Multi tank rainwater system

 

A quick sketch design for a few friends of mine with a sloping garden.

Self watering plant pots AKA wicking barrel

This video tutorial explains how to make a self watering barrel.

 

One of the common problems novice gardeners have is knowing how much to water their plants.

Too little water and they wither and die, too much water and the root can begin to rot. Either way the result is bad and means reduced crops which is a really big problem, especially if you are relying on them for food.

This watering barrel which you can make your self with simple tool  and techniques allow the water to ‘wick’ from a reservoir at the bottom of the barrel. The design also incorporates an overflow for the reservoir about 0.3m (12 inches) from the bottom to prevent the soil becoming too wet (waterlogged).

Other features is that the plant is raised above ground level and can have netting added to prevent animal eating or destroying crops.

Diagram of a cutaway to further explain wicking barrel.

 

Completed wicking barrel

 

The inlet pipe can be connected to a rain water collection system without fear of over watering.

 

the only thing i might add to this design is bare copper wire around the outside of the barrel to deter snails and slugs form entering the pot. The copper itself can also treat some micro-nutrient problems plants may develop.

The Bronze age collapse and you

Now firstly you may be thinking “What does the bronze age collapse have to do with me or the current world environment?”

More than you think it does.

The bronze age collapse occurred about 1200 BC after flourishing since 3000 BC, a period of 1800 years.

This was the single largest collapse of civilization known.

The important bronze age civilizations were centered in the area from modern-day Turkey, Iran, Iraq all the way south to Egypt.

The bronze age was the time just before the world power in the near east shifted to Greece and the fading empire of Egypt, which then moved to Rome and Carthage. Obviously the bronze age was based on bronze an alloy (mixture of) Tin (~10%) and Copper (~90%). Copper was quite common in the region of the fertile crescent but the tin ores were mined out quite fast requiring extensive trade networks to acquire it. Bronze was used for weapons and armor, allowing war as well as trade to be the mechanism used to acquire it. The trade networks to acquire the scarce tin extended all the way from Egypt to Brittan (which was actually named after its tin ores). It is believed that the bronze age trade networks were almost global, spanning at least 3 continents, Asia, Africa, and Europe, this can be demonstrated by the types of precious stones found  in the artistic styles of bronze age civilizations and other items that must have been sourced from very far away.

Bronze:

Bronze was first discovered by accident from smelting copper ore with arsenic impurities. different levels of arsenic impurities created soft or hard or brittle bronzes as the arsenic impurities increased. The smarter metallurgists of the time realized that by grading the bronze from soft to hard they could then remelt the high arsenic bronze 10% with the low arsenic bronze 1% to get  the best bronze 5%. Arsenic is of course toxic to the metallurgist  (causing paralysis)and eventually the metallurgists used tin instead of arsenic. All this smelting consumed large quantities of wood in an arid environment so supply caravans also had to source wood as well as tin  requiring extensive trade to create bronze, another way empires controlled bronze. Importantly bronze needed to be cast (poured molten into a mold) to create items, this required a lot of specialized artisans (including the mold maker) working together to create bronze items. This made bronze unlike iron which followed it.  Manufacture and distribution of bronze weapons and armor could be controlled by a hierarchy, the bronze armed soldiers could control everything else.

Bronze by its nature could be controlled, and it allowed control of populations. He who controlled bronze had total control of their society.

Iron:

Iron can simply be refined and shaped with just three tools, fire, a hammer and water which could be done alone and in isolation. Iron ores were common and impurities weren’t such a large factor in the production of the low quality steel needed to make swords. Iron did not need to be cast like bronze, it could simply be heated and hammered into shape then plunged into water to keep it hard. Iron didn’t generally contain toxic impurities like arsenic so it was safer to experiment with. Tin was not needed to make iron or steel. the most common impurity in the iron was carbon from the fires used to create it, carbon actually made the iron into carbon (mild) steel which was harder than iron.

Iron could not be controlled, it was too plentiful and too easy to make once the secret was discovered.

