EWB Challenge Floating Land Project

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2 Executive Summary The floating docks we have designed, through the Engineers Without Borders challenge, can dramatically improve the health and lifestyle of Cambodians living on the Tonle Sap river. These docks are designed so the floating houses can be moored, giving stability to the houses during storms. They also help families to support themselves financially through the growing of vegetables on the docks. Permanent mooring allows a sense of community to build among the locals because they have fixed neighbours. Our project's goal is to find a way to integrate our floating vegetable gardens into Cambodian society so it is beneficial and easily accepted by the villagers. Our suggested garden design provides additional varieties of food to the staple diet, thus improving health and general well-being of citizens. Currently, people in floating houses own no land and therefore struggle to form a livelihood. Most families rely on fishing but the fish supply is diminishing. The docks are a simple design, using accessible materials to make it easy for local Cambodians to learn how to make and maintain them. Each floating dock is a rectangular structure consisting of 6 separate gardens, of approximately 3m2 each, divided by walkways. For safety in extreme weather, each dock is anchored into position. The docks can be connected to similar docks to form a village, if desired. The materials used to make the docks are all able to survive exposure to water. For buoyancy, 220L oil drums are roped into a frame made of plastic posts. Vine is suggested as a cheap alternative to rope but it is not as strong or durable. Plastic garden liner or tarpaulin protects the drums and keeps soil from escaping, while wood and bamboo are used to create walkways between the gardens. Tyres along the sides assist with safe mooring. These docks cost between $ and $ each, including labour. The oil drums can sustain approximately 112kg each. Unfortunately, soil weighs between 1200kg and 1600kg per cubic metre. We have therefore designed the structure to have narrow but deep strips of garden between drums to minimise the amount of soil 2

3 needed. This allows the structure to stay afloat, taking into account that the docks must also be able to support the weight of a number of people. Research has been done into plants that can grow in the Cambodian climate with root systems that would work in our design. By planting a variety of these in their correct seasons, vegetables can be harvested throughout the year. All produce that is not required for immediate consumption by the family can be sold or traded. Each dock can produce 675kg of vegetables a year, which will feed about 30 people, thus providing enough for all the people living on the dock. The soil quality in Cambodia is poor but, as the majority of the waste produced by Cambodians is organic, assigning a separate vegetable patch for composting this waste would lessen waste disposal problems and increase soil quality. The project could be implemented in whole villages because there is a large expanse of water for these environmentally-friendly docks to float on. The materials are found locally, so the making of the docks engages local businesses as well as employing locals as labourers. The design is culturally appropriate because Cambodians are typically farmers and fishers, and their houses already float. Throughout the world floating gardens are rare and none of the designs we found elsewhere solved the problems of the Khmer people of Cambodia. Our design has successfully found a way to enable locals who live in the floating villages of the Tonle Sap to own land and supply their families with healthy food, as well as providing safety and stability in extreme weather conditions. This project has increased our knowledge of engineering concepts and our teamwork skills. It has showed us how our skills can make a difference in the world and has taught us to overcome problems and find alternative solutions. 3

4 Reflection Our group learned many skills, through this project. These included learning how to work as a team and communicate effectively, as well as time management and organisational skills. We now understand the importance of studying the culture and the surroundings that the project is being designed for, and realise that the work we do, as engineers, can have a huge impact on societies. It is exciting to know that, even as first years, we can make a difference in the world. Our goal, through this challenge, was to create something that can enable people that are too poor to survive without aid, to gain the knowledge, skills and items needed to help themselves out of poverty. When we began this project, through Engineers Without Borders, none of our group knew each other. From the start we had to work as a team to brainstorm and plan our design. This forced us to get to know each other and learn each person's strengths and weaknesses so we could adapt the ideas and the design process to create a well researched, high quality project. We set ourselves a time line so all the necessary work would be achieved in our time limit. Our design process started by researching Cambodian society and the needs of the people in the Tonle Sap area. This was because our main goal was to design something that would improve the lifestyle of the locals, and meet their needs. After discovering these needs, we brainstormed to find solutions to the problems. The idea of creating floating islands seemed to have the potential to help solve multiple problems that the Khmer people suffer. After much discussion, research and design, we ended up with our final product. We feel this project was a success because the design can dramatically improve the circumstances of the villagers, and our group learned many new skills in the process. Our group learned the importance of communication when doing group projects. We met together regularly for meetings, and kept in contact via and phone. We worked as a team to get ideas together and to help one another gain information on the topic. This group work helped us to appreciate the need for effective communication, when working as a team, in order to make it easier to tie all aspects together. As well as giving us an appreciation of group dynamics, this exercise taught us organisation and time management skills. Taking turns as chair for the group meetings helped us to 4

5 develop leadership skills as well as helping us to learn how people work together in a group. This design exercise, not only taught us about Cambodian culture, it showed our group that we can make a difference in the world. Through the design process, we gained an understanding of the need for our project to fit the culture, both in meeting the needs of the people and environment, and in being culturally appropriate so that the people do not lose their traditions. We also discovered the importance of enabling locals to contribute to the making of the docks, so they can take up the project as their own initiative and improve on it. This gives them a chance to be independent, rather than relying on engineers. Our group learned much about community development and how to create a sustainable product. We increased our knowledge of what an engineer's job may involve, and the necessary skills needed in order to be effective. We also learned many new engineering concepts through this process. Sometimes we ran into difficulties but we learned how to overcome these problems and find alternative solutions. This ability to overcome problems will help us throughout our careers. This project has been an excellent chance for us, as students, to use our skills to help others, and to learn more about what is required as an engineer, in the workplace. The skills we have learned through this engineering challenge will be of great value to us in the future. 5

6 Table of Contents Executive Summary...2 Reflection Introduction Cambodian Society Purpose of Chapter Cambodian Culture Design Cultural Aspects Health & Safety Available Resources Practicalities Educating Locals About the Docks Cambodian Communications Main Industries and Typical Work Practices Optional Teaching Methods Community Meetings Teaching in Schools Publicity Recommendations Chapter Overview Cambodian Environment History Climate Dry Season Wet Season Typhoons Geography Mekong River Tonle Sap Lake Wildlife and Ecology Fauna

7 3.5 Effect of our Project on Environment Negatives Positives Chapter Overview Soil and Produce Introduction Soil Soil weight Improving soil quality Fertiliser Composting Bone meal Produce Growing Restrictions Tropical Produce Seasonal Growth Amount Produced Chapter Overview Flotation Scope Constraints Potential problems Plastic Drums (220L) Dimensions Load Handling Maintenance Summary Empty Containers Enclosed in Netting Existing Examples Netting Waste bottles Load handling Maintenance

