Dry season枯水期
The gravel stays in the mountains. Only mud makes the whole trip.
礫石留在山裡，只有泥走完全程。
Earth and Weather · Unit 3 · Lesson 11 · 地球與天氣 單元三 第十一課
How Do Rivers Shape the Land?河流怎麼改變大地？
A river does not only carry water. It carries the mountains away, one grain at a time, and builds new land with the pieces. In a 3D model, follow gravel, sand, and mud down a river from the mountains to the sea, and watch a valley grow deeper and a plain grow higher. Then find out why the longest river in Taiwan is always the color of milk tea.
河流帶走的不只是水。它把山一粒一粒地搬走，再用這些碎屑造出新的土地。在 3D 模型裡，跟著礫石、沙和泥，順著一條河從山上一路走到海裡，看山谷怎麼越切越深、平原怎麼越墊越高。最後找出答案：台灣最長的河，為什麼永遠是奶茶的顏色？
Big idea · 一句話看懂
A river is a mover. Fast water is strong, so in the steep mountains it cuts into the rock and carries the pieces away. When the water slows down, it cannot carry as much, and it drops its load. The biggest pieces are dropped first, and the smallest are carried the farthest. That is how rivers cut valleys in the mountains and build flat plains near the sea.
河流是搬運工。水流得快，力氣就大，所以在陡峭的山區，它會切進岩石、把碎屑帶走。水一慢下來，就帶不動那麼多東西，只好把它們放下。最大的先放下，最小的被帶得最遠。河流就是這樣在山裡切出山谷，在靠海的地方鋪出平坦的平原。
3D Model · 3D 模型
From the Mountains to the Sea 從山上到海裡
Drag to turn the model, and scroll or pinch to zoom. The river runs from the steep mountains on the left to the sea on the right. Three kinds of grains ride in the water: gray gravel, yellow sand, and dark mud. Watch where each kind stops. Then change the amount of water. Where does the gravel stop in the dry season? Where does it stop in a typhoon flood? Let the model run for a while and look at the valley and the plain.
拖曳可以旋轉模型，滾輪或雙指可以縮放。這條河從左邊陡峭的山區，流到右邊的海。水裡有三種顆粒：灰色的礫石、黃色的沙、深色的泥。注意看每一種各停在哪裡。接著改變水量：枯水期的時候，礫石停在哪裡？颱風大水的時候呢？讓模型跑久一點，再看看山谷和平原變成什麼樣子。
Drag to turn · 拖曳旋轉 Scroll or pinch to zoom · 滾輪／雙指縮放
This 3D model needs WebGL, which this browser does not support. The reading and the cards below still explain everything.
這個瀏覽器不支援 WebGL，無法顯示 3D 模型；下方的課文與卡片一樣能看懂。
- Gray: gravel, the biggest grains
灰色：礫石，最大的顆粒 - Yellow: sand
黃色：沙 - Dark brown: mud, the finest grains
深褐色：泥，最細的顆粒 - The river: blue when clear, brown when it carries a lot
河水：清的時候是藍色，帶的東西多就變成土黃色
A teaching model, and its numbers are examples. Only the order is real: faster water can carry bigger grains, so the biggest grains are dropped first. The river is drawn far steeper and far shorter than a real one, and the changes you see in a minute would take a real river thousands of years or more. Real rivers also bend, split, and change course, which this straight model leaves out.
這是教學用的模型，裡面的數字都是示例。只有「順序」是真的：水越快，帶得動的顆粒越大，所以最大的顆粒最先被放下。模型裡的河畫得比真的河陡得多、也短得多；你在一分鐘裡看到的變化，真的河要花上幾千年甚至更久。真的河還會轉彎、分岔、改道，這個筆直的模型都沒有畫出來。
Model drawn by My Culture Connect as a teaching diagram. The ideas follow the sources listed at the bottom of this page. · 模型由人師教育協會自繪示意；原理依本頁最下方列出的出處。
Reading · 英文閱讀
11
Unit 11: How Do Rivers Shape the Land?
Pick up a stone from a riverbed and look at it. It is smooth and round. It did not start that way. Once it was a sharp piece of a mountain, far upstream. The river broke it off, rolled it along, and rubbed its corners away. Every river is doing this, all the time.