A scene from bronze age Europe. Five men are engaged in the complex process of smelting and casting bronze into a sword.
from http://fineartamerica.com/featured/bronze-age-granger.html

Bronze age society and politics

For much of the bronze age different states warred with each other, small empires expanded and contracted, rose and fell, merged or were taken over, one thing remained constant, bronze was the weapon and amour of the professional soldier. The professional soldier was charioteer dressed in heavy bronze chain mail, charioteers worked in a pair on each chariot. One charioteer was the driver armed with only a large knife and a few throwing spears, the other charioteer was an archer with the same knife and a bow with arrows. Chariot wars were quite a spectacle chariots and arrows going in all directions, eventually a chariot would become disabled and the runners would come. Runners were the mercenary army of  poorly armed ( non salaried ) peasants that would charge to a disabled chariot and swarm and kill the crew, who were too laden down with heavy armor to outrun the swarm. Each army would have their own army of runners, runners generally didn’t fight each other, they just attacked disabled enemy chariot crews. The Chariots themselves were expensive so were well out of the reach of the local peasant. All of the high technology weaponry was expensive and controlled.

Society was highly stratified with a large number of slaves, peasant farmers with smaller numbers of artisans and soldiers and at the top very small numbers of  aristocracy and royalty. This system was in place for  thousands of years and a real civilization sprung up along with it. The full extent technology of the Bronze age will likely never be known, only hinted at. The explosion in knowledge from this time period is quite staggering. Writing, Law, Stone architecture, Mathematics, complex society, pottery, metallurgy, coinage, irrigation, Navigation,the plow… The Egyptians inherited much of their civilization for the Bronze age near east civilizations, every innovation they had was simply imported from Sumer and its neighbors. Not all parts of the world experienced the bronze age, some societies were forced to wait for iron , either the bronze technology wasn’t available or the cost of tin and copper was just too high. The end of the bronze age wasn’t the end for bronze as a useful material it still had applications in swords but a cheaper alternative became available for the masses. Technology and knowledge for the masses was a hallmark of the iron age, the simplified phonetic alphabet of the Phoenicians was modified and adopted by Greece and later Rome, as it was a  simpler (less elitist) system than the hieroglyphic based system that were popular in the bronze age societies.

So what went wrong?

Several things all occurring at  about the same time.

Strangely no long-term bronze supply problems. Though a short-term supply issues may have created problems. Bronze is still plentiful today. Today bronze is about 1% of the price of silver of the same weight. So to this day, no bronze shortage. Today’s prices (February 2013) in  troy ounces (31.1 grams) and US $:

Silver $30.18  Bronze $0.33 Copper $0.27  Tin $0.82.

Bronze age collapse conditions

Environmental problems/ agricultural degradation  – Soil salination , Deforestation
After thousands of years of irrigation and deforestation soils became salty and less productive, sometimes non productive. Even today not an easy problem to fix, it required digging up all the soil and washing it in fresh water and then placing it all back in the ground. Remember this series of empires was built on agriculture and held together with military might and  control of bronze weapons. Because Bronze needed to be smelted and then cast vast quantities of wood were needed to be burned for this process. The region was deforested and in the process became more arid and this amplified the soil salination problem and droughts.

Natural disasters  – Earthquakes
For a period of 70 years before the collapse a series of major earthquakes occurred in the northern part of the fertile crescent. It became costly to repair a large amount of damage in agriculturally declining state without a war of conquest. Earthquake damage to major cities would have disrupted  major trade routes at the center of the Bronze age empires.

Destabilizing technology  – Development of iron smelting
Iron smelting, a relatively simple process took away the control of hard metal away from hierarchies. Now anyone could make a sword (and possibly armor) and many people made the Naue type II sword. Iron rich rocks could simple be heated in a large fire to create the pure iron, Iron once created could be beaten into shape with another fire and a hammer. Hot iron could be quenched ( hot iron put into cold water) to increase its hardness.  Iron ores were plentiful, iron working quite easy compared to bronze casting, and people were angry.

Naue II sword. The first popular sword of the Iron age.
From http://www.templeresearch.eclipse.co.uk/bronze/images/Naue_II_for_sale.jpg

Economic changes – Iron economy
The development of iron as a replacement for bronze would have disrupted bronze economies. As trade routes  changed and previously profitable businesses, town and entire infrastructure became marginal because of competition with the iron economy and products. The change to iron would have caused significant social upheaval. Imagine a centuries old industry with all its vested interests suddenly coming into competition where none existed before. Huge monopolies would have collapsed.

A period of extended peace – The Pax
For about 100 years (1300BC – 1200BC approx) there were no wars between major powers, leaving the mercenary armies with little money and growing ranks, and states reluctant to attack each other to solve economic problems.
Peasants weren’t accustomed to fighting against peasants from neighboring states and were more likely to see them as friends and not enemies, perhaps seeing their own greedy faltering state as a real enemy.

