Evaluation of impact of soil properties on strength of flood levees in Indus River Basin of Pakistan

Flood bunds are earthen embankments constructed along rivers to control the floods. Historically speaking, floods in Indus River Basin (IRB) in Pakistan have been posing serious threats and damages to infrastructure and human lives. A long infrastructure of flood bunds (about 6807km) exists parallel to the main river to agricultural crops, human settlements, livestock, industries etc. from the hydro-disasters arising from the floods in the country. Punjab Province has been severely hit by heavy floods causing severe loss to human lives, infrastructure, crops and livestock, etc. A study was carried out to evaluate the “health” of flood bunds by investigating their geotechnical, geometrical, geochemical and hydraulic properties to ascertain strength against breaching during floods. A length of about 731 km of river Chenab in Punjab Province of Pakistan was selected to investigate vulnerability of flood embankments at 78 sites of 38 flood bunds which were found critical after 2014 flood in Pakistan. Different field activities including density test, measurement of geometrical parameters, collection of undisturbed/disturbed soil samples, physical inspections and collection of ground water samples from bore holes were performed. Laboratory tests including soil texture, Atterberg’s limits, compaction, unconfined compressive strength, permeability, direct shear etc. were performed in laboratories of Irrigation Research Institute, Lahore, Pakistan. An Index called river embankment breaching vulnerability index (REBVI) has been prescribed and calculated to evaluate the strength of the flood embankments against breaching. A cluster analysis has been carried out for different indicators keeping in view the value of REBVI. On the basis of REBVI and Cluster analysis, it was concluded that 11 out of 78 sites are showing high strength against the breaching action, while 35 sites indicated low potential against the breaching action. In other words, it has been found that consistency of the embankment is very high for 11sites and high for 35 flood bund sites. The consistency of the embankments is medium, low and very low at remaining 16, 12 and 4 flood bund sites due to moderate vulnerability, high probability of embankment breaching and very high vulnerability respectively.