and providing access to the island's interior for surveyors and geologists in search of resources and settlement sites. Although the river offered only a limited view of the land from its waters, it played a crucial role in making the area accessible to state actors. Surveyors, seeking to excise what they deemed as wild and “barbarian” elements from the region, re-imagining Ezochi as terra nullius, and to do so required the engineering of rivers. In the quest to establish settlements and develop the land, the river was dredged and channelized to allow for the passage of ships. This strategic alteration of the river mirrored the broader objectives of the Commission at the onset of Hokkaido's colonization.

In this initial phase, the Commission aimed to strengthen the empire's northern defenses by founding settlements and developing the infrastructure, technology, and industry needed for harnessing the region's resources. Viewing Hokkaido as an untapped frontier, the emerging state invited experts, mostly from the USA, to plan civil engineering projects and introduce agricultural, mining, and forestry practices. The establishment of colonial settlements served as a key strategy for national defense, a justification publicly stated during a government session with the Meiji Emperor on June 30, 1869, just weeks after the defeat of the last anti-imperial forces in Hakodate. The statement, in presenting Hokkaido as “the Northern Gates of the Imperium,” admonished the geopolitical fallout caused by the prior maltreatment of the Ainu:

This statement discursively tied the northern defenses to the creation of colonial settlements. Simultaneously, the Commission promoted agriculture and sedentism through “education” as a way to convert Ainu people into imperial subjects.

This molding of indigenous people was closely linked to the expropriation of rivers in Hokkaido. In 1871, the same year that the Household Registry Law recognized Ainu individuals as Japanese nationals (Chapman Reference Chapman2011), the newly established Nemuro Prefecture enacted a law against poaching in “salmon seed rivers,” which included the Nishibetsu River.Footnote ⁶ At the time, the Meiji state adopted a policy of resource propagation – a commanding concept for modernizing natural resource extraction (Takahashi Reference Takahashi2007). With a focus on salmon as a key source of foreign currency, the Commission initially granted fishery rights, prohibited poaching, relocated Ainu villages along rivers, and, in 1878, erected a salmon cannery at the river's mouth. The enclosure of Nishibetsu was completed with the founding of the Nemuro Salmon Fishery Cooperative, deployment of prefectural guards along the river, and the construction of a salmon hatchery at the headwaters (Akiba Reference Akiba1980). The prohibition against salmon fishing and the dispossession of rivers from indigenous communities were part of the Meiji state's strategy to expand its control over natural resources, thus complementing cultural and linguistic assimilation policies.

Similar changes unfolded with the Kushiro River. Despite the official dissolution of the trading post system in 1869,Footnote ⁷ in practice, the closure of trading posts resulted in an administrative void that enabled merchants to continue their operations and to benefit from the state's reappropriation of land and fishery grounds. One influential figure in the river's development was Sano Magoemon (?–1881), a merchant who headed the Kushiro trading post. He assumed control of his Matsumae-based merchant family in 1856 and expanded its fishery business in Ezochi, initially focusing on the kelp trade, for which he retained rights into the modern era. It was sulfur deposits near volcanic vents, however, that drove Sano upstream. In 1876, Sano secured a 15-year permit for the Atosanupuri Sulfur Mine near the river's headwater and constructed a road connecting the mine to Shibecha, which linked it to the Kushiro Port via the river. Completed in 1878 to transport sulfur ore by horses, it was also intended to be used for establishing settlements inland, with little effect (Kushiro sōsho henshu iinkai 1988, p. 107; Shibecha chōshi hensan iinkai 1998, p. 716). But sulfur production laid the groundwork for future development of the Kushiro River.

In 1882, the Commission was dissolved due to a scandal involving a land purchase in Hokkaido, political assassinations, and a constitutional crisis spurred by the Freedom and People's Rights Movement. Consequently, Hokkaido underwent reorganization into three prefectures, each entrusted with establishing settlements for former samurai families (Takahashi et al. Reference Takahashi, Tokushuku, Okuno, Kitano, Nakajima, Tokunaga and Iwanaga1958). In the subsequent year, Nemuro Prefecture dispatched two surveyors to find potential settlement sites along the Kushiro River. Their report included their observation of the river, as they journeyed upstream, disembarked midway in Shibecha, and trekked to the sulfur mine.