Complex extensive trade networks
As an economy develops there is a chance it will become too specialized and too reliant on monopolies. If critical monopolies fail, the entire structure of the economy can fail. Needing tin from Britain, a break in the supply line could be disastrous, could there have been a tin and/or bronze supply monopoly that failed, leading to a collapse?

Catastrophe design – Centralized power and control
With just a hand full of states all located in a relatively small geographic region having the majority of power, any small localized event could destroy the entire empire. Apart from Egypt all the power and grandeur of the bronze age was located in the east and north. A calamity in the center restricting trade would be disastrous. Egypt’s major contribution to the empires was slaves and food, once the flow of theses resources was restricted a collapse was inevitable.

Map of the near east Bronze age civilizations just 50 years before collapse. This region was the Centre of power for north Africa, the near east and much of Europe.

Social upheaval – Sea people and civil unrest
All of these factors lead to a group of people called the sea people forming a large army (armed with home-made iron swords) and sweeping through the region from north to south basically destroying everything in their path and collecting more recruits from the disenfranchised populous destroyed cities (many of which had already been damaged by earthquakes in the preceding decades). The sea peoples traveled by small civilian ships frequently but fought on land. Because the sea people destroyed almost every thing. There are few records of exactly who they were or their exact path of destruction. Like the atomic bomb attack on Hiroshima, Nagasaki had no idea of imminent danger, the devastation in Hiroshima so complete, that no one was alive and credible enough to recount the event. Many cities had no warning the sea people were coming. Any one likely to have told them was either dead or had joined the sea people. One thing is known, The Egyptians had learned of them before they arrived and battled them at sea and destroyed their army. Afterward Egypt had lost its major bronze age trading partners and went into decline. Looking at the map of the central bronze age civilizations it seems that the sea peoples attacks cut the empire in half, cutting Egypt away and destroyed all the trade routes to Egypt. Catastrophe design in trade networks. the Sea people were the catalyst for the complete overthrow of the bronze age empires.

Addition: Likely identity of the sea people; Aegean Greeks.

Research seem to point to a confederation of Greek sea going pirates from the Aegean sea. Several thing point to this. The early Greeks would have had access to Iron from Azarwa or Hatti in modern day Turkey. Their homeland was made from many small islands which made them good sailors and sea travel was normal for most people. The large number of islands would make a perfect place for pirates to hide their loot and ships and forma natural barrier to invaders or reprisals.  Sailing into uncharted island chains is hazardous as reef (rock or coral) can easily destroy invading ships. Tales from he Iliad effectively tell of the raids the Aegean Greek pirates did in the Mediterranean. The pattern of raid match the sea people raiding from the north and then clockwise around the Levant until finally reaching Egypt when all other the loot had been picked clean. The sea people most likely followed the coast line and didn’t require complex navigation and hence made longer and longer journeys hugging the coastline until finally reaching  and being defeated by the Egyptians. It likely the original Sea People added other nations and even refugees to the pirate confederation as the raids continued so it became not just one ethic group doing the raiding to confuse matters for historians further. The tales from the Iliad span several generations which seem to mirror the transition period from Bronze age to Iron age. Some island settlements in the region show special defenses against sea borne attack having  bee created on mountain tops with difficult to see trails leading up. Such a settlement would be quite impractical unless a pirate raid was a serious risk, this of course points to pirate raids being a serous problem for an extended period of time. The land based raid (possibily supported by sea going vesssels) seem to fan out from the city of Troy in more or less the same direction as the sea based raids supporting the idea of one localized confederation being the source of the pirate raids.

The Sea Peoples and their invasions into the Bronze age civilizations. While no-one is certain where they came from, Cyprus is one of the possibilities.
From http://www.tagmata.it/the_human_wave_that_toppled_the.htm

Transition
In the approximately 70 years following the bronze age collapse there was no real order any where, just groups of despots with militias attempting to take what ever they could, where ever it was. 70 years at the time would have been
about 2 new generation of people growing up in the chaos of transition from Bronze to Iron, in a world where ancient empire once controlled everything, now everything was uncontrolled. Then Greece and Phoenicia started to form as the first iron age empires, on the north-western and western outskirts of the former bronze age fertile crescent. The rest of history since the Greeks and Romans is known quite well, But have we learned lessons from the circumstances of their rise from the ashes of the previous empires?