從河床上撿一顆石頭起來看看。它又圓又滑。它本來不是這個樣子的：它曾經是上游很遠的地方，山上一塊有稜有角的碎石。是河流把它敲下來、一路滾著它走，把它的稜角都磨掉了。每一條河，時時刻刻都在做這件事。
A river has three jobs. First, it wears away the land. This is called erosion. Second, it carries the pieces downstream. Third, it puts them down again somewhere else. Which job it does depends on one thing: how fast the water is moving.
河流有三件工作。第一，把地面一點一點削掉，這叫做「侵蝕」。第二，把削下來的碎屑往下游「搬運」。第三，在別的地方把它們放下來，叫做「堆積」。河流在做哪一件，只看一件事：水流得多快。
In the mountains, the land is steep and the water runs fast. Fast water is strong. It can roll gravel and even large rocks along the bottom, and these scrape the riverbed like tools. Little by little, the river cuts down into the rock. Over a very long time, this makes a deep valley.
在山區，地勢很陡，水流得很快。水流得快，力氣就大，可以推著礫石甚至大石頭在河底滾動；這些石頭像工具一樣刮著河床。河流就這樣一點一點地往下切進岩石裡。經過非常久的時間，就切出了很深的山谷。
Then the river leaves the mountains. The land becomes flatter, the river spreads out, and the water slows down. Slow water cannot carry heavy things, so the river drops the gravel right there, at the foot of the mountains. The pile it builds is shaped like an open fan, so it is called an alluvial fan.
然後，河流出了山。地勢變平，河面變寬，水也慢了下來。慢的水帶不動重的東西，所以河流就在山腳把礫石放下來。這一堆東西的形狀像一把打開的扇子，所以叫做「沖積扇」。
The lighter grains keep going. Sand is carried farther and settles across the lowland. Each flood spreads a new, thin layer, and after thousands of floods the layers add up to a wide, flat plain. The finest mud stays in the water the longest. Much of it reaches the sea, where the river finally stops moving, and settles there.
比較輕的顆粒繼續往前走。沙被帶得更遠，沉在低平的地方。每一次洪水都鋪上薄薄的一層新土；經過幾千次洪水，一層一層疊起來，就成了又寬又平的平原。最細的泥在水裡待得最久，很多都到了海裡；河流到了那裡終於停下來，泥也就沉下去了。
Taiwan shows all of this in a short distance. The mountains are high and steep, the rain is heavy, and the sea is close, so the rivers are short and fast. The Zhuoshui River, the longest in Taiwan, carries so much sand and mud that its water is cloudy all year. Its name means muddy water river. The wide farmland on both sides of its lower course is made of what the river brought down from the mountains.
台灣把這整個過程擠在很短的距離裡。山又高又陡，雨下得多，海又很近，所以河流都又短又急。台灣最長的河是濁水溪，它帶的泥沙多到溪水一整年都是混濁的，所以叫做「濁水」溪。它下游兩岸那一大片農田，就是這條河從山上搬下來的東西鋪成的。
Read aloud · 課文朗讀
Questions · 閱讀理解
What are the three jobs of a river?
It wears away the land, it carries the pieces downstream, and it puts them down again somewhere else.
Why does a river drop its gravel at the foot of the mountains?
The land becomes flatter there, so the water slows down. Slow water cannot carry heavy things, and gravel is the heaviest thing in the river.
Why is the water of the Zhuoshui River cloudy?
It carries a great deal of sand and mud that it has worn away from the mountains.
Words & Phrases · 生字及片語
river(n.)河流The river runs from the mountains to the sea.這條河從山上流到海裡。flow(v.)流動Water flows downhill.水往低處流。carry(v.)攜帶；搬運Fast water can carry big stones.湍急的水可以帶動大石頭。gravel(n.)礫石；碎石The riverbed is covered with gravel.河床上鋪滿了礫石。sand(n.)沙The children played in the sand.孩子們在沙子裡玩。mud(n.)泥After the flood, the road was covered with mud.洪水過後，路上都是泥。flood(n.)洪水；大水The flood came after three days of rain.下了三天雨之後，洪水來了。valley(n.)山谷A small village lies in the valley.山谷裡有一個小村莊。
Quick Check · 小測驗
1. What does erosion mean?
2. Where does a river usually run fastest?
3. When a river slows down, what does it drop first?
4. What is an alluvial fan?
5. Why is the Zhuoshui River cloudy all year?
Try It · 動手試試
What can this water carry? 這樣的水帶得動什麼？
Make the water faster or slower, and watch which grains begin to move. This one rule explains valleys, fans, plains, and muddy seas.