This expedition marked the start of several state surveys of the Kushiro River. Reports based on these survey expeditions echoed the Meiji State's goals for colonizing Hokkaido: prioritize agriculture, identify resources for industrial growth, and secure a reliable transportation route. Focused on establishing inland settlements, their recommendations became a blueprint for subsequent plans, reflecting elements of “high modernist ideology” as described by James Scott – designed spaces based on science, a preference for small-scale prototypes, and a modernist aesthetic of grids and lines (Scott Reference Scott1998, pp. 4–5). The surveyors pinpointed four potential settlement sites that promised “fertile soil conducive to land development and the ease of traveling,” but they also acknowledged the challenges of “very muddy” wetland conditions unsuitable to habitation.Footnote ⁸ One settler encountered difficulties when converting his assigned area into farmland because it was already occupied by Ainu locals (Shibecha chōshi hensan iinkai 1998, pp. 718–719). The report also noted trees that may hinder land reclamation but has potential use for match production, due to the nearby sulfur source (a match factory was built there in the 1890s) (Shibecha chōshi hensan iinkai 1966, pp. 156–158). The report also foresaw the growth of a livestock industry, advising that that “grass from the fields” could feed workhorses.

The report also recommended changes to the Kushiro River, anticipating future flood-control measures. It evaluated the river's potential as a shipping route and suggested “dredging of shallow beds, removal of woody debris, and the cutting through of the meandering sections” to accommodate “the passage of steamships of 150 koku capacity” in one section and “70 to 80 koku ships” in another.Footnote ⁹ Additionally, the report proposed that it would “cost an extremely small sum to open a road for horse-drawn carriage” from Shibecha to the sulfur mine (Shibecha chōshi hensan iinkai 1998, pp. 719–720). Although some of the engineering techniques recommended by the surveyors, such as dredging, debris removal, and channelization, were used during the Tokugawa period (Wilson Reference Wilson2021), and Ainu communities deployed minor and temporary river modification for salmon fishing, the proposed construction plans were unprecedented in scale and permanence.

Establishing settlements in Hokkaido required the implementation of new river management and engineering methods, as well as large-scale modifications such as draining wetlands and logging forests. These projects not only reflected the colonial policy of imposing Japanese agricultural practices but also the introduction of water technologies and management plans to Kushiro's riverine landscape. The surveyors' vision for the future river encapsulated Imperial Japan's urgent need to construct both social and physical infrastructure essential for Hokkaido's colonization thus accelerating the transformation of the river from a key component of ecological dynamics to an infrastructure.

Coercing settlements by steam power

This colonial vision reframed the Kushiro River, shifting its primary use from a transportation route to a flood-control infrastructure. Stripped of local lore and leadership, the river was reworked for boat travel, which enabled the establishment of settlements and industry. Notably, a penal colony was central to the effort to populate the region and develop the land. This mobilization of forced labor bore deep consequences for the riverine ecosystem. The “settlement” of prisoners, coupled with the dispossession experienced by indigenous communities, underscored the colonial state's approach to territorial control through the forced restructuring of entire communities. When the penal colony supplied free labor for dredging rivers and draining wetlands, unintended consequences began to emerge. Unwittingly, the plans for harnessing the land's resources heightened the risks of floods as riverside settlements expanded, thus highlighting the complex interplay between state-driven land development and the region's hydrologic dynamics. The completion of the railway network marked a major shift, transforming the river into a precisely controlled and managed infrastructural asset, poised to further propel the region's economic development.

Establishing a penal colony was a state strategy to facilitate northward Japanese migration. Initially, settlers encountered harsh conditions and high taxes, leading to the abandonment of their new homes and return to the mainland. This setback caught the attention of Japan's highest authorities. Recognizing these impediments to colonization, Itō Hirobumi (1841–1909), then the head of the Great Council of State, the most influential ministry of Imperial Japan, advocated for the creation of penal colonies in Hokkaido. He reasoned that penal colonies in the north would address two pressing issues: the overcrowded prisons on the mainland and the difficulties in establishing settlements in Hokkaido.Footnote ¹⁰ Few years later, when serving as Prime Minister, Itō dispatched his secretary on a three-month survey mission to evaluate the progress of colonization in Hokkaido. The resulting report, which led to the 1886 decree to re-unify Hokkaido into one administrative unit, confirmed that many settlers were leaving Hokkaido.Footnote ¹¹ In a petition included in the report, a local man named Kentarō, writing in part about the Kushiro area, expressed his indignation at paying heavy taxes when farming in his adopted land proved unprofitable (Hokkaido chō 1991, pp. 602–603). Based on this report, Itō issued a directive in 1880 to relocate prisoners to Hokkaido, marking the beginning of the Commission's founding of penal colonies (Joliffe Reference Joliffe2019; Sakata Reference Sakata2018).