Oil age collapse conditions

Icon of the 20th century, the Oil age.

Environmental problems/ agricultural degradation – mining and fracking
Hard rock mining and fracking, both are creating major environmental problems,  fracking threatens to poison the  water table important for agriculture and drinking water supplies. Fracking shows the true desperation to gain the last remaining combustible liquid hydrocarbons from the earth at the expense of any other current or future use of the soil. The oil age is ending. Remember the bronze age ended with an abundance of bronze, and there is still plentiful bronze now 3200 years later. As oil ends so does trade and large amounts of industrialized food production. In  sad irony oil is required for the industrial scale production of food, but destroying the land and water table required to grow the food to get the oil seems counter intuitive. Counter intuitive until you realize that corporatist thinking only focuses on profit and all other matter are externalized to the point of being non-existent. Incredibly blinkered thinking enshrined in corporate mentality.

Natural disasters -US Hurricanes, Earthquakes, oil void collapses?

The US has endured some significant hurricanes and ocean borne storms in the last 5 years in the region of the business banking and government hubs on the east coast of the USA. Not to forget deep water horizon a major oil exploration disaster poisoning fisheries and riparian zones in the south-east. Oil once removed from the ground leaves a void which i often filled with water to help float the oil to the surface. Water is unlike petroleum in that it does not create pressure by releasing gas in response to shock. A void filled with oil stabilized the void, how else could it have been in the ground so long? A void filled with water will not significantly out gas to pressurize the void. the water will instead seep into fractures and lubricate them (better than oil strangely) and exacerbate any earthquake conditions. eventually the void will collapse creating or amplifying an earthquake. How many of these void do you think there are? Are they a ticking time bomb ready to detonate at the end of the oil age?

Destabilizing technology – Internet, 3D printing, others?
The established order is under threat from many sources who seek to change the way things are done. Information can now be spread wide fast and low-cost. The 3D printer allows a thing to travel in information format and be replicated almost anywhere. A recent development in 3D printing is rifle parts, rifle are  in most places a  restricted (controlled) item. these controls are dissolving. A very strong parallel to iron make the sword common place in the  beginning of the iron age. Could the 3D printed rifle be the last gasp of the oil age? A large-scale war of ‘new sea people’ armed with plastic home printed guns?

Economic changes – Fiat currency under threat.
People are beginning to realize fiat currency is just a scam. The established order relies on this scam not being revealed as they are reliant on fiat currency to maintain the empire. Will a real economy emerge to challenge the old one? A great deal of the major parts of the economy are monopolies or are near monopolies, all primed for a single event  to collapse their networks.

A period of extended peace – The (ongoing) cold war
Did the cold war ever really finish or did the bad guy just get out sourced to N Korea? Starting in about 1946 we have about 67 years of relative peace in the world. WWI (1914 – 1918) and WW2 (1939-1945) were large wars designed to
accomplish two goals. reduce working class population and reinforce/reorganize states as the mechanisms of power with more ethnically homogenous populations. Even after WW2 had ended people were relocated all over Europe (and the world) based on ethnic lines.

WWI to reduce the population levels of working class people as they have become somewhat unnecessary due to industrialization. (37 million killed – soldiers and civilians ) (Spanish Flu adds another 20 – 50 million deaths)

WW2 to relocate the population of Europe and the middle east into artificial states and reinforce state power over the older established order of monarchs and emperors. (60 million killed –  soldiers and civilians )

1914- 1945 A period of 31 years where about 6% of the world’s population was killed,  the survivors became under the control of states (not ancestral monarchs) and the newly developed, city destroying, atomic bomb.

So in the last 67 years population have grown significantly, with no wars to cull out people, a population bubble is forming.

Complex extensive trade networks –  World trade and Globalization
Our economic networks are complex and fragile, more so than was ever possible in the bronze age, just in time supply and algorithmic trading being examples. Much of our world trade is based on oil, the transport of people, things and food; all reliant on oil. Oil as we know is running out. Trade networks face total collapse once oil becomes too expensive or unavailable.

Catastrophe design – Centralized power and control
Power centralized in a few places in the world, Washington DC (military),  City of London (financial), Vatican City (religious), Mecca (religious), Zürich (financial) Frankfurt (financial), Beijing (Military, Financial, Manufacturing). Four of these centers of power  are in Europe currently under its own economic and currency crisis. On the population map look at how power seems to be where population is small and concentrated. Three continents seem to have no power at all South America, Africa, Australia.

