DOCSLIB.ORG

Credit River, MN Final Report - Fluvial Geomorphic Assessment

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text

Load more

Credit River, MN Final Report - Fluvial Geomorphic Assessment March 5, 2008 Prepared for: Scott County Community Development Natural Resources Department Government Center 14 200 Fourth Avenue West Shakopee, MN 55379-1220 3602 Atwood Avenue Suite 3 Madison, WI 53714 2007 Inter-Fluve Inc. Credit River Geomorphic Assessment 2 TABLE OF CONTENTS 1. Introduction.....................................................................................................................3 1.1. Review of Fluvial Geomorphology Principles.......................................................5 2. Data Collection / Methods ............................................................................................10 2.1. Existing data.........................................................................................................10 2.2. Fluvial Geomorphology .......................................................................................10 2.3. Hydrology.............................................................................................................10 3. Results...........................................................................................................................12 3.1. Geology, topography and soils.............................................................................12 3.2. Historic Conditions..............................................................................................13 3.3. Existing Geomorphology .....................................................................................18 3.4. Surface Water Hydrology.....................................................................................31 4. Management Recommendations...................................................................................34 4.1. Project Type - Natural Channel Restoration/Relocation ......................................34 4.2. Project Type - Grade Control ...............................................................................38 4.3. Project Type – Floodplain Management ..............................................................38 4.4. Project Type – Riparian Management..................................................................38 4.5. Project Type – Crossing. ......................................................................................39 4.6. Project Type - Bank Stabilization ........................................................................40 4.7. General Recommendations...................................................................................42 4.8. Specific Potential Projects....................................................................................42 5. References........................................................................................................................43 6. Appendices.......................................................................................................................44 2007 Inter-Fluve Inc. Credit River Geomorphic Assessment 3 1. Introduction conditions by reach for the main stem and In the spring of 2007, the Scott County tributaries. This report is supplemented by Natural Resources Department contracted with completed project forms which the County will Inter-Fluve to conduct a fluvial geomorphic integrate into the Scott County GIS platform. assessment of the Credit River Watershed. The This fluvial geomorphic assessment was project is an attempt to locate channel stability geared toward project identification so that Scott problems, assess overall stream condition and County can eventually develop a long term address the concerns of landowners regarding restoration and watershed management strategy. erosion, flooding and threats to infrastructure. This type of assessment typically results in a large Through several meetings, Inter-Fluve and number of total projects; in this case 48 County officials identified the following significant projects were identified on the Credit objectives: River mainstem. In order to prioritize these projects for funding allocation, a ranking system 1) Conduct a reconnaissance level geomorphic assessment that collects for potential restoration projects was developed information regarding channel stability, for the watershed. This ranking system scores infrastructure, fish habitat, and general stream health potential project sites based on 11 metrics (Table 2) Identify potential restoration or 1). Each metric contributes a value of 1 through 7 reclamation projects in the watershed for the site, and the total of all of the metrics is 3) Create a system of prioritization for the potential project score. Each project can be identified projects ranked by a single metric or multiple metrics, so 4) Integrate the results of the study with the that priority can be a result of any combination of existing Scott County Geographic metrics chosen by Scott County staff. Information System (GIS) platform In this system, metrics refer mainly to the degree that a completed project will affect each Scott County staff assisted with collection of metric. For example, an infrastructure risk score existing data (aerial photographs, maps etc.) and of 1 reflects that if nothing is done, there will still created field maps. Inter-Fluve scientists be no risk to infrastructure from channel identified distinct study reaches within the Credit instability, either because no infrastructure exists River watershed. Fieldwork commenced in June at the site, or risk is extremely low. Conversely, a and July 2007, and Inter-Fluve met with score of 7 indicates that if nothing is done, public interested landowners on site and with officials safety and property are under immanent risk. This from the City of Savage. project did not include any formal structural The report that follows is a brief summary of engineering survey or risk assessment. If the data collected, and outlines general stream infrastructure is determined in this survey to be at 2007 Inter-Fluve Inc. Credit River Geomorphic Assessment 2007 Inter-Fluve Inc. 2007 Inter-Fluve Inc. Cred Table 1: Metrics for scoring potential projects. Metric Score: 1 3 5 7 Low to moderate infrastructure risk Infrastructure at moderate but not immedi- Infrastructure at high or immanent risk No risk to infrastructure with no action, Infrastructure risk and minimal risk to public safety with ate risk, moderate public safety risk, or of failure with no action. Public safety or no infrastructure present no action, or inf. value <$100,000 infrastructure value <$200,000 at risk or infrastructure value >$200,000 Minimal improvement to overall stream Low to moderate improvement of 250- Moderate improvement 1000-2500 ft of Significant improvement to overall Erosion/channel stability stability and function, <250 ft of channel 1000 ft of channel bank channel bank stream stability and function or >2500 ft bank Groundwater and surface water issues, Surface water restoration, engineering Moderately complex, no specialty engi- Elementary solution, shelf design, vol- professional specialty design services Project complexity plans required, earthwork involved, neering required, minor earthwork, some unteer and hand labor implementation, required, heavy oversight, major earth- significant permitting basic permitting no permits work, EAW/EIS permitting Location Mouth to lower ¼ of watershed Lower 1/4 to 1/2 of watershed 1/2 to upper 3/4 of watershed Upper 3/4 to headwaters Some minor reduction in sediment Moderate reduction in bank erosion and Major erosion control through signifi- Sediment/nutrient load- No load reduction resulting pollution, increased filtration of nutri- surface runoff entering stream through cant BMP installation, stormwater ing ents buffer or other BMPs > 30 ft detention, infiltration or buffer filter. Project cost > $300K $201 - $300K $51 - 200K $0 - $50K Aesthetic impact No impact Low impact Moderate positive impact High positive impact Low impact (eg. improve depth Moderate impact (removes perch or other Fish passage No impact on fish passage through culvert, minimal velocity small barrier, natural bottom culvert re- High impact (dam removal) it River GeomorphicAssessment it reduction) placement) High value - Easy access, cooperating Low value - Poor site access, difficult Moderate value - Good access, moderate Public Education No public education value landowner, good demonstration and to see, small project demonstration value high visual impact In-stream Ecological Moderate benefit - subreach based, moder- High benefit - Reach based, >1000 ft of No in-stream ecological benefit Low benefit - Spot location, small size Benefit ate sized project stream Riparian Ecological Moderate benefit - subreach based, moder- High benefit - Reach based, large ripar- No riparian ecological benefit Low benefit - Spot location, small size Benefit ate sized project ian areas, floodplain scale 4 5 some risk, we advise local officials to conduct 1.1. Review of fluvial geomorphology principles their own formal structural engineering In order to fully visualize the relationships assessment. This scoring does not reflect any risk between habitat formation and stream ecology, it from flooding. Other metrics gauge the potential is important to have a basic understanding of project’s effect on channel stability, ecological fluvial geomorphology. This section discusses the benefit, nutrient loading and fish passage. principles behind fluvial processes and how they Because of the interconnectivity of river systems, relate to stream habitat. Stable stream systems are
Recommended publications
  • VOLCANIC INFLUENCE OVER FLUVIAL SEDIMENTATION in the CRETACEOUS Mcdermott MEMBER, ANIMAS FORMATION, SOUTHWESTERN COLORADO

