Arc GIS Hydro Data Model David R. Maidment Director, Center for Research in Water Resources University of Texas at Austin CRWR

GIS in Water Resources Consortium Bringing together these two communities by using a common geospatial data model GIS CRWR Water Resources

ArcGIS Hydro Data Model Hydrography Hydrology

Hydrography “The description, study, and charting of bodies of water, such as rivers, lakes and seas”

Hydrology “A science dealing with the properties, distribution, and circulation of water on the surface of the land, in the soil and underlying rocks, and in the atmosphere”

Geodatabase Book Series General Geodatabase in ArcInfo 8 Geodatabase models for application areas

CD-ROM at back of book ArcGIS Hydro UML diagrams, Repository, Example Geodatabases

UML Jacobson Objectory Meyer Pre- and post- conditions Harel State charts Wirfs-Brock Responsibilities Fusion Operation descriptions, message numbering Embly Singleton classes Gamma et al. Frameworks, patterns, notes Schlaer-Mellor Object life cycles Odell Classification Rumbaugh OMT Booch Booch method Unified Modeling Language Source: T. Quatrani, Visual Modeling with Rational Rose and UML, p.6.

ESRI Provides Vanilla Objects esriCoreRow.1 esriCoreObject.1 esriCoreFeature.1 esriCoreSimpleJunctionFeature.1 esriCoreComplexJunctionFeature.1 esriCoreSimpleEdgeFeature.1 esriCoreComplexEdgeFeature.1 Feature NetworkFeature JunctionFeatureEdgeFeature SimpleJunctionComplexJunctionSimpleEdgeComplexEdge Object Row 2..* *

Encapsulation X: 79 W Y: 34 N Z: 185 m PointFeature setCoords( X, Y, Z ) queryCoords( X, Y, Z ) Example of user interaction with an object --

ArcGIS Hydro Components

ArcGIS Hydro Core Model Packages

HydroFeatures Hydro Feature classes are sets of points, lines or areas that describe water features of the landscape.

HydroFeatures Hydrofeatures inherit from the ESRI Feature class

Hydro Points, Lines, Areas These are subclasses of HydroFeature Abstract superclass (has no objects) Instantiable Subclasses (can have objects)

HydroPoints SeedPoint – outlet cell for DEM watershed MonitoringPoint – Gage or sampling location FlowChangePoint – Withdrawal or discharge Structure – Dam, bridge, wier, …. UserPoint – any other point of interest Add more attributes

Attributes of HydroPoint Point with (x,y,z) coordinates (default z = 0) LocationID links points to associated time series of measured or calculated data IsNetworkFlag = 1 means point is included in the HydroNetwork, (converse is IsnetworkFlag = 0)

Seedpoint A seedpoint locates the center of the outlet cell of a DEM watershed OutletOID links this point to the corresponding OutletJunction on the Hydronetwork Since the seedpoints are just upstream of the confluence, they unique identify separate upstream drainage areas 1 and confluence

Feature Types – Coded Value Domains A coded value domain is an attribute which can take on only one of a specific set of coded values The ArcGIS Hydro data model has no fixed Ftype definitions Those shown here are from the National Hydrography Dataset

NHD Feature Types NHD has ~ 52 Feature types, two of which are Stream/River and Pipeline

HydroLines ReachID – label for addressing and linear referenceing IsNetworkFlag = 1 means include this line in the network Hydrolines inherit Ftype and Name A special class of Hydrolines for storing the vectorized streams delineated from DEMs

HydroArea A Waterbody is a special class of HydroArea defining water bodies. A single water body Reach may contain many HydroArea Features Outlet to HydroNetwork

Drainage Areas DrainageArea is a superclass For any kind of drainage area OutletOID defines the outlet to the HydroNetwork AreaInSquareMeters specifies area independent of map projection Subclasses: Catchment, Watershed, Basin, HydroResponseUnit

Catchment A catchment is the local drainage area of a Reach

Shoreline Catchment The local drainage area of a shoreline reach Its drainage enters a waterbody directly without passing through a river or stream

Waterbody Catchment Waterbody is a catchment and separate catchments are defined for shorelines A single catchment polygon includes both the waterbody and its local drainage area Two ways of defining catchments for water bodies

Watershed Watersheds defined for points on the HydroNetwork Watershed defined for a Waterbody The Watershed class is used for any subdivision of the landscape into drainage units

Basin A standardized set of watersheds defined for the purposes of formal subdivision of the landscape into labeled drainage areas e.g. Watershed Boundary Dataset This example shows 8-digit HUC boundaries so BasinID = HUC8 Basin Outlet

Basins contain Catchments and Watersheds

HydroResponseUnit The HydroResponseUnit class be defined by soil or land use polygons, by climate or rainfall cells, by political or administrative boundaries, by aquifer or drainage boundaries, or by any combination of such areas. HRUs defined by intersecting Nexrad rainfall cells and catchments HRU’s account for the vertical water exchange between the atmosphere, surface water and groundwater