8 5.3.6 Summary Chapter Overview Anchorage Scope Problem Constraints Options Dead weight moorings Advantages Disadvantages Summary Pyramid Anchor Advantages Disadvantages Summary Danforth Anchor Advantages Disadvantages Summary Scope of Anchor System Multi-point Moorings Recommendations Structure and Materials Introduction Structure Dock for housing Materials Final Dimensions Cost Material Costs Labour Costs Currency Rates Funding the Project

9 7.6.1 Organisations Distribution Chapter Overview Conclusions References Glossary of Terms

10 1 Introduction The purpose of this report is to provide Engineers Without Borders with a feasible way for Cambodians who live in floating houses on the Tonle Sap to supply their families with healthy food by creating floating vegetable gardens. It also aims to provide a dock for floating houses to moor to so as to stabilise the houses, which gives some protection from the violent storms, and builds a sense of community amongst the refugees and marginalised Cambodians. Our solution is explained in detail on the following pages. Different approaches have been looked at and our reasons for choosing the final design over the alternatives have been explained. Our priorities have been to achieve the most affordable, effective, safe and sustainable option. By designing our project to fit the community in the Tonle Sap we hope Cambodians will take this project on as their own. The floating docks have been designed so local Cambodians can be taught how to make and maintain these floating gardens themselves, giving them an opportunity to help themselves get out of poverty. This report explains the value, both short and long term, of having these floating docks that can grow vegetables. This report aims to predict the economic, social, environmental, cultural and political implications our project will have on Khmer society as accurately as possible with the resources available to us. This is based on our research through books, websites, interviews and other sources. Few places around the world have floating land in place. None of the techniques we found elsewhere fitted culturally or economically into Khmer society so our design is based on similar projects but is necessary because no other project could work in place of ours. The aim of this report is to get aid organisations who already work in the Tonle Sap area to read it and look at the possibility of funding the project so that the project can be put into action. 10

11 2 Cambodian Society 2.1 Purpose of Chapter The purpose of this chapter is to determine the best way to integrate our floating vegetable gardens into Cambodian society so it is most beneficial and easily accepted by the villagers. Due to lack of education and financial struggles, many families do not have the knowledge or the means to keep their families healthy. They lack food and an income. Most rely on fishing for their main income generator as well as food for the family, but the supplies of fish are running out (Lim Song 2005). The poorest people in the Tonle Sap area live in floating houses (EWB 2009). Many are refugees from Vietnam and people rejected from Cambodia's wealthier society (Dhammataree 2007). Our aim is to build a dock for houses to be permanently moored to that provides an atmosphere of community where people can get to know one another and look out for each other. The dock will be designed to grow vegetables on, so the families can satisfy some of their dietary needs and perhaps even produce enough to sell or trade small amounts. Building floating docks that houses can be attached to gives the houses added stability during the violent storms that frequent the area of the Tonle Sap. By training the people to make their own on-water farms we give them the chance to have pride in their home and give them a hope for a brighter future. To work out the best way to create our project so it is the most accepted and beneficial design for the people of the Tonle Sap, we must know something about the culture they live in. 2.2 Cambodian Culture This report is aimed at improving the quality of living for the people who live on houseboats in the Tonle Sap area in Cambodia. The reason for choosing this is because 37% of the people who live on and around the Tonle Sap river system live below the poverty line (EWB 2009). Most of these people live in floating villages (EWB 11

12 2009). They own no land and struggle to form a livelihood or even to obtain enough food to feed their families. Much of Khmer culture is based around status, including where a person sleeps in the house and how much a person is allowed to eat (Dittmeier 2008). Men have a higher status than women, who themselves have a higher status than children. The average size of a Cambodian family is 5.1 people (Cambodian Herald 2008, p.2). The whole family sleeps on one wooden platform with parents at the head and the youngest children at the foot. Most houses are between 3m2 and 7m2 and contain one or two rooms (EWB 2009). Cambodia became independent from France in 1953 and has both a king and a prime minister. The government is a multi-party democracy (Central Intelligence Agency 2009). During the Pol Pot regime and thirty years of civil war, many Khmer fled to the West as refugees. This political turmoil has caused the majority of remaining Cambodians to fear change in case it creates instability once more. Most do not wish to stand out from the crowd because of this fear. There is also distrust due to the different races and religions of villagers on the lake. Khmer have their own style of Buddhism which mixes Theravada Buddhism, Hinduism, animism and ancestor-spirit worship. The Tonle Sap river system, however, is also home to many Vietnamese migrants and Cham people (Dhammataree 2007). The Cham people are mostly Muslim (Tsui 2007, p. 96). This means that despite 95% of the 14.2 million people in Cambodia (Central Intelligence Agency 2009) speaking the same language, Khmer, communal activities are unlikely to run smoothly due to differences in culture and beliefs. In rural areas, the poorest half of the population own around 10% of the land. Some areas are reserved for traditional fishing for families, but not for large-scale produce. The Ministry of Agriculture, Forestry and Fisheries gives land ownership rights to people (Fisheries Administration 2007). Despite this, laws on land use and distribution are not followed closely. 12

13 2.3 Design Cultural Aspects Cambodian society places a strong emphasis on traditional practices. Because of this and the unrest caused by thirty years of civil war, people are suspicious of change (Asker 2004). As there is low tolerance of the new, we must implement our project by showing the locals that there is great benefit but little change from their original practices. Each dock could be designed as a community farm looked after by the locals working together, or it could be divided into small connected blocks with one vegetable garden per house. By looking at the way people relate to one another an option can be chosen that will work in the chosen community. TABLE 2.1: Comparing communal farms and individual gardens (author created) COMMUNAL FARMS INDIVIDUAL VEGETABLE PATCHES POSITIVES NEGATIVES POSITIVES NEGATIVES - Builds - People will gain - Builds a sense of - Could cause interdependence from being selfish ownership and jealousy. and community. and lazy. responsibility. - Less overall - People can use - Arguments - Families can choose monetary profit. their strengths and between practices, how they use the - Hard to choose count on others to race and religion are space and what to who gets to own compensate for likely to occur. grow. land. their weaknesses. - Difficult to - Less change from - Could cause rivalry distribute fairly. the way local gardens between neighbours. are run presently. Looking at the pros and cons of both options our group have decided to design small vegetable patches for each family, joined together to form a larger dock. This has less chance of failing because of being similar to original practices and avoiding problems with harvest distribution. 13

