No abstract

Development of robust ground models is essential to ensure that geohazards are mitigated during design and a scheme is safely built and operated. To support this aim for HS2, an engineering geomorphological assessment (EGA) was undertaken for the Phase One and 2a route between London and Crewe.The EGA is a systematic terrain evaluation using LiDAR (Light Detection and Ranging) and aerial imagery data in GIS. A nested approach was adopted whereby regional Quaternary and physiographic domains, landforms, and geohazard features are mapped at progressively larger scales. LiDAR reveals landscape details not visible in aerial photos.A distinction was made between actual and potential geohazards: the former with clear surface expression; the latter with no surface expression but predicted based on the geomorphology. The assessment revealed features interpreted as shallow and deep instability features, solution cavities and kettle holes. Potential geohazards were identified from landform-geology assemblages using a qualitative framework. It was predicted that shallow instability features, such as mudslides or gelifluction lobes, could be present on very shallow angle debris-mantled slopes and deep instability features, such as cambered bedrock and valley bulging, may be present on limestone scarps and valleys cut in clay.Comparison with pre-existing records licensed to HS2 suggested several national geohazard databases are incomplete. The findings of an EGA are used to inform ground investigation acquisition and interpretation of ground models to be used in the design of the route.Thematic collection: This article is part of the Remote sensing for site investigations on Earth and other planets collection available at: https://www.lyellcollection.org/cc/remote-sensing-for-site-investigations-on-earth-and-other-planets

In 2017 two landslides resulted in temporary closure of the main access road to Scrabster Harbour, located in the north of the Scottish mainland. A slope stability assessment was commissioned to investigate the occurrence, causes and mechanisms of historical landslides and their associated consequences to inform future landslide hazard potential. Within Scotland, most slope stability studies are undertaken using qualitative rather than quantitative methods, largely due to insufficient historical data. This paper presents a case study where a semi-quantitative risk assessment was used to assess the stability of coastal slopes above the A9 Trunk Road at Scrabster Harbour. A database of historical landslides and slope characteristics was compiled and used in a semi-quantitative risk assessment to provide the client with targeted information on which areas of the slope can be stabilised most effectively. This was based on ranking the slopes in terms of relative risk, thus providing the road operator and maintenance contractor with an indication of those slopes presenting a higher risk so that these areas could be prioritised for remedial works. The analysis showed that surface water drainage intersecting the slopes and locally over-steepened slopes were primary controls for the observed landslides.

No abstract