Open Seminar

Feedbacks of physical processes affect the  and function of Earth surface and atmosphere system over different temporal and spatial scales. Rivers are the feedback product of turbulent stream flow and earth surface material. This seminar explores how river channels change until they fall into a “most stable” state and the multiscale nature of the feedbacks that link earth’s surface and the lower atmosphere.

Time: 2019-09-26 9:00-12:00 (Thursday)  Room: Digital room(水利系泥沙馆数字厅



Marwan Hassan   


Department of Geography

The University of British Columbia, Vancouver, BC



Patterns of   in/stability and channel morphology of

mountain   streams


Rivers   are the product of turbulent stream flow over myriad granular elements,   vegetable matter and solid refractory materials, under strong, irregular   forcing. Principal sources of stability in mountain streams are different in   different parts of the drainage system. In uplands, channels are steep and attain stability by development of aggregate structures in   bed material. In lowlands (alluvial channels), vertical aggradations of   sediment appear and sediment transport becomes more pervasive and channel   stability is controlled by bed and banks strength. Using field observation,   flume experiments and modelling, I will explore how river channels change   until they fall into a “most stable” state.

John D. Albertson   


Civil and Environmental Engineering, Cornell   University, Ithaca, NY (USA)


A Tour of   Feedbacks in the Land-Atmosphere System


Many of the contemporary research questions in the environmental sciences   and engineering involve ever-increasing spatial and temporal scales, and   intertwined features of the physical and biological sciences. Examples of   this are found in the connection between hydrology and meteorology, ranging   from plant controls on the energy and water exchange processes to the   subsequent connections to convective rainfall generation. Ultimately, these   fast processes (e.g. transpiration and photosynthesis), when integrated   through time, manifest themselves as changes in the vegetation structure that   then induce feedbacks on the land-atmosphere fluxes over longer time scales.   This seminar explores the multiscale nature of the feedbacks that link that   earth’s surface and the lower atmosphere with an emphasis on causal   connections important to hydrology.