Table 3 Comparative GTG Characteristics of the Charlotte, Regent and Madina landslides

Charlotte Landslide (S1-CH)

Rock type is Norite with an altitude of 320 /40 SW.

Elevation: 270 m; Slope angle: 45⁰& Slope aspect: NE. The 4 + m regolith section on the right forms immediate post slide gully

Longitudinal open cracks (NE-SW) on both flanks of the landslide and trellised open joints (<  2.5 cm) with running water attached to them.

Rainfall, Orugu stream erosion & urbanisation

Rock joint orientation and Clay rich layer towards the bedrock. This zone is overlain by porous and permeable regolith.

Clayey gravel

(Low plasticity clay)

Composite type (Rock fall & Rotational)

Regent Landslide (S2-RT)

Olivine gabbro (OG with Dolerite dykes. It is slightly weathered to fresh. ≈ 10 m upper part of the rock is weathered. Rock altitude: 320/ 40 SW

Elevation: 470 m; Slope angle: 60⁰& Slope aspect: N

Jointed rock with two different joint orientations or more (NNW-SSE & NNE-SSW) caused two phases of failures.

Rainfall & urbanisation

Geology (Slide prone zones linked to weathering along WNW-ESE joints) and steep slope (> 59⁰)

Silty gravel

(Highq12 plasticity silt)

Translational &Wedge-typesliding(Broadly deepseatedtranslationalslide

MadinaLandslide(S3-MD)

Olivine gabbro intrudedby Dolerite dykes.Shallow colluvial soil of ≈ 1.3 m at headscarp,which thickens at flanks.Rock altitude is290/60NNE

Elevation: 200 m; Slopeangle: 540& Slopeaspect: SW. Debrisbulge at slide toe andsedimentary pile 1 m tothe NW-SE valley(fault zone)

No visible lineaments (fractures/cracks and joints) on the main body.

Rainfall, stone mining & Slope excavations

Combination of shallow colluvial soil and presence of tension cracks behind the edge of the slope.

Silty-Clayey gravel

(High plasticity)

Shallow Translational slide