HydroNetwork The Hydro Network is the backbone of the ArcGIS Hydro data model. It defines the connections among points, lines and areas to describe the pathways of water flow through the landscape

HydroNetwork The HydroNetwork is built from ESRI Network Feature classes Two key classes HydroEdge and OutletJunction

Geometric Network A Geometric network is defined by: geometry – (x, y) of edges, junctions connectivity – junction-edge-junction Generic junctions (created automatically) OutletJunctions HydroEdges

HydroEdge Color and Select edges A HydroEdge is a Complex Edge Feature so it can have interior junctions

OutletJunction The OutletJunction of a Watershed is located on the Hydronetwork as close as possible to the seedpoint location on the DEM

Seedpoints as OutletJunctions 10-digit watersheds 19 seedpoints NED-H Catchments (~ 8km 2 ) 1026 seed points The same concept can be used to connect drainage areas to the Hydronetwork regardless of spatial scale

OutletJunction to Watershed Relationship 11 Outlets are 1:1 related to watersheds through the ObjectId of the Outlet (OutletOID). Traces on the HydroNetwork identify OutletJunctions, and by invoking the relationship, the associated Watersheds are identified

HydroEdgeTypes HydroEdges have three subtypes: FlowEdges, VirtualFlowEdges and ShorelineEdges

Flow Lines for Water Modeling A Flow Line is a linear sequence of flow edges and/or virtual Flow Edges Strictly speaking, the flow line is located at the Center of Flow but its location is usually approximated to the channel centerline or thalweg Equations of motion are written in terms of flow distance for 1-D flow models

Flow Network HydroNetwork = Flow Network + Shorelines A flow network is a connected set of flow lines When a waterbody is placed on the network, it can be represented by Virtual Flow Edges, by Shoreline Edges or by both edge types

Flow Direction 2 1 Flow Direction in the HydroNetwork is downstream toward a sink Flow direction can be stored as an edge attribute by comparing it with the direction in which the edge was digitized as given by the order of its vertices

HydroEdge Attributes ReachID labels the HydroEdges for linear referencing e.g. RchComID linked to Rch_Code in NHD LengthinMeters stores the length of the edge irrespective of map projection LengthDownstream stores the length to a downstream reference point, such as the mouth of the river or the basin outlet

Hydro Objects An object has an ObjectId and attributes but no spatial coordinates HydroNetwork Objects –Reaches and Hydrographic Units –Point and Line events CrossSection Objects –Point and Line events Temporal Objects

Reach A Reach is an expanse of water uniquely labeled for hydrographic purposes (a river reach, waterbody or shoreline). Reaches inherit from ESRI class Object ReachID

Reach to HydroEdge Relationship connects Reach to HydroEdge to identify Features in the Reach A reach is an Object, which means that it has an ObjectID and attributes but does not have spatial coordinates 1 * (many)

Waterbody Reach catchment River Reach catchment Reach Catchments developed using the NED-H Flow Direction Grid, and Reach Features as outlet zones in the Grid Watershed function

Hydrographic Unit A HydrographicUnit is an object describing a set of connected reaches, such as a river, or a section of coastline East Fork of the Trinity River Hydrographic Units are connected to Reaches through a 1 to many relationship

Linear Referencing (Requires ArcInfo 8.1) Where are we on a line?

0% 100% Linear Referencing using Percent distance from bottom end of reach (NHD approach)

Linear Referencing using “Chainage” from the Upper End of the Reach in meters (European approach)

Measure in kilometers pMSeg.SetAndInterpolateMsBetween 0, ([Shape_Length] /1000) Measure in km from bottom end of line (like river miles or Kilometers)

HydroEvent Objects Events can be defined using measure defined on each HydroEdge or each Reach (easiest if each Reach is one Edge) Sets of points or Line events can form Groups

Displaying Events

Channel Features represent 3-D river morphology Mainly designed by Michael Blongewicz, DHI, Nawajish Noman and Jim Nelson, BYU, Tom Evans, HEC

Channel Features ProfileLines run along the channel CrossSections run transverse to the channel Each vertex has (x, y, z, m)

ProfileLines HydroEdge = “Thalweg” Profileline ReachID links Channel to Network “Left” and “Right” are determined looking Downstream 5 Subtypes

CrossSections ReachID and ReachMeasure give the River Stationing or Chainage for Hydraulic Models CrossSectionType specifies how it was developed

CrossSection Geometry Object stores (m,z) coordinates when (x, y) are unknown Large amounts of historical CrossSection data in this form

CrossSectionEvents Objects with attributes of points or linear segments of the CrossSection

Time Series Objects LocationID links to the Feature TSDateTime specifies date (and time of day) TSValue gives the data value (may be multiple data values) Mainly designed by Scott Morehouse and David Arctur, ESRI, and Michael Blongewicz, DHI

TimeSeries

Sources of Time Series Data ArcGIS HydroUSGS NWIS EPA Storet Paper on this on Wednesday by Tim Whiteaker