3.1 TOPIC OVERVIEW AND LEARNING OBJECTIVES

This section presents a description of rivers as natural systems including the structure of rivers, and explains how the form and function of the river results from physical processes. The physical need for water to dissipate its energy and the erosion-deposition processes are identified and explained as the two major factors influencing the physical nature of rivers. Descriptions are provided for the form and function  of the upper, middle lower and delta sections of the river, using the longitudinal profile and river order using the Mekong River as a model.  The concept that wetlands associated with rivers including floodplains, lakes, the estuary and delta, form part of the river system is introduced.

After completing this Section, the user should be able to:

• Describe the main components of the hydrological cycle.

• Explain the relationships between stream discharge and the transport of dissolved and particulate materials in water.

• Describe the major sections of a river: upland rivers, middle rivers, lowland rivers, floodplains and the delta.

• Explain how floodplains are formed.

• Explain the relationship between floodplains, the flood-pulse and seasonality of aquatic habitat.

• Describe the main features of sediment erosion and deposition processes in rivers.

• Describe the concept of river order.

• Explain the salinity regime in a typical river delta and estuary.

• Explain why estuaries are highly productive environments.