World population map. Stars indicate approximate location of world centers of power. L-R, Washington DC, City of London, Zürich – Switzerland, Frankfurt – Germany, Vatican City- Rome-Italy, Mecca Saudi Arabia, Beijing China . Notice how close the four European powers are together, centered around Zürich. Source image from http://goumbook.com/?attachment_id=14413

Social upheaval – The bank  bailouts and Austerity
People are being robbed by their governments and are understandably angry, but what form will their resistance take, and how long will they wait before demanding change that can’t be ignored. Could fiat currency be phased out without significant transition problems? Europe with four significant centers of world power  in the grip of austerity and a unified currency that is rapidly loosing confidence. Is another European war in the future likely? Could the center of world power move after a collapse of European power, to one of the other centers of world power, Washington, Beijing or Mecca? Will people accept being squeezed economically into an even lower standard of living? When will people reach their breaking point and simply rebel?

Transition – To what and how long will it take?
People want life to be different, what do they want and how long will it take to achieve amid the chaos of transition? Will people fall into the trap of simply recreating the same unstable, unfair system all over again? Will another’ sea people’ arise? what role will the internet play in the end of oil and the beginning of something new? Could the internet reduce the transition time? Could the internet allow for a completely new type of economy based on 3D printing and virtually free information?

Soil stove

If found this looking through old documents.

A stove made from a mix of sand, soil sand an dung slowly piled up in the corner of a house. I think anthill sand is coarse sand, soil being loamy soil, and dung having fibre binder like mud daub houses.

All natural products, no metal or money required. Get primative but use your head, this likely to  work only in hotter/ drier regions. Uses less fuel and produces less smoke.

3 week construction time.

A stove for free made from soil, sand and some cattle dung with straight stem branches for moulds.

Rocketstove: Making one from metal Olive oil container

For the last few months I have have comments turned off. There was a lot to say and I didn’t want distraction. But don’t think that meant I wasn’t listening to you. I pay attention to what people read and what search terms lead them here.

Rocket stoves have been a popular search item so its time to give you even more information.

I’m going to make one. I’m starting with a 13kg Olive oil can and I’ll have photos for all the relevant steps and a boil time test.

13 Kg olive oil can.  31 pounds in weight

The starting material a large Olive oil can. restaurants and other food businesses throw these away quite regularly, so that’s a good place to start looking if you don’t usually buy oil in this size container.

It’s convenient that there is a large round hole in the center of the top so I wont need to cut one there. Somewhere in the purple band is where I will cut a hole for the pipe which will be the elbow bend pipe.

There is a small handle on the front which i will probably keep as it will be useful for carrying the stove if I need to move it. i think the handle will be better at the front rather than the back as it will stop the ashes falling out for the bottom of the elbow.

 

The next step will be using sand paper to remove the paint from the can. If the paint is left on the can, it will burn and produce unpleasant and possibly toxic fumes.

 

<more to come>

Scrambag: folding pruning saw

Apart from the obvious intended use of pruning trees, the compact folding pruning saw allows you to collect small branches easily.

A saw is safer to use that a axe or heavy knife in cutting wood. One of the most common sources of dry wood in a forest is dead-fall.

Dead-fall is dead or broken branches fallen to the ground, and are often very dry and difficult to cut will axes as the will act like a spring when hit.

Sometimes dead-fall is a branch upside down and very dry, because of this it makes excellent fire wood or construction material.

The saw can elegantly cut of the exact pieces you want and even help you create items form the wood with precise cut lengths and flat ends of wood.

The saw is also very light compared to a small axe and very small, about the size of a small axe handle.

Folding pruning saw, compact and allows straight cuts in wood with little effort.

 

Price about $10 for average quality.

Available from hardware stores and gardening supply stores.

Fire: Swedish fire torch

This is a really neat technique of conserving wood and getting a fire going fast and making a stable cooking platform. You will need an axe and a saw to shape the wood block, but it looks worth it.

I just had another thought, all the things are familiar but arranged in a different way and its suddenly so much better, what a concept.

Scram Bag: Protective gloves

Your hands are very important so you must protect them from harm.

You may need to handle sharp or toxic materials so you should have some kind of protective gloves.

