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CASE: SOIL BUNDS IN PAKISTAN. 6.7. SOIL BUNDS: MOST COMMON WAY OF DIVERTING WATER. Diversion cum guide bunds: In upper part of river, where slope is higher, water force is higher and there are mainly gravel and coarse sand deposits Crossbunds cum guide bunds:
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SOIL BUNDS: MOST COMMON WAY OF DIVERTING WATER • Diversion cum guide bunds: • In upper part of river, where slope is higher, water force is higher and there are mainly gravel and coarse sand deposits • Crossbunds cum guide bunds: • In lower part of the river, more gentle slopes, sandy-loamy deposits, water velocity is less
SOIL BUNDS: DIMENSIONS OF SAD/GANDIS IN DI KHAN Source: Khan and Marwat, 2004
Constructing soil bunds • Location: • Determined by lay of the land • Manage water levels and avoid overflow/ flooding • In case of cross bund - preferably at angle, try to dissipate energy • In case of cross bund -may have upstream offtakes too • Construction • Look for good loamy soil – avoid gravel and sand • Avoid saline soil and do rat control – to prevent piping • Develop layer by layer • Compaction with bulldozer driving across the bund • Protect against animal tresspassing • Protect with some vegetation and brushwood • Special issue • Often flood channels are not well maintained and silted up causing pressure on the soil bunds
SOIL BUNDS: MAINTENANCE Source: Khan and Marwat, 2004
Reinforcing earthen bunds: Gabions
Reinforcing earthen bunds:plastic sheeting Material Black polyethelene plastic 150-250 micron Cost 0.35 USD/m2 Construction Avoid puncture Use steps to contruct to Avoid slippage Anchor at toe and head Cover with 50 cm soil