Evidence of a changing size-frequency distribution of landslides in the Kyrgyz Tien Shan, Central Asia

in Earth Surface Processes & Landforms (2011), 36/12

There is a strong possibility that environmental change (whether climate or land use) will be manifest as changes in the size–frequency distribution of landslides. Here, evidence is presented for this ... [more ▼]

There is a strong possibility that environmental change (whether climate or land use) will be manifest as changes in the size–frequency distribution of landslides. Here, evidence is presented for this from western Kyrgyzstan, Central Asia. Remote sensing and spatial analysis have been applied to map mass movements in the central part of the Maily‐Say Valley and to detect recent landslide activations. The evolution of landslide activity over the past 50 years has been analysed on the basis of pre‐existing landslide maps and new analyses of aerial photographs as well as Quickbird images. Five inventories were produced for the years 1962 (based on the existing map of 1962 and aerial photographs of 1962), 1984 (based on the existing map of 1977 and aerial photographs of 1984), 1996 (based on aerial photographs of 1996), 2002 (based on the existing map of 2003 and Quickbird imagery of 2002) and 2007 (based on Quickbird imagery of 2007). The geomorphologic features contained in the catalogues represent the landslide bodies observed from remote imagery of the corresponding year. Mapped landslides are generally considered as the result of a series of slope failure events. Size–frequency analyses applied to the five landslide inventories show that both the number and size of unstable slopes increased from 1962 (162 objects) to 2007 (208 objects) and the power‐law exponent decreased over time. This changing power‐law exponent may indicate that landslide‐related hazards are increasing. This tendency is documented in more detail for two active landslide zones, one in the main valley and one located to the west of it. Landslide detection methods were used to assist the evolution of slope instabilities. Choosing appropriate thresholds, the image subtraction method based on normalized difference vegetation index (NDVI) allowed accurate detection of new sliding activation in these two zones. This confirmed the results of the more extensive survey that there is a systematic shift in power law exponents and size–frequency distributions for Central Asian landslides. [less ▲]

Amount and controls of the Quaternary denudation in the Ardennes massif (western Europe)

in Earth Surface Processes & Landforms (2009), 34

It is still debated whether the primary control on the middle Pleistocene denudation of the uplifted Ardennes massif (western Europe) is tectonic or climatic. Here, based on geomorphological observations ... [more ▼]

It is still debated whether the primary control on the middle Pleistocene denudation of the uplifted Ardennes massif (western Europe) is tectonic or climatic. Here, based on geomorphological observations, we calculate the amount of river incision and interfluve denudation in the Meuse basin upstream of Maastricht since 0·7 Ma and we show that the main response to tectonic forcing was incision. This allows us to provide first-order estimates of the tectonic and climatic contributions to the denudation of the Ardennes. From a dataset of 71 remnants of a terrace level dated ~0·7 Ma, we first derive a basin-scale functional relationship linking incision with distances to the regional base level (Lc) and to the source (Ls) in the Ourthe basin (pertaining to the Ardennian part of the Meuse basin). Expressed as I = I0*(1 – a*Lcb/Lsc), I0 being the incision measured at the basin outlet, this relationship calculates that river incision has removed 84 km3 of rock in the Meuse basin upstream of Maastricht since 0·7 Ma. In the same time, 292 km3 were eroded from the interfluves. A comparison of these volumes shows that the tectonically forced river incision accounts for ~22% of the total post-0·7 Ma denudation. Furthermore, the mean denudation rate corresponding to our geomorphological estimate of the overall denudation in the Meuse basin since 0·7 Ma amounts to 27 mm/ky, a figure significantly lower than the ~40 mm/ky mean rate derived from 10Be studies of terrace deposits of the Meuse (Schaller et al., 2004). This suggests that, taken as a basin average, the 10Be-derived rate is overestimated, probably due to an overrepresentation of the erosion products of the rapidly incising valleys in the alluvial deposits. [less ▲]

Bankfull discharge recurrence interval in gravel bed rivers

in Earth Surface Processes & Landforms (1997)

Evaluation of grain shear stresses required to initiate movement of particles in natural rivers

in Earth Surface Processes & Landforms (1990)

Contribution to the development of an erosivity index adapted to the prediction of erosion in Belgium

in Earth Surface Processes & Landforms (1989), 14