Make more land

We used to make land. We built long wharves for docking ships, and then over time filled in the areas between them. Later we built up mudflats wholesale to make even larger areas. Here's a map of Boston showing how much of the land wasn't previously dry:

(Map reproduction courtesy of the Norman B. Leventhal Map & Education Center at the Boston Public Library)

In expensive areas, converting wetlands and shallow water into usable land is a very good thing on balance, and we should start doing it again. To take a specific example, we should make land out of the San Francisco Bay, at least South of the Dumbarton Bridge:

This is about 50mi2, a bit bigger than San Fransisco. This would be enough new central land to bring rents down dramatically across the region. It can be built to a higher density than SF, because no one is having their neighborhood Manhattanized. Millions of people could live there.

So, ok, let's address some likely objections:

This would be an environmental disaster. Some of that area is a wildlife refuge, and all of it should be protected.

The world is very large, and cities are a very small portion of it. The land we set aside for animals should be outside of cities, where far more land is available at far less impact to people.

Sprawl has a much larger impact on wildlife than infill, and allowing people to live closer in is the most powerful way to address sprawl. Additionally, sprawl leads to much higher carbon emissions through less efficient transportation. While development of the Bay would be harmful to the specific animals that live there today, it would be better for animals (and people) overall.

The Bay is beautiful and this would ruin it.

This part of the Bay is primarily industrial salt ponds.

This is just a few miles from a major fault line, and made land can liquify in earthquakes.

You do need to take fill into account to build in an earthquake-safe way, but modern engineering is well up to the task.

Traffic would be even worse.

The biggest contribution to traffic in the Bay Area is that people aren't allowed to live where the jobs are. The second biggest is that BART doesn't have enough coverage to make living without a car practical in most of the area. This would help with both of these, since this project would allow millions of people to live closer in and would easily fund massive subway expansion.

Wait, how many people are you saying would live there?

Here's SF's density in the 2010 census:

Relatively dense portions of the city have a density of ~40k people per square mile, which would be ~2M people over this 50mi2 area. At a density of ~80k people per square mile, something like NYC's East Village, this could be ~4M people. Much higher densities are possible but not a good idea.

This would undo decades of work aimed at preserving the Bay and restoring its wetlands.


Sea-level rise means we shouldn't be building more in low-lying areas.

Building dikes to keep the water out is very practical. A third of the Netherlands is below sea level, with most of that expansion happening before modern technology. By decreasing the amount of coastline in the Bay this project would make it easier to prevent flooding caused by sea-level rise.

Didn't someone already propose this decades ago?

The Reber Plan of the 1940s was a similar large project planned farther North, primarily for the East Bay. It was intended to both make land and create freshwater lakes, and testing with a scale-model showed major issues. This plan is much simpler, and more similar to past successful land reclamation projects.

There's not enough water for the people we already have; what will people drink?

There's plenty of water already, we just need to prioritize people drinking it over crops, which would happen naturally if we priced it. But even without that, desalination is cheap enough that a person's daily water use would be a matter of cents.

Is this a serious proposal?

Yes. We should do this.

(I previously suggested this kind of infill development with Boston's Fort Point Channel.)

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The problem with this proposal is not that it's a bad idea.

The problem is that you--a smart individual with no domain experience--can come up with an extremely sensible and pragmatic way to address a problem that:

  • Is causing over a trillion dollars of economic misallocation.
  • Has existed for 2 decades and gotten significantly worse over time.
  • Has reached a crisis point such that it has visceral effects on the day-to-day life of millionaires that they can't buy their way out of (e.g. faeces everywhere, being attacked by crazy homeless people).
  • Has a laundry list of founders, VCs and tech CEOs desperately trying to solve it.

...yet is still not solved. Which should make you wonder, is a lack of sensible ideas really the main bottleneck?

[-]G A230

Hi. I work in the area, and occasionally my job takes me out into this part of the bay. The author is correct...although a portion of this area is a designated wildlife refuge, the majority of it fairly useless. Most of the salt production has moved to cheaper regions. Also consider this...when the tide is out, that portion of the bay is literally only feet deep. Seriously, on average 1-3 feet’s a giant mud flat. You can’t boat in it or use it for recreation (without sinking into the mud). I’ve tried to walk in that mud...and sank past my waist! There’s very little wildlife out there, the water is pretty stagnant and on some days very smelly. I’ve traveled out into that water (obviously during high tide) and looked at the crowded land mass in every direction and thought the same thing...this spot would be so useful if it wasn’t mud and water!

I think one of my favorite things about LW is that it has a clear-eyed view of the future, and things will be different and we should pick which way to make them different. While I don't think the theory of change underlying this specific proposal is here, I think having these sorts of proposals around, and being the sort of people who share these proposals instead of write them off, is important, and I think I've moved more in this direction over the intervening year, in part because of how positive my reaction was to this post.

