Forschungsprojekt ::

SEHAG Subproject 8 - Sediment connectivity, delivery, and the propagation of changes in high Alpine geosystems

Dieses Projekt ist Teil des Forschungsprojektes Research Unit SEHAG - Sensitivity of high Alpine geosystems to climate change since 1850 (SEHAG)

Projektbeschreibung

Subproject SP8 deals with the extent to which local responses of subareas or –systems to climate change are propagated and lead to observable change in the main valley and at the catchment outlet. For example, changes in sediment delivery to the main valley from hillslopes by different processes may cause rivers to accumulate or erode sediments, consequentially altering sediment yield at the catchment outlet. The propagation of changes is influenced by a system property called “connectivity”, that is the degree to which subsystems of the study areas are coupled with respect to sediment transfer. TP8 has the following objectives: (1) To detect and analyse changes in factors influencing connectivity since 1850, specifically landcover and geomorphology. This will be achieved through the photogrammetric processing and digital evaluation of historical photographs that all SPs will retrieve from archives. At the catchment scale, this systematic quantitative analysis of such data is unprecedented. (2) The spatial distribution and temporal changes of (dis-)connectivity will be analysed using connectivity indices computed from data generated in (1) and digital elevation models (DEMs). (3) Changes in sediment delivery from hillslopes and in river discharge are expected to cause observable changes in rivers and floodplains. SP8 will map and quantify surface changes since 1850 from historical photos and DEMs. Historical DEMs will be generated photogrammetrically from historical photos; airborne LiDAR surveys are available since 2006 and will be continued by SEHAG, additionally we will use drones to survey selected river reaches. Changes in the channel network will be interpreted in light of changing river discharge, sediment supply, and transport capacity. Additionally, we will measure annual sediment yield at catchment outlets. (4) As a synthesis of the results of all SPs, SP8 will produce and analyse network models of sediment transport pathways. These will combine information on geomorphic activity, sensitivity to climate change, and connectivity: Where and when active and/or sensitive areas are coupled to the channels, we expect a (more) pronounced response related to sediment transfer within the valley, and sediment yield. This innovative analysis is based on graph theory; it opens opportunities for comparative analysis and interpretation on multiple scales. The understanding of changes and their propagation in the past will help to better estimate the consequences of future changes.