14 2.3.2 Health & Safety It is necessary to decide whether these garden blocks should all be joined permanently or whether they should be able to move and reconnect to other docks. TABLE 2.2: Small connectable docks versus a permanent dock (author created) POSITIVES OF SMALL JOINED POSITIVES OF A SINGLE FIXED DOCKS DOCK -Easier to move. -Easier to stabilise the dock. -More likely to fit in convenient places. -Less likely to be destroyed by storms. -Easier to fix faults like leaking floatation -Less likely that the garden will sink if devices. something goes wrong. -Able to escape noisy neighbours. -Greater sense of community formed -Easier to increase size as wealth increases. because of having permanent neighbours. Based on the table above, a single, permanent dock was chosen because we felt that safety was a higher priority than convenience. For purposes of floating the dock it is important to know how many people are likely to be on a floating dock at a time. The average family size in Cambodia is 5.1 people (Cambodian Herald 2008). The dock should at least be able to hold the weight of all family members from each houseboat, and not tip with the movement of people walking around the dock. Having the houses moored to the dock will help to keep it steady and afloat but the weight of people and soil is a large amount. Overcoming this problem will be dealt with in following chapters. Some safety considerations that need to be looked at are how to connect the houses securely to the docks, what the effect of a leaking barrel would have on the dock, and how to fix any problems, including those created by storms and fires, safely. Tyres have been placed in regular intervals along the sides of the docks so that houses can moor without being damaged. There are mooring poles by these tyres to secure the houses firmly, using rope. The dock has been designed large enough and buoyant enough that a hole in one of the barrels will not cause it to sink. By putting the barrels with the opening upwards, it is easy to examine the damage and pump water out of a 14

15 barrel if water gets in. The bamboo walkways could be lifted to get at the barrels because they are directly over them. The size of the dock and the easy accessibility also means it can be fixed without too much difficulty if damaged by storms, fires or other calamities Available Resources Most of the soil around the Tonle Sap is poor quality, lacking the necessary nutrients needed to grow productive crops (EWB 2009). This means to get decent soil we cannot take it from surrounding areas. Many of the farmers have taken up using pesticides and fertilizers (EWB 2009). These create more pollution in the Tonle Sap river system. Because 66% of the weight of overall waste products produced by Cambodian society is organic, with only 5% being recyclable materials (Parizeaua 2005), it would be sensible to incorporate a technique for dealing with compost into our dock. This would help with the waste disposal problem in the Tonle Sap as well as enriching the soil so that the gardens can be more productive. Composting techniques are covered in chapter 4. Plastic bottles are frequently used for drinks. These bottles are often refilled with oil or petrol to be resold to neighbours as a small business. These bottles could be resealed after use, cleaned and tied together to form a flotation device. Double L-Ring drums are also available reasonably cheaply for using as floatation devices (EWB 2009). Plastic bags are commonly used in Cambodia. It may be possible to combine these with plastic bottles, melting them down and shaping them into large platforms that reusable bottles could float under to keep the platform buoyant. These would not be easy for locals to make though. As can be seen, the materials are available but the feasibility of these ideas will be discussed in a later chapter. Boats and housing are generally made out of wood from local forests. Wood is also used as fuel for the fire. The three types of boats used on the lake are houseboats (EWB 2009), temporary houses built from light materials so they can be moved when the water levels rise (Dhammataree 2007), and houses built on stilts that are about 10m high so that they stay out of the water in the wet season (Dhammataree 2007). Farmers often 15

16 live near the edge of the forest. Most of the villagers in the Tonle Sap Basin do not expect to ever be able to own their own land Practicalities Maximising the size of the dock will increase the amount of land owned by each family and thus increase the productivity and benefit of the farm. This is countered, however, by the inconvenience of each dock having less manoeuvrability and costing more. To come to a compromise we looked at the smallest amount of space needed for the garden to be beneficial, and how few dwellings can be docked together and still have a stable structure and a neighbouring community (see later chapters for reasons). We decided that 3m2 would be enough for each household. A sensible structure, therefore, would be around 6 by 9m with 6 houses moored to each dock. The docks could be connected to form a village if desired. The image below is an example of our project (created in Photoshop) to give a basic idea of how the final product will look. Figure 2.1 Final Structure (created in Photoshop) 16

17 2.4 Educating Locals About the Docks Cambodian Communications Telephones are still uncommon in Cambodia. In 2004, research showed that approximately 3.5% of the population had access to a phone on a regular basis. They estimated that 8% would have access by 2008 (Dittmeier 2008). Because of the lack of telecommunications and infrastructure such as roads, news travels slowly. This mostly affects the people living rurally, such as those in the Tonle Sap area. The lack of roads and communication limits job opportunities and chances for farmers to sell their produce. Cambodian culture is one in which people must save face. To not know the answer to a question is of great embarrassment to a Cambodian. A person must ask anyone they meet where they are going and tell people where they themselves are going and when they plan to return, so the opportunity does not arise for the other person to lose face if someone asks where that person went. This also provides a safety net where telecommunication is lacking (Dittmeier 2008). These communication practices have implications for teaching Cambodians about the new docks Main Industries and Typical Work Practices 25% of the Tonle Sap area is used for farming. These farmers generally fish in the rice farms or nearby streams to supplement their income. 70% of the protein in an average Cambodian's diet comes from fish. With 200 different species of fish in the waters of the Tonle Sap Basin, it is one of the richest fisheries in the world. However, this supply of fish is diminishing over time. This means fishermen are keeping the smaller fish which are now not living to spawn offspring (Lim Song 2005). Any produce from the garden docks that is not needed to sustain the family can be sold or traded without a permit, as there are no health codes, food restrictions or regulations (Dittmeier 2008). By providing another way to create income, our project will hopefully provide some relief to the fishery. The most farmed crop in Cambodia is rice, which is their staple food. Other crops grown include corn, beans, cucumber and various spices. These tend to take three to six months 17

18 from sowing to harvest time. Many of the local families own livestock but these are expensive to look after and often get sick. It is rare to find large scale rearing of livestock. Cambodians are used to long hours of hard physical labour. Waking up after sunrise is a sign of laziness (Dittmeier 2008). A job is often not done efficiently by Australian standards though, because Khmer culture holds proper behaviour and good relationships with those in power above getting the work done (Dittmeier 2008). Only those of high ranking may make decisions. Those of lesser status are wise to agree even if they find fault with the chosen outcome (Dittmeier 2008). It is important to take account of such cultural norms when seeking to encourage new practices Optional Teaching Methods In order to train the locals in how to build and run these garden docks efficiently it is important to discover the teaching methods and structures already in place in the Tonle Sap. Teaching in ways that are traditional to the Khmer people helps participants to cope better with taking risks (Asker 2004, p39) Community Meetings In Khmer society it is expected that an expert such as elders, monks and Khmer traditional singers will teach the people. This means it would be wise to train people who have a high profile in society to teach their own community. Unfortunately people live busy lives and are unlikely to fit training or information sessions into their schedule. This means community meetings are unlikely to be well attended Teaching in Schools The floating land project could be taught in schools. The project would need to be proven to fit the Cambodian main education goals for it to be considered as part of the curriculum (Asker 2004). This would be a long and laborious process. On top of this problem, children have little chance to impact the community. They have the lowest status and are expected not to question their elders. This means that putting their training into practice would be difficult before the children grow into leaders in society. 18