I'm trying out making some polls about posts for the Review (using the predictions feature). You can answer by hovering over the scale and clicking a number to indicate your agreement with the claim. 

Making more land out of the about 50mi^2 shallow water in the San Francisco Bay, South of the Dumbarton Bridge, would... 

For some of these questions, I tried to operationalise them to be less ambiguous than Jeff's original formulation. 

This sort of thing is exactly what Less Wrong is supposed to produce. It's a simple, straightforward and generally correct argument, with important consequences for the world, which other people mostly aren't making. That LW can produce posts like this—especially with positive reception and useful discussion—is a vindication of this community's style of thought.

Awesome, I think the Western world currently has a shortage of specific ambitious proposals like this. Strong upvote.

In Zero to One, Peter Thiel calls this "definite future" mindset and specifically mentions the Reber Plan as an example.

Seconding Vaniver. I very much like the thinking involved in this simple proposal.

I like this post and would like to see it curated, conditional on the idea actually being good. There are a few places where I'd want more details about the world before knowing if this was true.

  • Who owns this land? I'm guessing this is part of the Guadalupe Watershed, though I'm not sure how I'd confirm that.

This watershed is owned and managed by the Santa Clara Valley Water District.

  • What legal limits are there on use of the land? Wikipedia notes:

The bay was designated a Ramsar Wetland of International Importance on February 2, 2012.

I don't know what that means, but it might be important.

  • How much does it cost to fill in land like this?

It looks like for pool removal there's a cost of between $20-$130 per cubic foot yard (thanks johnswentworth). Making the bad simplifying assumption of 6ft of depth and 50 square miles that's 8.3 billion ft^3 310 million cubic yards. Since the state of CA is very bad at cutting costs, let's use the high end cost estimate which is about 1/8 of $1000 so that makes the cost estimate $1 trillion $300 billion. 

With a trillion dollar price tag, this stops looking worthwhile pretty fast.

Spitballing about price estimates:

  • People have filled in things like this in the past, which suggests lower costs
  • Human effort may be much more expensive than it was previously
  • pool filling prices might include massive fixed costs and regulatory costs that wouldn't scale with volume
  • The state could auction the land to a private company that might do a better job negotiating costs

If fixed costs are 90% of pool fillings and will be negligible by volume for this, and if we further use the lower bound of cost per filling, then we reduce cost by 60x to about $5 billion. Let's call that an 80% confidence interval, where the low end is clearly worth it and the high end clearly not.

  • How much does it cost to build a bunch of housing there?

First Google result says $65k-86k per unit, though economies of scale might bring that down. Then the suggested 2 million units would cost ~$130-170 billion; potentially significantly more or less.

  • How much value does the housing create?

The cheapest rents I could see with a casual search was something around $900/bedroom/month in Fremont.

Rounding up to $11k/year, it would take 6-8 years to recoup construction costs, not counting maintenance.

At the low end of land filling costs, $16 billion, adds less than one year to the recoup timeline. At the high end around $1 trillion, it would take about 50 years to recoup the costs. $300 billion, that ~triples to ~20 years.


Reaching the end of this, I think I'm uncertain about how economical the idea is. This is mostly because of large error bars around my cost calculations.

An investment that pays off in value created 50 years down the line is probably worth it for society, but very unlikely to happen given the investment environment today.

My ending impression is I want this post curated, because I want city managers and real estate investors to run these numbers (ideally being nerd-sniped by my terrible naïve calculations) and make the decision for themselves.

It looks like for pool removal there's a cost of between $20-$130 per cubic foot.

Minor correction: that source says filling in a pool is $20-80 per cubic yard, which would only be ~$1-3 per cubic foot. The higher numbers are for demolition, but that's presumably dominated by the cost of the demolition rather than the fill - jackhammers are a pain in the ass.

Thanks! Updated.

It looks to me like you're comparing the cost of constructing a unit to the price of renting a bedroom?

I don't think you're counting the cost of infrastructure construction?

Bulk fill is massively cheaper than the quantities you would use for pool removal.

Since this is a seismic area you can't just use bulk fill: you need to do some amount of reinforcement/stabilization.

You're talking about this as if the government would pay for all construction and then own all units and rent them out? I agree that governments are not typically interested in that kind of financing, especially in the US. If you sell the units, or the buildings, however, there is a thriving real estate market that does operate on these time scales.

I was trying to do a back of the envelope calculations of total cost of work and total value created (where I'm using cost of rent as a (bad) proxy for (capturable) value created).

I definitely wouldn't assume that the government or any single agent would be doing the project, just that the overall amount of capturable value must be worth it for the investment costs, then different parties can pay portions of those costs in exchange for portions of or rights to that value, but I doubt adding in the different parties involved would make my estimates more accurate.

Do you have a source for cost of similar projects? My estimates are definitely very bad for many reasons.

You could use the proceeds from this new land to put the remaining non-urban estuaries in California under permanent protection. Interesting proposition. The Dutch equivalent would be Almere, by the way.

