Of floods, droughts, land cover, aquifers & insurance

Restoring our lands to mitigate natural disaster and water supply issues

Imagine holding a running hose, and standing at the top of a forested hill with a paved path running through it. If you point the hose at the path, the water will run down quickly all the way to the bottom. But if you point the hose in the direction of the forest, the forest will absorb a lot of the water, and much less water will get to the bottom. The water that does get to the bottom will come in a trickle spread out over a much longer period of time.

This is the kind of situation we are faced with when torrential rains hit. Rich soils and vegetation upslope can absorb the rains so that much less reaches towns downslope. Each 1% increase of carbon in our soils allows them to absorb 20,000 gallons more water per acre-foot. Increasing 1% carbon over 100,000 hectares would lead to 1 billion gallons more of water absorbed. Some of that water is then funneled down to fill the aquifers.

Last week, a cutoff part of the atmospheric jet stream, parked itself over Spain and poured out a torrential storm. Global warming and land degradation have increased abnormal jet stream behaviors. This huge rain came down on lands that has lost a lot of trees and soil over the decades. It then gained velocity as it moved to the urban areas. It pummeled towns from Valenicia to Andalusia.

[Valenica, Spain]

This phenomena of land degradation leading to larger floods is happening all around the world.

Rebecca Bartley is an Australian researcher who studies watershed hydrology and geomorphology. She and her colleagues studied tropical savannahs, some of which had patches of bare land, and some of which did not. They found that there were 6 to 9 times as much runoff in the places with patches of bare land, and up to 60 times more sediment loss. [Bartley 2006]

Corey Bradshaw is a professor of global ecology, he said he studies “how human endeavour and climate fluctuations have altered past, present and future ecosystems”. He is a prolific researcher, who’s findings have influenced many policies. He and his colleagues undertook a large survey of floods in 56 countries to see what pattern human disruption to our ecosystems had influenced the impact of the floods. They found that if there was more than a 10% decrease in native tree cover then flood frequency increased by about 4% to 28%, people killed increased by about 1% to 7%, and people displaced by 1% to 5%. [Bradshaw 2007]

Earlier this year I was reading a post by a Pakistani water colleague, Ali Bin Shahid. He was writing about his calculations of how much land cover could absorb rains. It struck me that his calculations could be applied to Pakistan as a whole. In 2022 devastasting floods hit Pakistan. Over 1000 people died, and over trillion dollars in damage were incurred. I asked Ali if he could analyse how much land cover restoration would be required to mitigate the Pakistani flooding damage. Here is his analysis of his on his Re:genesis blog; one of his conclusions “By targeting areas along the Indus River to achieve an infiltration rate of 60 mm/hr, it is estimated that approximately 36,742 hectares (367.42 square kilometers) are needed to manage the excess water exceeding the Sukkur Barrage's safe capacity. This area represents about 14.70% of the total 2,500 sq. km. Implementing this strategy could significantly mitigate flood impacts by enabling the infiltration of a substantial volume of excess water.” If we plan large scale restoration efforts we can mitigate floods.

A financial solution to how we can fund this large scale land restoration has been proposed by Tim Coates, a UK banker. He suggests that businesses can by flood insurance, and that flood insurance money can then used to restore the land in order that it can absorb the rain. Here is an interview with him on this topic on the “Investing in Regenerative Agriculture” podcast. Floods cost businesses many millions of dollars. A portion of this can be invested into mitigating the flood.

In the Altiplano plains on the southeastern edge of Spain, which was also hit with big rains last week, though not as large as in Valencia, the large scale restoration efforts that have happened over the years there, helped to absorb some of the rains. There was still damage, but wetlands and earthwork ponds helped to soak in the rain, and prevent larger landslides. The Alvelal movement there weaves together hundreds of farms, businesses, and researchers to restore the land. They’ve emerged a collective movement through a lot of community building and facilitation work. (I recently interviewed Silvia Quarta from one of the farms there about their work.)

Such multistakeholder bioregional land restoration projects can be weaved in other areas of Iberia, and also other parts of the world. A flood insurance model could be one way to help fund these collective land restoration projects. We’ve also recently talked about in this newsletter about how regenerative tourism could help with land and water restoration.

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As we know land restoration is not just for flood mitigation, it also helps with building water resources, and bringing back summer rains.

Our aquifers are like water banks. We can withdraw from them in the dry season to provide water for people and agriculture. Certain trees (usually bigger ones) are able to bring groundwater up and hydrate the environment, in a process called hydraulic redistribution. (See my previous article “The secret life of groundwater”). We want to make deposits during the wet season so that we can have something to withdraw in the dry season.

Water deposits follow an interesting kind of scaling law. Earthquakes exhibit this kind of scaling law called a power law. An earthquake can be 10 times as big, and 100 times as big as another earthquakes. An earthquake that is 6 on the Richter scale is 10 times as big as an earthquake of size 5. This kind of scaling law distribution is different than a bell curve distribution. Bell curves are for peoples heights, which vary around an average height of around 5 to 6 feet. There are no people 10 times as tall, nor 100 times as tall as the average person. Floods don’t follow a bell curve, they follow a power law. There are rains 10 times as big, and 100 times as big as other rains.

That makes it very important that we capture as much of the big rains as possible. They will make up the bulk of our aquifer water deposits. Its what makes up our society’s water supply. In order to take those deposits though, we need to have land cover and forests to slow the rain.

When we have more groundwater, trees can bring up that water in the dry season, evapotranspire it and create more summer rains (as explored in “The missing link: Groundwater creates rain”) . Millan Millan’s studies was about restoring the summer rains to Valencia. If we had refilled the aquifers with the recent huge rains, that would have played a decent part in helping bring back the summer rains.

Refilling the aquifers will also help to lessen wildfires, as trees can bring up water to create humider wind, moister soil, and more rains.

Restoring our lands on a large scale, accelerated through a multistakeholder bioregional approach, bolstered by partnerships between the hospitality sector and the regenerative sector, and aided with insurance models, can help mitigate flood, drought and water supply issues.

References

Bradshaw, Corey JA, Navjot S. Sodhi, KELVIN S‐H. PEH, and Barry W. Brook. "Global evidence that deforestation amplifies flood risk and severity in the developing world." Global change biology 13, no. 11 (2007): 2379-2395.

https://conservationbytes.com/wp-content/uploads/2011/03/bradshaw-et-al-2009-ambio.pdf

Bartley, Rebecca, Christian H. Roth, John Ludwig, David McJannet, Adam Liedloff, Jeff Corfield, Aaron Hawdon, and Brett Abbott. "Runoff and erosion from Australia's tropical semi‐arid rangelands: Influence of ground cover for differing space and time scales." Hydrological Processes: An International Journal 20, no. 15 (2006): 3317-3333