Slope hazards on the Ethiopian road network

Abstract

Jointed rock masses, adverse lithological sequences, often deeply-weathered soil profiles, seasonal rainfall, stream erosion and seismicity have created conditions favourable to the development of landslides in many parts of Ethiopia. Large, deep-seated landslides occupy many hillsides and some may date from the late Pleistocene–mid Holocene. Others are more recent and their activity is controlled by rainfall and, in some cases, the effects of land use change and road construction and widening schemes. The road network of Ethiopia has been expanding significantly over recent decades and has been impacted in many areas by reactivated ground movements and new, first-time failures. The Ethiopian Roads Authority (ERA) has undertaken a number of initiatives to combat these problems, including a research programme aimed at developing mitigation designs for 118 locations on the federal road network of the country. Engineering geological mapping formed the cornerstone of the geotechnical investigations, together with targeted trial pitting, drilling and geophysical investigations, that allowed remedial options to be scheduled. Nevertheless, geotechnical uncertainty prevailed at several locations, especially where ground investigation was precluded by budget constraints. A pragmatic approach had to be applied to the construction contract documentation that made provision for confirmatory ground investigation prior to design finalization and geotechnical inspection and interpretation during construction.

Main Ethiopian Rift landslides formed in contrasting geological settings and climatic conditions

“…Notable geohazard features across and along the MER range from intense erosion to slope-instability-related mass wasting processes, including rockfalls and debris flows up to shallow and deep-seated landslides, all with immense costs in terms of casualty and infrastructure loss (Abebe et al, 2005;Ayalew, 1999;Hearn, 2018). Landslides are rather more common in the highlands of Ethiopia.…”

Online digital archive of aerial photographs (1935–1941) of Ethiopia

“…In the 1930s, the APs were used to study the structural geomorphology of Tigray (Merla & Minucci, 1938) and more recently the long‐term dynamics of mountain streams (Ghebreyohannes et al ., 2015). The APs were also successfully used in a study on historical road engineering geology in the Blue Nile gorge (Hearn, 2019).…”

A methodology for road cutting design guidelines based on field observations

“…Roads are fundamental to the development of low and lower-middle income countries (LIC/LMICs) for the transportation of goods and the connection of people to services, especially in rural communities (Sudmeier-Rieux et al, 2019). For this reason, the expansion of road networks is a priority for many LIC/LMICs governments such as Nepal (Sudmeier-Rieux et al, 2019) and Ethiopia (Hearn, 2018). Despite the significant allocation of government and donor agency spending on road building, roads still experience frequent disruptions due to cutting instabilities, especially in countries that host steep landscapes and that experience prolonged or intense rainfall (Hearn and Shakya, 2017).…”