Lesson 5 what causes flooding洪水是怎样形成的

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2024年5月23日发(作者：)

Lesson 5 what causes flooding洪水是怎样形成的

What causes flooding? The basic cause is excessive runoff from catchment s

into river systems incapable of carrying this extra volume. Can science and

technology prevent flooding or, at least, reduce its severity ? Unfortunately, this is

a complex problem to which as yet there is no very satisfactory solution.洪水是怎样

形成的？根本的原因是流域内过多的径流汇入河系，超过了河系的承载能力。科学技术能

防止洪水发生吗？或者至少能降低洪水的危害吗？遗憾的是，这是一个迄今为止还没有满

意答复的复杂问题。

Let us consider first the reduction of runoff from catchment areas. Some

regions have soils which have low absorbing capacity. In a heavy rainstorm such

soil is quickly saturated and all additional rainfall then runs off into the river. A

seasonal variable is the moisture status of the soil at the commencement of a

rainstorm. If the soil is already moist, a relatively minor storm could still cause

heavy runoff because the soil is incapable of retaining additional moisture. These

factors are not easily influenced by man. However, man’s utilization of the

catchment area can have an important influence on flooding. Large scale cleaning

of trees and scrub greatly reduces the capacity of the soil to retain water. It also

tends to cause soil erosion which aggravates flooding by chocking rivers and

streams with deposited silt. Correct management of catchment areas is therefore

one important approach to the problem of flood control.

让我们首先考虑一下如何减少流域的径流。有些地区的土壤吸水能力很低。下暴雨时，

这种土壤很快就饱和了，多余的雨水全部流入河道。季节性的变量就是暴雨开始时土壤的

水分状态。如果土壤已经湿润，较小的暴雨也会引起大量的径流，因为这种土壤已不能保

持更多的水分。这些因素不易受人类的影响。然而，人类对流域土地的利用情况会对洪水

产生重要影响。大规模地砍伐树木会降低土壤保持水分的能力。砍伐树木也会加剧土壤侵

蚀，导致河道淤塞，从而加剧了洪水。所以对流域正确的开发利用是控制洪水的一项重要

方法。

More direct approach which is used in an emergency is the construction of

levee s. when rising floodwaters threaten a township the citizens form work-parties

to build barricade s of sandbags along the river bank, hoping that those barricades

will hold back the flood waters until the emergency passes. It may be wandered

why levees are not usually built as permanent structures to which the town is

protected at all times. The reason is that levees are an unsatisfactory solution to

the problem. If a levees collapses, the floodwaters escape as a sudden deluge with

increased capacity for destruction. Levees as they divert the floodwater from one

area frequently create or aggravate problems in another. They can be a cause of

enmity between communities for this reason.

筑堤是在紧急情况下可采用的更加直接的方法。当上涨的洪水威胁城镇时，居民通常

组成修堤队，沿河岸用沙袋筑堤，想用岸堤挡住洪水，直到紧急状态消失。人们或许想知

道为什么通常不把河堤建成永久性设施，让城镇永保安宁。原因在于筑堤不是解决问题的

圆满方法。如果堤岸崩溃，洪水涌出，就成为破坏能力剧增的突发性水灾。大堤会使一个

区域来洪水转向，常常在另一地区引起问题或使问题变得更为严重。因此大堤也会成为居

民点之间不和的原因。

Anther approach is the construction of dams so that floodwaters can be

retained in a reservoir until the crisis is over, slow release of the water during the

succeeding weeks or months would then be possible. Combined purpose

irrigation and flood control dams would seem to be a logical solution.

Unfortunately, a reservoir which is to be used for irrigation needs to be kept nearly

full in winter, while one which is to be used for flood control needs to be kept

empty, so that it is available as a water store when needed. This conflict of

operating requirements means that combined purpose dams are rarely feasible.

Separate dams would be required for flood control and their very high cost makes

this an impractical solution. The next approach to the problem is that of improving

the capacity of the river to carry larger volumes of water without overflowing its

banks. A number of measures are available, some simple, some complex. They all

have widespread effects on the river so any of these measures should be used as

part of a comprehensive plan. Work of this kind is known as “river

improvement ” or “river management”.

另一种方法是筑坝，让洪水存蓄在书库里，而在随后的几周或几个月内把洪水慢慢地

放掉以度过危机。灌溉和防洪两用的坝似乎是合理的解决方法。遗憾的是，用于灌溉的水

库冬季要蓄水，而用于防洪的水库却要放空，以便需要时，可以蓄水。运行要求的矛盾意

味着两用坝很少能办得到。防洪需要单独筑坝，造价很高，这又使它成为不切实际的解决

办法。能解决这一问题的另一个办法是改善河道的过水能力，使河道能宣泄更多的水量而

两岸并不漫溢。有许多措施都是可行的。有的简单，有的复杂。所有这些方法对河流都普

遍有效。所以任何一种措施都应作为全盘计划的一部分。这种工作称作“河道整治”或“河

道管理”

One simple, but important step is to ensure that the water course of a river is

kept free of obstruction s. These frequently consist of dead trees which have fallen

into the river, where they remain to impede the flow of water. They are called

“snags ” and the removal work “snagging”. Many of the trees that line

Australian River banks are hardwoods, which are too heavy to float so they remain

where they fall. Furthermore, hardwoods are very durable; large red gum logs have

been known to survive over a hundred years under water.

一种简单而有效的方法是确保河道不被阻塞。阻塞物常为倾倒在河内的枯树，一直阻

碍水流。这些阻塞物称为“水中隐树（沉木）” ；而清除工作称为“清除隐患（沉木）”。

在澳大利亚，河流两岸的许多树木都是硬木。树木太重浮不起来，所以就一直留在树木倒

下去的地方。此外，硬木经久不烂，如大红枫树原木，在水下经过了100年还保持完好。

Another method of increasing the capacity of the river is to remove choking

plant growth. Early settlers introduced willow trees to many of our river banks,

partly for shade, partly to recall old England and hopefully to reduce the erosion of

the river banks. Unfortunately, these trees are difficult to control and willow

infestation is now quite commonly a problem. Protection of the banks of a river

from erosion by the stream of water is another measure. Rivers which follow a

meandering, or winding course tend to erode their banks along the outer curves.

This can mean a loss of valuable soil from the eroded bank area and is also a cause

of local flooding. Means of protecting banks from erosion have been devised.

还有一种增加河道过水能力的方法是清除阻塞河道的植物。早期的移民在河岸上载插

了许多柳树。这样做的部分原因是为了遮荫，部分原因是为了回忆古老的英格兰，同时也

希望减少河岸的侵蚀。遗憾的是，这是树很难控制，柳树蔓延现已成为普遍的难题。保护

河岸免受水流的侵蚀也是一种措施。弯曲河道的凹岸总是遭受侵蚀，这意味着可贵的土壤

因河岸侵蚀而流失，也是当地洪水的一种起因。人们已经想出多种保护河岸免受侵蚀的方

法。

The simplest device used for this purpose is that of anchored or tied tree

trunks along the eroded bank. The trunks protect the bank and encourage the

deposition of silt on the bank so that it is gradually built up.

最简单的护岸方法是沿着受侵蚀的河岸固定或系上树干。树干能保护河岸，促使淤泥

在河岸沉积，使被侵蚀的河岸逐渐得到修复。

本文标签： 河道土壤能力侵蚀方法