Impact of Variable Rainfall on the Stability of Gypsiferous Soils in Iraq. A Comprehensive Review

Abstract

In Iraq, from 28.6% to 31.7% of its land area that is gypseous which makes up 7.3% – 10% of the world’s total gypsey areas. Also in these dry and semi dry regions whichis recedence to these types of soils, they present a large scale technical issue which is in great part due to their tendency to collapse when they come into contact with water. At the same time climate change has transformed rain patterns in Iraq, out of 81.25% of weather stations at over the 1990 to 2023 period there has been a large scale reduction in precipitation which also has shifted away from the former heavy winter time rainfall to a more even distribution through the year. This review looks at how changing rain patterns play out in terms of the stability of gypsum soils in Iraq, which look at through the lens of geotech engineering, climatology, and soil health literature. In analysis, there are two main ways in which gypseous soils collapse – in the short term have immediate compressibility from flooding, but also a slow progressive issue of plastic deformation which is 2 to 26 times that of just soaking and which even at 5% gypsum content. Climate projections show that precipitation will not be a consistent story geographically – for example in northern Iraq, the coming of a 5.92 to 13.70% less rain by 2100 under the RCP scenarios, to the south there is high interannual variability with what does appear to be a 19.26 mm increase in some of the seasons, and in the central parts of Iraq that very different and complex picture. In each weather zone there’s a different rain pattern that affects gypsey soil stability in unique ways. In the north, decreased land collapse as a positive but also a rise in soil dissolution as a negative, at the same time in the south are seeing more issues with the intensification of the extreme rainfall events. This review present large scale issues with regard to hydro-mechanical response in a variable wetting drying environment, long term leaching rates at which can expect to see changes in climate, and also stability of remediation methods in a changing environmental picture. Out of the emerging sustainable solutions which include bio-enzymatic treatment, nanomaterial incorporation, and use of industrial byproducts some see a 50% or greater reduction in collapse that requires that we validate results in climate altered rainfall conditions. The study results present a framework for incorporating climate projections into analysis of gypsic soil risk which in turn informs adaptive engineering solutions for infrastructure resilience in Iraq as precipitation patterns change.