Rubber gloves

minimal protection form sharp objects, good protection from many toxic materials.

low durability

Garden gloves

medium protection from sharp objects, low protection from toxic materials.

medium durability

Leather ‘riggers’ gloves

good protection from sharp objects, medium protection from toxic materials.

high durability

When in an outdoors environment your hands a likely to get small cuts. While this may not sound significant small cuts can become infected easily and allow pathogens easy entry to the body. Small band aids may seem to be a solution but preventing the problem is better. band aids may not stick for very long and become in effective quickly.

Gloves a good idea.

Example scenarios for use:

removal of broken glass

moving a rotten log which nay have venomous insects under it.

handling a fish which has one or more spines.

gardening or handling potting mix.

 

Online resources

Journey to forever.

 

Sometimes when I’m doing research for a post I stumble onto something really good.

This is one of those occasions.

http://journeytoforever.org/index.html

Lots of resources for organic farming and off grid living.

Also a lot of similar things to what I discuss here.

Food collecting : Fish traps – Huge atrificial reef

When I started searching for information on fish traps I was originally thing of small traps that could be made from flexible branches or maybe stainless steel mesh.

Certainly a small fish trap would be good if you are traveling to the local river or lake.

Then I saw this:

Fish trap at Poppit sands, Wales UK. 250m long approx.

http://www.dailymail.co.uk/sciencetech/article-1162395/Google-Earth-reveals-fish-trap-rocks-1-000-years-ago-British-coast.html

I was really blown away by the simplicity, permanence, age and scale of this thing.

It’s estimated to be 1000 years old, but no longer able to be used as the boulders have sunken into the sand.

The latest Google earth pictures are taken at high tide and this structure can’t be seen because of that (the original pictures were taken in 2006 at low tide).

But feel fee to search for ‘Poppit sands’ on Google maps

Its worth pointing out that the trap is constructed close to a major estuary and estuaries attract fish.

This type of structure might not work as well if not placed near an estuary. Other important feature are the shallow sloping sandy bottom of the sea bed and the local abundance of rock.

The natural rock reefs attract fish as the tide is lower and a fish swim out of the estuary.

Fish traps were so efficient they were banned from fresh water by the Magna Carta (1215) because they could simply empty the entire river of fish, they were also a hazard to shipping.

Poppit sands fish trap near very large estuary.

So how does it work?

As the tide flows out the water level drops and some fish will be trapped in the artificially constricted reef. Some  modern observers believe that the fish were only netted at the opening apex of the trap.

I suspect that because there are two large opening in the sides of the trap (seeming to be too large for coincidence) the fish may have also been netted there.

Likely people were sent into the trap at low tide to scare the fish into one of the 3 openings, possibly using a moveable drag net in the process.

The other possible reasons for the gaps in the sides of the trap are:

To allow storm surges to move through he trap better and make it less likely to be destroyed in a storm.

To make the wall seem like less of a trap and to make the fish accustomed to swimming through the gap.

Prevent buildup of sand in the trap.

Damage from storm surges that was not intentional.

I have a feeling the construction of this structure would have been a community effort and likely the use of it would have been a community activity, certainly the number of fish caught could have easily fed a village.

If you consider at each of the three openings, two people holding the net and one collecting the fish in baskets, you are looking at a minimum of nine people not including the fish scaring and the transporting of the baskets to shore.

How to make one?

I’m really not sure and I’ll have to research this some more.

my speculation so far:

As even light rock weight about 2700 Kg per cubic meter, It’s not going to be easy to move these boulders very far easily, so a the local source of rock is key. Perhaps the local river system was used to transport the rock from upstream.

Of course moving things heavy on water is easier because of boast and rafts, and submerged rock looses some weight due to buoyancy. so perhaps the rocks were suspended in the water and moved with boats and rafts or possibly rolled into position under water using logs and smaller rocks as pivots and levers. I suspect the proximity of the river would have meant there would have been boats available. Nothing attracts boats like a river mouth or estuary.

Which part to build first?

Apex stones first? place furthermost stones in water first and work your way back to the shore?

Start at the shore and use the out going current to assist dragging the rest of the boulders into place?

Utilization of leeward scour?  A solid rock place on sand will create a scoured out depression in the turbulent current leeward (down current) from the rock, eventually the depression will become so large the rock will roll in this depression.

If the slope of the floor is correct and the rock if roundish, it will continue to roll until it falls into the depression created by another rock. If the walls closet to the shore were created first the rest of the rock might have just been dumped in the trap and the natural out going current could have done a lot of the work.

Cost: a lot of time, rocks and cleverness and probably boats. Having people scratch their heads a thousand years later, priceless…