Stream Ecology: River Structure and Hydrology Unit 1: Module 4, Lectures 1

Developed by: Merrick, Richards Updated: August 2003 U1-m4-s2 Objectives  Students will able to:  describe how evaporation and precipitation influence river formation.  diagram the distribution of water on Earth.  define and provide examples of a watershed.  diagram stream networks and drainages.  explain how a meandering stream can form an oxbow lake.  predict riffle and pool formation in a stream segment.

Developed by: Merrick, Richards Updated: August 2003 U1-m4-s3 Module 4 introduces students to:  Lecture1:  The Importance of Rivers  The Hydrologic Cycle  Watersheds as a concept  Geomorphology  watersheds and drainage networks  channel morphology  habitat scales  Lecture 2:  Hydrology  flow and discharge  storm and annual hydrographs  flood probability  sediment transport and deposition

Developed by: Merrick, Richards Updated: August 2003 U1-m4-s4  Rivers:  Provide water and nutrients for agriculture  Provide habitat to diverse flora and fauna  Provide routes for commerce  Provide recreation  Provide electricity Importance of rivers

Developed by: Merrick, Richards Updated: August 2003 U1-m4-s5  Existence depends on:  Availability of surface water  A channel in the ground  An inclined surface Natural watercourses

Developed by: Merrick, Richards Updated: August 2003 U1-m4-s6  Four dimensions:  Longitudinal  Lateral  Vertical  Time Lotic systems The four dimensions of a lotic system

Developed by: Merrick, Richards Updated: August 2003 U1-m4-s7  The shape, size and content of a river are constantly changing, forming a close and mutual interdependence between the river and the land it traverses. Variation in time and space

Developed by: Merrick, Richards Updated: August 2003 U1-m4-s8 Effect of climate  Rivers are very dependent on climate and their characteristics are closely related to the precipitation and evaporation regimes in their drainage areas.  Three types:  Perennial or permanent rivers  Periodic rivers  Episodic rivers

Developed by: Merrick, Richards Updated: August 2003 U1-m4-s9 The hydrologic cycle ga.water.usgs.gov/edu/charts/waterdistribution.gif

Developed by: Merrick, Richards Updated: August 2003 U1-m4-s10 ga.water.usgs.gov/edu/charts/waterdistribution.gif Distribution of water on earth

Developed by: Merrick, Richards Updated: August 2003 U1-m4-s11 What is a watershed?

Developed by: Merrick, Richards Updated: August 2003 U1-m4-s12 What is a watershed?

Developed by: Merrick, Richards Updated: August 2003 U1-m4-s13 Spatial scale: Stream segments

Developed by: Merrick, Richards Updated: August 2003 U1-m4-s Stream networks or drainages

Developed by: Merrick, Richards Updated: August 2003 U1-m4-s15 Stream order  A method of classifying or ordering the hierarchy of natural channels.  Strahler (1957) is the most widely used system.  Stream order correlates well with drainage area, but is also regionally controlled by topography & geology.

Developed by: Merrick, Richards Updated: August 2003 U1-m4-s16 Spatial scale: Segment system

Developed by: Merrick, Richards Updated: August 2003 U1-m4-s17 Stream corridor and channel morphology

Developed by: Merrick, Richards Updated: August 2003 U1-m4-s18 Cross section of a channel

Developed by: Merrick, Richards Updated: August 2003 U1-m4-s19 Floodplain Figure 1.21

Developed by: Merrick, Richards Updated: August 2003 U1-m4-s20 Meandering rivers A meander becomes more pronounced as the streamline shifts between the river banks. Formation of an oxbow lake

Developed by: Merrick, Richards Updated: August 2003 U1-m4-s21  Small meanders  high gradient  coarse substrates Sinuosity: Gradient and substrate  Big meanders  low gradient  fine substrates

Developed by: Merrick, Richards Updated: August 2003 U1-m4-s22  Braided Pattern = high slope + high stream power + coarse bed materials Braided channel earthsci.org/teacher/basicgeol/stream/stream.html#Erosion%20by%20Streams

Developed by: Merrick, Richards Updated: August 2003 U1-m4-s23 dnr.metrokc.gov/WTD/wetland79/images/oxbow jpg An oxbow lake

Developed by: Merrick, Richards Updated: August 2003 U1-m4-s24 Spatial scale: Reach system

Developed by: Merrick, Richards Updated: August 2003 U1-m4-s25 Riffles, pools, and cascades  Riffles and pools alternate in somewhat predictable patterns

Developed by: Merrick, Richards Updated: August 2003 U1-m4-s26 Pool - riffle sequence  Riffle to riffle = channel widths