HOW DO RIVERS CONVEY EARTH MATERIALS TO THE OCEAN? If the “objective” of all these landscape shaping processes is to take earth materials from high locations and deposit it in low locations (flatten the landscape) how does the material get from the highlands to the oceans?

THUS FAR: uniform bed and uniform velocity

DEEPER SLOWER DEEPER SLOWER SHALLOWER FASTER REALITY: Irregular bed, with varying depths of flow. In order to pass the required volume of water down the river, the water has to accelerate through the shallower sections t0 compensate for the decrease in depth.

CONSERVATION OF MASS The Volume of Water (cubic feet, cubic meters), or DISCHARGE, passing cross cross-section 2 every second (Q 2 ), must equal the Volume passing cross-section 1 every second (Q 1 ) as the river passes water from one stretch to the next down towards the ocean. So, Q 2 = Q Cross- section 2 Cross- section 1

CONSERVATION OF MASS Cross- section 2 Cross- section 1 The Volume of Water (cubic feet, cubic meters), or DISCHARGE, passing cross cross-section 2 every second (Q 2 ), must equal the Volume passing cross-section 1 every second (Q 1 ) as the river passes water from one stretch to the next down towards the ocean. So, Q 2 = Q 1 Volume is expressed in units of Length (L) cubed (L 3 ). “per unit second” is a measure of Time (T) Therefore DISCHARGE has units of L 3 T -1.

CONSERVATION OF MASS Cross- section 2 Cross- section 1 The DISCHARGE at cross-section 2 is calculated as the product of the cross- sectional area, A 2 (L 2 ),and velocity of flow, V 2 (LT -1 ) at that point. Thus Q 2 = A 2. V 2 or [L 2. LT -1 = L 3 T -1 ] W D

CONSERVATION OF MASS Cross- section 2 Cross- section 1 The DISCHARGE at cross-section 2 is calculated as the product of the cross- sectional area, A 2 (L 2 ),and velocity of flow, V 2 (LT -1 ) at that point. Thus Q 2 = A 2. V 2 or [L 2. LT -1 = L 3 T -1 ] Cross-sectional area is some product of width, W 2 and depth, D 2. A 2 = W 2. D 2 W D

CONSERVATION OF MASS Cross- section 2 Cross- section 1 The DISCHARGE at cross-section 2 is calculated as the product of the cross- sectional area, A 2 (L 2 ),and velocity of flow, V 2 (LT -1 ) at that point. Thus Q 2 = A 2. V 2 or [L 2. LT -1 = L 3 T -1 ] Cross-sectional area is some product of width, W 2 and depth, D 2. A 2 = W 2. D 2 And therefore Q 2 = W 2. D 2. V 2 W D

CONSERVATION OF MASS Cross- section 2 Cross- section 1 CONSERVATION OF MASS STATES THAT: Q 1 = Q 2 Or W D1D1 W 1. D 1. V 1 = W 2. D 2. V 2 D2D2

CONSERVATION OF MASS Cross- section 2 Cross- section 1 CONSERVATION OF MASS STATES THAT: Q 1 = Q 2 Or W D1D1 W 1. D 1. V 1 = W 2. D 2. V 2 If D 2 is less than D 1 (i.e. the river is shallower, then W 2 and/or V 2 must increase to compensate so that Q 1 stiil equals Q 2. So the river must be wider and/or faster flowing at cross section 2 than cross section 1. D2D2

CONSERVATION OF MASS Cross- section 2 Cross- section 1 CONSERVATION OF MASS STATES THAT: Q 1 = Q 2 Or W D1D1 W 1. D 1. V 1 = W 2. D 2. V 2 If D 2 is less than D 1 (i.e. the river is shallower, then W 2 and/or V 2 must increase to compensate so that Q 1 stiil equals Q 2. So the river must be wider and/or faster flowing at cross section 2 than cross section 1. Rivers are therefore constantly widening/narrowing, Speeding up/slowing down, getting deeper/shallower as they proceed towards the ocean. Their HYDRAULIC GEOMETRY is always changing. D2D2

BEFORE FLOOD – VELOCITY INSUFFICIENT TO INITIATE MOTION.

FINE MATERIAL HEAVIER MATERIAL DURING FLOOD – VELOCITY INITIATES MOTION. FINE MATERIAL TRANSPORTED OUT OF SECTION. HEAVIER MATERIAL CONTINUOUSLY ERODED AND DEPOSITED.

SAND BARS MOVE DOWNSTREAM.

FLOOD PASSES – VELOCITY DROPS – SAND BAR STOPS MOVING.

Dams River Input Potential Energy Kinetic Energy drives turbines

Dams River Input Potential Energy Kinetic Energy drives turbines Lower the position of the outflow and turbines and the potential energy and ability to provide electricity during prolonged droughts (i.e, useable water stored) increases. However the chances of clastic material fouling the turbines also increases.

Dams River Input Potential Energy Kinetic Energy drives turbines Raise the position of the outflow and turbines and the potential energy and ability to provide electricity during prolonged droughts (i.e, useable water stored) decreases. Mreanwhile the chances of clastic material fouling the turbines has decreased.

Above the Dam Fast flowing, often mountainous, river input carries a variety of clasts into reservoir.

Above the Dam Fast flowing, often mountainous, river input carries a variety of clasts into reservoir. As water enters reservoir its velocity drops so the largest clasts are deposited.

Above the Dam Fast flowing, often mountainous, river input carries a variety of clasts into reservoir. The progressively lighter clasts get carried further into the reservoir fore being deposited, creating a DELTA.

