8  Features

FluvialGeomorph defines a standard set of feature classes that are used through the tool chain. The definition of a common set of derived features is an important step in standardizing the FluvialGeomorph workflow. These database objects form a tightly linked set of features that work together in a particular order to accomplish the analysis. They are presented here in the approximate order in which they are produced.

Study Area

The study_area polygon feature class is created manually by the analyst using these instructions from the user manual.

Study Area Fields.
Field Name Type Description Units Level
none 1

Terrain Model Raster

The GIS analyst follows these instructions from the user manual using standard ESRI geoprocessing tools to transform a LiDAR point cloud dataset covering the study area into an appropriately resolute (pixel cell size) digital elevation model (DEM). Only points representing the ground or water surface are selected from the point cloud to derive the terrain surface DEM. This raster dataset is named dem, but can also have a suffix added to represent its year of collection in change studies. Follow these instructions from

DEM Raster Pixel Values.
Field Name Type Description Units Level
Z 32 bit float The z-coordinate value (elevation). feet, NAVD88 1

Cutlines

The cutlines polyline feature class is created manually by the analyst using these instructions from the user manual. The cutlines polyline feature class is used to store geometry needed to hydrologically modify a terrain model to ensure that water can accurately flow over the land surface as it does in the real world. LiDAR derived terrain models frequently contain flow blockages (e.g., road berms) that must be “cut-through” to represent the presence of flow structures (e.g., culverts, bridges) that cannot be resolved directly from the LiDAR terrain model.

Cutlines Fields.
Field Name Type Description Units Level
none 1

Hydro Modified Raster

Before the dem terrain model raster can be used for synthetically deriving stream features, it must first be hydrologically modified using the cutlines feature class to “burn” flow paths into the dem raster. The 02 - Hydro DEM tool creates a “hydro-enforced” DEM named dem_hydro using these instructions from the user manual.

Hydro DEM Raster Pixel Values.
Field Name Type Description Units Level
Z 32 bit float The z-coordinate value (elevation). feet, NAVD88 1

Contributing Area Raster

The 03 - Contributing Area tool uses the dem_hydro raster to create a contributing_area raster whose values store the drainage area upstream of each pixel using these instructions from the user manual.

Contributing Area Raster Pixel Values.
Field Name Type Description Units Level
contributing_area 32 bit float The specific catchment area. linear units of fc 1

Flow Accumulation Raster

The 03a - Contributing Area D8 tool is used to calculate the flow_accumulation_d8 raster whose values represent the number of upstream pixels using these instructions from the user manual.

Flow Accumulation D8 Raster Pixel Values.
Field Name Type Description Units Level

Flow Direction Raster

The 03a - Contributing Area D8 tool is used to calculate the flow_direction_d8 raster whose values represent the direction of flow across each pixel using these instructions from the user manual.

Flow Direction D8 Raster Pixel Values.
Field Name Type Description Units Level
flow_direction_d8 32 bit float The direction of flow from each cell to its downslope neighbor. D8 flow direction 1

Stream Network

The 04 - Stream Network tool uses the contributing_area raster to derive a synthetic stream_network polyline feature class representing the stream network of the study area using these instructions from the user manual.

Stream Network Fields.
Field Name Type Description Units Level
ReachName text Name of the reach. 1

Stream Network Points

The 04a - Stream Network Points tool creates the stream_network_points point feature class to represent regularly spaced points along a stream_network feature class using these instructions from the user manual. These stream_network_points features are used to store elevation and route position (longitudinal stream stationing) information for a stream_network feature.

Stream Network Points Fields.
Field Name Type Description Units Level
ReachName text Name of the reach. 1
POINT_X double The x-coordinate value (longitude). linear units of fc 1
POINT_Y double The y-coordinate value (latitude). linear units of fc 1
POINT_M double The m-coordinate value (route position). linear units of fc 1
Watershed_Area_SqMile double The upstream watershed drainage area. square miles 1
Z double The z-coordinate value (elevation). feet, NAVD88 1

Gradient

The 04b - Slope and Sinuosity tool creates the gradient_* point feature class that calculates slope and sinuosity for a stream_network_points point feature class using these instructions in the user manual. The gradient_* point feature class is named using the moving window size specified.