Or we could change zoning laws. But then again, the American political landscape is deadlocked. Perhaps you need to reboot on that great experiment?

Our great experiment has a reboot mechanism. It's called an election.

Not arguing against this proposal, but want to note that there's plenty of land in the Bay Area that's only developed to low density or hasn't been developed at all.

Changing housing policy such that it's easier to build is probably upstream of both making new land and making existing land higher density.

Where is the land that hasn't been developed at all?

These are all abandoned:

  • Oakland army base
  • Oakland outer harbor
  • Naval Air Station Alameda
  • Yerba Buena Island coast guard base
  • Most of Treasure Island
  • Parts of Hunters Point

Parts of South San Francisco are undeveloped, though I don't know how that interacts with San Bruno Mountain State Park.

Large swaths of the western side of the Peninsula are undeveloped.


One example: Most of Marin, immediately north of San Francisco across the Golden Gate, is devoid of development and housing. It is truly striking to see, in a place where the value of each square foot is higher than nearly anywhere else in the world.

More undeveloped land, much of it mountainous, is plainly visible in the satellite photo included in the article.

Though note most of this (in Marin) is park land.

This idea seems obviously correct, all the responses to objections seem correct, and the chance of this happening any time soon is about epsilon. 

In some sense I wish the reasons it will never happen were less obvious than they are, so it would be a better example of our inability to do things that are obviously correct. 

The question is, how much does this add to the collection. Do we want to use a slot on practical good ideas that we could totally do if we could do things, and used to do? I'm not sure. 

This isn't my area of expertise, but I found this quote in an article about anticipating climate change in the Netherlands to be food for thought:

If we turn the Netherlands into a fort, we will need to build gigantic dikes, but also, and perhaps more importantly, gigantic pumping stations. This is essential, because at some point we will need to pump all of the water from the Rhine, Meuse, Scheldt and Ems – which by that time will be lower than sea level – over those enormous dikes. The energy costs will be higher – but that is not the only problem, because when the enormous pumping stations pump out the fresh water, the heavier salt water will seep in under the ground. You can get rid of the water, but not the salt, which is disastrous for agriculture in its current form. Instead of a fort, it may make more sense to talk about a semi-porous bath tub.


The South Bay infill wouldn't be the same - much smaller, creeks instead of rivers (though flooding is still a concern), and probably no agriculture. But I wonder what other engineering problems are swept under the rug by assuming that "modern engineering is well up to the task?" Thinking about such questions from a very high-level view often misses important details.

This is just spitballing, but it seems like it would be prudent to build up the new land higher than the new anticipated sea level. And the very expensive land around the infill might actually end up downhill, below sea level. Which might make drainage interesting.

Include bendini's post with it.

But it shows all the free energy in the world. Good nod to Inadequate Equilibriua.

I feel like housing exists in equilibrium with governance quality. When the prices get high enough due to good governance, people in the area will vote in increasingly bad government until bad policies decrease house pricing.

People vote in bad government because of NIMBY-ism, or something else?

Bad policy as a luxury good.

Okay, but I don't really understand the incentives here. Why is bad policy attractive to anyone? Is it all NIMBY-ism or are you pointing to other drivers also?

Why is bad policy attractive to anyone?

Three easy reasons:

Finally, my favorite quote from Edmund Burke (inventor of the political party)

There are but very few, who are capable of comparing and digesting what passes before their eyes at different times and occasions, so as to form the whole into a distinct system. But in books every thing is settled for them, without the exertion of any considerable diligence or sagacity. For which reason men are wise with but little reflexion, and good with little denial, in the business of all times except their own.

Happy to chat about this elsewhere (too many politics tentacles)

This plan has been proposed before. It was called the Reber Plan, and was deemed infeasible by the U.S. Army Corps of Engineers, after testing of a physical model of the Bay Area.

The Reber plan was a very different proposal, involving barriers farther North. This is a much simpler proposal, which doesn't create any freshwater lakes.

Much higher densities are possible but not a good idea.

Not with that attitude! Also, Manhattan daytime and Paris densities are already much higher (~200k / sq mi).

Here is a nice map of the parts of the Netherlands that are under sea level. I live in Amsterdam. Not on the ground floor :)

People in the Netherlands are very concerned about environmentalism and climate change. But not so much about sea level rise. I imagine it has to do with the opportunity to help cities like Miami build infrastructure that can help them livel below sea level, too

help cities like Miami build infrastructure that can help them live below sea level, too

Miami is in a terrible position, geologically, because it's built on top of porous rock:

Can We Build Levees Around Miami? -- This works for places like New Orleans and The Netherlands because these places are built on top of dense clay so the water cannot percolate through the ground easily. In the case of Miami, water is not just coming up on the beach, it is coming through the ground below us because we are built on top of limestone that is full of holes. So even if we built walls on the coast, the water will just creep in under the walls through the limestone. --