Types of Floods

Flash Flooding

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Types of Floods

Floods can happen for many different reasons, they all involve more water than is ideal, but apart from that the possible reasons and types of floods are just about endless.

What Causes Floods

Floods can happen at any time of year, although they’re usually more frequent in the rainy season . . . however, just when we start to enjoy the warmer weather of the springtime and dare to look forward to a long hot summer, we often don’t realize what an effect these warmer temperatures can be having in places other than our own backyards. The snow on the distant mountain tops can look extremely pretty, but once the warmer weather arrives and it starts to melt, combined with the odd rain shower and storm and bingo . . . what have you got, maybe not “The Perfect Storm”, but certainly “The Perfect Flood Conditions”.  If a river or a lake bursts its banks it can affect communities which are literally miles away, not just those on the waterfront, well, you could very well end up on the waterfront . . .  temporarily.

Let’s look at the different types of floods in a little more detail, and maybe even get to the bottom of what event (or combination of events) causes them to happen in the first place.

  • Flash Floods – are pretty much the most dangerous type to deal with, the sheer force and magnitude of a flash flood can move boulders, bridges, uproot trees and even destroy buildings. Flash floods happen when an area of low-lying ground is flooded over a period of less than 6 hours . . . what do they call them if they take 7 hours I wonder! Anyway, the most common cause of a flash flood is a torrential downpour because of a thunderstorm (or several thunderstorms together).
  • Heavy Rains – cause all types of flooding (including flash floods) but there is one saving grace . . . sometimes (not always, but sometimes) we get a warning from the weather channel. Heavy rain over the United States can often start as storms in the Pacific Ocean, particularly from around November through April time.  If you know that heavy rains are coming (and even if you don’t), there are some things which you can do to help protect your home from floods due to heavy rains – 1)  make sure that you have a flood plan (which the whole family are in on) and plan your evacuation route, 2) make sure that you have an itemized list of your valuables, including photographic evidence if possible and receipts – just in case you need to claim on your flood insurance 3) take anything valuable upstairs (if it isn’t up there already).
  • Post Fire Flooding – whenever there’s been a serious fire, flooding might (understandably) be pretty low down on your list of things to worry about, but many areas are at an increased risk of flooding after wildfires, particularly in the western states.  Burned ground doesn’t easily absorb newly falling rainwater, so what happens, it runs off increasing the risk of floods and mud flows.
  • Mudflows – you can guess what they are can’t you, and they’re pretty unpleasant both to watch and to clean up after too! A river of liquid mud flowing over what should ordinarily be dry land can happen if the land becomes saturated too quickly and simply cannot absorb any more rainwater or snowmelt which has happened just too rapidly for the land to cope with. Yuk.
  • Ice Jams – happen much more frequently than you might expect. The sequence of events is generally as follows: – 1) a long spell of extremely cold weather causing the surface of a river to freeze 2) the water levels rise which breaks off chunks of ice from the frozen river 3) these chunks set off along their merry way downstream but become jammed at either natural or man-made obstacles, potentially causing some serious amounts of flooding.
  • Levees – I know, levees are supposed to stop flooding, but what happens is that over time they begin to decay and it can be pretty difficult to fix them. If a levee is suddenly overwhelmed by the force of the flood water it can cause a kind of “mini flash flood” which causes more damage than if the water was left to its own devices. Nothing can really stop the force of nature you know, it’s all powerful!
  • La Nina – is similar but different to “El Nino”. Basically, La Nina is what they call it when the Equatorial Pacific water temperatures are particularly cold. All La Ninas are different, they have different strengths, different durations and different characteristics (a bit like children really). 
  • Snowmelt – ah, the first thaws of the year can herald the end of winter and tell us that spring is definitely on her way, however, if it happens too quickly it can also herald the potential problems of flooding with large amounts of runoff water appearing in a very short amount of time.  If the ground is still frozen and hard it can’t be absorbed, so where does it go? Over the top of course, into the streams and rivers . . . but if there’s too much excess water they can easily burst their banks and then its flood time once again.
  • Spring Thaw is a similar thing to snowmelt, and if spring thaw happens quickly during spring storms what do you get? Spring flooding, that’s what!
  • New Development is a real culprit which has added to the problems of flooding. Building on or otherwise developing lands can completely alter the natural drainage of the land (which God created and he wasn’t doing a bad job of it really was he) and create a whole heap of new flooding risks. Think of this too, if lots of flooding is caused because the water can’t soak away naturally into the land, the more roads, parking lots and ground we cover in concrete all means that there is less “proper” land available to do this soaking whenever we do have a tropical storm or some other heavy downpour.
  • Rainy Season – this is really only for those who live on the west coast, but hey, they’ll probably know already that it rains a lot between November and April time. Flooding can, and does, however, happen at any time of the year.  Scan your eyes up this page a bit and remind yourself of the increased risk of flooding in places which have been destroyed by wildfires . . . well it can take literally decades before the vegetation is replaced sufficiently to help to stabilize the areas. Add to that the miles and miles of levees along the west coast (yes, look back up the list a little) and you’ll see that the west coast of America ought to be a flood insurance agents dream . . . is your home insured against floods?

I think that’s about covered it. Floods really do happen for many different reasons don’t they?

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