Docstoc
EXCLUSIVE OFFER FOR DOCSTOC USERS
Try the all-new QuickBooks Online for FREE.  No credit card required.

Channel

Document Sample
Channel Powered By Docstoc
					   River Channels in GIS


 Venkatesh Merwade, Center for Research
in Water Resources, University of Texas at
                 Austin
                Overview
• Fish Habitat Modeling using GIS
• Standardized 3D representation of river
  channels
• River Channel Morphology Model
• RCMM and Hydraulic Modeling
        Instream flow studies
• How do we quantify the impact of changing
  the naturalized flow of a river on species
  habitat?

• How do we set the minimum reservoir
  releases that would satisfy the instream flow
  requirement?
                  Objective
• Objective
  – To model species habitat as a function of flow
    conditions and help decision making


• Instream Flow
  – Flow necessary to maintain habitat in natural
    channel.
              Methodology
• Species habitat are dependent on channel
  hydrodynamics – hydrodynamic modeling
• Criteria to classify species depending on the
  conditions in the river channel – biological
  studies
• Combine hydrodynamics and biological
  studies to make decisions – ArcGIS
       Fish Habitat Modeling


                          Criterion
               Depth &                Species
Hydrodynamic   velocity    Habitat    groups      Habitat
   Model                   Model                Descriptions

   RMA2                                            Biological
                            GIS                    Sampling


                      Instream Flow
                     Decision Making
                 Data Requirement
• Hydrodynamic Modeling
      Bathymetry Data (to define the channel bed)

      Substrate Materials (to find the roughness)

      Boundary Conditions (for hydrodynamic model)

      Calibration Data (to check the model)

• Biological Studies
      Fish Sampling (for classification of different species)

      Velocity and depth at sampling points
Study Area (Guadalupe river near Seguin, TX)




     1/2 meter Digital Ortho Photography
     Depth Sounder (Echo Sounder)




The electronic depth sounder operates in a similar way to radar It
sends out an electronic pulse which echoes back from the bed. The
echo is timed electronically and transposed into a reading of the
depth of water.
    Acoustic Doppler Current Profiler




Provides full profiles of water current speed and
direction in the ocean, rivers, and lakes. Also used
for discharge, scour and river bed topography.
Global Positioning System (GPS)




      Tells you where you are on the earth!
          Final Setup

                        GPS
                        Antenna
Computer and power
setup




                        Depth
                        Sounder
Final Data View
       2D Hydrodynamic Model
• SMS (Surface Water Modeling System)
  – RMA2 Interface
• Input DataWater Modeling System
     Surface
         (Environmental Modeling Systems, Inc.)
      Bathymetry Data

     Substrate Materials

     Boundary Conditions
       RMA2
  
            (US Data
      Calibration Army Corps of Engineers)
           SMS mesh




Finite element mesh and bathymetric data
SMS Results
    Biological Studies (TAMU)
• Meso Habitat and Micro Habitat
• Use Vadas & Orth (1998) criterion for Meso
  Habitats
• Electrofishing or seining to collect fish samples
  for Micro Habitat analysis
• Sample at several flow rates and seasons
• Measure Velocity and depth at seining points
• Statistical analysis to get a table for Micro
  Habitats classification.
   Deep Pool


                             Run

Medium Pool



Shallow
                               Fast Riffle
Pool
               Slow Riffle




Mesohabitat Criteria: V, D, V/D, FR
  (Vadas & Orth, 1998)
           Micro Habitat Table
Species    50% MinD 50% MaxD 50% MinV 50% MaxV
Group 1    1.5      2.7      1.5      2.9
Group 2    0.9      1.7      0.9      2.3
Group 3    0.5      1.2      0.6      2
Group 4    0.6      1.2      1.6      2.3
Group 5    1.8      4.6      0.3      1.6
Group 6    4.3      6.5      0.5      0.9
Group 7    1.5      3.3      0.1      1.2
Group 8    1.1      10       0.01     0.9
Group 9    0.5      2.0      0.4      1.6
Group 10   0.3      1.5      0.01     0.8
    Hydraulic and Biological Data
                       Attribute Table