19 Publicity Many in rural Cambodian society cannot read or write so creating an instruction book or manual would not help people. Many do listen to radio shows though. By explaining the idea on popular radio shows, people might listen and take an interest. Creating a video, documentary or another form of entertainment with locals acting in it could be used to educate people while entertaining them. All people need time to relax, so if we could teach in a way that entertained, people might make the effort to listen Recommendations We suggest that the best option for teaching locals of the benefits of the docks and how to make and maintain them is to train locals to teach. Training people who have a high status in Khmer society to teach the villagers means that the villagers will be taught in ways appropriate to the culture and they will be taught by people they trust and respect. By paying locals to teach, we are supplying them with jobs and a chance to take this project on as their own. They might wish to teach the locals via radio shows or other forms of entertainment or they may have other ways that would suit their personal style or the culture better. 2.5 Chapter Overview By researching Cambodian culture our group has a better idea of what design is appropriate for the area and how best to integrate our floating vegetable gardens into Cambodian society so it is most beneficial and easily accepted by the villagers. In order to help reduce the poverty of those who live in floating villages on the Tonle Sap, our group has designed a floating dock that is divided into individual gardens for families to grow food on. This will give the families dignity and hope as well as helping to feed the family and expand their income. It should also help with endurance and stability of the houses during storms and create an atmosphere where community can thrive. The project has been designed with a focus on low cost and safety. We hope that elders, monks and others in positions of power in the villages will see the benefit of having these docks and choose to take this project on, training others in the building and maintenance of them. 19

20 3 Cambodian Environment 3.1 History For thousands of years, the people of Cambodia and those who populate the Lower Mekong Basin have fashioned a life amid a landscape unlike any other found on Earth. From adapting to the fluctuations of the water level in the Tonle Sap Lake, to utilising the fertile lands of the floodplain, Cambodia s populace had thrived for many centuries. Likewise, the environment with which they lived remained relatively unharmed due to their care for the rich and diverse flora and fauna. However, as the rest of the world became more interested in this unique country, outside influences began to change the lives of the Cambodian people. Organic materials were replaced with synthetic products and without sufficient knowledge of the effects that dumping these products can have on the environment, their surroundings grew more and more polluted. The world evolved at such a rapid rate, Cambodia was unable to remain up-to-date and as a result, much of its people are facing conditions that classify them as living below the poverty line. We feel that by developing a sustainable farming system atop the Tonle Sap Lake, this will provide the opportunity for additional varieties of food and consequently, an improvement to the public s health and general well-being. With a farming system in place and the education to use it effectively, Cambodian people will have the ability to utilise the environment to a much higher standard, thus improving their quality of life. By building these floating structures from pollutants found in the vicinity of the Tonle Sap, e.g. empty plastic barrels, the lake may be beautified in the process. Creating another food source also eases the pressure on the ecology of the Tonle Sap, as the demand for over-fishing in the area diminishes. 20

21 3.2 Climate Due to Cambodia s close proximity to the equator (between 10 and 14 north of the equator) it, much like the rest of south-east Asia, experiences warm to hot temperatures all year round. To give an idea of what it would be like to live in Cambodia, we will compare Cambodia to Adelaide. Generally, Cambodia is considerably warmer than Adelaide (refer Figure 3.1 and Figure 3.2) and has a much higher average annual precipitation (refer Figure 3.3). Figure 3.1 Daily Mean Minimum Temperature adapted from and 21

22 Figure 3.2 Daily Mean Maximum Temperature adapted from and Figure 3.3 Mean Monthly Rainfall adapted from and Similar to many neighbouring countries, Cambodia has only two individual seasons: a wet season and a dry season. Monsoonal airflows that change direction seasonally govern the beginning of the wet and dry seasons. 22

23 3.2.1 Dry Season Brought about by the monsoonal winds from the north-east, which begin in October and last through to May of the following year, the hot inland breezes ensure the average daily maximum temperature remains above the 30 C mark throughout (refer Figure 3.2). The dry season brings Cambodia very small amounts of rain for the duration; the driest month of the year is January, averaging less than 1 millimetre of precipitation over the five-year 1996 to 2001 period (refer Figure 3.3). As well as having the driest months, Cambodia s dry season has both the hottest and coldest annual average temperatures, April being the hottest month of the year with an average daily maximum temperature of 35.5 C and November being their coldest month with an average daily maximum temperature of 30.6 C. When compared with the data of the same months in Adelaide, they are 13.4 C and 7.2 C higher respectively (refer Figure 3.1 and Figure 3.2) Wet Season As the dry monsoonal winds from the north-east subside and the moisture-rich winds from the south-west begin to sweep across Cambodia from the Gulf of Thailand, the wet season begins to have an effect. The winds during the wet season bring large amounts of rain to the region. The wet season endures from the middle of May to approximately October and during this time, Siem Reap, a town on the Tonle Sap, can expect somewhere in the range of 1000 to 1500 millimetres of precipitation; the highlands of Cambodia averages even more. This figure is four to five times greater than the average annual rainfall in Adelaide of the same months (refer to Figure 3.3). Additional rain, however, does not decrease the temperature, with mean daily maximum temperatures remaining in the mid to low 30 C range. The warm weather combined with the increased moisture creates high humidity, often exceeding 90% and rarely falling below 60% (World Facts Index 2008), and this can result in evenings being relatively uncomfortable for the lake s residents. 23

24 3.2.3 Typhoons A typhoon (known as a tropical cyclone in the southern hemisphere) is an important natural event that acts as a regulator of global heat, by travelling toward the poles, distributing energy as it goes. Without typhoons, countries close to the equator would be far hotter and those further from the equator would be significantly colder. Typhoons form over deep, warm waters, generally warmer than 26 C. This difference between the temperature of the water and the atmospheric temperature causes unstable conditions in the troposphere above, resulting in storms. When the air above the water is cool, as the warm air rises, it rapidly decreases in temperature. The gusts related to a typhoon can be in excess of 300km/hr with sustained winds of over 250km/hr. Coupled with torrential rain and electrical storms, typhoons have the ability of leaving catastrophe in their wake. As damaging as the winds and rain may be, the deadliest and most feared element of this natural disaster is the extremely high seas which have been known to wash many kilometres inland, leaving coastal communities completely flooded. Typhoons very rarely form within 5 of the equator as the deflection of any moving object air included due to the rotation of Earth, increases as the distance from the equator increases (NASA Jet Propulsion Laboratory 2003). Cambodia, however, is between 10 and 14 north of the equator. Compared to Cambodia s surrounding countries, particularly Vietnam, it is relatively sheltered from typhoons; however they have occurred and affected Cambodian communities in years past. As such, it is necessary to take certain precautions to ensure that the floating land structures we are proposing will be able to withstand the high winds and remain afloat once saturated by the rain and turbulent waters of the Tonle Sap in the event of a powerful storm. 3.3 Geography Covering a total land area of 181,040 square kilometres, Cambodia is the 63rd largest country in the world. Cambodia is a country located in south-east Asia, sharing its 24