    VOLCANIC INFLUENCE OVER FLUVIAL SEDIMENTATION in the CRETACEOUS Mcdermott MEMBER, ANIMAS FORMATION, SOUTHWESTERN COLORADO

    VOLCANIC INFLUENCE OVER FLUVIAL SEDIMENTATION IN THE CRETACEOUS McDERMOTT MEMBER, ANIMAS FORMATION, SOUTHWESTERN COLORADO Colleen O’Shea A Thesis Submitted to the Graduate College of Bowling Green State University in partial fulfillment of the requirements for the degree of MASTER OF SCIENCE August: 2009 Committee: James Evans, advisor Kurt Panter, co-advisor John Farver ii Abstract James Evans, advisor Volcanic processes during and after an eruption can impact adjacent fluvial systems by high influx rates of volcaniclastic sediment, drainage disruption, formation and failure of natural dams, changes in channel geometry and changes in channel pattern. Depending on the magnitude and frequency of disruptive events, the fluvial system might “recover” over a period of years or might change to some other morphology. The goal of this study is to evaluate the preservation potential of volcanic features in the fluvial environment and assess fluvial system recovery in a probable ancient analog of a fluvial-volcanic system. The McDermott Member is the lower member of the Late Cretaceous - Tertiary Animas Formation in SW Colorado. Field studies were based on a southwest-northeast transect of six measured sections near Durango, Colorado. In the field, 13 lithofacies have been identified including various types of sandstones, conglomerates, and mudrocks interbedded with lahars, mildly reworked tuff, and primary pyroclastic units. Subsequent microfacies analysis suggests the lahar lithofacies can be subdivided into three types based on clast composition and matrix color, this might indicate different volcanic sources or sequential changes in the volcanic center. In addition, microfacies analysis of the primary pyroclastic units suggests both surge and block-and-ash types are present.
  • Classifying Rivers - Three Stages of River Development

