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 Instream Flow 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 GIS RMA2 Biological Sampling Instream Flow Decision Making Hydrodynamic Model Habitat Descriptions GIS RMA2 Biological Sampling Depth & velocity Species groups Criterion

Data Requirement Hydrodynamic Modeling Biological Studies 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) Input Data (Environmental Modeling Systems, Inc.) RMA2 (US Army Corps of Engineers) SMS (Surface Water Modeling System) RMA2 Interface Input Data Bathymetry Data Substrate Materials Boundary Conditions Calibration Data

Finite element mesh and bathymetric data 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.

Mesohabitat Criteria: V, D, V/D, FR (Vadas & Orth, 1998) Depth [feet] Run Fast Riffle Slow Riffle Deep Pool Medium Pool Shallow Pool 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 2.9 Group 2 0.9 1.7 2.3 Group 3 0.5 1.2 0.6 2 Group 4 1.6 Group 5 1.8 4.6 0.3 Group 6 4.3 6.5 Group 7 3.3 0.1 Group 8 1.1 10 0.01 Group 9 2.0 0.4 Group 10 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 Source: RMA2 reference manual, 2002

Channel Representation in Arc Hydro River channels are represented as a set of cross-sections and profile-lines in Arc Hydro

GIS database for river channels Thalweg Cross-sections ProfileLines 3D Network Measurement points Surface Develop generic ways to create all the channel features from measurement points.

Data analysis Start with points Create surface from points Centerline/Thalweg Cross-sections ProfileLines Start with points Create surface from points Extract all the 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 Plot the data in a flow-oriented coordinate system (s,n,z). Interpolate the data to create a surface. Create a FishNet from the interpolated surface. Transform the FishNet to (x,y,z).

Measure in ArcGIS A PolylineMZ can store m and z at each vertex along with x and y coordinates. 112.3213 64.0056

(s,n,z) coordinate system P Q Centerlin e Bankline s (s = 0, n = 0) P(n1, s1) Q(n2, s2) n2 s1 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 Output Step 2 Steps 3, 4 Steps 5,6,7 Step 8 User defines an arbitrary centerline over the measurement points Thalweg tool creates a surface using the measurement points Densify the initial centerline to get more points Normals are drawn at each vertex of the centerline to locate deepest points All the deepest points replace the vertices of the old centerline Final result is a 3D polyline defining the thalweg Old vertices New vertices

(x,y,z) (s,n,z) x y o - n + s (x,y,z) (s,n,z)

Spatial interpolation Bathymetry Points IDW EIDW Splines Tension Regularized Kriging Ordinary Anisotropic Interpolated Raster

Spatial Interpolation Results Spatial Interpolation Method RMSE (m) Rank 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 in (s,n,z) is flow-oriented! FishNet (x,y,z) to (s,n,z) s n x y FishNet in (s,n,z) is flow-oriented!

FishNet comparison Hydraulic FishNet Regular 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 Meandering shape Thalweg location Cross-section form B C Cross-section form

Deterministic Component Channel Bathymetry = + Channel Bathymetry Deterministic Component Stochastic Component Channel bathymetry is complex This research is focused on the deterministic component only

River Channel Morphology Model 4 1 2 3 Get the shape (blue line or DOQ) Using the shape, locate the thalweg Using thalweg location, create cross-sections Network of cross-sections and profile lines

Site1 and Site2 on Brazos River @ 30 miles @ 5 miles The data for Site 1 and Site 2 are available as (x,y,z) points.

Step 1: Normalizing the data nL nR - + Zd P(ni, zi) w = nL + nR For any point P(ni,zi), the normalized coordinates are: nnew = (ni – nL)/w znew = (Z – zi)/d For nL = -15, nR = 35, d = 5, Z=10 P (10, 7.5) becomes Pnew(0.5, 0.5)

Original cross-section Modified cross-section Normalized Data Original cross-section Modified cross-section 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 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 Y = 0.087*log(x) – 0.32 0.5 1.0

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 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 single pdf has a flat tail, which is undesirable. The condition of unit area under the pdf makes it difficult to maintain z*< 1. A combination of two beta pdfs offers flexibility to fit any form of cross-sectional shape.

Hydraulic Geometry Relationships 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-lines Set of Volume objects

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