Bathymetry Points




Habitat Descriptions
Habitat Modeling using ArcGIS
Results
                Overview
• Fish Habitat Modeling using GIS
• Standardized 3D representation of river
  channels
• River Channel Morphology Model
• RCMM and Hydraulic Modeling
Channel bathymetry in Hydraulic Modeling

                                  Other
                      Viscosity
                                   4%
                         6%
           Roughness
              10%




         Boundary                         Geometry
         Conditions                       and Study
            20%                            Design
                                             60%




       Source: RMA2 reference manual, 2002
 Channel Representation in Arc Hydro




                                              Channel

River channels are represented as a set of cross-sections and profile-lines in
Arc Hydro
     GIS database for river channels



                                   Thalweg       Cross-sections




Measurement points   Surface

                                   3D Network     ProfileLines

Develop generic ways to create all the channel features from
measurement points.
                    Data analysis

                                      Centerline/Thalweg

                                      Cross-sections

                                      ProfileLines



Start with points     Create surface   Extract all the
                       from points necessary information

                     How can we do this…….
    Development of Geospatial Structure for
              River Channels
                     Thought Process:
                     • Regular FishNet in ArcGIS
                       provides a network of 3D lines,
                       which are not flow oriented
                     • If the data are plotted in a flow-
                       oriented system, the regular
                       FishNet becomes flow-oriented.
                     • Flow-oriented coordinate system
                       is useful for getting cross-
                       sections and profile-lines.
Regular FishNet
      Geospatial Structure for River Channels -
                    Methodology


1. Plot the data in a flow-
   oriented coordinate system
   (s,n,z).
2. Interpolate the data to create a
   surface.
3. Create a FishNet from the
   interpolated surface.
4. Transform the FishNet to
   (x,y,z).
          Measure in ArcGIS
A PolylineMZ can store       64.0056   112.3213
                         0
m and z at each vertex
along with x and y
coordinates.
      (s,n,z) coordinate system

                    s1
                                 P          Centerline
                     s2         n1

   (s = 0, n = 0)                    n2
                                      Q
                                                    Banklines
                    P(n1, s1)
                    Q(n2, s2)




• s-coordinate is the flow length along the river channel
• n-coordinate is the perpendicular distance from the centerline
• n-coordinate is negative to the LHS and positive to the RHS of
  the centerline
                    Defining a Thalweg
   Input        Step 2         Steps 3, 4        Steps 5,6,7      Step 8         Output




User defines   Thalweg tool    Densify the      Normals are      All the       Final
an arbitrary   creates a       initial          drawn at each    deepest       result is a
centerline     surface using   centerline to    vertex of the    points        3D
over the       the             get more         centerline to    replace the   polyline
measurement    measurement     points           locate deepest   vertices of   defining
points         points            Old vertices   points           the old       the
                                 New vertices                    centerline    thalweg
              (x,y,z) (s,n,z)
                        +n
                        o
                        -n
y




                         n
                    s
                             +n

                x             o                 s
                             -n
    (x,y,z)


                                            s
                                  (s,n,z)
    Spatial interpolation

Bathymetry Points
                      • IDW
                      • EIDW
                      • Splines
                        – Tension
Interpolated Raster
                        – Regularized
                      • Kriging
                        – Ordinary
                        – Anisotropic
Spatial Interpolation Results
     Spatial Interpolation Method        RMSE   Rank
                                          (m)
 Inverse Distance Weighting              0.53    5
 Elliptical Inverse Distance Weighting   0.32    2
 Regularized Spline                      0.59    6
 Tension Spline                          0.45    4
 Ordinary Kriging                        0.44    3
 Anisotropic Kriging                     0.31    1


      Anisotropic kriging gave the least RMSE
    FishNet (x,y,z) to (s,n,z)


          n




                            s
y




      x       FishNet in (s,n,z) is flow-oriented!
       FishNet comparison




Regular FishNet    Hydraulic FishNet
Profile Lines and Cross Sections in 3D


    Bird’s eye view!
Instream flow studies in
        Texas              Priority segments
                           are 100s of miles
                           long

