Extreme weather is transforming the world’s rivers. We need new ways to protect them

[John Nissen]

Extreme weather is transforming the world’s rivers. We need new ways to protect them https://share.google/BSDJB88BTttFeCxRQ 

[Paul Klinkman]

Hi Restorers,

Kings are unable to successfully tell high tide to go back down at will.  Nor can politicians and wealthy people decree the absolute limits of how high a river can rise when it floods, but that never seems to stop people from trying.  Engineers inevitably build concrete walls on both sides of the river and they expect the river to stay between those two walls, even if 10 or 100 times normal flow has to fit down that narrow channel today.  In practice when the water coming down from above can't get down the channel fast enough, the river rises until it can use the rest of the river valley.  Only then will outflow equal inflow.

If two different states or two different companies build levees on opposite sides of the river, at least one of those levees will eventually overtop and it will probably crumble and fail.  Invariably, banks discover that great numbers of home mortgages are now underwater and that no insurance company ever wants to cover flooding, so the FDIC must regularly bail out some bankrupt bank.

 The Netherlands builds to survive a 10,000 year flooding event.  Too many USA levees are built to be 5 feet taller than the previous levee which recently failed.   

Now we get to climate change, where a 100 year flood now seems to be coming every 10 years.  The first engineering solution is to get real about climate resilience.  The greater part of resilience is inhibiting all of climate change in the first place,.  This would require international cooperation, such as we already saw in the Montreal protocols against ozone-destroying refrigerant chemicals.

The ultimate flood solution is to assume that every river must flood someday.  Build houses on stilts in floodplains or else tax them heavily.  When the megaflood comes, each house's ground level walls must wash away and let the river run through.  This will keep the river from being blocked and from rising even higher.  Often roads are elevated near bridges, but the elevated roads just block river flow over the floodplain.  Build such roads with hundreds of small culverts so that megaflood water flows through all of these culverts and doesn't pile up on the upstream side of that road.  

The best place to store floodwaters is right where the rain or the snow fell.  We need more groundwater and less instant floodwater.  Every forest hillside denuded by a wildfire could use tiny ditches leading to tiny hillside swales.  Each swale helps to water one tree.

Water-saving terraces are being tried in arid countries.  My concern with terraces is that a huge 20 inch rainfall could erode the terraces.  Therefore, build terraces in a gentle spiral around each hill.  The first inch of rainwater will sink into the local groundwater supply, and the rest will gently flow around and around the hill's side until it reaches a stream.  

Yours in Hope,

Paul Klinkman