Gradient Points Fields.
Field Name Type Description Units Level
ReachName text Name of the reach. 1
POINT_X double The x-coordinate value (longitude). linear units of fc 1
POINT_Y double The y-coordinate value (latitude). linear units of fc 1
POINT_M double The m-coordinate value (route position). linear units of fc 1
Z double The z-coordinate value (elevation). feet, NAVD88 1
z_smooth double The smoothed z-coordinate value (elevation). feet, NAVD88 1
upstream_x double The x-coordinate value (longitude) of the next upsteam point in the moving window. linear units of fc 1
upstream_y double The y-coordinate value (latitude) of the next upsteam point in the moving window. linear units of fc 1
downstream_x double The x-coordinate value (longitude) of the next downsteam point in the moving window. linear units of fc 1
downstream_y double The y-coordinate value (latitude) of the next downsteam point in the moving window. linear units of fc 1
upstream_z double The z-coordinate value (elevation) of the next upstream point in the moving window. feet, NAVD88 1
downstream_z double The z-coordinate value (elevation) of the next downstream point in the moving window. feet, NAVD88 1
upstream_m double The m-coordinate value (route position) of the next upstream point in the moving window. linear units of fc 1
downstream_m double The m-coordinate value (route position) of the next downstreampoint in the moving window. linear units of fc 1
rise double The elevation difference between the downstream and upstream point in the moving window. feet 1
run double The longitudinal distance along the stream network between the downstream and upstream point in the moving window. feet 1
stream_length double The longitudinal distance along the stream network between the downstream and upstream point in the moving window. feet 1
valley_length double The longitudinal distance along the valleyline between the downstream and upstream stream network point in the moving window. feet 1
sinuosity double The sinuosity of the stream within the moving window (valley_length/stream_length). 1
sinuosity_gte_one double The sinuosity metric, values greater than or equal to one. 1
slope double The slope of the stream within the moving window (rise/run). degree 1
slope_gte_zero double The slope metric, values greater than of equal to zero. degree 1

Watershed Points

The watershed_points feature class is manually created by the analyst using the stream_network_points feature class following these instructions from the user manual. The watershed_points point feature class is used to represent the downstream location of watersheds whose areal extent is to be calculated. These single points are sometimes referred to as “pour points” located along a stream network.

Watershed Points Fields.
Field Name Type Description Units Level
ReachName text Name of the reach. 1
POINT_X double The x-coordinate value (longitude). linear units of fc 1
POINT_Y double The y-coordinate value (latitude). linear units of fc 1
POINT_M double The m-coordinate value (route position). linear units of fc 1
Watershed_Area_SqMile double The upstream watershed drainage area. square miles 1
Z double The z-coordinate value (elevation). feet, NAVD88 1

Watershed

The 04c - Watershed tool creates the watershed polygon feature class and represent the drainage area upstream of a single point (aka “pour point”) located along a stream network. All pixels within each watershed polygon feature flow to the stream network point used to derive the watershed using these instructions from the user manual.

Watershed Fields.
Field Name Type Description Units Level
ReachName text Name of the reach. 1
Shape_Area double The area of the watershed. linear units of fc 1

Flowline

The 05 - Flowline tool creates the flowline polyline feature class and is used to represent the likely flow path of a stream reach within a study area using these instructions from the user manual. This is the primary flow path feature used in the FluvialGeomorph toolbox. Since non-bathymetric LiDAR is often used to derive flowline features, this should not be interpreted as the thalweg when water is present in the DEM.

Flowline Fields.
Field Name Type Description Units Level
ReachName text Name of the reach. 1
from_measure double The start longitudinal stationing value for the reach. kilometers 1
to_measure double The end longitudinal stationing value for the reach. kilometers 1

Flowline Points

The 06 - Flowline Points tool creates the flowline_points point feature class and is used to represent regularly spaced points along a flowline feature class using these instructions from the user manual. These flowline_points features are used to store elevation and route position (longitudinal stream stationing) information for a flowline feature. flowline_points are used to calculate a series of stream longitudinal dimensions.

