A statistical population is a set of entities from which statistical inferences are to be drawn, often based on a random sample taken from the population. For example, if we are interested in making generalizations about all crows, then the statistical population is the set of all crows that exist now, ever existed, or will exist in the future. Since in this case and many others it is impossible to observe the entire statistical population, due to time constraints, constraints of geographical accessibility, and constraints on the researcher’s resources, a researcher would instead observe a statistical sample from the population in order to attempt to learn something about the population as a whole.
The river would break through its natural levees, depositing sediment and fresh water in the surrounding wetlands, keeping them healthy, productive and intact.
Transport of sediments causes them to become rounder as their irregular edges are removed both by abrasion and corrosion. Beach sand becomes highly rounded due to its endless rolling and bouncing in the surf.
