Mapping the Unknown: Worldbuilding Rivers

Welcome to our Worldbuilding Wednesday! This series, Mapping the Unknown, focuses on creating your own world, and how best to make it believable while still filling it with wonder. It's a limited series meant to give advice to budding writers and worldbuilders about the best practices in developing your setting!

In our last post, we started talking about mapmaking, using northeastern Teidar - the land where North Star, Ghostblood and Leaves take place - as an example. We discussed mountains and mountain ranges, their role in framing and guiding the map, and their importance as barriers to trade, obstacles to war, but also elements that can significantly affect the climate of the region. Once you have placed your mountain ranges, and are satisfied with the way the map looks, don't forget to decorate the ends of mountain ranges with foothills. Afterwards, the next natural development is to plan your rivers. This is something you can do only once you have a sense of the elevations in your map, so if you need to put any additional elevation-related features, such as cliffs, escarpments, or chasms, now it's the time to decorate the map.

Once you are ready, you can start drawing rivers. Rivers are the lifeblood of a landscape: they shape the terrain, sustain life, serve as trade routes, and often define political boundaries. Unlike mountains, which anchor your map, rivers add movement—they flow, they connect, and they carry stories with them. They also shape the environment around them (the Nile in Egypt is a great example of what a river can do, even in an otherwise desertic environment) and, doing so, they can profoundly shape the culture of the realms that border them.

At their core, rivers follow a simple rule: they flow downhill, from higher elevations to lower ones. This means they often begin in the mountains (or other elevated regions) and work their way to lakes, seas, or oceans. Rivers don’t branch upstream—a common mistake new mapmakers sometimes make. Instead, they gather smaller tributaries as they descend. By starting with your mountains, you’ve already set the stage for rivers to flow naturally across your world. Draw your rivers from the mountains, where their springs will be, to the sea. Choose the path of least resistance - if they have to cross another mountain range, you'll have to assume there is a gorge they go through, since they can't go up. But typically, they'll flow from mountains to hills to plains, until they reach the sea.

Rivers carve valleys, irrigate farmlands, and give rise to settlements—many real-world cities began along riverbanks because of the fresh water, fertile land, and trade opportunities. A river might act as the dividing line between rival kingdoms, or it could hold mythical significance, such as a sacred river believed to be associated with a god or a natural process. In fantasy settings, rivers can also be enchanted, cursed, imbued with ancient secrets, inhabited by elemental powers, and so on. All these decisions will shape the people and cultures that live along the river. Of course, as with mountains, less is more - most of your world's rivers should not have magical properties, although there can certainly be plenty of legends about them.

Rivers are versatile tools for worldbuilding. Here are a few ways you can use them:

1. Natural Borders: Rivers naturally divide regions and can serve as boundaries for kingdoms or territories. They provide a sense of realism and give a logical reason for borders to exist. A wide, deep river might be nearly impassable without bridges or ferries, while smaller rivers might be more porous and prone to disputes.

   
   

2. Trade and Commerce: Rivers are natural highways. Before roads and canals, rivers were the primary means of moving goods over long distances. A river connecting distant regions can foster economic growth, the rise of cities, and cultural exchange.

   
   

3. Conflict and Strategy: Rivers can be a boon or a bane in war. They might act as a defensive barrier, forcing invaders to find narrow fords or construct costly bridges. A key river crossing could be the site of battles, fortresses, and strategic chokepoints.

   
   

4. Culture and Religion: Rivers are often central to cultural or religious traditions. They might be considered sacred or cursed, hold spirits and guardians, or serve as places of ritual and pilgrimage.

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6. Shaping the Land: Rivers create lush floodplains, fertile deltas, and marshes. They also shape the environment around them, nurturing forests or carving dramatic canyons and waterfalls.

Let’s look at a concrete example from Teidar: the Neviryl. Born in the icy peaks of the Craveth Elyar mountain range, the Neviryl flows southeast through the kingdom of Brightland, nourishing its fertile fields and bustling towns. Together with the milder climate caused by the existence of the northern Craveth Peloryn, the river provides Brightland with fertile farmland, so much so that the region of the kingdom it crosses is often known as the Breadbasket of Brightland. But the Neviryl is more than just a waterway—it is the spine of Brightland’s trade prosperity, providing a vital avenue to trade Brightland's goods with Erkanth, Ailund, and Meverne.

As the river winds its way southeast, it marks the natural border between Erkanth and Ailund. For both the older kingdom and the newer one, the Neviryl shapes their fortunes (and has stymied Erkanthian invasions on Ailund twice already). Traders from Erkanth ply its currents on barges laden with grain, pottery, and wool, while merchants from Ailund sail upstream, bringing iron, timber, and crafted goods. Where the Neviryl narrows, toll stations and ferries dot its banks, extracting a price for the river’s bounty. There, Erkanth's borders end and Meverne's borders begin. The princedom of Meverne was once part of Erkanth, but it broke away centuries ago, forming its own country; the Neviryl also forms its northern border, with eastern Ailund on the other side, and provides Meverne a vital trading lane, which was even more important at the beginning of its existence, when Erkanth sought to block Meverne from trade, otherwise creating a stranglehold meant to force Meverne back into the kingdom's arms.

Further downstream, the Neviryl forms the majestic Nazmi Waterfall, where it tumbles from the rocky heights into the Heartlake and the fertile lowland plains below. This waterfall is both a wonder of nature and a barrier, separating the river’s upper trade routes from its lower basin. The towns below the Waterfall, on the shores of the Heartlake, have developed their own culture and economy, relying on flat-bottomed boats to carry goods across the lake's waters.

From there, the Neviryl flows south, forming another natural border between Audirge and Arenin to the east, and Tonalay to the west. Eventually, the Neviryl is joined near the city of Carmun by the slower Legard river, which flows across Mathklyr and Tonalay. From there, the Neviryl forms the northern border of Irig (the country of origin of Riyya, from North Star) and cuts between the forest of Anaturë and the swamps of Feytarn before spills into the Sunburst Sea, its waters fanning into marshy deltas.

The Neviryl is more than a line on a map. It is a character in its own right, shaping the economies, borders, and cultures of the lands it touches. If another war ever broke out between Brightland and its neighbors, you can be sure the Neviryl would play a starring role—contested crossings, blockaded ports, and supply routes disrupted by fire and steel.

With the rivers in place, your map begins to come alive. Water flows, trade grows, and conflicts brew. Next time on Worldbuilding Wednesday, we’ll talk about forest. Until then, thanks for reading!