This paper presents the hydraulic geometry of stream channels and its implications for physiography. It describes how the width, depth, velocity, and suspended sediment load of a stream channel vary with discharge as simple power functions. These relationships are termed "hydraulic geometry" and are expressed as: w = aQ^b d = cQ^f v = kQ^m L = pQ^j where w, d, v, and L represent width, depth, velocity, and suspended sediment load, respectively, and Q is discharge. The coefficients (a, c, k, p) and exponents (b, f, m, j) are numerical constants that vary between different streams but are consistent within a given stream. These relationships are illustrated in figures and show that, despite differences in physiographic settings, the relationships between hydraulic characteristics and discharge are similar across various river systems. The paper also discusses the relationship between hydraulic characteristics and sediment load. It shows that suspended sediment load is an index to total load and that the average relationship between hydraulic characteristics and sediment load provides a logical explanation of the observed channel shape. The hydraulic geometry of river channels is presented for several river systems, showing that similar equations apply to both rivers and stable irrigation canals. The paper concludes that the average river channel system tends to develop in a way to produce an approximate equilibrium between the channel and the water and sediment it must transport. This equilibrium appears to exist even in headward ungraded tributaries and in a given cross section for all discharges up to the bankful stage. The paper emphasizes that the study is preliminary and that the data used are not necessarily the best type for an analysis of stream processes. The data are primarily derived from Western streams, and comparable data on streams in humid areas are limited. The paper also discusses the importance of frequency of discharge in understanding the hydraulic geometry of river systems and how the width, depth, and velocity of natural rivers change in a downstream direction. It shows that these characteristics tend to increase with discharge as power functions, and that the relationships are consistent across various river systems. The paper concludes that the hydraulic geometry of stream channels is a fundamental concept in understanding the shape and behavior of natural river systems.This paper presents the hydraulic geometry of stream channels and its implications for physiography. It describes how the width, depth, velocity, and suspended sediment load of a stream channel vary with discharge as simple power functions. These relationships are termed "hydraulic geometry" and are expressed as: w = aQ^b d = cQ^f v = kQ^m L = pQ^j where w, d, v, and L represent width, depth, velocity, and suspended sediment load, respectively, and Q is discharge. The coefficients (a, c, k, p) and exponents (b, f, m, j) are numerical constants that vary between different streams but are consistent within a given stream. These relationships are illustrated in figures and show that, despite differences in physiographic settings, the relationships between hydraulic characteristics and discharge are similar across various river systems. The paper also discusses the relationship between hydraulic characteristics and sediment load. It shows that suspended sediment load is an index to total load and that the average relationship between hydraulic characteristics and sediment load provides a logical explanation of the observed channel shape. The hydraulic geometry of river channels is presented for several river systems, showing that similar equations apply to both rivers and stable irrigation canals. The paper concludes that the average river channel system tends to develop in a way to produce an approximate equilibrium between the channel and the water and sediment it must transport. This equilibrium appears to exist even in headward ungraded tributaries and in a given cross section for all discharges up to the bankful stage. The paper emphasizes that the study is preliminary and that the data used are not necessarily the best type for an analysis of stream processes. The data are primarily derived from Western streams, and comparable data on streams in humid areas are limited. The paper also discusses the importance of frequency of discharge in understanding the hydraulic geometry of river systems and how the width, depth, and velocity of natural rivers change in a downstream direction. It shows that these characteristics tend to increase with discharge as power functions, and that the relationships are consistent across various river systems. The paper concludes that the hydraulic geometry of stream channels is a fundamental concept in understanding the shape and behavior of natural river systems.