Fish Paths Are Created: The Intersection of Civil Engineering and Life

Introduction | For Fish, the River Was a "Staircase"

The rivers we look at so casually.

Their appearance—bank-protected, flow-regulated, and lined with high levees—has been praised as a "disaster-resilient structure."

But how does it look to a fish?

• Weirs with steps

• Drop structures that cause sudden plunges

• Structures where waterways and main streams are severed

To fish, these were"insurmountable staircases."In other words, we were depriving them of the "freedom of life" that is the free movement of fish.

Chapter 1 | The Paradoxical Kindness of Fishways

In recent years, river construction has actively introduced designs known as"fishways."At first glance, this is a modest piece of infrastructure, but its structure is extremely precise.

• "Slopes" or "staircase structures" that allow fish to climb upstream along the river's elevation changes

• Spaces where fish can "rest" without being swept away, accommodating changes in water level and flow velocity

• Some even include "junctions where fish can return to the main stream from side paths"

This has made it possible for ayu, salmon, dace, mullet, sculpin, and others to migrate upstream.

The moment civil engineering finally turned its attention to the "design of life."

Chapter 2 | Past Civil Engineering Ignored Life

Former river construction was designed solely based on the logic of flood control and logistics.

• Enclosing with concrete to prevent floods

• Increasing flow velocity to avoid sediment accumulation

• Prioritizing domestic wastewater and industrial use, with the existence of fish being "outside the scope"

The result:

• Fish could not migrate upstream and lost spawning grounds

• Small fish could no longer move between the upper and lower reaches of the river, isolating populations

• The chain ecosystem of algae, shellfish, and birds was also severed

The "vertical connection of river life" was cut.

Chapter 3 | Civil Engineering and Ecosystems Do Not Conflict: Toward the Philosophy of "Co-structures"

Now, albeit slowly, attempts to fuse "human civil engineering" with "natural flow" are spreading.

• Ecologists and local fisheries cooperatives are involved in fishway design

• Creating "natural regeneration zones" in parts of rivers to provide places for fish to rest

• "Fish paths" are beginning to be developed even in urban culverts (underground waterways)

Here, there is an"evolution of design philosophy"that goes beyond mere "environmental consideration."

Fixing a river means restoring not just the flow, but the routes of life.

Conclusion | Fish Paths Are the Shape of Human Ethics

A fishway is not just a "slope for fish."

It is a symbol of"the effort to reconnect the flow that humans once severed."It represents:

• Respecting the continuity of life

• Viewing civil engineering and ecosystems not as a conflict, but as a "dialogue"

• Technology being used for "coexistence" rather than "domination"

Though a small structure, a fishway is a form of ethical expression.

Appendix | Flow Becomes Life by Connecting

Behind the fact that "there is a fish path" lies the memory that "that path was once severed."
That is why we should ask ourselves once more.

Is there a path in your town's river that allows fish to swim upstream?

And who designed it?

That is the shape of the "ethics of civilization."

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