25 border with Thailand, Laos, Vietnam and the Gulf of Thailand to the south. Gifted with an abundance of flora and fauna, the expansive and relatively untouched Cambodian environment is steeped with history and culture, drawing thousands of tourists every year. From the lofty Cardamom Mountains and Dangrek Mountains located in the southwest and north of the country respectively, to the sprawling expanses of the Tonle Sap Basin-Mekong Lowlands, the geographical features are impressive and varied (World Facts Index 2008) Mekong River Winding its way through five different countries before entering Cambodia, the Mekong River is 4909km in length (Knowledgerush.com 2003), making it the world s twelfth longest river (University of Kyoto 2006). As well as being a significant river on a global scale, its importance to Cambodia and the mechanics of the Tonle Sap Basin are significant. Along the entirety of the river, more than 90 million people depend on it for their livelihoods. Starting in northern China, the Mekong River flows southward towards Cambodia until it reaches the Mekong delta in Phnom Penh. The flow rate of the river during the dry season allows for the water to continue south-east through Vietnam and escape into the South China Sea. However, as the monsoonal winds bring excessive rain to south-east Asia, the Mekong river swells and flow rate increases from approximately 2000m3/s in the dry season to as much as 50,000m3/s in the wet season (GIS Development 2004). The previously manageable release of floodwater reaches a level far greater than the system can withstand, and to accommodate and minimise flooding in Cambodia, the river system reverses its flow. All of the excess run-off is carried up the Tonle Sap River and into the Tonle Sap Lake, having a dramatic effect on the geography of the area. Study shows that each year approximately 45 billion m3 of water travels into the Tonle Sap Lake via the Tonle Sap River during this reversal period (Infrastructure Development Institute of Japan, 2002). 25

26 3.3.2 Tonle Sap Lake As the largest body of freshwater in south-east Asia, Lake Tonle Sap naturally has a huge impact on the lifestyles of Cambodians. Its importance extends far beyond being a unique geographical landmark. The 340,000 people living on the lake (EWB 2009) depend on it for their livelihoods, to provide for their families and to boost the overall economy of Cambodia. This dependence is so great that the Tonle Sap Lake has often been referred to as The Beating Heart of Cambodia. In the midst of the dry season (refer to 3.1.1), the Tonle Sap covers a total land area of 2,500km2 to 3,000km2 with a depth of no more than about 1m. It is during these months that the fertile floodplain is dry and landowners are able to capitalise by planting crops, both for personal consumption and for trade. The monsoonal winds swing around to the south-west bringing the wet season and enormous amounts of rain teems down upon Cambodia, causing the Mekong River to reverse its flow (refer to 3.2.1). The millions of cubic litres of water that now flow into the Tonle Sap cause the lake to swell approximately fivefold. Now covering 10,000km2 to 16,000km2 and rising to up to 10m deep in certain places, the areas where farming was happening during the drier months are now under water (refer Figure 3.4). As a result, the fishing industry is put under immense pressure and the lake is over-fished. Figure 3.4 Floodplain of the Tonle Sap 26

27 3.4 Wildlife and Ecology Fauna The cyclic rise and fall of the Tonle Sap Lake promotes an abundance of animal life, none more so than a plethora of fish species which use the lake as an annual breeding ground. 3 million people living on the lake take full advantage of this, fishing approximately 41,740 tons/year (University of Kyoto 2006). Although this accounts for a large portion of Cambodia s fishing industry and feeds much of the country s population, overfishing places strain on the ecology of the area. Our floating land scheme does not aim to eliminate the need for fishing in the Tonle Sap, but rather complements it. By offering Cambodians an additional food source, the pressure felt by the environment will be reduced and fish numbers can continue to prosper. Additional to the decrease in fish consumption by the people of the Tonle Sap, Cambodia s economy will be boosted with the extra reserves of fish allocated for trade and export. 3.5 Effect of our Project on Environment Negatives Although this design solves many problems in Cambodia, it is not without a slight environmental drawback. Aquatic plant life directly beneath the floating pontoon will suffer if the structure is moored in the same position for extended periods, due to a lack of sunlight. Like all plants, if they are not able to harness sunlight, a vital component of photosynthesis, they are not able to survive. This issue however, will be confined to flora in close proximity to the floating land itself, so will not have an adverse effect on the aquatic environment as a whole Positives Despite the aforementioned downfall associated with the floating land scheme, a raft of positives suggests that this project is an effective and viable solution to numerous problems faced by the people of Cambodia each and every day. 27

28 Securing housing together upon the lake by connecting multiple houses to floating farms will increase the strength of structures so that they can weather the ferocious storms that frequent Cambodia. When the lake swells and much of the agricultural land is under water, a great deal of pressure is placed upon the fishing industry to provide for Cambodia s nutritional needs. With the 'floating land' scheme in place, houses will be relatively self-sufficient and the demand on fish will decrease, thus the fish population will thrive and the Tonle Sap ecology will benefit. Additionally, our proposition of building our design using, if possible, discarded plastic containers which currently pollute the area will ultimately lead to beautification as well as improving the general cleanliness of the lake. 3.6 Chapter Overview Having researched the environment of Cambodia, our group have come to realise what a unique and picturesque place it is, but with its beauty comes fragility. The geological mechanics and plant and animal species are currently functioning as they should but humans have become a bad influence on nature. The rubbish that is being disposed of in the Tonle Sap Lake is having a detrimental effect on the life on the lake and it is only a matter of time before these harsh pollutants take their toll. The 'floating land' scheme will remove litter from the delicate environment and use it to better the lifestyles of the occupants of the Tonle Sap Lake. 28

