# Presentation: 061632

## Floodplain ManagementSESSION 2

**Stream Systems on**
**Dynamic Earth**
**River Basins & Tectonics**
**Prepared By**
**Donald R. Reichmuth, PhD.**

**Notes:**
Title Page for Session 2

## River Basin & Tectonic Framework

**Objectives:**
**1****	****Major landscape parameters that are involved in Floodplain Management.**
**2****	****Four fundamental functions of stream systems. **
**3****	****Size, shape, structure, and location of the major tectonic plates affect stream behavior.**
**4****	****Vertical plate motion affects sediment production.**
**5****	****Regional tectonic domains in the United States and their affect on floodplains. (Optional Objective)**
**6****	****Select a course case study exercise and form teams. **

**Notes:**
Objectives -- This slide lays out the objectives to be presented in this session.  The instructor should be tell the students what they are going to hear; then present the information and finally tell them what was said.

## Floodplain Definition

**That portion of a Drainage Basin**
**that is covered by **_**Transported Sediment**_
**that was deposited in or near a stream channel.**

**Notes:**
Floodplain Definition -- This slide shows that transported sediment can be found on Active and Inactive Stream Terraces; on Alluvial Fans; on Bedrock Canyon Floors and as Buried Fill covering valley floors. Note that Transported Sediment needs to be differentiated from Residual Soil that forms in place when bedrock disintegrates.
 Diagram used with the permission of Geomax, P.C., Spokane, WA

## River Basin Definition

**A region or area**
**bounded by a topographic divide**
**that contributes water**
**to a particular stream channel (corridor)**
**or other water body.**
**---------------------------------------------------**
**Sometimes called **
**a “catchment” or a “watershed”.**

**Notes:**
River Basin Definition -- The session is started by defining a “River Basin”.  It should be made clear that “River Basin” is preferred over “watershed”  because watershed has a dual meaning that can cause confusion.  The term “catchment” is best reserved for that portion of a river (drainage) basin above some specific measuring point on the stream.

## FUNCTIONS OF RIVER SYSTEMS

**Removes Erosional Debris**
**Most Important**
**Acts Over Long Periods**
**Removes Excess Water**
**Importance Secondary**
**Acts Sporadically Over Short Periods**
**Provides Fresh Water Supply**
**Necessary To Sustain Life**
**Transports Chemicals & Nutrients**

**Notes:**
Functions of River Systems -- It is extremely important to stress that a River System involves more than water.  The four primary functions cannot be separated and problems associated with the removal of erosional debris usually cause the largest instabilities in river basins.

## Geologic Framework

**Tectonics**
**Passive Margins**
**Stable Platforms**
**Active Margins**
**Hot Spots**

**Notes:**
Geologic Framework -- There are three branches of geology that must be understood if floodplain management is to successfully solve site specific problems.  The earth’s dynamics, often not appreciated by the lay public because the processes are often slow and subtle, determine how the earth’s surface is sculptured.  

## Present Plate Boundaries

**Notes:**
Present Plate Boundaries -- This slide shows the locations and sizes of the seven continental-sized and eight minor plates of the earth’s surface.  It is important to explain:  1) North America separated from Eurasian and African plates about 200 million years ago.  2)  North American and South American plates have only had a surface connection for the last 2 million years and   3)  Western Siberia is part of the North American Plate.  Taken from Kious & Tilling, 1996, USGS

## BASIC TYPES OF PLATE INTERACTION

- Stream Systems on
- Dynamic Earth

**Notes:**
Basic Types of Plate Interactions --  This slide depicts an idealized cross-section through the earth that shows various conditions that affect tectonic plates.  Included are Convergent, Transform and Divergent Plate Boundaries.  Additionally, hot spots, volcanoes, trenches and rifts zones are shown.
Taken from Kious & Tilling, 1996, USGS

## North America

**Structure**
**Craton**
**Shield**
**Stable Platform**
**Mobile Belts**
**Tectonic Activity**
**Active Margin**
**Passive Margin**

**Notes:**
North America --  This slide shows the location of the major structural units that form North America.  These units consist of the Craton that includes the Shield and Stable Platform and the surrounding Mobile Belt.  Because the North American Plate is moving westward, the West Coast is an Active Margin while the East Coast is a Passive Margin. It is important to note that the Stable Platform contains considerable limestone that formed in warm shallow seas when the area was much nearer to the equator.  Base Adapted from Dott and Batten, 1971

## Karst TopographyExample

**Solution Cavities In Limestone**
**Streams Can Have Subsurface Connections**

**Notes:**
Karst Topography -- This slide is an example of topography that forms on limestone.  In humid climates, organic acids attack limestone creating solution cavities.  These cavities often capture surface drainage creating sinkholes, Uvalas, and blind valleys. These surfaces are called Karst Topography.  When limestone migrates (by tectonic plate movement) into dryer, colder climates further attack by organic acid significantly slows and limestone becomes one of the stronger rock formations.  Adapted from a William J. Wayne Drawing

## Cretaceous Inland Sea100 Million Years Ago

**Notes:**
Cretaceous Inland Sea --  This slide depicts surface conditions that existed in the U.S. during the Cretaceous Period 100 million years ago. There were the old worn down Appalachian Mtns. in northeastern U.S. and young high mountains in the Rocky Mtn. region.  Between these two land masses was a Shallow Sea that cover the Central Plains and the Gulf Coast.  Large shale deposits formed in the shallow sea.  These shale deposits are now on the surface and are easily eroded.

