3 ms·

"Your policy response, which can be paraphrased as 'don't build dams, move major cities' is idealogically warped and just wishful thinking." I could be wrong,

by panacea 16y ago

"Your policy response, which can be paraphrased as 'don't build dams, move major cities' is idealogically warped and just wishful thinking." I could be wrong, but I think he's suggesting not building on the areas of the city which form the flood plain, not the whole city. We have an accurate record of which areas of the City were flooded in 1974. The areas that flooded recently are a subset of those areas. People were allowed to build in these areas because the Dam was supposed to have mitigated the risk. We could have kept zoning plans in place to deter building in these areas and still had a vibrant city built up around them. More river-front parkland to boot!

brc 16y ago
It doesn't matter if it is 5% of a city or the whole city, it's not going to happen. The areas that were flooded now were mostly populated in 1974. There's a popular meme going around that huge areas of previously-vacant land was built upon. While that might be true in some instances of outer suburbs, in general the flooded suburbs of Brisbane were the same ones as all the previous floods. As I've already stated, if you want to clear the city from the low-lying areas, you'll have to forcibly acquire a large amount of private property, which is either an expensive (if the law is followed) route, or a suspension of the current law. So suggesting the low lying areas be forcibly cleared is clearly unworkable. And it involves acquiring and demolishing the majority of the CBD. If you think that is even remotely possible then I've got the Story Bridge to sell you. Everyone who purchases property in Brisbane is well aware of the 1974 floods. I know, because I purchased a property knowing full well it could be flooded one day as it was in 1974. And last week it was. But I'm not about to sell it or have the government confiscate it because it gets flooded once every 40 years. About the best thing that could happen is something along the lines of a) new developments must have critical infrastructure (electrical circuits etc) about the 100-year flood leve b) flood prone suburbs could have prominent markers, such as bands around power poles to remind people of previous flood heights. There's a popular one in the Breakfast Creek Hotel. c) new housing in flood zones could have a mandate not to use water soluble materials such as plasterboard in lower levels, and could be mandated to have the main living area above flood height. People with older houses often came out with no problems because the old houses were built with floods in mind. This idea of avoiding flood risk by avoiding waterfront areas is silly. By the same token, all residents should abandon Cairns and Townsville because of the cyclone risk. And cyclones in the north happen far more frequently, and with more devastation than Brisbane floods.
speleding 16y ago
I agree with the sentiment but dams can only do so much. In particular, dams don't absorb water, they move the problem somewhere else. There may be enough unused room outside Brisbane, I don't now the situation, but in any area of sufficient population density that won't be the case, unless you want 10 meter high dams throughout your country side. In the Netherlands where I live, dams are combined with controlled flooding areas. The dams should hold most of the time, but the system is designed in such a way that once in 20-50 years when there is too much water it can be directed to low value areas like farm fields. That's logical to an engineer, but it takes serious political courage to build a dam in the middle of an area where there is no water to account for a once in 50 year event, and even more courage to declare one side of that dam as "lower value". It makes economic sense though, 10 meter high dams are very expensive (and ugly), more expensive than rebuilding a few houses every generation.
- brc 16y ago
  There's plenty of space in the Brisbane river valley for more Dams. One was planned about 15 years back, the land was purchased and it was ready to go. One political group campaigned on having it scrapped so the land was sold off. The largest Dam servicing Brisbane has a total capacity of 220% - that being 100% is the 'normal' water storage level, the rest is for flood mitigation. So the Dam can temporarily hold more than double its usual capacity. Elsewhere in this topic you'll see people discussing whether that flood mitigation capacity was used correctly, and only time and investigation will tell. I would assume any new Dams planned would also incorporate a flood mitigation feature, particularly after this last flood. The population density outside of Brisbane drops very low, very quickly. It's nothing like the Netherlands. Australia has one of the lowest population densities in the world, whereas I think the Netherlands has one of the highest.

by panacea 16y ago

brc 16y ago

It doesn't matter if it is 5% of a city or the whole city, it's not going to happen. The areas that were flooded now were mostly populated in 1974. There's a popular meme going around that huge areas of previously-vacant land was built upon. While that might be true in some instances of outer suburbs, in general the flooded suburbs of Brisbane were the same ones as all the previous floods. As I've already stated, if you want to clear the city from the low-lying areas, you'll have to forcibly acquire a large amount of private property, which is either an expensive (if the law is followed) route, or a suspension of the current law. So suggesting the low lying areas be forcibly cleared is clearly unworkable. And it involves acquiring and demolishing the majority of the CBD. If you think that is even remotely possible then I've got the Story Bridge to sell you. Everyone who purchases property in Brisbane is well aware of the 1974 floods. I know, because I purchased a property knowing full well it could be flooded one day as it was in 1974. And last week it was. But I'm not about to sell it or have the government confiscate it because it gets flooded once every 40 years. About the best thing that could happen is something along the lines of a) new developments must have critical infrastructure (electrical circuits etc) about the 100-year flood leve b) flood prone suburbs could have prominent markers, such as bands around power poles to remind people of previous flood heights. There's a popular one in the Breakfast Creek Hotel. c) new housing in flood zones could have a mandate not to use water soluble materials such as plasterboard in lower levels, and could be mandated to have the main living area above flood height. People with older houses often came out with no problems because the old houses were built with floods in mind. This idea of avoiding flood risk by avoiding waterfront areas is silly. By the same token, all residents should abandon Cairns and Townsville because of the cyclone risk. And cyclones in the north happen far more frequently, and with more devastation than Brisbane floods.

speleding 16y ago

I agree with the sentiment but dams can only do so much. In particular, dams don't absorb water, they move the problem somewhere else. There may be enough unused room outside Brisbane, I don't now the situation, but in any area of sufficient population density that won't be the case, unless you want 10 meter high dams throughout your country side. In the Netherlands where I live, dams are combined with controlled flooding areas. The dams should hold most of the time, but the system is designed in such a way that once in 20-50 years when there is too much water it can be directed to low value areas like farm fields. That's logical to an engineer, but it takes serious political courage to build a dam in the middle of an area where there is no water to account for a once in 50 year event, and even more courage to declare one side of that dam as "lower value". It makes economic sense though, 10 meter high dams are very expensive (and ugly), more expensive than rebuilding a few houses every generation.

brc 16y ago
There's plenty of space in the Brisbane river valley for more Dams. One was planned about 15 years back, the land was purchased and it was ready to go. One political group campaigned on having it scrapped so the land was sold off. The largest Dam servicing Brisbane has a total capacity of 220% - that being 100% is the 'normal' water storage level, the rest is for flood mitigation. So the Dam can temporarily hold more than double its usual capacity. Elsewhere in this topic you'll see people discussing whether that flood mitigation capacity was used correctly, and only time and investigation will tell. I would assume any new Dams planned would also incorporate a flood mitigation feature, particularly after this last flood. The population density outside of Brisbane drops very low, very quickly. It's nothing like the Netherlands. Australia has one of the lowest population densities in the world, whereas I think the Netherlands has one of the highest.