Why build a wall and pump? Just start dumping rocks at the center in the planned volume or a few % more to account for subsidence at the edges to the known angle of repose. Voila, your land mass for less. And it would be quicker - probably done by next April Fools' Day.
Thanks for the suggestion - we did consider this, but our current understanding is that just dumping material (during current much smaller scale land reclamation projects) tends to leave the reclaimed land highly vulnerable to erosion, meaning that the land would quickly shrink (while the referenced Dutch wall should last for >200 years). Specifically, extrapolating from the rate of erosion between Flamborough and Spurn Heads (https://bigthink.com/strange-maps/a-map-of-europes-fastest-eroding-coast/ - and the soil here would likely be even weaker) the island would shrink by ~1.5%/year, and presumably faster at the surface, which seems much too high for stability. We do agree that the wall section assembly would likely form most of the construction time though.
Wel, there must be a reason the Dutch and the Venetians opted for a "wall" instead of a long breakwater of the type that has protected Buffalo's harbor from winter's fury on Lake Erie for 150 years, with maintenance, so probably you're right. Pictures of the Dutch wall, though, seem to indicate that a lot of it looks like breakwater.
If your land's made of demolished Welsh mountains (reminds me of the beautiful karst mountains being taken down in the Yangshuo region of China), though, it seems easy enough to make sure the edges of Doggerbank are made of large rocks, not the soft clay that's eroding between Flamborough and Spurn. One also wonders about the relative cost of wall+pumping vs retaining one work crew to dump around the edges perpetually to counteract the erosion you foresee. Or about the propriety of dumping first, then building the wall around the edges of what you've dumped. No pumping, shallower foundations, cheaper wall. Anyway, an interesting thought experiment. Who knows what will be possible once energy's too cheap to meter?
I don't understand why you need to fill in crushed rock or sand. Just build the wall and be done? the entire area would be below sea level but that's not unheard of: The lowest spot in the Netherlands being nearly 7 m below sea level.
Guessing you'd have to keep pumping anyway. A question is how long it would take for rain input to turn water bodies from salt- to freshwater.
PS Understandable but shame to have it as an April Fool's thing. Seems sensible to me. An instance of pushback against innovation starvation (Neal Stephenson's phrase).
Under the cost estimates we have in the article, it would be substantially cheaper to fill it in - cost of doing so is only 9% of the total cost, compared to 12% from merely having the pumps active for 100 days - of which half is the cost of the backflow during that length of time. We now think our backflow estimates were probably too high (especially as rain seems to be a substantial portion of the water ingress in similar projects), but it remains the case that it seems that managing to avoid pumping altogether after filling has begun would probably be cheaper on net.
If backflow is lower that's great news for wanting fewer pumps that you'd never need to use again (unless maybe for a next project) after the intial drainage phase. Don't quite see though how the optimization works out to want to do it so quick: My logic says as long as you pump faster than backflow it'll eventually empty out. So the minimum number of pumps to maintain a narrow surplus should be optimal? Understood its *desirable* to not let it take too long.
We include electricity costs in the cost of pumping at current UK market prices (due to proximity to wind we might be able to do this slightly cheaper), so it does minimise total expenses to do it at the calculated rate (and these do end up as a substantial portion of the total at the optimal choice). Optimal rate will necessarily be slightly faster than this due to including the delay on benefits from longer construction times etc.
Yup, gotcha. Also thought if the planned Dogger Bank wind farm was fully operational at construction start proximity might facilitate deals to use excess capacity the grid can't handle when there is a lot of wind across the region to lower power cost even more. Anyway, again, great piece. I really do wonder why it feels fantastical when it checks out as a financial proposal in terms of ROI and represents a credible nuts & bolts plan to alleviate population pressure & massively stimulate growth across the board, not just particular industries.
Pumping while getting paid is nice of course—but then the question arises whether to keep pumping at a higher price or wait for the next oversupply window to then compensate with negative cost for back seepage that happened while pumps were stalled? Wind prediction enters the picture!
Why build a wall and pump? Just start dumping rocks at the center in the planned volume or a few % more to account for subsidence at the edges to the known angle of repose. Voila, your land mass for less. And it would be quicker - probably done by next April Fools' Day.