Above the Dam Fast flowing, often mountainous, river input carries a variety of clasts into reservoir. The progressively lighter clasts get carried further into the reservoir fore being deposited, creating a DELTA. Sediment deposited in DELTA takes up potentially valuable storage space

Above the Dam Steep slope of the delta beneath the surface is prone to “landslides” which send denser water-sediment mixtures down the bed of the reservoir as TURBIDITY CURRENTS.

Published by AAAS J. Bohannon Science 327, (2010) BELOW THE DAM Aswan High Dam and Laker Nasser created in the 1960s to provide electricity and water to irrigate the desert of Egypt and Sudan

Published by AAAS J. Bohannon Science 327, (2010) BELOW THE DAM Sediment which had previously flowed all the way down to the Nile Delta, replenishing soil and fertility.

Published by AAAS J. Bohannon Science 327, (2010) BELOW THE DAM Dam also used to store waters which had for thousands of years periodically flooded the Nile Delta. Dams for reduction of flood hazard.

Published by AAAS J. Bohannon Science 327, (2010) BELOW THE DAM Soil lost due to agriculture on Delta is no longer replaced annually.

Published by AAAS J. Bohannon Science 327, (2010) BELOW THE DAM Soil lost due to agriculture on Delta is no longer replaced annually. The absence of annual inundation has dried out the soils, causing them to also shrink.

Published by AAAS J. Bohannon Science 327, (2010) BELOW THE DAM Soil lost due to agriculture on Delta is no longer replaced annually. The absence of annual inundation has dried out the soils, causing them to also shrink. Net result is that Delta is becoming lower and therefore, a) more susceptible to flooding by Mediterranean (exacerbating potential sea level rise),.

Published by AAAS J. Bohannon Science 327, (2010) BELOW THE DAM Soil lost due to agriculture on Delta is no longer replaced annually. The absence of annual inundation has dried out the soils, causing them to also shrink. Net result is that Delta is becoming lower and therefore, a) more susceptible to flooding by Mediterranean (exacerbating potential sea level rise), and b) Salt water intrusion is making many areas too saline for agriculture.

Published by AAAS J. Bohannon Science 327, (2010) BELOW THE DAM THERE ARE ABOUT 66,000 DAMS ON RIVERS IN THE UNITED STATES.

WHAT IS ATTRITION?

HOW DO CLASTS ENTER THE FLOW?

HOW DOES THE VELOCITY OF FLOW VARY WITH DEPTH? FLOW Time = 0

HOW DOES THE VELOCITY OF FLOW VARY WITH DEPTH? FLOW Time = 1 Boundary Layer – zero flow.

HOW DOES THE VELOCITY OF FLOW VARY WITH DEPTH? FLOW Time = 1

HOW DOES THE VELOCITY OF FLOW VARY WITH DEPTH? FLOW Time = 1

HOW DOES THE VELOCITY OF FLOW VARY WITH DEPTH? FLOW Time = 1

HOW DOES THE VELOCITY OF FLOW VARY WITH DEPTH? FLOW Time = 1

HOW DOES THE VELOCITY OF FLOW VARY WITH DEPTH? FLOW Time = 1

HOW DOES THE VELOCITY OF FLOW VARY WITH DEPTH? FLOW Time = 1

HOW DOES THE VELOCITY OF FLOW VARY WITH DEPTH? FLOW Time = 1

HOW DOES THE VELOCITY OF FLOW VARY WITH DEPTH? FLOW Time = 1

HOW DOES THE VELOCITY OF FLOW VARY WITH DEPTH? FLOW Time = 1

HOW DOES THE VELOCITY OF FLOW VARY WITH DEPTH? FLOW Time = 1 LOGARITHMIC VELOCITY PROFILE.

HOW DOES THE VELOCITY OF FLOW VARY WITH DEPTH? FLOW Time = 1 LOGARITHMIC VELOCITY PROFILE.

HOW DOES THE VELOCITY OF FLOW VARY WITH DEPTH? FLOW Time = 1 High Flow Velocities Low Flow Velocities

AIRPLANE WINGS?

“Streamlines” CONSERVATION OF ENERGY Energy cannot be created or destroyed but it can change the form in which it is manifested

“Streamlines” Fixed Energy, E. BERNOULLI

“Streamlines” Fixed Energy, E. BERNOULLI 1. Kinetic Energy

“Streamlines” Fixed Energy, E. BERNOULLI 1.Kinetic Energy 2.Potential Energy

“Streamlines” Fixed Energy, E. BERNOULLI 1.Kinetic Energy 2.Potential Energy 3.Mechanical Energy (Pressure)

“Streamlines” Fixed Energy, E. BERNOULLI 1.Kinetic Energy 2.Potential Energy 3.Mechanical Energy (Pressure) E = V + P + M

“Streamlines” Fixed Energy, E. BERNOULLI 1.Kinetic Energy 2.Potential Energy 3.Mechanical Energy (Pressure) E = V + P + M Air forced over wing upper surface and accelerated

“Streamlines” Fixed Energy, E. BERNOULLI 1.Kinetic Energy 2.Potential Energy 3.Mechanical Energy (Pressure) E = V + P + M Pot↑ Vel↑ Press↓

“Streamlines” Fixed Energy, E. BERNOULLI 1.Kinetic Energy 2.Potential Energy 3.Mechanical Energy (Pressure) E = V + P + M Lower Pressure Higher Pressure

“Streamlines” Fixed Energy, E. BERNOULLI 1.Kinetic Energy 2.Potential Energy 3.Mechanical Energy (Pressure) E = V + P + M Lower Pressure Higher Pressure LIFT

HOW DOES THE VELOCITY OF FLOW VARY WITH DEPTH? FLOW Time = 1 High Flow Velocities Low Flow Velocities LIFT

BEDLOAD

SUSPENDED LOAD