## Vertical Plate Motion

**Causes:**
- 	**Tectonic/Earthquake Activity**
**	****Erosion & Sediment Loading**
**	****Glaciation**
**	****Human Activities**

**Notes:**
Vertical Plate Motion -- The earth’s surface is constantly moving.  Vertical shifts can alter stream gradients and change erosion rates.

## Uplift Example

**Notes:**
Uplift Example -- This slide shows the movement and collision of the Indian Plate.  The Indian Plate rammed into the Eurasian Plate about 10 million years ago.  Because both plates consist of lighter granitic rock (continental crust) neither would subduct, therefore the collision zone thickened forming the Himalayan Mtns.  This collision provides an excellent model of uplift and erosion because the relative plate motion is about the highest seen; the mountains have been uplifted to be the tallest mountains that currently exist and sediment concentration in the area’s rivers is the highest known.
Taken from Kious & Tilling, 1996, USGS

## Himalayan Data 

**Present Height ---**** **
**	****	****	****30,000 Ft (9,500 m)**
**Tectonic Uplift Rate  ---**
**	****	****	****More Than 1 cm/yr**
**Erosion Rate ---**
**	****	****	****Now Equals Uplift Rate**
**	****	****	****Sediment Yields Highest Known**

**Notes:**
Himalayan Data -- This slide provides the basic data to illustrate the end point when tectonic uplift equals erosion rate.  This balance is achieved because erosion increases dramatically as surface elevation increases.

## Worldwide Erosion Rates

**Notes:**
Worldwide Erosion Rates -- This slide shows the Denudation Rates for many of the earth’s major river basins. Note: Rates are Basin Wide Averages.  
The highest rates (500 mm/1000yrs) are concentrated around the Himalaya Mtns. and in eastern China.  Africa and Siberia have some of the lowest erosion rates (10 to 25 mm/1000 years).  North America has rates that range between 10 and 100 mm/1000 years.  The Colorado River Basin has the highest rate in North America.
Adapted from Skinner & Porter, 2000

## Oceanic-Continental Convergence

**Oceanic Crust Subducts**
**Ocean Trench Forms**
**Lighter Melted Material Rises**
**Volcanoes Form**
**Lithosphere Plunges Into Asthenosphere**

**Notes:**
Oceanic-Continental Convergence -- This slide shows how an Oceanic Plate subducts under a Continental Plate and causes Volcanoes to form as lighter Lithospheric material melts and raises through the Continental Crust.  Additionally, the downward bending Oceanic Plate causes a Trench to form along the Continental coast.
Taken from Kious & Tilling, 1996, USGS

## Effects Of Plate Locking

**Notes:**
Effects of Plate Locking -- This slide depicts the vertical ground movements that occur a subducting Oceanic Plate locks to a Continental Plate as they converge.  A buckle forms when the Trench is dragged downward.  The buckle can raise 2 to 4 mm/year, while further inland the Plate sinks.  When the lock is broken during an Earthquake, the Continental Plate snaps back to its unstrained (unbuckled) position causing Continental Plate to move vertically back to it unstrained position.
Adapted from Geological Survey of Canada, Pacific Geoscience Center diagram.

## Effects Of Erosion

**Notes:**
Slide PP2.4-7 Effects of Erosion -- This slide illustrates how isostatic equilibrium is maintained when mountains are eroded away.  Mountains have roots of lighter rock extending into the Asthenosphere that provide buoyancy for the uplifted mass.  As the mountain surface is eroded away, the entire mountain rises making the root smaller.  The sediment produced during this erosion is transported to basins (either river or ocean) where it is deposited.  This deposition adds weight that causes the basin to sink so isostatic equilibrium is maintained. Based on diagrams of Tarbuck & Lutgens, 1976

## Man Induced Vertical Movement

**Notes:**
Man Induced Vertical Movement -- This slide shows the settlement that occurred between 1935 and 1950 at Las Vegas, Nevada and in the vicinity of Lake Mead on the Colorado River upstream from Hoover Dam.  Las Vegas settled a maximum of 340 mm and a large cone of depression centered on the lake sank 170 mm.  The Las Vegas settlement was due to groundwater withdrawal while the Lake Mead settlement was due to the weight of add water when the lake was filled.
Adapted from USGS Circular 346, 1954

