Saturday, 18 June 2011

Kempsey and floods

Recent media suggests that Kempsey has dodged a bullet in avoiding a flood. If you read the papers you'd perhaps think that somehow Kempsey was getting some wild weather. People are all squealing (again) about the weather, some are even dribbling climate change.

What pisses me off is the most is people with no history in the areas (who are essentially itinerants) say stuff like:
"I've never seen anything like this in all the years (3) I've been living here."

So, for the newcomers, (and those with no memory) lets start by looking at the rainfall in the last 10 years or so..

This figure above shows the monthly totals of the years from 1996 to 2009. Looking at that there's nothing much above 200mm, only a few occasions. Probably back in 2001 or in 1996 we could mine the media archives and read about flood events.

Certainly this month has had high rainfalls in the area, with Kempsey totaling 474mm so far (as at writing) this month. So from that background lets look further back, and keep in mind we've been in a drought cycle for 10 years now.

Below is a graph with the average totals for each month since records started in 1889.

The vertical bars above each month show you the maximum recorded for each month, which in contrast to the "average" you can see the sort of peaks we can expect in rainfall.

So, well before we get into discussions of "change" lets look at what's likely and what the current climate is before we begin charging into "its changed". Since we're in June, lets look at June records where ge got more than 300mm of rain:
  • 464mm in 1889
  • 419 mm in 1933
  • 329 mm in 1944
  • 302mm in 1948
  • 556mm in 1950
  • 558mm in 1967
  • 381mm in 1991
and now something over 474mm in 2011. So it looks like something between 40 and 20 years we have a deeply wet cycle.

Lets look at what that may look like in comparison to the first bar graph above.

Below are some of the periods where there was high rainfall:

The period around the seventies:

back to the twenties:

and just a few of the "high rainfall" years grouped together.
The late twenties looked like a standout with 882mm of rain in Kempsey in Feb of that year (and the rest of the month looking more even), but with a significantly smaller population I'm willing to bet that they were smart enough to perched in places which weren't effected as much by flooding. Today when driving through areas I see time and time again development happening in places "where only a fool or an angel would build".

Lastly, lets look where Kempsey is geographically:

Gosh, its in the flood plain of a river (the Macleay River), that drains a major mountain range. Flood plains are called Flood Plains because they FLOOD ... so where's the surprise?

Even more so Kempsey is described as:
Geographically, Kempsey stretches out around a long loop of the Macleay River at the top of the flood-plain. It is famous for its floods. The 1949 flood was particularly destructive, having washed a large part of the town centre away when the railway viaduct which was acting as a dam-wall due a build-up of debris against the railway bridge gave way. The area most affected by this flood is now the site of playing fields. The shire council has a policy of buying up land in areas designated as flood plains and many houses have been transported to higher ground in recent years. Other major floods occurred in 1949, 1950, 1963, 2001 and 2009.

So my question arising this research is "who are the fools: the media or the public?" I can only feel that increasingly the media and the general public are best described by "hysterical screamers" without a clue.

Sad really

1 comment:

Noons said...

Don't worry: if all else fails our government will slap another "price" on it and that'll fix the "flood" problem in Kempsey for sure!

I can remember going to South West Rocks on hols in the mid 80s and having to drive out through the beach South to Crescent Head because the road to Kempsey was under water...