---
title: "Dam Removal — AP Environmental Science Definition & Guide"
description: "Dam removal is tearing down a dam to restore a river's natural flow and habitat. Know the ecological gains vs. lost hydroelectric power for APES Topic 6.9."
canonical: "https://fiveable.me/ap-enviro/key-terms/dam-removal"
type: "key-term"
subject: "AP Environmental Science"
unit: "Unit 6"
---

# Dam Removal — AP Environmental Science Definition & Guide

## Definition

Dam removal is the deconstruction of a dam to restore a river's natural flow, sediment movement, and aquatic habitat, trading away the dam's benefits (hydroelectric power, flood control, irrigation) for ecological recovery like returning fish populations. In APES it lives in Topic 6.9, Hydroelectric Power.

## What It Is

Dam removal is exactly what it sounds like. Engineers take a dam apart so the river behind it can flow freely again. When a dam comes down, the [reservoir](/ap-enviro/key-terms/reservoir "fv-autolink") drains, trapped sediment moves downstream to rebuild deltas and beaches, [water temperature](/ap-enviro/unit-8/thermal-pollution/study-guide/hhXqgEYKmPzaZcFD6uLT "fv-autolink") and oxygen levels return to more natural patterns, and migratory fish like salmon can finally reach upstream spawning grounds that the dam blocked off.

The APES framing is all about trade-offs. The CED (6.9.B) tells you that hydroelectric dams produce no [air pollution](/ap-enviro/unit-6/hydroelectric-power/study-guide/r95V6RauJ8xe1P3Os36x "fv-autolink") or waste, but their construction causes a loss of or change in habitats. Dam removal is the reverse move. You give up clean, reliable electricity, plus the reservoir's flood control and irrigation water, in exchange for restoring the habitat the dam destroyed. The Elwha River in Washington is the classic real-world example, where salmon rebounded and river deltas recovered after two dams were removed.

## Why It Matters

Dam removal sits in **[Unit 6](/ap-enviro/unit-6 "fv-autolink"): Energy Resources and Consumption, Topic 6.9 (Hydroelectric Power)**. It directly supports **6.9.A** (describing how [dams](/ap-enviro/key-terms/dams "fv-autolink") generate electricity by collecting water in reservoirs to spin turbines) and especially **6.9.B** (describing hydroelectricity's environmental effects). You can't argue intelligently for or against removing a dam unless you can list what the dam does, both good and bad. That makes this term a perfect vehicle for the cost-benefit, trade-off style reasoning APES rewards everywhere, from MCQs to the solution-proposing FRQ. It also quietly connects energy (Unit 6) to aquatic biodiversity and habitat (earlier units), since the whole argument for removal is ecological restoration.

## Connections

### [Reservoir (Unit 6)](/ap-enviro/key-terms/reservoir)

The reservoir is what dam removal undoes. Draining it restores flowing-river [habitat](/ap-enviro/key-terms/habitat "fv-autolink") but also eliminates the stored water that powered turbines and supplied irrigation, so every removal argument starts with what the reservoir was providing.

### [Flood Control (Unit 6)](/ap-enviro/key-terms/flood-control)

Dams hold back floodwaters, and that's one of the strongest arguments against removal. The 2017 FRQ framed dams around exactly this pairing of hydroelectric power and downstream [flood control](/ap-enviro/key-terms/flood-control "fv-autolink"), so treat them as a package deal.

### [Kinetic Energy (Unit 6)](/ap-enviro/key-terms/kinetic-energy)

Hydroelectric dams convert the [kinetic energy](/ap-enviro/key-terms/kinetic-energy "fv-autolink") of moving water into electricity via spinning turbines. Removing a dam means that kinetic energy flows downstream unused, which is the energy cost society pays for the ecological gain.

### [Tidal Turbines (Unit 6)](/ap-enviro/key-terms/tidal-turbines)

Tidal energy and small in-river turbines (run-of-river setups) generate hydropower without a big reservoir. They're useful in FRQ answers as the 'replacement power' that softens the blow of removing a large dam.

## On the AP Exam

Dam removal almost always shows up as a trade-off scenario. A stimulus describes a real case like the Elwha River, where salmon rebounded and deltas recovered after removal, then asks you to identify the main claim, weigh ecological restoration against lost power generation and flood control, or spot the assumptions in an economist's cost-benefit argument. The 2017 SAQ framed dams around their human purposes, hydroelectric power and downstream flood control, which is exactly the 'what do we lose if it's gone' half of the removal debate. Your job is never just to say removal is good or bad. You need to name a specific ecological benefit (restored fish migration, sediment flow, habitat) and a specific cost (lost electricity, flooding risk, irrigation water), and ideally propose a balance, like replacing a removed dam's output with run-of-river or tidal turbines.

## Dam removal vs Fish ladders

Both address the same problem, dams blocking migratory fish, but they are opposite strategies. A fish ladder is a mitigation. It keeps the dam (and its electricity and flood control) and adds a stair-step bypass so fish can climb past it. Dam removal eliminates the dam entirely, restoring the whole river system, not just fish passage, but sacrificing all the dam's benefits. On an FRQ, a fish ladder is your 'balance both sides' answer; removal is the full-restoration answer.

## Key Takeaways

- Dam removal means deconstructing a dam to restore a river's natural flow, sediment transport, and aquatic habitat.
- The CED says dam construction causes loss of or change in habitats (6.9.B), and dam removal is the attempt to reverse that damage.
- Removal sacrifices the dam's benefits, including hydroelectric power, flood control, and irrigation water, so every exam answer should weigh both sides.
- The Elwha River is the go-to example, where salmon populations rebounded and river deltas recovered after the dams came down.
- A strong FRQ move is proposing replacement power, like run-of-river or tidal turbines, to offset the electricity lost when a dam is removed.

## FAQs

### What is dam removal in AP Environmental Science?

It's the deconstruction of a dam to restore a river's natural hydrology and ecology, letting fish migrate, sediment flow, and habitats recover. In APES it falls under Topic 6.9, Hydroelectric Power, and learning objective 6.9.B on hydroelectricity's environmental effects.

### Is dam removal always environmentally good?

Mostly yes ecologically, but it's not cost-free. Removal restores habitat and fish migration, but it eliminates a zero-air-pollution electricity source plus flood control and irrigation, and that lost power often gets replaced by fossil fuels. APES wants you to argue the trade-off, not pick a side blindly.

### How is dam removal different from a fish ladder?

A fish ladder keeps the dam and just adds a bypass so migratory fish can get around it. Dam removal takes the entire structure out, restoring sediment flow, water temperature, and habitat along with fish passage, but giving up the dam's power and flood control.

### What happened on the Elwha River after dam removal?

After two dams on Washington's Elwha River were removed, salmon populations rebounded and sediment flowing downstream rebuilt the river's deltas. It's the standard real-world example exam questions use for the benefits of dam removal.

### Why would anyone oppose removing a dam?

Because dams provide hydroelectric power with no air pollution, control downstream flooding, and store water for irrigation. The 2017 SAQ highlighted exactly those purposes, and losing them is the economic and safety case against removal.

## Related Study Guides

- [6.9 Hydroelectric Power](/ap-enviro/unit-6/hydroelectric-power/study-guide/r95V6RauJ8xe1P3Os36x)

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