把水調快或調慢，看看哪些顆粒開始動。山谷、沖積扇、平原，還有混濁的海水，都可以用這一條規則來解釋。
Only the order is shown here, not real speeds. The speed that a grain needs depends on its size, its shape, and how deep the water is. Never go near a river in flood to look or listen.這裡只表示「順序」，沒有用真實的流速。一顆顆粒需要多快的水才會動，要看它的大小、形狀和水的深淺。河水暴漲的時候，千萬不要為了看或聽而靠近河邊。
The water is · 現在的水
·
Try It in the Model · 在模型裡試試
Four rivers 四種河
After A very long time, turn the model and look at the mountains from the side. Where did all the missing rock go?
看完「很久很久以後」，把模型轉過來，從側面看看山區。那些不見了的岩石跑到哪裡去了？
An ordinary day平常的日子
Gravel at the foot of the mountains, sand on the plain, mud in the sea.
礫石在山腳，沙在平原，泥在海裡。
After a typhoon颱風過後
The brown river pushes everything farther downstream.
土黃色的河水把所有東西都往下游推得更遠。
A very long time很久很久以後
The valley is deeper, and the riverbed on the plain is higher.
山谷變深了，平原上的河床墊高了。
Go Further · 延伸閱讀
Where the rock and the water come from 石頭和水是從哪裡來的
Earth and Weather · Lesson 4 · 地球與天氣 第四課How Did Taiwan's Mountains Rise?台灣的山是怎麼來的？The land pushes the mountains up while the rivers wear them down.大地把山往上推，河流同時把山往下削。Go to the lesson · 前往這一課 →Earth and Weather · Lesson 6 · 地球與天氣 第六課Why Does It Rain?為什麼會下雨？Why so much rain falls on the mountains where the rivers begin.為什麼河流發源的山區會下那麼多雨。Go to the lesson · 前往這一課 →
Rivers by the Numbers · 河流的數字
Six numbers about a river 六個和河流有關的數字
Most of them belong to the Zhuoshui River.
大部分都是濁水溪的數字。
3jobs · 件工作
Every river wears the land away, carries the pieces, and puts them down again: erosion, transport, and deposition.每一條河都在做三件事：把地面削掉、把碎屑帶走、再把它們放下來，也就是侵蝕、搬運和堆積。
No. 1in Taiwan · 全台
The Zhuoshui River is the longest river in Taiwan.濁水溪是台灣最長的河川。
4counties · 個縣
The Zhuoshui flows through Nantou, Chiayi, Yunlin, and Changhua. Its lower course is the border between Changhua and Yunlin.濁水溪流經南投、嘉義、雲林、彰化四個縣；下游是彰化縣和雲林縣的界河。
3,100+square km · 平方公里
Rain that falls on more than 3,100 square kilometers of land drains into the Zhuoshui River.超過 3,100 平方公里土地上的雨水，最後都流進濁水溪。
2,000–3,000mm a year · 毫米／年
This much rain falls each year on the mountains where the Zhuoshui begins.濁水溪上游的山區，每年下這麼多的雨。
1920about · 年前後
Before long banks were built at about this time, the lower Zhuoshui swung widely across the plain from one flood to the next.在這個時候築起長長的堤防之前，濁水溪下游的河道會隨著一次次洪水，在平原上大幅擺盪。
River Stories · 河流的故事
The muddy river, the land it built, the bends, and the gorge 混濁的河、它鋪出來的土地、河的彎，還有峽谷
Four things rivers do, with places in Taiwan where you can see them.
河流做的四件事，以及在台灣哪裡看得到。
Changhua · 彰化
Why the Zhuoshui is muddy濁水溪為什麼是濁的
The Zhuoshui River got its name because its water is cloudy with sand and mud all year. The reason is in the mountains where it begins. A great deal of rain falls there, and much of the rock is slate, shale, and sandstone, which break up and wear away easily. The river is never short of things to carry.
