Between 2625 - 2800 KS, The Riverine Culture underwent a major decline, with their language and institutions fading into obscurity in just under two centuries. As the most populous and the richest culture within the 6th Dynasty of the Wajahe, their decline is directly tied to the slow decline of the 6th Dynasty (which end at about the same point in time). The institutions of the Riverine civilization, representing the cultural and economic forces that in the past, dominated the entire region, began to unravel due to a variety of factors. While never explicitly suppressed, their decline would go largely ignored by the 6th Dynasty, inaction that would be to the direct detriment of the state.
Below are listed the major institutions of the Riverine civilization, the cause and course of their collapse, and the consequences of this collapse.
The Guild System
The guilds were the heart of Riverine society. Riverine labor was divided along professional lines, and professions would organize into Guilds - a body consisting of its members. This body had, at its head, a representative council (not quite elected, but chosen through complex systems of social and economic seniority, personal achievement, and age). These councils existed at various levels, in complicated hierarchies, and decided the interaction of professions with other professions, merchants, the religious authorities (which operated as a guild of philosophers) and the state itself (which operated as a guild of bureaucrats). It was in this interaction that the Riverine state was centered, and these institutions governed the economic actions of the state. Their collapse was caused by foreign occupation across the entire river - in the lower and middle river, by the Wajahe 6th dynasty, and in the upper river, by a mixture of hʷɔ.ʂə.hʷuɥ successor states, mercenary groups, and a collection of wze.t͡sɥew states. The guild system was unique to the rivermen, and the collapse or neglect of the riverine state systems and bureaucracy meant that the other guilds had little legal ability to engage with the new states in any significant manner. Rather than encourage and involve the guilds, these new states instead imported local institutions, that slowly, over time, replaced the guilds in the cities. This left the guilds as purely rural institutions, with no urban support - something which, slowly but surely, caused major economic decline due to the lack of any economic cohesion between cities and their hinterlands, and the general decline of surplus agriculture as members began ending their association and involvement in guilds dedicated to agriculture. While not enough of a problem to cause urban decline, it contributed to collapse of centralized authority, to the general decline of regional trade, and to a significant reduction in civic tax revenue.
The Longhouse and Riverine Settlement Structures
The structure of riverine settlements was quite different from the Wajahe, as it was centered on the Longhouse - a large building in which 100-500 people lived, divided into family units. Settlements were collections of these houses, and cities had anywhere between 20 to 100 of these longhouses. Their decline was quite simple - when the time came for the state to refurbish these, they instead just constructed the smaller, single-family houses of the Wajahe. This is because these were constructed by the military, who as noted above was largely responsible for construction of any infrastructure - and the military officers, who were mostly Wajahe, built what they were used to. This drastic change in urban organization contributed to the decline of the Riverine language - children, who were often exposed to the language in the longhouse setting, now interacted with it a lot less in this new environment that was significantly less communal in nature.
The Great Libraries
It was said the Great Libraries of the riverine cities held within them the sum total of human knowledge. Centers of culture, philosophy, mathematics, engineering, and architecture, these libraries acted also as a center for education. Their decline was connected to the larger decline of the Riverine languages, and generally of scribal traditions. There was simply not the will, funding, or manpower to translate these works, and as the language was forgotten by all but the most learned, these Libraries fell into disuse and decay. The Wajahe, after all, knew of most every innovation of this great civilization that they deemed important - what reason was there to preserve this institution? The collapse of the libraries had no direct impact on the 6th dynasty, but indirectly significantly sped up the collapse of the entire Riverine civilization. These were mostly located in the lower and middle river, with few libraries in the less populated upper river - the decline of these libraries led directly to a collapse of the riverine language, and the philosophy, architecture, and political organization of that great and ancient culture.
The Barge Networks
Riverine trade was carried out by a specific guild, one which managed the various barges across the river, a system that helped establish relatively uniform price controls for goods across the river. The collapse of the guild system also led to the collapse of this specific guild - trade became a lot less centralized or cohesive, prices began to fluctuate heavily to market pressures, and as a result, trade across the river generally declined. This, of course, led to a greater economic decline in the 6th Dynasty.
The Wildmen
The Wildmen were a group of rivermen who lived in the inland forests, existing as a subculture. These were much more militarized, and lacked the urbanization of riverine culture, yet were crucial in propping up the states as they provided a higher standard of wage soldier that were core to the riverine armies. The general replacement of military structures with exarchial ones, who greatly disliked the Wildmen (who relied on individual prowess and lacked any centralized, structural discipline) led to a general depopulation of the riverine hinterland, as the main economic lifeline of the region (military participation) was placed in a state of decline.
The collapse
As a result of these factors, the riverine civilization would eventually completely collapse. In the lower and middle rivers, they would fully assimilate into the Wajahe culture, while in the upper river, they would partially assimilate into and partially be replaced by the wze.t͡sɥew culture (where they still existed as a regional minority). Less than two centuries after their lands were conquered by the 6th dynasty, the Riverine civilization ceased to exist in even a provisional capacity. Its structures had collapsed, its language was no longer spoken, and those institutions that the Wajahe did not adopt fell entirely out of favor. Once the foremost civilization, a truly ancient and widespread force that could be said to characterize the entire region, the Rivermen were now gone - but the Wajahe 6th Dynasty would end with them.
Though some Great Libraries would later be rediscovered and many of their works translated into Wajahic languages, the breadth of knowledge of the Riverine culture has been largely lost. With it are lost many of the specific details of how that culture lived, its religion and philosophies, and its many achievements. Outside of scattered references in Wajahe and Ejee literature, and some scant archaeological evidence, the actual documentation of their decline remains the best source for understanding that civilization.