The floods we’ve seen over the past few days are a sobering reminder of how our lives are subject to natural forces largely beyond our control. For most of us, such floods will be at the front of our minds for only a few days.
When the flood waters recede, we will be distracted by other world events, and other sequences of dramatic imagery. But those who fell into the flood directly would not be able to move forward so quickly. Such floods can have devastating and long-term effects on mental and financial health. May their lives change forever.
A woman carries her luggage through flood waters in South Shepparton.attributed to him:Jason South
Why do these events keep happening? Why can’t we learn from past events and fix things so we can all be safe? Well, as someone who has spent the past 40 years investigating flood behaviour, I can confidently say that we can never hope to prevent flooding – at least not as major floods as we saw along the east coast of Australia this year – all we can hope to learn how to Better live with them.
It is common in the immediate aftermath of these events to look for someone to blame. It would be nice to think that our current disaster is the result of negligence in some way, and that we can claim compensation. I am aware, for example, of concerns about the flood wall that was built to protect the Flemington racetrack from submersion.
Well, I can think of many reasons why such a wall might have “unintended consequences” on neighboring properties, but I can also think of several similarly good reasons why no negative effects would occur. All we can be sure of at this time is that the original development would have been carefully scrutinized when it was first proposed, and if there were any lessons to be learned, finding them wouldn’t be quick or easy.
The immediate cause of the recent floods is simple: a large amount of rain fell in a short period. But there are other factors at play here, some just a random result of Mother Nature and others the result of human activity. We are in the third consecutive La Niña season, and the watershed is already wet. The soil cannot absorb more rain, and soon most of the rain appears as flood runoff.
The size of the flood also depends on where exactly the most rain falls in the watershed, and whether the most intense rainfall occurs within a few hours or a few days. We have significantly modified the landscape, and nearly all of these changes have made flooding worse: we have cleared forests, channeled rivers and streams, reduced the capacity of floodplains to store water, and made large parts of our urban areas impervious.
We like to think that dams and levees keep us safe from flooding, but the truth is that they tend to generate a false sense of security as there always comes a point where the flood capacity of these structures is exceeded. So, yes, dams and dams protect us from small floods, but they can further exacerbate the consequences of large floods, as we are encouraged to expand our cities and towns into floodplains that are best avoided.
Originally published at Melbourne News Vine
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