A prison in Shibecha made possible the implementation of the colonial policy on the Kushiro River and the surrounding basin. Military families had already begun to settle along the coast and by the river's mouth, but the upstream regions were avoided. In 1884, an engineer scouted for an optimal location for the colony and identified Shibecha as an ideal site, citing that “the Kushiro River flows through the middle [of the site], flanked by forests and endowed with soil of the highest quality, and the water sufficiently deep to make [boat] travel easy” (Shibecha chōshi hensan iinkai 1966, p. 60). The Kushiro Penal Colony, which became operational in 1885, was built on riparian land and designed to detain over 1,000 convicts for hard labor. Throughout its 16-year operation, prisoners worked in the sulfur mine, excavated drainage canals, developed farmland and residential areas, and engaged in river infrastructure work. Between 1887 and 1899, inmates dredged and cleared debris along a stretch of about 23 kilometers of the river to ensure navigability from Shibecha to the coast. Prison labor made possible Shibecha's emergence as a key river port that connected Kushiro to the island's northern coast.

By this time, plans were in motion to replace the river with a land-based, railway-centered network. The 1885 report suggested assigning the work of “clearing thick forests,” “flattening steep mountain peaks,” and “draining marshes,” needed to construct roads and railway tracks, to the penal colony (Hokkaido chō 1991, p. 618). Roads posed a particular challenge, given that “much of the land in Hokkaido are inundated fields and marshes,” making it “impassable for people and horses alike” (ibid., p. 618). Without proper drainage, farms and pastures would remain “soaked in bad water, and it would be impossible to create a long-lasting farming industry.” The report recommended constructing “a large drainage channel to redirect water [from the marsh] before building a road” and proposed that “sediment removed to dig drainage channels could be used for road construction, while the drainage itself could be widened to accommodate shipping” (ibid., p. 619).

The unsuitability of this boggy land for development continued to worry the colonial administration. In 1887, with the establishment of the Hokkaido Agency to replace the three prefectures, Iwamura Michitoshi (1840–1915), a military officer and later a colonial administrator in Okinawa, Japan's southern colony, was appointed as the first governor. In his appointment speech, he underlined the importance of building a transportation network as a basis for a more durable settlement program. He proposed to select potential sites through careful land surveys that investigated “the locations of mountain peaks, the shapes of rivers, and the borders of the provinces.” He listed items that needed investigation for a better colonization plan:

Here, the governor proposed to bring order to the land and create a clearly defined geography that could facilitate greater control and manipulation of nature. Additionally, these policies legitimized scientific survey data as the preferred source of knowledge, presenting the practice of data gathering as an extension of government procedure and portraying these categories as politically neutral. The detailed surveys also had the discursive effect of granting the state the authority to subsume local communities and their life-worlds under large-scale hierarchies of infrastructure and the natural landscape.

During the same year as Iwamura's appointment, steam power modernized the route for hauling sulfur in eastern Hokkaido: the railway tracks from the mine to Shibecha were completed, thereby replacing horses with locomotives, and steamboats commenced travel between Shibecha and Kushiro. This coincided with two major developments. First, the Commission, anticipating the area's potential for industrial growth, planned the Kushiro Port to be a major port due to its geopolitical and economic importance as the northernmost ice-free port in the Japanese Empire. It was designated as a special export port in 1890 and a trading port in 1899 (Kushiro sōsho henshū iinkai 1994, pp. 31–33; Sakai Reference Sakai1993). Second, steamboat and locomotive use increased the demand for coal. Yasuda Zenjirō (1838–1921), founder of a major business conglomerate, purchased the Atosanupuri Sulfur Mine and oversaw the mine, railroad, and steamboat operations. He gained rights to Harutori Coal Mine, located near Kushiro, and began mining in 1888, thus completing the vertical integration of sulfur production (Ijichi Reference Ijichi1969). The mechanization of transportation enhanced the river's key function as a shipping route, spurring the growth of several stopping points along the river, including police stations, inns, and the 1887 opening of a post office in Shibecha (Shibecha chōshi hensan iinkai 1966, pp. 28–30).

