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Hydrogeological models need to be supported by a clear understanding of the subsurface geology to provide effective assessment, flow modelling, or management of groundwater regimes. This paper illustrates how geophysical and sedimentological data can be used to significantly improve watershed-scale hydrostratigraphic models by advancing our understanding of the subsurface through regional hydrogeological investigations in the Greater Toronto Area. The example of a 3 km shallow seismic reflection survey that traverses a buried channel within Bowmanville Creek watershed, Oak Ridges Moraine, Ontario, illustrates a basis for linking geophysical and sedimentological properties to regional hydrostratigraphic parameters. Seismic reflection methods plus seismic stratigraphy and a well-constrained three-dimensional geological framework have helped to (i) identify regional hydrostratigraphic units, (ii) define properties and trends of these units–facies, (iii) improve depositional models that assist hydrogeological analysis, and (iv) establish a hydrostratigraphic framework within a watershed. The extent, proportions, boundaries, and variation in internal properties of major hydrostratigraphic units could be identified to greater than 100 m depth. Geostatistical analysis of seismic amplitudes was used to provide a quantitative measure of heterogeneity in a glaciofluvial aquifer with inadequate parameter support. Benefits to engineering practice include improved siting of monitors and tests from portrayal of the spatial organization, geometry, and variability of hydrostratigraphic units based on sedimentary architecture and environments of deposition. Hydrogeological modelling can be improved with better knowledge of the geometry of aquifers and aquitards and grid-cell boundaries that correspond with the defined sediment boundaries that control properties.Key words: Oak Ridges Moraine, hydrogeology, seismic stratigraphy, southern Ontario, sedimentology.

This paper describes the regional geology, dimensions, morphology, sedimentology, and age relations of the Holocene "Carlson landslide," a large moist landslide composed of basalt breccia located on the eastern margin of the Lost River Range, Idaho. These data are combined to deduce the factors that prompted the slope failure, the kinematics of initiation, travel, and stopping of the landslide, as well as its postemplacement degradation. The landslide is compared with other terrestrial mass movements on the basis of morphology, sedimentology, log(volume) versus fall height –runout length (H/L) relations and estimated Bingham plastic yield strength. Morphology and sedimentology distinguish dry landslides from moist and water-saturated deposits. However, moist and water-saturated landslides plot well within the log(volume) versus H/L envelope for dry terrestrial landslides and exhibit overlapping ranges of estimated Bingham plastic yield strength values with dry landslides, indicating that moist and water-saturated landslides must travel much like dry rock avalanches of similar volume. Thus the mechanism(s) responsible for causing anomalous runout in large dry landslides could operate in moist and water-saturated landslides as well. Morphological comparison of the Carlson landslide with lobate martian landslides suggests a role for water in the martian landslides. Key words: landslides, debris flows, long runout, morphology, water, Mars.