Coping with the flood:floating gardens

 Imagine that you dwelt in a land prone to flooding, or that there were land pressures that meant that you had no access to agricultural land, but you needed it. The solution is to grow on floating rafts made of vegetation. This technology is very ancient. At In Le Lake in Myanmar the locals dwell on the shore, but makes rafts out of plentiful weeds to which they sail out to cultivate their crops. As the lake rises when it rains, the gardens rise with the water, and so never flood. The simple houses can be flooded, but the food supply remains safe. The advantage is that as the lake is an enclosed space the rafts never drift far, and they can be tethered to long ropes and given markers so that families know whose raft is whose. This technique of tethering is used in Mexico. 

Bangla Desh, a flood-prone land, is taking an interest. Many peasants have their land flooded and their crop destroyed by massive floods surging down from the deforested Himalayas, but now peasants in some areas are being encouraged to design floating, flood proof gardens. These are particularly suitable for areas such as lake sides where currents are not likely to sweep away the garden. Bangla Deshis are encouraged to keep fish in wire cages, so that if their fish farms flood their stock does not wash away. 

The charity,Practical Action, advocates intermediate technology, which is half way between low technology, which impoverished communities possess and which keeps the poor impoverished, and high technology, which cannot easily be installed or maintained in many communities. Intermediate technology uses local knowledge, skills, and resources to achieve its goals, and it empowers communities and individuals, particularly marginal or oppressed groups, rather than large companies. The floating gardens of Bangla Desh have been advocated by Practical Action and have particularly empowered women, giving them the ability to  own some productive land. 

In fact, floating gardens have a long history. They are natural occurrences which arise when vegetation mats at lake sides break away from the shore. In Britain they probably occurred when we had more lakes, and when lake shores were not as tidy as they are now. In age when many Britons dwelt in Crannogs, villages built on piles in the lake, floating islands were probably common, though there is no evidence of vegetable growing on them, but such evidence would soon have disappeared,so  absence of evidence is not evidence of absence. In Lake Titicaca Amerindians have long dwelt on floating islands, which were places where they felt safe from raiders. 

The technique is remarkably similar across the world. A raft of vegetation is detached from the shore and tethered to where the growers want it.It is generally a metre by eight metres long and eventually up to a metre deep.  In Myanmar and Bangla Desh the raft is composed of a mat of the plentiful weed water hyacinth. On top of this there is a network of  bamboo poles to form a lattice which will be the basis of the next layer of hyacinth. In other parts of the world reeds and sedge are used instead of hyacinth, and these can be used in Myanmar and Bangla Desh if they are available. When this layer has settled the bamboo is withdrawn for re-use. Further layers are piled on. After this mud, compost, soil and dung are laid atop the mat. the presence of soil means that the mat needs a metre or so of thickness to give it enough flotation to prevent it from sinking. Pits can be dug in the soil to allow for deep rooted plants. 

The great advantage is that watering is never needed. The mat starts moist and has its roots in water. Furthermore, when a mat is worn out, as it is in Winter, it is composted and spread as fertiliizer on the year's vegetation mat. Moreover, the benefits of the mats extend to aquaculture, for fish in abundance are found beneath them. Fish like to hide from predatory birds, such as herons, in reeds, and a mat makes a safe environment. The locals can then fish around and through the mats.

This brings me to  a technique, the mats often contain pits, which are dug into the weed and filled with compost. These are suitable for plants with deeper roots. In Myanmar and Bangladesh ground nuts, onions, gourds, okra and leafy vegetables are grown.

You can see a pile building in he picture. Built into the shallow lake it forms a place where gardeners can work away from their homes and be have a place to sleep and eat in some comfort, especially when it rains. Note that the islands in the picture are pinned to the lake bed by bamboo poles and that there is a small fruit tree near the edge. There is no space or time in temporary mats for large trees. 

The Mexican Indians were experts at floating gardens, though theirs were semi-fixed. Lake Texcoco near the Aztec capital used this technique. An area of floating vegetation was fixed to the lake bed by willows planted at each corner. Then it was sometimes surrounded by dykes made by mud. Between the garden and the dyke a waterway wide enough for canoe was establshed. This meant that a network of semi-floating gardens was able to be created to feed the Aztec capital.

Sometimes this technique involved building out from the shore in what is something between an island and marshland. The technique here was to fix poles into the area to be covered and then wall them with wattle mats right down to the lake bed. This technique works on shallow lakes. Then the enclosed area was filled with mud, dung and compost. The advantage of the chinampa technique is that it is easier to grow fruit trees and deep rooted plants, such as maize on it than it is on fully floating gardens, but the disadvantage is that it is less attractive to fish than a fully floating garden is.

I have a hunch that the chinampa technique might have been in use in other parts of the world in the distant past. We know that the inhabitants of parts of Britain were Crannog dwellers. A crannog [Irish Cranneog] was a village built on stilts [piles in a lake.] We know that there were still Crannogs in the time of Queen Ethelfleadda in the late first millenium, as this no-nonsense daughter of  King Alfred had a Welsh king's crannog-palace burned down because he had murdered a bishop whom she was protecting. England has produced some mighty tough women. These lake dwellers were safer from raiders than land dwellers were [though not from Ethelfeadda's army of well-armed thanes and warriors], but they were further from their gardens than the land dwellers. Having a floating garden on one of the reed islands that floated on their lake would have made great sense. Such gardens could have been built around the sides of islands  in the lake and  been semi-permanent. 

As the world warms and becomes more likely to flood we will need all the gardening techniques we can muster. Floating gardens are certainly an addition to the gardener's  arsenal. We have to get away from the snooty western mindset that devalues the traditional knowledge of ancient cultures. Ancient and non-European cultures often have much to teach us about gardening techniques and how to live in harmony with the environment. Open minds, skilled hands and non-materialistic hearts, that is the way.