The natural hazards posed by a river system depend on the river's changing ability to convey its water and sediment loads. This ability is affected by patterns of erosion and deposition that are ultimately determined by base level, the lowest elevation to which the river can flow. Base level, in turn, is set by the interplay between tectonic deformation of the land surface and sediment supply - quantities that can vary both in space and time. Thus, base level plays a dynamic, but poorly understood role in determining the evolution of a river system and its associated natural hazards.

The above concept has serious implications for understanding the recent development of the major river systems draining the Lesser Himalayas and the Gangetic Plain in northern India. Here, large rivers with high sediment load flow south from the Himalayas into a series of narrow valleys, or dun that runs parallel to the mountain front. While many of these rivers are deeply incised where they exit the Himalaya, there are large spatial differences in valley incision across the Gangetic Plain.

For this the following set of key questions have been identified:

1. What is the spatial variation in erosion and deposition across the Himalayan foreland?

2. How does this feed back into sediment delivery by landsliding at the mountain front?

3. What are the geomorphic and stratigraphic records of river system response to base level change in the Himalayan foreland? Can we use these records to disentangle tectonic and climatic influences on river incision?

4. Is there a relationship between incision along the Himalayan front and aggradation in the Gangetic Plain?

5. How do these patterns relate to downstream flood hazard, and how persistent is that hazard likely to be?