## Ongoing Elevation Changes

**Notes:**
Ongoing Elevation Changes --  This slide depicts the present vertical movement within the U.S. (lower 48 states).  There are three large areas of uplift  They are 1) The Rocky Mtn. region (1-10 mm/year) caused tectonic (mountain building) activity;  2)  Upper Mid-West (5-15 mm/year) caused by glacial rebound and  3)  Southeast region (1-10 mm/year) caused buckling, weight removal and tectonic activity.  Areas that are settling include: 1)  East Coast (1-10 mm/year) caused by plate cooling along the Passive Margin; 2)  Gulf Coast (5-10 mm/year) caused by weight from deposition of sediment in the Gulf of Mexico and 3) Central Valleys of California (5-10 mm/year) caused by Active Margin plate tectonics.

## Active Margin

**Note:**
**Aleutian Trench**
**Canada**
-  **Strike-Slip Faulting**
**Mobile Belt Deposits**
**California**
**Strike-Slip Faulting**

**Notes:**
Active Margin -- This slide shows the tectonic conditions along the Pacific Rim from Mexico to the Aleutian Islands.  Most significant is the subduction along the Aleutian Island creating the Aleutian Trench and the Transform Boundary along the U.S. West Coast that contains the San Andreas Fault. Taken from Kious & Tilling, 1996, USGS

## Active Margin

**Ocean-Continent Subduction**
**Strike Slip Faulting**

**Notes:**
Active Margin --  This slide depicts the tectonic activity taking place along Washington, Oregon and California coasts. There is a subduction zone off Washington and Oregon coast. Numerous
 Strike-slip Faults (Blanco, Mendocino, Murray and Molokai) occur in the ocean in this region.  The San Andreas Fault which is the southern extension of the Mendocino Fracture Zone is the only Strike-slip Fault exposed on land in this area. Taken from Kious & Tilling, 1996, USGS

## Hot Spot Locations

**Notes:**
Hot Spot Locations -- Some of the more prominent hot spots on earth are shown on this slide. There appears to be no clear correlation between surface tectonic features and the hot spots.  Hot Spots and created the Hawaiian Islands and the Yellowstone Park features in the U.S. Taken from Kious & Tilling, 1996, USGS

## Hawaiian Hotspot

**Notes:**
Hawaiian Hotspot -- The formation of the Hawaiian Islands by Hot Spot activity is illustrated in this slide.  Note that the islands get progressively older to the north because the Pacific Plate is moving northward with respect to the subsurface thermal plume. Taken from Kious & Tilling, 1996, USGS

## Passive Margin

**Coastline Sinking**
**Drowned River Valleys**
**Numerous Near-shore Islands**
**Shoreline Migrating Landward**

**Notes:**
Passive Margin --  This slide depicts the part of the South Carolina, Georgia and Florida coast that forms part of the East Coast Passive Margin. Most notable are the drowned river valleys; near shore islands and retreating shoreline that is caused by Plate settlement.  Adapted from Zeigler, 1959

## Uplift ForcesEarth’s Internal Heating ProvidesEnergy To Cause Surface UpliftErosion Can Then Proceed

**Notes:**
Uplift Forces – The earth’s internal heating produced by radioactive decay and gravitational compression causes land areas and the sea floor to deform and fracture.  These processes often cause the land surface to be uplifted.  Before geological understanding developed, Paleo-cultures developed myths and gods to explain the observed surface disruptions.  Unfortunately today, there are still many individuals who do not understand geological processes. Diagram used with the permission of Geomax, P.C., Spokane, WA

## CASE  STUDIES

**Columbia River**
**Mississippi River**
**Ohio River**
**Potomac River**
**Red River of the North**
**Rio Grande River**
**Santa Ana River**

**Notes:**
Case Studies -- This slide contains a list of Rivers whose basins are to be studied.  These systems were picked to provide a range of conditions and environments that can be encountered within the U.S. 

## Geologic Setting (Refer to Handout)

**Notes:**
Geologic Setting -- This slide lists some of the more significant Geologic factors that need to be considered for each of the River Basins included for case study.

## JURISDICTION  &  CONCERNS (Refer to Handout)

**Notes:**
Jurisdiction & Concerns --  This slide lists some of the more significant Non-Geologic factors that need to be considered for each of the River Basins included for case study.

## Slide Presentation Prepared ByGeomax, P.C.Dr. Donald R. Reichmuth, President1023 W. 30th Ave.Spokane, WA 99203-1324Phone & FAX – 509-838-6390E-mail – geomax@comcast.net

**Notes:**
This slide set for Session 2 was last edited on 12/15/04.