1. Erosion and Transport Processes
Flow in rivers is turbulent; can erode unconsolidated materials and transport particles ranging from clay to gravel-size.

• Three types of river load
• bed load - coarse sands and gravel that is dragged/rolled along bed.
• suspended load - fine sands to clay permanently or temporarily suspended in the water column; procees of saltation; relationship to water velocity.
• dissolved load - ions in solution from chemical weathering.
• Concepts of:
• competency - largest-sized particle that stream can carry.
• capacity - total amount of load.
• Bedrock erosional mechanisms:
• chemical and physical weathering (collisions) and hydraulic lift.
• abrasion (sandblasting).
• undercutting at waterfalls.

2. River Geomorphology
stream valleys, channel, floodplain

• channel patterns:
• straight-
• meandering- typical of low gradients, easily erodable material, wide floodplain.  erosion on outside (cutbank) and depostion on inside of bend (point bars);meanders evolve producing oxbow lakes.
• braided- typical of streams with high sediment loads. Glacial streams or in tectonically active areas.

3. River Equilibrium
Rivers constantly seek a dynamic balance between channel erosion and deposition; dependent on gradient, discharge, and sediment load.  Gradient of rivers typically has concave downward logitudinal profile when in equilibrium.

• concept of base level; response to changing base levels
• dams cause local base level; deposition behind and erosion below dam.
• sea level rise/fall

4. Discharge

• Discharge is the volume of water passing a particularly point per unit time (m³/s, ft³/s or cfs). Q = vA.
• Determined by measuring the flow velocity and the cross-sectional area of the channel (usually just depth is all that is necessary).
• Increases downstream as more tributary streams add to the flow of the main river.

5. Floods
Floods are when discharge is sufficient to cause overbank flow. The floodplain becomes part of the channel. Formation of natural levees.  Several causes: tropical storms, melting snow, local thunderstorms (flash floods), dam breaks, or prolonged rainfall over large regions.

• Recurrence interval is a statistical analysis of yearly maximum discharges. R = (N + 1)/ M. Discharge vs. recurrence interval graphs are used to estimate floods of various sizes and their recurrence interval. Probability (in %) of flood of any size in a given year is P = (1/R)*100.
• Flood Hydrographs- plot of discharge vs. time at individual gauging stations. Used to predict velocity and characteristics of the flood wave as it travels downstream. Shape of the hydrograph is controlled by the size of the stream.  Human Effects on Flooding and Hydrograph: agriculture and urbanization increase the size and frequency of floods, and decreases lag-time between precip and flood-peak.
• Flood Hazard Mitigation
• Physical barriers: levees, floodwalls, and dams have both pros and cons.
• Management techniques usually involve detailed flood hazard mapping and computer modeling to identify hazardous areas on the floodplain.
• Floodplain zoning (floodway and floodway fringe).

6. Drainage Patterns

• highly dependent on local bedrock structure;  dendritic, rectangular, trellis, radial.
• Special cases where rate of downcutting = uplift of land surface.
• antecedent - downcutting and active deformation are simultaneous.
• superposed - established drainage downcuts through buried rock structures. Delaware Water Gap is classic example!

7. Deltas

• form when streams and rivers enter lakes or the ocean (base level). Current velocity drops and sediment is deposited. Channel branches into numerous distributaries.
• generally occur in tectonically stable coastlines with minimal wave and tide action.
• sand is deposited as topset beds; fine sand and silt as inclined foreset beds; silt and clay as bottomset beds.
• deltas "grow" by building outward and shifting location of the main distributaries over geologic time (thousands to millions of years!).