Flowline Points Fields.
Field Name Type Description Units Level
ReachName text Name of the reach. 1
POINT_X double The x-coordinate value (longitude). linear units of fc 1
POINT_Y double The y-coordinate value (latitude). linear units of fc 1
POINT_M double The m-coordinate value (route position). 1
Z double The z-coordinate value (elevation). feet, NAVD88 1

Detrended Raster

The 07 - Detrend DEM tool creates the detrend raster dataset using these instruction from the user manual. The detrend raster is an elevation model where the downstream slope of the dem_hydro has been removed.

Hydro DEM Raster Pixel Values.
Field Name Type Description Units Level
detrend_Z 32 bit float The detrended z-coordinate value (elevation). feet, detrended 1

Channel Slope Raster

The 09 - Channel Slope tool creates the channel_slope raster using these instructions from the user manual. The channel_slope raster represents the slope of the dem_hydro within the channel. This is not to be confused with the longitudinal slope of the stream reach, but is the pixel-wise, raster surface slope of the channel area.

Channel Slope Raster Pixel Values.
Field Name Type Description Units Level
slope 32 bit float The terrain slope. degree 1

Centerline

The 10 - Centerline tool creates the centerline polyline feature class using these instructions from the user manual. The centerline polyline feature class is used to represent a stream flow path that falls roughly equidistant between the banklines at bankfull water surface elevation.

Centerline Fields.
Field Name Type Description Units Level
none 2

Regular Cross Sections

The 11 - XS Layout tool is used to create a regularly spaced cross section xs_* polyline feature class using these instructions from the user manual. Cross sections are polyline feature classes drawn perpendicular to the flowline feature and are long enough to extend across some portion of the channel and floodplain. Cross section features are used to define channel cross section dimensions. Regular cross sections are spaced equal distances longitudinally along the flowline. Regularly spaced cross sections are used to sample conditions within a stream reach to display a continuous series of values and calculate aggregate stream values.

Regular Cross Section Fields.
Field Name Type Description Units Level
ReachName text Name of the reach. 1
Seq short The cross section unique identifier. 1
x_start double The x-coordinate value at the start of the cross section. linear units of fc 1
y_start double The y-coordinate value at the start of the cross section. linear units of fc 1
x_end double The x-coordinate value at the end of the cross section. linear units of fc 1
y_end double The y-coordinate value at the end of the cross section. linear units of fc 1
Watershed_Area_SqMile double The upstream watershed drainage area. square miles 1
from_measure double The start longitudinal stationing value for the reach. kilometers 1
to_measure double The end longitudinal stationing value for the reach. kilometers 1
POINT_X double The x-coordinate value (longitude). linear units of fc 1
POINT_Y double The y-coordinate value (latitude). linear units of fc 1
POINT_M double The m-coordinate value (route position). linear units of fc 1
Z double The z-coordinate value (elevation). feet, NAVD88 1
km_to_mouth double The distance to the mouth of the site. kilometers 1
loop long The loop number. 3
bend long The bend number. 3

Riffle Cross Sections

Riffle cross sections (i.e., riffle_floodplain, riffle_channel) are a unique type of cross section manually drawn by the analyst within a riffle stream feature using these instructions from the user manual. In contrast to regularly spaced cross sections that are delineated by a script, riffles irregularly spaced along a stream and are manually drawn by a GIS analyst. Analysts are trained to identify riffles using a set of guidelines from the literature and interpretation of the DEM and aerial imagery. The riffle_floodplain polyline feature class is drawn longitudinally within riffle features and extend laterally across the active floodplain. The riffle_channel polyline feature class is also drawn longitudinally within riffle features, but only extend laterally across the bankfull channel area.