    Classifying Rivers - Three Stages of River Development

    Classifying Rivers - Three Stages of River Development River Characteristics - Sediment Transport - River Velocity - Terminology The illustrations below represent the 3 general classifications into which rivers are placed according to specific characteristics. These categories are: Youthful, Mature and Old Age. A Rejuvenated River, one with a gradient that is raised by the earth's movement, can be an old age river that returns to a Youthful State, and which repeats the cycle of stages once again. A brief overview of each stage of river development begins after the images. A list of pertinent vocabulary appears at the bottom of this document. You may wish to consult it so that you will be aware of terminology used in the descriptive text that follows. Characteristics found in the 3 Stages of River Development: L. Immoor 2006 Geoteach.com 1 Youthful River: Perhaps the most dynamic of all rivers is a Youthful River. Rafters seeking an exciting ride will surely gravitate towards a young river for their recreational thrills. Characteristically youthful rivers are found at higher elevations, in mountainous areas, where the slope of the land is steeper. Water that flows over such a landscape will flow very fast. Youthful rivers can be a tributary of a larger and older river, hundreds of miles away and, in fact, they may be close to the headwaters (the beginning) of that larger river. Upon observation of a Youthful River, here is what one might see: 1. The river flowing down a steep gradient (slope). 2. The channel is deeper than it is wide and V-shaped due to downcutting rather than lateral (side-to-side) erosion.
  • Stream Visual Assessment Manual

    Stream Visual Assessment Manual

    U.S. Fish & Wildlife Service Stream Visual Assessment Manual Cane River, credit USFWS/Gary Peeples U.S. Fish & Wildlife Service Conasauga River, credit USFWS Table of Contents Introduction ..............................................................................................................................1 What is a Stream? .............................................................................................................1 What Makes a Stream “Healthy”? .................................................................................1 Pollution Types and How Pollutants are Harmful ........................................................1 What is a “Reach”? ...........................................................................................................1 Using This Protocol..................................................................................................................2 Reach Identification ..........................................................................................................2 Context for Use of this Guide .................................................................................................2 Assessment ........................................................................................................................3 Scoring Details ..................................................................................................................4 Channel Conditions ...........................................................................................................4
  • Drainage Basin Morphology in the Central Coast Range of Oregon

    Drainage Basin Morphology in the Central Coast Range of Oregon

    AN ABSTRACT OF THE THESIS OF WENDY ADAMS NIEM for the degree of MASTER OF SCIENCE in GEOGRAPHY presented on July 21, 1976 Title: DRAINAGE BASIN MORPHOLOGY IN THE CENTRAL COAST RANGE OF OREGON Abstract approved: Redacted for privacy Dr. James F. Lahey / The four major streams of the central Coast Range of Oregon are: the westward-flowing Siletz and Yaquina Rivers and the eastward-flowing Luckiamute and Marys Rivers. These fifth- and sixth-order streams conform to the laws of drain- age composition of R. E. Horton. The drainage densities and texture ratios calculated for these streams indicate coarse to medium texture compa- rable to basins in the Carboniferous sandstones of the Appalachian Plateau in Pennsylvania. Little variation in the values of these parameters occurs between basins on igneous rook and basins on sedimentary rock. The length of overland flow ranges from approximately i mile to i mile. Two thousand eight hundred twenty-five to 6,140 square feet are necessary to support one foot of channel in the central Coast Range. Maximum elevation in the area is 4,097 feet at Marys Peak which is the highest point in the Oregon Coast Range. The average elevation of summits in the thesis area is ap- proximately 1500 feet. The calculated relief ratios for the Siletz, Yaquina, Marys, and Luckiamute Rivers are compara- ble to relief ratios of streams on the Gulf and Atlantic coastal plains and on the Appalachian Piedmont. Coast Range streams respond quickly to increased rain- fall, and runoff is rapid. The Siletz has the largest an- nual discharge and the highest sustained discharge during the dry summer months.
  • Streams and Running Water Streams Are Part of the Hydrologic Cycle (Figure 10.1)

    Streams and Running Water Streams Are Part of the Hydrologic Cycle (Figure 10.1)