Thanks for the suggestion - we did consider this, but our current understanding is that just dumping material (during current much smaller scale land reclamation projects) tends to leave the reclaimed land highly vulnerable to erosion, meaning that the land would quickly shrink (while the referenced Dutch wall should last for >200 years). Specifically, extrapolating from the rate of erosion between Flamborough and Spurn Heads (https://bigthink.com/strange-maps/a-map-of-europes-fastest-eroding-coast/ - and the soil here would likely be even weaker) the island would shrink by ~1.5%/year, and presumably faster at the surface, which seems much too high for stability. We do agree that the wall section assembly would likely form most of the construction time though.
Wel, there must be a reason the Dutch and the Venetians opted for a "wall" instead of a long breakwater of the type that has protected Buffalo's harbor from winter's fury on Lake Erie for 150 years, with maintenance, so probably you're right. Pictures of the Dutch wall, though, seem to indicate that a lot of it looks like breakwater.
If your land's made of demolished Welsh mountains (reminds me of the beautiful karst mountains being taken down in the Yangshuo region of China), though, it seems easy enough to make sure the edges of Doggerbank are made of large rocks, not the soft clay that's eroding between Flamborough and Spurn. One also wonders about the relative cost of wall+pumping vs retaining one work crew to dump around the edges perpetually to counteract the erosion you foresee. Or about the propriety of dumping first, then building the wall around the edges of what you've dumped. No pumping, shallower foundations, cheaper wall. Anyway, an interesting thought experiment. Who knows what will be possible once energy's too cheap to meter?
I don't understand why you need to fill in crushed rock or sand. Just build the wall and be done? the entire area would be below sea level but that's not unheard of: The lowest spot in the Netherlands being nearly 7 m below sea level.
Guessing you'd have to keep pumping anyway. A question is how long it would take for rain input to turn water bodies from salt- to freshwater.
PS Understandable but shame to have it as an April Fool's thing. Seems sensible to me. An instance of pushback against innovation starvation (Neal Stephenson's phrase).
Under the cost estimates we have in the article, it would be substantially cheaper to fill it in - cost of doing so is only 9% of the total cost, compared to 12% from merely having the pumps active for 100 days - of which half is the cost of the backflow during that length of time. We now think our backflow estimates were probably too high (especially as rain seems to be a substantial portion of the water ingress in similar projects), but it remains the case that it seems that managing to avoid pumping altogether after filling has begun would probably be cheaper on net.
Thanks, great explanation!
If backflow is lower that's great news for wanting fewer pumps that you'd never need to use again (unless maybe for a next project) after the intial drainage phase. Don't quite see though how the optimization works out to want to do it so quick: My logic says as long as you pump faster than backflow it'll eventually empty out. So the minimum number of pumps to maintain a narrow surplus should be optimal? Understood its *desirable* to not let it take too long.
We include electricity costs in the cost of pumping at current UK market prices (due to proximity to wind we might be able to do this slightly cheaper), so it does minimise total expenses to do it at the calculated rate (and these do end up as a substantial portion of the total at the optimal choice). Optimal rate will necessarily be slightly faster than this due to including the delay on benefits from longer construction times etc.
Yup, gotcha. Also thought if the planned Dogger Bank wind farm was fully operational at construction start proximity might facilitate deals to use excess capacity the grid can't handle when there is a lot of wind across the region to lower power cost even more. Anyway, again, great piece. I really do wonder why it feels fantastical when it checks out as a financial proposal in terms of ROI and represents a credible nuts & bolts plan to alleviate population pressure & massively stimulate growth across the board, not just particular industries.
Actually negative power prices makes the optimization problem even more fun: https://www.theguardian.com/environment/2023/may/29/weather-tracker-power-prices-dip-to-negative-in-europe-amid-clean-energy-boost
Pumping while getting paid is nice of course—but then the question arises whether to keep pumping at a higher price or wait for the next oversupply window to then compensate with negative cost for back seepage that happened while pumps were stalled? Wind prediction enters the picture!