                           Study area is only
                           few miles long

                           Results from
                           small studies are
                           extrapolated

                           Are the results
                           valid?? Can we
                           cross-check??
                Overview
• Fish Habitat Modeling using GIS
• Standardized 3D representation of river
  channels
• River Channel Morphology Model
• RCMM and Hydraulic Modeling
                  Goal
• Based on the knowledge gained from a
  detailed dataset collected for a reach of
  river, develop a model for describing
  the 3D river channel form at regional
  scale.
             Conceptual Model

                                          C          C
                    C             C




                                          B          B
                        B             B




                                          A          A
                A             A




Meandering              Thalweg           Cross-section
  shape                 location              form
                                             Channel Bathymetry
                         z( x, y)                  =                            ˆ
                                                                                z ( x , y)                 +                            ( x, y)
                14                                                     14                                                      8




                                                                                                               Elevation (m)
                                                       Elevation (m)
                12                                                     12
Elevation (m)




                10                                                     10                                                      0

                8                                                      8

                6                                                      6                                                   -8
                     0   25     50      75   100                            0   25      50      75   100                           0   25     50       75   100
                         n-coordinate (m)                                        n-coordinate (m)                                       n-coordinate (m)



                 Channel Bathymetry                    Deterministic Component                                                     Stochastic Component



                     • Channel bathymetry is complex
                     • This research is focused on the deterministic component
                       only
           River Channel Morphology Model




     1            2              3                       4

1.       Get the shape (blue line or DOQ)
2.       Using the shape, locate the thalweg
3.       Using thalweg location, create cross-sections
4.       Network of cross-sections and profile lines
    Site1 and Site2 on Brazos River
                                                          @ 5 miles




                                                 @ 30 miles




The data for Site 1 and Site 2 are available as (x,y,z) points.
     Step 1: Normalizing the data

   nL       0                  nR
        -                               For any point P(ni,zi), the
                   +                Z   normalized coordinates
                   P(ni, zi)            are:
            d                           nnew = (ni – nL)/w
                      Zd                znew = (Z – zi)/d
            w = nL + nR



For nL = -15, nR = 35, d = 5, Z=10
P (10, 7.5) becomes Pnew(0.5, 0.5)
                                                Normalized Data
                  Original cross-section                                              Modified cross-section
                 13                                                                                         Normalized width
                 12                                                                          0       0.25         0.5        0.75   1

                 11                                                                     0
 Elevation (m)




                                                                   Normalized depth
                 10
                                                                                      0.25
                 9
                 8                                                                     0.5
                 7          Bathymetry Points
                                                                                                 Bathymetry Points
                 6                                                                    0.75
                      -75        -50         -25          0   25
                                       n-Coordinate (m)                                 1




Depth and width going from zero to unity makes life easier
without changing the shape of the original cross-section
Shape characterization through radius
            of curvature

               r1
                                                    r3
                                       r2



• If radius of curvature is small, the thalweg is close to the bank and as it
  increases the thalweg moves towards the center of the channel.
• If the channel meanders to left, the center of curvature is to the right
  hand side of the centerline and vice versa.
• When the center of curvature is to the right, the radius of curvature is
  considered positive and vice versa
           Step 2: locate thalweg using shape
Y = 0.076*log(x) + 1.21

                                             1.00
Thalweg location




                                             0.75
                       2
                      R = 0.8238

                                             0.50
                                                                R2 = 0.8717
                                             0.25

                                             0.00
                   -15000   -10000   -5000          0    5000    10000        15000
                                     Radius of Curvature (m)
                                                                                      0   0.5 1.0

                                                        Y = 0.087*log(x) – 0.32
     Thalweg and cross-section
• Cross-section should have an analytical
  form to relate it to the thalweg location
• Many probability density functions (pdf)
  have shapes similar to the cross-section
• Beta pdf is found feasible
  – its domain is from zero to one
  – it has only two parameters (a,b)
Step 3: cross-sections as beta pdfs
                            beta c/s = (beta1 + beta2) * k