29 4 Soil and Produce 4.1 Introduction Many problems arise when trying to grow vegetables on a floating vegetable patch. Vegetables require a certain amount of space to grow properly, which means that designing the container to grow the vegetables needs to be done carefully to maximise productivity. Another problem is that the soil needs to be of a certain quality so that the vegetables are able to get the nutrients they need to grow properly. 4.2 Soil Soil is a natural compound that is formed from minerals, organic matter, gases and liquids on the earth s surface. It is a vital part of growth and development of land-based plants Soil weight Table 4.1 Soil weight (Adapted from Engineering Toolbox) Approximate Weight Type of Soil (kg/m3) Loose earth 1200 Rammed earth 1600 Average 1400 The weight of the soil will affect how we need to design the container, as it will need to be able to hold the weight of all the soil and vegetables while still being able to stay above the water. As we will not be ramming the earth solid we will use 1400kg per cubic metre as an estimated weight for soil Improving soil quality Soil quality will affect how well the produce will grow. Poor quality soil is unlikely to grow anything whereas top quality soil will produce the best yield. A perfect quality soil is almost impossible to come by but it is possible to improve soil quality through various methods of fertilisation. 29

30 Fertiliser Fertiliser adds essential minerals to soil to help produce the best quality produce. The problem with improving soil quality with commercial fertiliser is that although it is easy, it is also very expensive to buy. This causes affordability problems for the people on the Tonle Sap Composting Composting is one way to help improve the soil through natural means. It would also enable the people to dispose of organic waste safely, lessening pollution in the lake. When composting, there are several things that need to be kept in mind, such as it cannot be under too much sun. For composting to be done, a community group would have to have a separate vegetable patch that they could cover just for composting Bone meal Bone meal is both an effective and natural fertiliser. It is made up of any kind of bone which has been ground down to a powder. It is possible to make an effective bone meal at home. Families on the Tonle Sap could use bones such as fish bones which they would normally discard. They can boil the flesh off the bone, then charcoal the bones either on the stove or in a fire place. This makes the bones easier to grind. The family can then grind the bone and spread it onto the garden as a fertiliser. 4.3 Produce It is important to investigate what can grow in the area and what the Cambodians will eat, in order to design a useful floating island Growing Restrictions Vegetables require varying amounts of room to grow in. This makes growing in a restricted amount of space a little more complicated as everything cannot just be placed in randomly to grow. To maximise the space, each variety of vegetable needs to be taken into consideration. 30

31 Table 4.2 Agriculture and Natural Resources (Adapted from Plant Beets Leaf Lettuce Onions Radishes Spinach Swiss Chard Broccoli Cabbage Cauliflower Cherry tomatoes Eggplant Peas Peppers (Capsicum) Carrots Beans Cucumbers Potatoes Summer Squash Tomatoes Plant Spacing (Inches) to Soil depth (Inches) 9 to 12 9 to 12 9 to 12 9 to 12 9 to 12 9 to to to to to to to to 16 9 to to to to to to 18 In a 3m by 3m (118 inches by 118 inches) vegetable garden it would be possible to fit approximately 2000 radishes but this does not factor in the climate nor does it give much of a variety, let alone fit the culinary practices of Cambodians. This means we need to find other alternatives that produce a lot in a little space and work in the climate Tropical Produce The season affects what type of vegetables people will be able to grow. There are many varieties of the vegetables listed in Table 4.2. Some of particular interest are: Suyo long: A variety of cucumber which can withstand hotter weather then regular varieties of cucumber. Open leaf lettuce: These are more heat resistant then the closed leaf lettuce. Cabbage: Many of the cabbage family grow well in warm weather. These include Chinese cabbage, bok choi, rocket and Asian greens. Shallots: A smaller version of the onion which can grow in tropical conditions. A bonus is that it will require less space to grow. 31

32 Some vegetables, such as eggplants, chillies, capsicums and sweet corn will grow no matter how hot it gets (Bradtke, 2009). Using the information below, we can plan how much of each type of vegetable should be grown, taking into account what seasons the vegetables grow in, so people will be able to grow vegetables throughout the year Seasonal Growth Table 4.3 Seasonal Produce (Adapted from Wet Season Produce Dry Season Produce Suyo Long (Cucumber) Cabbage Lettuce (Open Leaf) Shallots Shallots Eggplant Chillies Capsicums Sweet Corn Sweet Potato The people of the Tonle Sap should be able to utilise their floating land to the full extent by exploiting the seasons in which produce grows. By swapping between the wet season vegetables such as capsicums, lettuce and suyo lang and then growing various types of cabbage and some shallots during the dry season, the people will frequently have produce that is ready to harvest Amount Produced To fit the dimensions of our floating land, there will be 12 strips of soil 8.80m long by 20 centimetres wide. For suyo long, cabbage and capsicums which require the most spacing they will be able to grow up to 30 plants per row whereas for sweet potato they will be able to fit closer to 45 plants per row. From these numbers they will be able to grow approximately 360 cabbages during the dry season. During the wet season, depending on how the rows are split between vegetable, they will be able to grow up to 540 plants per dock. This gives a total of up to 900 plants grown on a dock each year. 32

33 A cucumber plant produces approximately 1kg of cucumbers per plant and a lettuce weighs approximately 500g. Based on these plants, we can assume that each plant produces approximately 750g. This means the maximum amount grown on a dock is 675kg per year. We could not find any information on how much an average Cambodian eats so we have based our results on the following statistics, to give a rough estimate of how many people each dock will sustain. The average adult American consumes approximately 10kg of green vegetables, 1.8kg of cucumber, 3.2kg of corn and 8kg of onion a year (Jeavons 1999). This totals 23kg per person, per year. This is obviously not all the types of vegetables eaten by an American, but as Cambodians are poorer, smaller in build, and we are including children in our calculations, this amount should be enough for a Cambodian to stay healthy. As each dock can produce 675kg, we divide that number by the amount of vegetables eaten by each person to get approximately 30 people able to be sustained on a 7.5m by 9.2m dock, which is the size of our final design. As each dock supports 6 families, and each family has approximately 5 people in it, the dock should be able to provide the vegetable requirements for all 30 people living there. 4.4 Chapter Overview By investigating and researching into how soil and produce factors are going to affect the floating land, we can analyse how best to design the land so that it can support the weight of the soil. It also helps us to provide information on what families can grow there. The ability to grow their own variety of vegetable will help provide a healthier diet as well as some income as excess produce can be sold. Growing vegetables will help reduce some of the financial pressure on a family to buy food as well as helping to slightly decrease some pressure on the decreasing fish number ecosystem. 33

34 5 Flotation Scope The scope of this chapter is to design a system to make our structure float. Our focus is on durability, cost, use of local materials, and ease of implementation. Our research has led us to two obvious flotation ideas: the first comprising the use of 220-litre plastic drums, the second involving placing empty sealable containers into netting Constraints The design choices we make will be guided by factors such as, the weight of the structure, the environment factors such as current, storms, and river height, and existing infrastructure e.g. floating housing and moorings. It is also important to consider the cost of the project because it is of no use to the community if the they cannot afford to implement the design Potential problems Our biggest concerns are weight, freeboard and durability (strength). If our structure (above water) is too heavy, we run the risk that our underwater structure will sit too deep in the water, creating a problem with clearance when water levels drop in the dry season. 5.2 Plastic Drums (220L) Dimensions Figure l plastic drums (pac tech, 2007) 34

