Geology 230 Groundwater/ surface water interaction Tim Horner Geology Department, CSU Sacramento

Geology 230Groundwater/ surface water

interaction

Tim HornerGeology Department, CSU Sacramento

Week 1: Stream classification

Reading assignment:

1) EPA Watershed Academy, 2005, Fundamentals of the Rosgen Stream Classification System: Accessed 8/29/05 at http://www.epa.gov/watertrain/stream_clas/index.htm. 2) Montgomery, D. R., and Buffington, J. M., 1994, Channel-reach morphology in mountain drainage basins: Geological Society of America Bulletin, v. 109, pp. 596-611.

3) Mial, A. D., 1977, Lithofacies Types and Vertical Profile Models in Braided River Deposits: A Summary, in, Fluvial Sedimentology — Memoir 5, Fluvial Facies Models, pp. 597-604.

SACRAMENTOSTATE

Methods used to characterize streams:

Miall- A sedimentologist’s approach

Rosgen- Based on channel morphology

Montgomery and Buffington- More process based

From Miall, 1977

Miall’s lithofaciesdesignations

Miall’s stream types- braided rivers

From Miall, 1977

Miall’s stream types- braided riversExamples are intended to show all of the variability in braided streams.Several are based on glacial outwash

From Miall, 1977

proximal -------------------------distal High energy with limited sediment supply

Debris flow

Rosgen’s classification system

Advantages Disadvantages• Simple key, can be used by inexperienced field hands• Looks mostly at form

• Simple key, can be used by inexperienced field hands• May not represent scale accurately

From: EPA Watershed Academy, 2005

Rosgen’s classification system Three main parts:

• Level I classification, which is based on the stream characteristics that result from relief, landform, and valley morphology;

• Valley type, a primary determinant of stream form; • Level II classification, which provides more detailed morphological description of stream type from field measurements of channel form and bed composition.


http://www.epa.gov/watertrain/stream_class/02lt03.htm



Level I Stream Classification

The Level I stream classification serves four primary functions:

1. Provide for the initial integration of basin characteristics, valley types, and landforms with stream system morphology.

2. Provide a consistent initial framework for organizing river information and communicating the aspects of river morphology. Mapping of physiographic attributes at Level I can quickly determine location and approximate percentage of river types within a watershed and/or valley type.

3. Assist in the setting of priorities for conducting more detailed assessments and/or companion inventories.

4. Correlate similar general level inventories such as fisheries habitat, river boating categories, and riparian habitat with companion river inventories.

The Level 1 Stream Classification produces a letter: A - G

Level I Stream Classification

• Is landscape scale• Can be accomplished with topo maps or air photos


Level 1 assessmentDepends on basin-scale factors:



Variables:• gradient• width/depth ratio• lateral confinement• sinuosity

High energy, high sediment load

• entrenchment• meander geometry• erosion• sinuosity

multiple channels

anastomosing stable channel, more entrenched, low relief

Level 2 assessment: Valley typeThere are 11 Valley Types. Valley types may correlate with Level 1 stream types


Level 2 assessment: Valley typeThere are 11 Valley Types. Valley types may correlate with Level 1 stream types


Type X, XI may include wetlands

Part 3: Level II Stream ClassificationCross-sectional measurements

Entrenchment Ratio: A computed index value which is used to describe the degree of vertical containment of a river channel (width of the flood prone area at an elevation twice the maximum bankfull depth/bankfull width). Width/depth Ratio: An index value which indicates the shape of the channel cross-section (ratio of bankfull width/mean bankfull depth). Dominant Channel Materials: A selected particle size index value, the D50, representing the most prevalent of one of six channel material types or size categories, as determined from a channel material size distribution analysis. Longitudinal Profile measurements

Slope: Slope of the water surface averaged for 20-30 channel widths. Bed Features: Secondary delineative criteria describing channel configuration in terms of riffle/pools, rapids, step/pools, cascades and convergence/divergence features which are inferred from channel plan form and gradient.

Plan-form (pattern) measurements

Sinuosity: Defined as stream length/valley length or valley slope/channel slope). Meander Width Ratio: A secondary delineative criteria defined as meander belt width/bankfull width that describes the degree of lateral channel containment, and is primarily used in assisting aerial photo delineation of stream types.


Part 3: Level II Stream ClassificationFrom: EPA Watershed Academy, 2005

Gathering field data for Level II Stream Classification:


Visual or physical indicators of the bankfull stage:

The presence of a floodplain at the elevation of incipient flooding.

The elevation associated with the top of the highest depositional features (e.g., point bars, central bars within the active channel). These depositional features are especially good stage indicators for channels in the presence of terraces or adjacent colluvial slopes.

A break in slope of the banks and/or a change in the particle size distribution, (since finer material is associated with deposition by overflow, rather than deposition of coarser material within the active channel).

Evidence of an inundation feature such as small benches. Staining of rocks.

Exposed root hairs below an intact soil layer indicating exposure to erosive flow.

Lichens and - for some stream types and locales - certain riparian vegetation species

Measuring bankfull stage in the field:


Estimating entrenchment ratio:


Estimating width/depth ratio:


Estimating sinuosity:


Estimating slope:


Estimating channel material (pebble counts):


Summary: Rosgen’s stream classification method


Montgomery and Buffington, 1997:

Montgomery and Buffington, 1997

Looks at reach-level stream features

7 alluvial channel types:

colluvial

bedrock

cascade

step pool

plane bed

pool riffle

dune riffle

Montgomery and Buffington channel types:

From: Montgomery and Buffington, 1997


Montgomery and Buffington: channel type vs. gradient


Montgomery and Buffington: channel type vs. drainage area


Montgomery and Buffington: channel type vs. roughness and grain size


Montgomery and Buffington: channel type transport capacity


Montgomery and Buffington: channel response to changes in sediment supply and discharge

Other methods of stream characterization:

Strahler, order of streams

Geology 230 Groundwater/ surface water interaction Tim Horner Geology Department, CSU Sacramento

Documents

Transcript of Geology 230 Groundwater/ surface water interaction Tim Horner Geology Department, CSU Sacramento