濁水溪的名字，就是因為溪水夾帶大量泥沙、長年混濁而來的。原因在它發源的山區：那裡雨下得很多，而且岩石大多是板岩、頁岩和砂岩，很容易破碎、被侵蝕。這條河從來不缺可以搬的東西。
Plain · 平原
The land a river built一條河鋪出來的土地
Where the Zhuoshui leaves the mountains, it has spread its sand and mud into a wide, gently sloping plain across southern Changhua and Yunlin. For a long time the river did not stay in one place. It swung across this plain, leaving a new layer wherever it went. Long banks built in the early twentieth century now hold it in a single course.
濁水溪出了山以後，把泥沙鋪成一片寬廣而平緩的平原，橫跨彰化南部和雲林。很長一段時間裡，這條河並不是固定待在一個地方：它在這片平原上擺來擺去，走到哪裡就鋪上新的一層。二十世紀初築起的長堤，才把它固定在現在這一條河道裡。
Bends · 河彎
Why rivers bend河流為什麼會彎
On a plain, a river seldom runs straight. Where it bends, the water on the outside of the bend is faster and wears the bank away, while the slower water on the inside drops sand. So the bend grows wider and wider. Sometimes the river cuts straight through the neck of a bend and leaves a curved lake behind. It is called an oxbow lake.
在平原上，河流很少走直線。在轉彎的地方，彎道外側的水比較快，會把河岸削掉；內側的水比較慢，會把沙放下來。所以彎會越來越大。有時候河水乾脆從彎道的頸部直接切過去，留下一個彎彎的湖，叫做「牛軛湖」。
Hualien · 花蓮
A river that cuts as the land rises一邊抬升、一邊往下切
In eastern Taiwan the mountains are still rising, and the rivers keep cutting down as fast as they can. The result is a narrow gorge with walls of rock on both sides, like the one at Taroko. A gorge is what you see when a river has been doing its first job, erosion, in the same place for a very long time.
在台灣東部，山還在繼續抬升，河流也拚命地往下切。結果就是兩邊都是岩壁的狹窄峽谷，像太魯閣那樣。峽谷，就是河流在同一個地方做第一件工作（侵蝕）做了非常久之後的樣子。
Myth vs. Fact · 常見迷思
Four things people get wrong 四個常見的誤會
✗ Myth · 迷思A river carries only water.河裡流的只有水。
✓ Fact · 事實It also carries gravel, sand, and mud. Over a long time, that load is enough to wear down mountains and build plains.河流還帶著礫石、沙和泥。時間久了，這些東西足以把山削低、把平原鋪出來。
✗ Myth · 迷思The biggest rocks are carried the farthest.最大的石頭被帶得最遠。
✓ Fact · 事實It is the other way around. Big rocks need fast water, so they are dropped first. The finest mud goes the farthest.正好相反。大石頭需要很快的水才帶得動，所以最先被放下；最細的泥才走得最遠。
✗ Myth · 迷思A river always stays in the same place.河流永遠待在同一個地方。
✓ Fact · 事實On a plain, a river shifts and bends over time. The lower Zhuoshui used to swing widely before banks were built to hold it.在平原上，河道會隨時間移動、轉彎。濁水溪下游在築堤固定之前，河道曾經大幅擺盪。
✗ Myth · 迷思Muddy river water means the river is polluted.河水混濁，就表示河被污染了。
✓ Fact · 事實Not always. A river can be cloudy simply because it is carrying sand and mud from the mountains, as the Zhuoshui does.不一定。河水混濁，可能只是因為它帶著從山上來的泥沙，濁水溪就是這樣。
Remember It · 記憶口訣
A river in a sentence 一句話記住河流
Fast water cuts快的水會切
Steep mountains, deep valleys.
陡的山，深的谷。
Moving water carries流動的水會搬
Gravel, sand, and mud.
礫石、沙和泥。
Slow water drops慢的水會放
The biggest grains first.
大的顆粒先放下。
Layers make a plain一層一層鋪成平原
One flood at a time.
一次洪水鋪一層。
Classroom Activity 1 · 課堂活動一
Big Grains First 大的先沉
You need · 準備材料
- A tall clear jar with a lid, and water一個有蓋子的透明高瓶子，還有水
- A few spoonfuls each of small pebbles, sand, and garden soil小石子、沙和花園的土，各幾湯匙
Steps · 步驟
- Put the pebbles, the sand, and the soil into the jar. Fill it almost to the top with water.把小石子、沙和土放進瓶子裡，加水到快要滿。
- Close the lid tightly. Shake the jar well for ten seconds, and then put it down.把蓋子蓋緊，用力搖十秒鐘，然後放下來。
- Watch closely for the first ten seconds. What reaches the bottom first?仔細觀察最初的十秒：什麼東西最先到底？
- Look again after ten minutes, and again the next day. Draw the layers. Is the water clear yet?十分鐘後再看一次，隔天再看一次。把一層一層畫下來。水變清了嗎？
Your jar is a river that has stopped. The order of the layers, from bottom to top, is the order in which a slowing river drops its load, from the mountains to the sea.