35 All dimensions are based on the pac tech product specification sheet. We are assuming barrels to be of similar type and dimensions to these. Length: 920mm Width: 580mm Wall thickness: >2.8mm Weight: 9.5kg Cost: $2 each (EWB, 2009) The barrels can be roped together and put in a bamboo or plastic framework. This structure is discussed in chapter Load Handling The aim of this section is to calculate the maximum weight that each barrel can support, and the combined weight handling of combinations of barrels. Our target is half submersion of each barrel. This will allow for spikes in weight such as unknown number of people on the structure, and water from monsoonal weather. Figure 5.2 Half submersion of cylinder (Blankleider, 2009) weight of structure = m empty weight of barrel = m o =9. 5kg radius of barrel = r = 580 mm length of barrel= l = 920 mm 35

36 density of water = ρ ω=1000 πr 2 l m+m o =m w =ρ ω V=ρ ω 2 m=ρ ω πr 2 l m 0 2 (Blankleider, Parappily,2009) m= 1000 π = kg 2 This means the target maximum weight is kg per barrel. Now we will work out the weight it takes for a barrel to sink. Figure 5.3 Full submersion of cylinder ( Blankleider, 2009) m=ρ ω πr 2 l m0 2 m= 1000 π = kg So kg are needed for the barrel to reach equilibrium. Proposed dock configuration: number of barrels = x = 13 10=130 Target maximum weight is: m x= = kg Weight applied for barrel equilibrium (almost sinking) is: M x= = kg 36

37 5.2.3 Maintenance The barrels' maintenance and durability will depend on the actual drums used. We are assuming the barrels will be of a similar type to our reference (pac tec, 2007). The barrels from pac tech use high density polyethylene (HDPE) for the main body and HDPE for the bungs (lids). HDPE is commonly recycled and is preferred over other materials for use in applications such as pyrotechnics, water pipes, food grade containers, plastic lumbar etc.(wikipedia, 2009). HDPE has good chemical resistance, is temperature resistant, has good impact resistance, and a good overall toughness.(ides, 2009). If we leave a bung above the water line, we can easily inspect and syphon any water that may be present (i.e. leaks) Summary This configuration is a realistic and viable solution to our problem. Using these barrels is a good way to recycle while creating a solid base for our structure. 5.3 Empty Containers Enclosed in Netting Existing Examples figure 5.4 Spiral Island and netting (Ecoble, 2007) Through our initial brainstorming, we identified plastic bottles as a means to float our structure. Further investigation revealed Spiral Island. 'The original Spiral Island was (as its successor will be) built upon a floating collection of used plastic bottles, all netted together to support a bamboo and plywood structure above. Located in Mexico, the 37

38 original was 66 by 54 feet and was able to support full-sized mangroves to provide shade and privacy, yet also able to be moved from place to place by its creator at need with a simple motorized system' (Ecoble, 2007) Netting After looking at pictures of existing infrastructure on the EWB website, we noticed various fishing nets (EWB, 2009). These nets would be a feasible way to hold the waste bottles together. Nets are durable, repairable and light weight. Locals would be able to make them to almost any shape Waste bottles Waste bottles are available in the Tonle Sap region. Waste bottles are sold in bulk from major cities such as Phnom Penh and Siem Reap for US$600 tonne (EWB f&q, 2009) or from general collecting. The size and shape will vary so we have picked some common shapes for our calculations Load handling The following calculations are only approximations because of unknown variables such as size and shape of plastic bottles to be used in actual construction. Here, we assume that bottles that are in the water are fully submerged (due to unknown variable, shape). Our benchmark will be our target weight for 220-litre plastic drums (chapter 5.3.3). Type Volume Weight Plastic bottle 600ml 40g Plastic bottle 1500ml 70g average 1050ml 55g m=ρ ωv m o m = =. 995 kg each unit could support approximately 0.995kg at equilibrium. 38

39 our target benchmark is kg = =1 1 3 bottles. 995 For our waste bottles to have similar characteristics as the 220l barrels, we double the amount of bottles to give us our 290mm of freeboard =22 6 bottles For our proposed structure size, we need: =2 2,3 7 4 bottles Maintenance Food grade plastic bottles are mainly made from Polyethylene Terephthalate (PET); some examples include soft drink bottles, food and produce containers (matweb, 2009). PET has a good resistance to mineral oils, solvents, and acids but not to bases (alkaline)(designinsite, 2006). Inspecting and repairing the bottles could cause a problem as access in limited Summary The main concern with this configuration is the uncertainty of available bottles. It is a viable solution, as the Spiral Island example proves, but the strength and durability is unknown because each bottle has different characteristics, and nets will vary. We would need to build a prototype to examine how the concept would behave. 5.4 Chapter Overview The final design for the floating land project uses the barrels for floatation because they are easier to fix than the structure made from bottles in netting, and more uniform for purposes of calculation. 39

40 6 Anchorage 6.1 Scope For our project to work effectively we need to secure our floating structure in a fixed position. Part of our design is for existing housing to have a dock that is fixed so that they can be safe in extreme weather and when the tide is strong. Our aim is to identify a means to efficiently secure the structure while maintaining our focus on affordability. It would be more convenient for the locals if the mooring system is able to move with the seasons (see chapter 3.3.1) so people can be near the lake's edge for transport purposes. 6.2 Problem A problem identified while looking though the pictures on the EWB photo gallery is that many of the floating houses/structures are arranged in a disorganised fashion. Further research found that there are very limited, and highly sought after, 'permanent moorings'. People mostly attach their houses to another structure or a tree. In a storm, some moorings are known to shift, which causes some major problems (EWB, f&q, 2009). Figure 6.1 Disorganised housing (EWB, 2009) 6.3 Constraints Some facts to take into consideration when choosing an appropriate anchor for the docks include the potential force on the anchor system due to tides, the river bed composition, made of sand and silt, and the movement of communities as the seasons change. It is 40

41 also important to look at the materials available and the expertise of locals. The movement (yaw) of the docks needs to be studied to keep the floating land from collisions. 6.4 Options After research we decided on some systems to pursue further. These include dead weight, pyramid and danforth anchors. We also considered multi point anchor setups Dead weight moorings Figure 6.2 Dead weight mooring (Sandifer,2009) Advantages The dead weight mooring is a very reliable system which gains greater holding power over time as the weight embeds into the bottom, creating suction. If a dead weight anchor breaks free, the weight provides constant force (Parenti, 2000). They are uncomplicated and the materials are readily available Disadvantages The dead weight anchor's effectiveness depends on material choice. When concrete is submerged, approximately 50% of its weight is reduced due to buoyant force (Parenti, 2000). Steel works the best as approximately only 20% of its weight is lost. 41