                           x                                        x
      0.00       0.25    0.50   0.75   1.00         0.00   0.25   0.50   0.75              1.00




                                              beta c/s
beta c/s




                                                                                Beta c/s
              Beta c/s
                                                                                Beta1
              Beta1
                                                                                Beta2
              Beta2




a1=5, b1=2, a2=3, b2=3, factor = 0.5          a1=2, b1=2, a2=3, b2=7, factor = 0.6



           Create beta cross-sections for different thalweg
                              locations
          Cross-sections as Beta pdf

          Single pdf               Combination of two pdfs




                                a1=5, b1=2, a2=3, b2=3, factor = 0.5
Simple, only two parameters,
0<x<1
                                 A combination of two beta
A single pdf has a flat tail,    pdfs offers flexibility to fit
which is undesirable.            any form of cross-sectional
                                 shape.
The condition of unit area
under the pdf makes it
difficult to maintain z*< 1.
                                            Hydraulic Geometry Relationships
                                            W  aQ b                                                                            d  cQ f                                                              v  kQ m
                          1000                                                                             100                                                                    10
Average Width, w (feet)




                                                                                 Average Depth, d (feet)
                                   w = 95.654Q0.1206    a = 95.654                                                 d = 1.4895Q 0.2537   c = 1.4895
                                                                                                                                                                                           y = 0.0094x 0.5894
                                      R2 = 0.8164       b = 0.1206                                                    R2 = 0.8672       f = 0.2537




                                                                                                                                                              Velocity, v (fps)
                                                                                                                                                                                             R2 = 0.9576

                                                                                                           10                                                                      1

                                                                                                                                                                                                                    k = 0.0094
                                                                                                                                                                                                                    m = 0.5894
                          100                                                                               1
                             100           1000          10000          100000                                                                                                    0.1
                                                                                                             100              1000           10000   100000
                                               Flow, Q(cfs)                                                                      Flow, Q (cfs)                                       100            1000           10000         100000
                                                                                                                                                                                                       Flow, Q (cfs)

                                                                     Hydraulic geometry relationships for Brazos River at Richmond.




                          Hydraulic geometry relationships are developed at USGS gaging stations.
                          W, d, and v obtained at the gaging stations are then interpolated to get the
                          corresponding values at other locations.
                          An ideal scenario would be to have gaging stations both upstream and
                          downstream from the point of interest.
            USGS Measurements




http://waterdata.usgs.gov/nwis/measurements
         The final framework
• Start with a blue line (s), locate the thalweg
  (t) using the relationship, t = f(s).
• Using t, describe cross-sections (c) using
  the relationship, c(a,b) = f(t).
• The resulting cross-sections have a unit
  width and unit depth.
• Rescale the normalized cross-sections using
  width and depth (hydraulic geometry)
Results
Lower Brazos in Texas
            3D Channel Representation




      Cross-sections
      Profile-lines



3D Mesh of cross-sections and profile-   Set of Volume objects
lines
                Overview
• Fish Habitat Modeling using GIS
• Standardized 3D representation of river
  channels
• River Channel Morphology Model
• RCMM and Hydraulic Modeling
       RCMM and Hydraulic Modeling
3D Channel
  Model         • Blue line to 3D channel using the shape and
                  hydraulic geometry

                • Interaction with external hydraulic models
                  (HEC-RAS) via XML
    Blue Line




  3D Channel           XML                       HEC-RAS

                      GIS / Hydraulic Model Data Exchange
Hydraulic Model Attributes
         •   Relationships – ReachHasCrossSection
                HydroID of Reach is ReachID of CrossSections
                              FTable
• Linking of 3D channel and hydraulic model can be used to
  run hydraulic simulations and create FTable in GIS
• FTable contains useful information on water surface
  elevations, velocity, volume, residence times

 Cross-section identifier   Hydraulic attributes   Reach identifier
Questions

				
DOCUMENT INFO
Shared By:
Categories:
Tags:
Stats:
views:0
posted:11/21/2012
language:English
pages:64