Riffle Floodplain Riffle Channel Cross Section Fields.
Field Name Type Description Units Level
ReachName text Name of the reach. 2
Seq short The cross section unique identifier. 2
Watershed_Area_SqMile double The upstream watershed drainage area. square miles 2
from_measure double The start longitudinal stationing value for the reach. kilometers 2
to_measure double The end longitudinal stationing value for the reach. kilometers 2
POINT_X double The x-coordinate value (longitude). linear units of fc 2
POINT_Y double The y-coordinate value (latitude). linear units of fc 2
POINT_M double The m-coordinate value (route position). linear units of fc 2
Z double The z-coordinate value (elevation). feet, NAVD88 2
km_to_mouth double The distance to the mouth of the site. kilometers 2
loop long The loop number. 3
bend long The bend number. 3

Cross Section Points

The 14 - XS Points tool creates the *_points points feature class using these instructions from the user manual for Level 1 and Level 2. Cross sections polyline feature classes (i.e., regularly spaced cross sections and riffle cross sections: riffle_floodplain, riffle_channel) can be converted to a set of regularly spaced points along the cross section. These points are used to store elevation and route position (lateral stream stationing) information for a cross section feature class. Cross section points are used to calculate a series of cross section dimensions.

Cross Section Points Fields.
Field Name Type Description Units Level
ReachName text Name of the reach. 1,2
Seq short The cross section unique identifier. 1,2
Watershed_Area_SqMile double The upstream watershed drainage area. square miles 1,2
from_measure double The start longitudinal stationing value for the reach. kilometers 1,2
to_measure double The end longitudinal stationing value for the reach. kilometers 1,2
POINT_X double The x-coordinate value (longitude). linear units of fc 1,2
POINT_Y double The y-coordinate value (latitude). linear units of fc 1,2
POINT_M double The m-coordinate value (route position). linear units of fc 1,2
POINT_M_units text The units of the POINT_M field. 1,2
km_to_mouth double The distance to the mouth of the site. kilometers 1,2
DEM_Z double The z-coordinate value (elevation). feet, NAVD88 1,2
dem_units double The units of theDEM_Z field. 1,2
Detrend_DEM_Z double The z-coordinate value on the detrended raster. feet, detrended 1,2
loop long The loop number. 3
bend long The bend number. 3

Cross Section Dimensions

Cross section dimension polyline feature classes are used to store the hydraulic dimensions calculated for each cross section. Since the FluvialGeomorph workflow is divided into three levels, cross section dimensions are calculated at each level. Each level allows for an increasingly complex set of dimensions to be calculated, with each level building on the complexity of the previous level. There are three cross section dimension feature classes, one for each level *_dims_L1, *_dims_L2, and *_dims_L3. Cross section dimensions are calculated using the following tools:

Cross section dimensions can be calculated for the various types of cross sections (regular cross sections or riffle cross sections). The name of the cross section feature for which dimensions were calculated is prepended to the output dimension feature class. Metrics calculated at previous levels are included in the attribute table of each dimension feature class. Therefore, to avoid repetition only the new fields calculated at each level are included in the tables of fields in this section. The attributes of the original cross section feature class are also omitted since they depend on the cross section type used.

