Puddle
This is about the liquid phenomenon. For other meanings, see Puddle (disambiguation) |
A puddle in a forest clearing |
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A water puddle on a Danish beach |
A
puddle is a small accumulation of a
liquid, usually
water, uncontained on a surface. They can form either in depressions in the surface, or directly upon the flat surface, held together by
surface tension. A puddle is generally considered to be small enough to step over or shallow enough to walk through, and too small to traverse with a
boat: larger accumulations tend to be referred to as
ponds,
pools or
floods, depending on the circumstances.
Puddles commonly form during
rainstorms, and can cause problems for transport, especially when combined with cold conditions to form patches of
ice, which is highly slippery and difficult to see. Due to the angle of the road, puddles tend to be forced by gravity to gather on the edge of the road. This causes the notorious '
splash' as cars drive quickly through the puddle, which causes water to be sprayed onto
pedestrians on the adjacent pavement. Sometimes, irresponsible drivers will do this deliberately. Such activity is frowned upon, and in some countries can lead to prosecutions for careless driving [
1].
Puddles tend to
evaporate quickly due to the high surface area-to-volume ratio, allowing a large number of molecules to be vapourised at once, and as such tend to be short lived. However, due to this property, puddles of chemicals such as
bromine, which produce highly toxic vapour, are considered highly dangerous and spillages of these chemicals must be dealt with immediately, with
evacuation a common step.
In order to deal with puddles, roads and pavements are often built with a
camber (technically called 'crowning'), being slightly
convex in nature, to force puddles to drain into the gutter, which has
storm drain grates to allow the water to drain into the sewers. In addition to this, some surfaces are made to be porous, allowing the water to drain straight through the surface to the
aquifer below.
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A child in a puddle in Vancouver, Canada |
Puddles are often considered a source of recreation by children, who consider jumping in puddles to be an "up-side" to rain.
Medieval legend spoke of one man who was desperate to find building materials for his house, so he stole
cobblestones from the road surface. The remaining hole filled with water and a horseman who later walked through the 'puddle' actually found himself drowning. A similar legend, of a young boy drowning in a puddle that formed in a
chuckhole in a major street in the early years of
Seattle,
Washington, is told as part of the
Seattle Underground Tour.
A children's nursery rhyme records the story of
Doctor Foster and his encounter with a puddle in Gloucester.
When
Walter Raleigh met
Queen Elizabeth I, Raleigh is reputed to have thrown his coat over a
muddy puddle to allow the Queen to cross without getting her feet wet. Such activities were once considered to be
chivalric, but are less common nowadays.
Animals often use puddles either as a drinking source, a bath, or, in the case of some smaller animals, an entire habitat. Puddles are also vital for bathing
birds.
Puddles which do not evaporate quickly can become
standing water, which can become
polluted by decaying organisms and are often home to breeding
mosquitos, which can act as vectors for diseases such as
malaria.
Swallows use the damp
loam which gathers in puddles as a form of
cement to help to build their nests. The reduction in the number of puddles in the countryside due to
intensive farming and
climate change is partially to blame for a decrease in the swallows' numbers.
*"
Doctor Foster"