    Streams and Running Water Streams are part of the hydrologic cycle (Figure 10.1) Stream: body of running water that is confined in a channel and moves downhill under the influence of gravity. Cross-section of a typical stream (Figure 10.2) 1) Channel Flow 2) Sheet Flow Drainage Basin: area of a stream and its’ tributaries. Tributary: small stream flowing into a large one. Divide: ridge seperating drainage basins. Drainage Patterns 1) Dendritic: resembles tree branches > occurs on uniformly resistant rock 2) Radial: streams diverge outward from a central point > occurs on conic shapes, like volcanoes 3) Rectangular: steams have sharp bends ¾ due to presence of faulting, river follows the fault 4) Trellis: Parallel main streams with right angle tributaries > occurs on valley and ridge geomorphologies Factors Affecting Stream Erosion and Deposition 1) Velocity = distance/time Fast = 5km/hr or 3mi/hr Flood = 25 km/hr or 15 mi/hr Figure 10.6: Fastest in the middle of the channel a) Gradient: downhill slope of the bed of the stream ¾ very high near the mountains ¾ 50-200 feet/ mile in highlands, 0.5 ft/mile in floodplain b) Channel Shape and Roughness (Friction) > Figure 10.9 ¾ Lots of fine particles – low roughness, faster river ¾ Lots of big particles – high roughness, slower river (more friction) High Velocity = erosion (upstream) Low Velocity = deposition (downstream) Figure 10.7 > Hjulstrom Diagram What do these lines represent? Salt and clay are hard to erode, and typically stay suspended 2) Discharge: amount of flow Q = width x depth
  • Us Department of the Interior Us Geological Survey

    Us Department of the Interior Us Geological Survey

    U.S. DEPARTMENT OF THE INTERIOR U.S. GEOLOGICAL SURVEY QUATERNARY GEOLOGY OF THE GRANITE PARK AREA, GRAND CANYON, ARIZONA: AGGRADATION-DOWNCUTTING CYCLES, CALIBRATION OF SOILS STAGES, AND RESPONSE OF FLUVIAL SYSTEM TO VOLCANIC ACTIVITY By Ivo Lucchitta1 , G.H. Curtis2, M.E. Davis3, S.W. Davis3, and Brent Turrin4. With an Appendix by Christopher Coder, Grand Canyon National Park, Grand Canyon, AZ 86040 Open-file Report 95-591 This report is preliminary and has not been reviewed for conformity with U.S. Geological Survey editorial standards. Any use of trade, firm, or product names is for descriptive purposes only and does not imply endorsement by the U.S. Government. J U.S. Geological Survey, Flagstaff, AZ 86001 2 Berkeley Geochronology Center, Berkeley, CA 94709 3 Davis2, Georgetown, CA 95634 4 U.S. Geological Survey, MenLo Park, CA 94025 nr ivv ^^^^t^^^^^'^S:^ ';;.; ;.:;. .../r. - '.''^.^.v*'' ^.vj v'""/^"i"%- 'JW" A- - - - -- - * GLEN CANYON ENVIRONMENTAL STUDIES QUATERNARY GEOLOGY-GEOMORPHOLOGY PROGRAM REPORT 2 QUATERNARY GEOLOGY OF THE GRANITE PARK AREA, GRAND CANYON, ARIZONA: DOWNCUTTING- AGGRADATION CYCLES, CALIBRATION OF SOIL STAGES, AND RESPONSE OF FLUVIAL SYSTEM TO VOLCANIC ACTIVITY CONTENTS ABSTRACT INTRODUCTION PURPOSE METHODS RESULTS Geology and geomorphology Soils Geo chronology SUMMARY AND CONCLUSIONS Geochronology Geology and geomorphology Soils Soil-stage calibration Processes REFERENCES ACKOWLEDGMENTS APPENDICES A Synopsis of Granite Park Archeology B Representative Soil Profile Descriptions C Step-heating spectra, isochrons and sampling comments for 39Ar-40Ar age determinations on Black Ledge basalt flow, Granite Park area, Grand Canyon FIGURES PLATES AND FIGURES Plate 1. View at mile 207.5 Plate 2. View of section at mile 208.9 Figure 1.
  • Stream Processes (Modified from Fetter and Muldoon, 2008)

    Stream Processes (Modified from Fetter and Muldoon, 2008)

