Soil erosion in the catchment areas leads to the silting of river beds, which soon offsets the protective value of embankments.
Troops rebuilt embankments and the air force dropped food to people who could not be rescued by boat.
Indeed, high embankments have served to raise the level of several rivers above that of the surrounding countryside; when a breach occurs, the result is disaster.Soil erosion is particularly bad in the Himalayan foothills where most north Indian rivers rise.
Flood protection demands embankments, or dams, or protected flood plains, or houses that rise and fall with the waters.
The main fear is that embankments might give way along the mighty Yangtze and around Dongting lake, which serves as an overflow for the flood-prone Yangtze and which is already heavily swollen.
But, in a poor district, only five engineers can be found of whom four have in fact been dragooned from other government service.Elsewhere, a surfeit of pointless earth embankments is the least of the trouble.
In Britain alone, over £400m ($725m) a year is spent defending the most vulnerable communities from river and coastal flooding using embankments and other structures.
Mr Coutts hopes an influx of aid will also allow "food-for-work" on repairs and expansions to dykes and embankments; silted-up rivers need dredging.Some things, however, are beyond the control of Bangladesh and its foreign donors.
In recent years the river has shifted westwards at a furious rate, last year seeping across Shirajganj's embankments.
Now the Asian Development Bank (ADB) and the World Bank have promised $1.5 billion to stabilise 150km of embankments along the Jamuna and the Padma rivers.The simple bagging technique used in Bangladesh could next be adopted across the border in India, which has plenty of fertile land to protect in its eastern provinces.
The money from the ADB and World Bank should go towards stabilising roughly 150km of embankments along the Jamuna and the Padma rivers.