42 Summary Dead weight would be a good solution if our final design required permanent mooring Pyramid Anchor Figure 6.3 Pyramid anchor (Sandifer, 2009) Advantages The pyramid anchor is a simple design which easily penetrates into the river bed. It has good holding power in soft sand and silt river beds (Sandifer, 2009). If the anchor drags, it will still try to bite into the river bed Disadvantages These anchors cost a lot because they are made of steel. They are also subject to corrosion. Because they are so heavy, it would be very hard to retrieve the anchor Summary This anchor is an ideal solution, as it could either be permanent or temporary. Our main concerns are weight and cost. 42

43 6.4.3 Danforth Anchor Figure 6.4 Danforth open (holiday sailover, 2008) Figure 6.5 Danforth (boatbits.co.nz, 2009) Advantages The danforth anchor is extremely light and therefore could be easily retrieved and fixed. It has good holding power in sand and silt. This simple design could be locally made without much cost Disadvantages The problems with the design of the danforth anchor are that it has moving parts and is not very durable, so will need regular maintenance, and it is going to corrode over time Summary The danforth anchor is ideal for a temporary solution because of its light weight and lower cost (it contains less steel than a pyramid anchor). Locals could make these 43

44 anchors themselves. By increasing their size, these anchors would have considerable holding power Scope of Anchor System To ensure that the anchors hold, we need to allow for a scope of no less than 2:1. A scope of 3:1 would be ideal as the greater the scope there is less chance of the anchor breaking out. Figure 6.6 Scope Multi-point Moorings We have identified that we need to control the yaw of our structure. We recommend that two anchors are deployed one at either end. This will help limit the yaw and provide greater holding power. Figure 6.7 Mooring 44

45 6.4.6 Recommendations We would recommend using two danforth style anchors on each dock due to their temporary nature and the community's needs to move with the seasons. We believe this configuration would help to keep the yaw of the structure to a minimum. 45

46 7 Structure and Materials 7.1 Introduction The floating land project requires many different materials in order for it to be built. This chapter outlines the basic structure and the materials as well as the costs involved in making our final product. 7.2 Structure The designed structure has been kept simple to make it easier to be maintained. If the structure is too complex the floating island would be more likely to have problems that would not be able to be fixed by the local Cambodians. If they cannot fix it, then they are unlikely to use it. The chosen structure is rectangular in shape, with a strong but lightweight frame. Bamboo, rope, wood and plastic are the main materials used on the top structure. The top structure will fit onto the bottom structure made of floating barrels (explained in chapter 5). There have been many different designs created for the floating island, which have come from brainstorming useful features. However, the final design was decided to consist of narrow strips of soil which are separated by bamboo walkways. The idea is to allow for houses to dock to the island and use the soil to grow food to either eat or sell. The dimensions of the structure are approximately 9x6m with a depth of 1m. Each of the six sections of 3x3m will have rows of soil. The idea of this is to keep the weight of the structure to a minimum. It also allows for six families to grow a variety of vegetables at any time. 46

47 7.2.1 Dock for housing The pictures below show the design of our proposed dock. Figure 7.1 The Dock Figure 7.2 Cross sectional view 47

48 Figure 7.3 Top view 7.3 Materials Below is a list and detailed explanation of the materials that will be used. Bamboo Grown in many regions in Asia, bamboo is a tough, durable and inexpensive material. For this project it is being used on the walkway in between the garden patches. The cost of bamboo varies depending in quality and size. Empty plastic barrels - (oil drums 220L) These barrels will provide the buoyancy needed to keep the island above water. They will be placed on the bottom of the structure for efficiency. The cheaper alternative to the barrels is using recycled plastic bottles. Soil/compost The soil used for farming on the island must have all the right components in order for the vegetation to thrive. Soil and compost can be bought from retailers in either Cambodia or can be transported at a cost from another country. 48

49 Another option is to use the pre-existing soil found around the Tonlè Sap Lake. However, the soil around the lake does not contain enough nutrients to grow the necessary crops. It has been suggested that villagers create a compost heap and to use worms to improve the soil. Rope The ropes will be used to hold much of the structure in place. Rope is tough and durable and can be used to create strong connections between materials. Vines These are the cheaper alternative to using ropes. They are not as strong as rope and may deteriorate over time. The locals are able to weave the vines in a rope-like manner. They can also twine together water reeds and palm fronds. However, they still need to be tested for their durability. Tyres These will provide adequate protection when boats or houses dock at the island. If used properly, they can also provide extra buoyancy. They should be available at little or no cost from an auto wrecker. Tarpaulin This will be used to cover the barrels under the water line. It will help to stop the barrels from being damaged. It will also store air which will help with buoyancy. A possible alternative is to use netting, but that would not provide any protection. Plastic posts These will be used as the main frame of the structure. They are much cheaper and lighter than metal and yet provide a strong frame. If used properly they could also be used to help with drainage. Plastic Garden Liner Also known as geotextile, the plastic liner will help to keep the soil from seeping through the bottom of the garden plots. The geotextile allows for water to pass through but will hold the soil. People usually use these liners to prevent weeds from growing in their gardens. The price of geotextile can range anywhere between $30 and $260 per dock, depending on quality. Polystyrene Although this is not used in the final design, it is a light material that 49

50 would increase buoyancy. It has been discussed whether it should be used but we were uncertain as to how it would weather. Emersion Paint The paint will help to keep the structure waterproof. This will prevent much water damage to the structure. The paint is expensive but it is crucial to use it, otherwise the dock will not be very durable. 7.4 Final Dimensions Figure 7.4 Cross view Figure 7.4 shows the dimensions for a dock that is 5 barrels wide. Our dock will have the same dimensions but will be 13 barrels wide by 10 barrels long (7.5m x 9.2m). Each barrel can hold 112kg, comfortably. This means the total structure can easily hold 14 tonnes. By making the dock 13 barrels wide, there is room for 12 rows of vegetables. This number has been chosen because it is easily divided into separate plots of land. The length of each row of soil will be 8.8m long, to allow for the framework and mooring structure. Each row contains 8.8m x 0.2m x 2.5m of soil above the height of the barrels, and it contains roughly 8.8m x 0.25m x 0.1m below (estimated based on the area of a triangular prism). 8.8m x 0.2m x 0.25m + 8.8m x 0.25m x 0.1m =0.66m3 of soil in each row. Based on the weight of soil (1400kg/m3), stated in chapter 4, this creates a total weight 50