    PHYSICAL GEOLOGY LABORATORY Stream Processes (modified from Fetter and Muldoon, 2008) Objectives: 1. To observe the processes of erosion, transportation, and deposition by running water. 2. To be able to predict how stream processes will affect a stream channel through time. 3. To observe the inter-relation between groundwater and surface water. 4. To observe formation of a delta. Definitions: Bed Load Sediment rolling and sliding on the bottom of a stream. Suspended load Sediment in suspension due to turbulence. Channel The trough through which a stream flows. Floodplain The low flat area surrounding the river channel that floods when the river overflows its banks Meander A bend in a stream where the stream is actively eroding the outside bank while depositing sediment along the inside bank. Gradient The slope of the river. Point Bars Shallows on the inside bank of meanders, developed by deposition. Base Level The lowest level to which a stream can erode. Ultimate base level is the ocean, but local base levels such as lakes may also exist. Competence The maximum size particle that can be transported. 1 Stream Table: The stream table will have a moderate amount of water flowing, creating three lakes, one impounded by a dam (Lake A), another impounded in the lower end of the tank (Lake C), and a third with no tributary channel draining into it (Lake B). There will be a large rock in the middle of the channel below the dam. Figure 1. Top view of stream table. Figure 2. Side view of stream table. Groundwater / Surface Water Relationships
  • Development Team

    Development Team

    Paper No: 4 Environmental Geology Module: 11 Streams and Flooding Development Team Prof. R.K. Kohli Principal Investigator & Prof. V.K. Garg & Prof. Ashok Dhawan Co- Principal Investigator Central University of Punjab, Bathinda Prof. R. Baskar, , Guru Jambheshwar University of Paper Coordinator Science and Technology, Hisar Dr. Renu Lata G. B. Pant National Institute of Himalayan Environment Content Writer and Sustainable Development (GBPNIHESD), Kosi- Katarmal, Almora Dr. Sushmitha Baskar, IGNOU, New Delhi Content Reviewer 1 Anchor Institute Central University of Punjab Environmental Geology Environmental Sciences Streams and Flooding Description of Module Subject Name Environmental Sciences Paper Name Environmental Geology Module Streams and Flooding Name/Title Module Id EVS/EG-IV/11 Pre-requisites Objectives Explain the hydrological cycle and its relevance to streams Explain different types of streams Describe a drainage basin and explain the origins of different types of drainage patterns Explain the flood hazards (causes, effects & management) in India Describe some of the important historical floods in India Explain some of the steps that we can take to limit the damage from flooding Keywords Streams and floods, topography, impacts, consequences, flood control, flood management, action plan, policies. 2 Environmental Geology Environmental Sciences Streams and Flooding 1.0 Title : STREAMS AND FLOODING 2.0 Objectives Explain the hydrological cycle and its relevance to streams Explain different types of streams Describe a drainage basin and explain the origins of different types of drainage patterns Explain the flood hazards (causes, effects & management) in India Describe some of the important historical floods in India Explain some of the steps that we can take to limit the damage from flooding 2.1 Introduction Streams are the most important agents of erosion and transportation of sediments on Earth’s surface.
  • 2002 Hancock.Pdf

    2002 Hancock.Pdf

    Downloaded from gsabulletin.gsapubs.org on December 21, 2010 Geological Society of America Bulletin Numerical modeling of fluvial strath-terrace formation in response to oscillating climate Gregory S. Hancock and Robert S. Anderson Geological Society of America Bulletin 2002;114;1131-1142 doi: 10.1130/0016-7606(2002)114<1131:NMOFST>2.0.CO;2 Email alerting services click www.gsapubs.org/cgi/alerts to receive free e-mail alerts when new articles cite this article Subscribe click www.gsapubs.org/subscriptions/ to subscribe to Geological Society of America Bulletin Permission request click http://www.geosociety.org/pubs/copyrt.htm#gsa to contact GSA Copyright not claimed on content prepared wholly by U.S. government employees within scope of their employment. Individual scientists are hereby granted permission, without fees or further requests to GSA, to use a single figure, a single table, and/or a brief paragraph of text in subsequent works and to make unlimited copies of items in GSA's journals for noncommercial use in classrooms to further education and science. This file may not be posted to any Web site, but authors may post the abstracts only of their articles on their own or their organization's Web site providing the posting includes a reference to the article's full citation. GSA provides this and other forums for the presentation of diverse opinions and positions by scientists worldwide, regardless of their race, citizenship, gender, religion, or political viewpoint. Opinions presented in this publication do not reflect official positions of the Society. Notes Geological Society of America Downloaded from gsabulletin.gsapubs.org on December 21, 2010 Numerical modeling of ¯uvial strath-terrace formation in response to oscillating climate Gregory S.
  • Chapter 60. Strath Terraces