你的瓶子就是一條停下來的河。這幾層由下往上的順序，就是河流慢下來的時候，從山邊到海邊放下東西的順序。
Classroom Activity 2 · 課堂活動二
A River in a Tray 托盤裡的河
You need · 準備材料
- A long tray or baking pan, damp sand mixed with a little fine gravel, and a book to lift one end一個長托盤或烤盤、摻了一點細碎石的溼沙，還有一本用來把一端墊高的書
- A cup of water, and a place where a little mess is all right一杯水，還有一個弄髒一點也沒關係的地方
Steps · 步驟
- Fill the upper half of the tray with the sand and pat it into a slope. Lift that end of the tray with the book.把沙鋪在托盤的上半部，拍成一個斜坡。用書把這一端墊高。
- Pour the water slowly onto the top of the slope, always at the same spot.把水慢慢地倒在斜坡的頂端，每次都倒在同一個地方。
- Watch the channel that forms. Where is the sand taken from? Where is it left?觀察沖出來的水道：沙是從哪裡被帶走的？又被放在哪裡？
- Look at the shape of the pile at the bottom of the slope. Then pour faster and see what changes.看看斜坡底下那一堆沙的形狀。然後倒快一點，看看有什麼改變。
You should see a small valley at the top and a small fan at the bottom. When you pour faster, you make a flood. Notice how much more it moves.
你應該會看到上面有一道小山谷，底下有一把小扇子。倒得快一點，就是一場洪水；注意它搬的東西多了多少。
Sources · 資料出處
Facts and numbers on this page were checked against these sources (October 2026). · 本頁的事實與數字依下列資料查證（2026 年 10 月）。
- Rivers erode their beds, carving canyons and valleys; the sediment they carry shapes the land and is laid down where the flow slows; rivers seldom run straight河流侵蝕河床，切出峽谷與山谷；攜帶的沉積物塑造地形，在水流變慢的地方堆積；河流很少走直線Wikipedia, “River” ↗
- Grains are moved along the bed by rolling and sliding, or carried in suspension in the flow顆粒以滾動、滑動的方式沿河床移動，或懸浮在水流中被帶走Wikipedia, “Sediment transport” ↗
- Alluvial fans form where a flow leaves a confined channel, as where a steep mountain valley meets a flat plain, and can no longer carry its load沖積扇形成於水流離開狹窄河道之處，例如陡峭山谷與平地相接的地方，水流的搬運能力下降而堆積Wikipedia, “Alluvial fan” ↗
- A river lays down its sediment where it enters slow-moving or still water河流進入流動緩慢或靜止的水體時，沉積物在那裡堆積Wikipedia, “River delta” ↗
- A river wears away the outer bank of a bend and lays down sediment on the inner bank; a bend that is cut off becomes an oxbow lake河流侵蝕彎道的外側（凹岸）、在內側（凸岸）堆積；被截斷的河彎成為牛軛湖Wikipedia, “Meander” and “Oxbow lake” ↗
- The Zhuoshui River: the longest river in Taiwan; named for its water, cloudy all year with sand and mud; 2,000–3,000 mm of rain a year in its upper basin, where the rock is mostly slate, shale, and sandstone that erode easily; flows through four counties, and its lower course is the border between Changhua and Yunlin; its channel swung widely until embankments were built around 1920濁水溪：台灣最長的河川；因溪水夾帶大量泥沙、長年混濁而得名；上游集水區年降水量 2,000–3,000 毫米，地層多屬易受侵蝕的板岩、頁岩、砂岩；流經 4 縣市，下游為彰化、雲林兩縣界河；築堤（1920 年前後）之前河道巨幅擺盪維基百科「濁水溪」（引經濟部水利署資料） ↗
- The Zhuoshui alluvial plain lies south of the Changhua Plain, across the old course of the river濁水溪沖積平原位在彰化平原之南，以舊濁水溪為界維基百科「彰化平原」 ↗