What is included in the survey of a river besides the flow characteristics?

The determination of the velocity of the flow is crucial in surveying a river as it directly relates to understanding the river's hydrodynamics and behavior. This measurement helps in assessing the river's energy and its potential for erosion, sediment transport, and ecological health. Velocity is a critical factor in flood risk assessment and can influence the design and placement of structures like bridges and levees. By analyzing the flow velocity, surveyors can gather important data that impacts water resource management, environmental conservation, and civil engineering projects.

While other choices might be relevant aspects of a broader environmental or ecological assessment, they are not direct measurements related to the river's characteristics necessary for a fundamental river survey. For instance, measurement of soil composition, assessment of wildlife habitats, and mapping of nearby land features may provide valuable context in environmental studies or land use planning, but they do not focus on the river's flow dynamics, which is the core concern of a river survey.