    Chapter 60. Strath Terraces

    Chapter 60 Strath Terraces All over the world we find terraces flanking the sides of valleys. Generally, they run parallel to and above a river and its immediate floodplain. Most of them are composed of gravel that was laid down when a river overflowed its banks. I call these gravel terraces for obvious reasons. Figure 60.1 shows a schematic of how they were formed. The largest ones were deposited by melt-water from the Ice Age. An example of this kind of terrace is found in the upper Snake River Valley of Jackson Hole Valley, Wyoming. It formed when the Yellowstone ice cap melted (Figure 60.2). Strath terraces are similar to gravel terraces in that they lie along the sides of a valley. Their uniqueness lies in that they are elongated planation surfaces cut in bedrock and covered with a thin layer of gravel, cobbles, and boulders (Figure 60.3). Uniformitarian scientists think strath terraces are remnants of a flat, broad valley floor (a strath) that was carved flat in bedrock, with subsequent downcutting leaving the side of the old rock floor hanging along the sides of the valley.1 Flat bottom valleys, according to their hypothesis, represent a period of valley widening with no deepening. I mostly agree with their interpretation, except I am convinced a river did not erode the old bedrock floor nor did it cause the subsequent downward erosion. Rivers tend to mostly cut downward, for planatin across the whole valley, a valley-side flow of water is required. Melting at the end of the Ice Age with its occasional turbid valley-wide flooding could carve strath terraces.
  • Grade Control

    Grade Control

    River Restoration Toolbox Practice Guide 1 Grade Control Iowa Department of Natural Resources April, 2018 RIVER RESTORATION TOOLBOX PRACTICE GUIDE 1 Table of Contents EXECUTIVE SUMMARY ............................................................................................................... I 1.0 INTRODUCTION ............................................................................................................. 1 1.1 GEOMORPHIC DESIGN CONSIDERATIONS .................................................................... 1 1.2 HYDROLOGIC AND HYDRAULIC COMPUTATIONS ........................................................ 2 1.3 MATERIALS .......................................................................................................................... 2 1.3.1 Rock Materials ................................................................................................. 2 1.3.2 Filter Fabric....................................................................................................... 3 1.4 FLOODPLAIN (CUT-OFF) SILLS OR KEYWAYS .................................................................. 3 1.5 FISH PASSAGE .................................................................................................................... 3 2.0 GRADE CONTROL TECHNIQUES .................................................................................... 4 2.1 FREESTANDING ROCK ARCH RAPIDS .............................................................................. 4 2.1.1 Narrative Description ....................................................................................
  • Fluvial Landforms & Processes

    Fluvial Landforms & Processes

    Fluvial Landforms & Processes River Systems and Fluvial Landforms Longitudinal Profile and Equilibrium Drainage Basins, classic patterns Lakes and Dams Mountain Streams Straight Rivers Braided Rivers Meandering Rivers Anabranching Rivers Gulleys River Terraces Waterfalls Photo: SCGS Flood plains Alluvial Fans 1 Fluvial Landforms & Processes Rivers are one of the most dominant agents of landscape change Flowing waters are continually eroding, transporting, and depositing sediments (Fluvial Processes). River based flooding is among one of the most frequent and widespread natural hazards. 2 Longitudinal Profile and Watersheds longitudinal profile: an elevation cross-section of the entire watershed from the source of flowing water to the mouth of the stream. headwaters: the highest elevation where water collects to form a stream network. base level: the lowest elevation that a stream can erode its channel. Local or temporary base levels may be formed by reservoirs or waterfalls. Headwaters 3,000 Ultimate Base level Elevation (feet) 0 100 0 River Length (Miles) 3 Longitudinal Profile and Watersheds A river’s gradient (slope) is steepest near the headwaters and gentlest near the mouth. As rivers flow from their headwaters to their base level they carve valleys into the landscape by eroding, transporting, and depositing weathered rocks, soil, and sediment. Headwaters more erosion 3,000 more deposition Ultimate Base level Elevation (feet) 0 100 0 River Length (Miles) 4 Fluvial Equilibrium • Stream gradient is related to water velocity and sediment load • A change in any of these affects the other two. • base level fluctuations (gradient) • precipitation changes (discharge) • sediment character Fluvial Equilibrium Recent uplift in excess of erosional rates results in a system that is out of equilibrium.