Safe lifting limits
Ergonomic guidance for agricultural work puts safe loads around 20–25 kg for men and 15–20 kg for women, so one person should never handle more than a single sack.
ErgonomicsSemester 1 · 2025
Floating Granary
Flood-proof crop storage for farmers on Assam’s river islands, built from bamboo and coconut husk.
39.58%of Assam is flood-prone
81.6%of surveyed farmers report crop damage
70.4%report damage to stored produce
Context
Every monsoon, floods on the Brahmaputra’s char (river island) areas destroy stored grain, wiping out a year’s food and income for families who live almost entirely off rice, jute and seasonal vegetables.
Problem
Traditional raised platforms, earthen pots and hanging baskets work for small floods but fail in long ones, while silos and hermetic bags are too costly or not built to float.
Stack below the shoulder
Stack height was capped at about 140–145 cm, the shoulder height of a 5th-percentile woman, to avoid overhead lifting.
Cost decides adoption
A market study of ten storage types showed the gap: nothing cheap, buoyant, repairable and locally made at the same time.
Solution
A raft that holds three sacks
Twenty material concepts were compared in a Pugh chart. The winner: a bamboo platform on two rolled bundles of coconut husk netted with fishing net and tied with coir.
- 2000 × 1400 mm deck for 3 gunny bags (60 kg)
- Two husk pontoons, 300 mm diameter, 2 m long
- Built from materials farmers already have
- Husk reused as a wall, then coir or compost after the flood
85 kgloaded weight (raft 25 kg + 3 sacks)
≈112 kgnet lift from the husk pontoons
₹50–350estimated cost per unit
Ergonomics here meant more than handles: loads, stacking height, cost and what happens to the materials after the flood all had to fit how char farmers already live.
01 · Users
Who stores the grain
Char farmers are small landholders with little access to consistent government aid, but deep river knowledge: they already build stilt houses and move grain to community halls (namghars), schools and embankments when the water rises. Our job was to fit that culture, not replace it.
- Rice, jute and seasonal vegetables are almost the whole livelihood
- Storage today: mud-plastered bins, raised bamboo platforms, earthen pots and drums, hanging baskets
- All of them fail in long floods
02 · Bodies
Ergonomic challenges in a flood
We mapped what storing and moving grain does to the body. Farmers in Assam are shorter on average (men ≈163–167 cm, women ≈151–155 cm), so loft storage means overhead lifts. Sacks often weigh 25–30 kg, beyond safe limits, and get heavier and slipperier when wet.
- Stepping down into boats with 20–30 kg on the shoulder twists the trunk and loads the knees
- Rope and rough sack edges cut into smaller hands, worse when wet
- Many trips through waterlogged ground add up to chronic back, hip and knee injuries
03 · Rules
Design rules from the research
The research turned into four hard rules for any concept.
- Keep each load at or under 20–25 kg for men and 15–20 kg for women
- Never stack above ≈140–145 cm, the shoulder of a 5th-percentile woman
- Design for two-person carry: handles on opposite ends at waist height, centre of gravity marked
- Let units connect into one floating platform, so farmers move a raft, not every sack
04 · Ideas
Twenty concepts, one chart
A morphology chart crossed buoyancy devices, materials (bamboo, banana stem, HDPE, PVC, coconut husk, tyres), water protection, connections and handles. That produced twenty concepts, from bottle pontoons and half-drum boats to banana-stem rafts.
05 · Decision
Scoring them honestly
A Pugh chart scored the concepts on cost, ergonomics, portability, durability, multi-use, sustainability, ease of making, flotation, flood resistance and modularity. Coconut husk with bamboo came out ahead: nearly free, buoyant, local and compostable.
06 · Proof
Will it float?
We checked buoyancy by hand: two husk rolls 30 cm across and 2 m long displace about 141 kg of water, for a net lift of about 112 kg. The loaded raft weighs 85 kg, so it floats with margin. Most materials are already on the farm, so cost runs from about ₹50 to ₹350.
07 · Lifecycle
Before, during and after the flood
The husk isn’t waste at any stage. Before the monsoon it stands as a husk wall for farm shelter; during the flood it floats the grain; afterwards it becomes coir rope or compost for the next season.
What I learned
Takeaways
- 01Ergonomics in rural design is about loads, heights and repeated trips, not just handles.
- 02Anthropometric data from the actual population (not generic tables) changes the numbers that matter.
- 03A Pugh chart is most useful when the criteria include cost and cultural fit, not only performance.
- 04Simple physics on paper (buoyancy, net lift) can make a concept believable before any prototype.
- 05Thinking about end-of-life early turned a material choice into a sustainability story.