Level 1 Cross Section Dimension Fields.
Field Name Type Description Units Level
z_smooth double The smoothed z-coordinate value (elevation). feet, NAVD88 1
upstream_x double The x-coordinate value (longitude) of the next upsteam cross section in the moving window. linear units of fc 1
upstream_y double The y-coordinate value (latitude) of the next upsteam cross section in the moving window. linear units of fc 1
downstream_x double The x-coordinate value (longitude) of the next downsteam cross section in the moving window. linear units of fc 1
downstream_y double The y-coordinate value (latitude) of the next downsteam cross section in the moving window. linear units of fc 1
upstream_z double The z-coordinate value (elevation) of the next upstream cross section in the moving window. feet, NAVD88 1
downstream_z double The z-coordinate value (elevation) of the next downstream cross section in the moving window. feet, NAVD88 1
upstream_m double The m-coordinate value (route position) of the next upstream cross section in the moving window. linear units of fc 1
downstream_m double The m-coordinate value (route position) of the next downstream cross section in the moving window. linear units of fc 1
rise double The elevation difference between the downstream and upstream cross section in the moving window. feet 1
run double The longitudinal distance along the flowline between the downstream and upstream cross sections in the moving window. feet 1
stream_length double The longitudinal distance along the flowline between the downstream and upstream cross sections in the moving window. feet 1
valley_length double The longitudinal distance along the valleyline between the downstream and upstream cross sections in the moving window. feet 1
sinuosity double The sinuosity of the stream within the moving window (valley_length/stream_length). 1
sinuosity_gte_one double The sinuosity metric, values greater than or equal to one. 1
slope double The slope of the stream within the moving window (rise/run). degree 1
slope_gte_zero double The slope metric, values greater than of equal to zero. degree 1
Level 2 Cross Section Dimension Fields.
Field Name Type Description Units Level
bankfull_elevation double The detrended elevation of the water surface at bankfull discharge. feet, detrended 2
drainage_area double The upstream watershed drainage area. square miles 2
xs_area double The cross sectional area at the estimated bankfull water surface elevation. square feet 2
xs_width double The cross section width at the estimated bankfull water surface elevation. square feet 2
xs_depth double The cross section depth at the estimated bankfull water surface elevation. square feet 2
discharge double The stream discharge. cubic m/s 2
fp_area double The cross sectional area at the estimated floodprone water surface elevation. square feet 2
fp_width double The cross section width at the estimated floodprone water surface elevation. feet 2
fp_depth double The cross sectional depth at the estimated floodprone water surface elevation. feet 2
xs_width_depth_ratio double The width to depth ratio. 2
xs_width_depth_ratio_gte_one double The width to depth ratio metric, gteater than or equal to one. 2
xs_entrenchment_ratio double The entrenchment ratio. 2
xs_entrenchment_ratio_gte_one double The entrenchment ratio metric, greater than or equal to one. 2
watersurface_elev double The as-measured water surface elevation. feet, NAVD88 2
bankfull_elev double The estimated bankfull water surface elevation. feet, NAVD88 2
floodprone_elev double The estimated floodprone water surface elevation. feet, NAVD88 2
xs_mean_depth double The cross section mean depth at the estimated bankfull water surface elevation. feet 2
shear_stress_density double The fluid shear stress, calculated using the density of water. kg/m^2 2
shear_stress_density_gte_zero double The fluid shear stress density metric, greater than or equal to zero. kg/m^2 2
shear_stress_weight double The fluid shear stress, calculated using the specific weight of water. lb/ft^2 2
shear_stress_weight_gte_zero double The fluid shear stress specific weight metric, greater than or equal to zero. lb/ft^2 2
shear_stress_lane double The fluid shear stress, calculated using the Lane’s Balance method. 2
shear_stress_lane_gte_zero double The fluid shear stress Lane’s metric, greater than or equal to zero. 2
unit_stream_power double The unit stream power. kg/m/s 2
unit_stream_power_gte_zero double The unit stream power metric, greater than or equal to zero. kg/m/s 2
Level 3 Cross Section Dimension Fields.
Field Name Type Description Units Level
bend_num double The bend number. 3
bend_POINT_X double The x-coordinate value (longitude) of the center of the bend. linear units of fc 3
bend_POINT_Y double The y-coordinate value (latitude) of the center of the bend. linear units of fc 3
loop_POINT_X double The x-coordinate value (longitude) of the center of the loop. linear units of fc 3
loop_POINT_Y double The y-coordinate value (latitude) of the center of the loop. linear units of fc 3
bend_radius double The radius of the bend. linear units of fc 3
meander_length double The meander length. feet 3
meander_width double The meander width. feet 3
rc_bfw_ratio double The radius of curvature to bankfull width ratio. 3
rc_bfw_ratio_lte_30 double The radius of curvature to bankfull width ratio less than or equale to 30. 3
mbw_bfw_ratio double The meander bend width to bankfull width ratio. 3
mbw_bfw_ratio_lte_30 double The meander bend width to bankfull width ratio less than or equal to 30. 3

Bankfull Area

The 08 - Water Surface Extent tool is used to create the bankfull_area polygon feature class using these instructions from the user manual. The bankfull_area polygon feature class represents the channel area typically inundated during bankfull events. The detrend raster dataset is used to interactively “flood” the channel to define this extent.