Even after the closure of the sulfur mine in 1896 and the penal colony in 1901, the river gave rise to other industries that further impacted the basin. Steam and machines accelerated the movement of goods and people, and they also helped engineered the terrain for faster water flow. Reclaiming productive lands required the construction of drainages in wetlands, expediting the movement of water away from desired lands and into the river's mainstem. Among those industries that benefitted from land reclamation, horse husbandry and forestry played a significant role. Originally for raising military horses, horse husbandry also supplied draft horses for construction, forestry, and agricultural work, as well as for transportation duties such as pulling ships and hauling freight on land routes, eventually leading to the development of dairy agriculture (Kushiro sōsho henshū iinkai 1988, p. 161). Another key beneficiary was the forestry industry, which relied on the Kushiro River to float logs downstream and gather them by the port for timber and paper production (Yamaguchi Reference Yamaguchi2012). In the Kushiro River basin, intensive logging first occurred along the lower reaches of Beppo and Akan rivers, Kushiro's tributaries, and later reached the island's interior via the river system. Railroad ties, manufactured with oak from the basin and shipped from Kushiro, became a significant export for railroad constructions in China and India, sometimes accounting for over 90% of the port's total exports (Kushiro sōsho henshū iinkai 1969, p. 367).

The river's coal-fueled mechanization also catalyzed the construction of a railway network and consequently diminished the waterway's role as a transportation conduit. The 1896, Hokkaido Railroad Construction Law mandated the construction of a major railway hub in eastern Hokkaido,Footnote ¹³ with Kushiro serving as the starting point for railway lines along the coast (Kushiro sōsho henshū iinkai 1988, p. 205). Upon the completion of rail tracks to Asahikawa in 1907, Kushiro became linked to Sapporo, Hokkaido's prefectural capital, and other southern industrial cities (Kushiro sōsho henshū iinkai 1994, p. 24). Although railway lines did not reach Shibecha until 1927, it gradually freed the river from its transportation role, allowing planners to address water drainage and flooding issues.

When the Kushiro River shifted primarily to a water delivery infrastructure, engineers proposed large-scale, comprehensive alterations to the river system. Land-use changes resulted in drier lands and topsoil erosion, causing sediment buildup that clogged the Kushiro Port, much to the dismay of shipping and fishery operators. These hydrologic changes also heightened flooding risks in urban and industrial areas. By this time, the River Law had been passed in 1897, which under Article 23 had granted government agencies the right to “immediately use the necessary land” and “corvee labor” for “defense against imminent dangers of flooding.”Footnote ¹⁴ Legally, therefore, the “defense” against flood risks was prioritized over private property claims and other uses of the river, thus paving the way for an integrated solution that would be aligned with “Japan's modern river regime” (Wilson Reference Wilson2021).

To address these issues of flooding and sediment release, the Akan River was diverted from the Kushiro River in a project that mimicked the common engineering solution at that time for flood-proofing cities. Planning began with the installation of a hydrometric station in 1903, and construction began in 1914 (Hokkaido kaihatsukyoku kushiro kaihatsu kensetsu bu 1983, p. 75). Despite the meticulous planning, Akan violently severed itself from the mainstem during a 1920 flood, which broke the riverbanks and permanently altered the river's path (Kushiro sōsho henshū iinkai 1969, pp. 304–310). Another major project involved the construction of an 11.2-kilometer channel to redirecting the river away from the port and the city's center. Began in 1921 and completed a decade later, the new channel effectively became the mainstem, as a sluice blocked the water from returning to the river's original path. The construction of these two diversion channels protected the port city but also altered the region's hydrology.

The modern transformation of the Kushiro River stemmed from the colonial policies aimed at bolstering its geopolitical presence in the Pacific North by developing land and populating it with imperial subjects. Initially used as a transportation artery, the river's role shifted with the establishment of a penal colony in Shibecha. This decision, driven by the imperative to populate and develop the region, mobilized prison labor to initiate extensive river infrastructure projects. However, as industrialization and land development advanced, unintended consequences emerged, exacerbating flood risks and reshaping the region's hydrological dynamics. The completion of a railway network further reshaped the river's function as an infrastructure safeguarding the growing port city of Kushiro by controlling water and sediment flow. Through these changes, the Kushiro River evolved into a measurable and manageable infrastructure, facilitating increased land reclamation, urbanization, and the intensification of agricultural and industrial production. It became emblematic of the intricate relationship between human intervention and natural landscapes, revealing the lasting impacts of colonial policies and technological innovation on regional ecosystems and communities.