Bankfull Area Fields.
Field Name Type Description Units Level
Id long The polygon unique identifier. 2
gridcode long Indicates if a polygon is innundated at the specified detrended elevation (1 = innundated, 0 = not innundated). 2
Shape_Area double Area of the polygon. linear units of fc 2

Banklines

The banklines feature class is manually created from the bankfull_area using these instructions from the user manual. The banklines polyline feature class represents the stream banks at bankfull. The edge of the bankfull_area polygon features are used to create to banklines, one representing the left descending bank and another the right descending bank.

Banklines Fields.
Field Name Type Description Units Level
ReachName text Name of the reach. 2
bank_id long Bankline numeric unique identifier. 2
bank text Bankline text unique identifier (one of “left descending” or “right descending”). 2
from_measure double The start longitudinal stationing value for the bankline. 2
to_measure double The end longitudinal stationing value for the bankline. 2

Bankline Points

The 14b - Bankline Points tool creates the bankline_points point feature class using these instructions in the user manual. The bankline_points point feature class is a set of regularly spaced point features located along each banklines feature. These points are used to store elevation and route position (longitudinal bankline stationing) information for each bankline.

Bankline Points Fields.
Field Name Type Description Units Level
ReachName text Name of the reach. 3
bank_id long Bankline numeric unique identifier. 3
bank text Bankline text unique identifier (one of “left descending” or “right descending”). 3
bank_POINT_X double The x-coordinate value (longitude) of the bankline point. linear units of fc 3
bank_POINT_Y double The y-coordinate value (latitude) of the bankline point. linear units of fc 3
bank_POINT_M double The m-coordinate value (route position) of the bankline point. linear units of fc 3
DEM_Z double The z-coordinate value (elevation) of the bankline point. feet, NAVD88 3
loop long The loop number. 3
bend long The bend number. 3
position text The planform location indicator. Indicates if a bankline point represents the “start” of a loop bend, the “end” of a loop bend, or the “apex” of a loop. 3
valley_POINT_X double The x-coordinate value (longitude) of the closest point on the valley line. linear units of fc 3
valley_POINT_Y double The y-coordinate value (latitude) of the closest point on the valley line. linear units of fc 3
valley_POINT_M double The m-coordinate value (route position) of the closest point on the valley line. linear units of fc 3

Valleyline

The valleyline is created using these instructions from the user manual. The valleyline polyline feature class represents the trend line of the down-valley axis. It bisects stream meanders as the stream swings from side to side across its floodplain.

Valleyline Fields.
Field Name Type Description Units Level
ReachName text Name of the reach. 3
from_measure double The start longitudinal stationing value for the reach. kilometers 3
to_measure double The end longitudinal stationing value for the reach. kilometers 3

Loop Points

The loop_points point feature class is manually created by the analyst using these instructions from the user manual. The loop_points point feature class is used to store the longitudinal extents of loops and bends used for planform analysis. Within the FluvialGeomorph toolbox, the term “loop” is defined as a single meander as it swings across the valleyline. Moving downstream along a single loop, once the stream swings substantially across the valleyline, another loop begins. The point of maximum distance of a flowline from the valeyline (laterally across the floodplain) defines a loop “apex”. Moving to a finer scale, “bends” are defined as stream undulations within a particular loop. Therefore, a single loop may contain many bends. These loop and bend extents and loop apices are used to calculate a set of planform dimensions.

Loop Points Fields.
Field Name Type Description Units Level
ReachName text Name of the reach. 3
loop long The loop number. 3
bend long The bend number. 3
position text The planform location indicator. Indicates if a bankline point represents the “start” of a loop bend, the “end” of a loop bend, or the “apex” of a loop. 3

Features

The features point feature class is created manually by the analyst using these instructions in the user manual. The features point feature class is used to identify and label key stream features and their longitudinal position. Instances of features typically include relevant tributaries, localities, and infrastructure built within the floodplain affecting flow.

Features Fields.
Field Name Type Description Units Level
Name text Name of the stream feature. 1
km_to_mouth double The distance to the mouth of the site. kilometers 1