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Super-Charging the NHD with Value-Added Attributes. Cindy McKay, Horizon Systems Jennifer Hill, Horizon Systems Tim Bondelid, RTI International Ian Stack, Indus Sponsored by: US Environmental Protection Agency Office of Water. The Value-Added Attributes:. A set of network characteristics

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Presentation Transcript
slide2

Cindy McKay, Horizon Systems

Jennifer Hill, Horizon Systems

Tim Bondelid, RTI International

Ian Stack, Indus

Sponsored by:

US Environmental Protection Agency

Office of Water

the value added attributes
The Value-Added Attributes:
  • A set of network characteristics
  • Provide fast network navigation functions
  • Based solely on native NHD content
  • Created with software
  • Built using the national NHD
  • Eliminate the use of the NHD flow table
  • Inspired by the EPA Reach File Version 1
slide5

DRAINS

- Feature Typing

- Confluence-to-

Confluence Feature

Delineation

- Rich Attribution

Drains

Full NHD

slide6

REACHES

- Permanent Features

with Public Identifiers

- Scale Independent

- Changes Tracked

- Hydrologic-based

Delineation

- Linear Referencing

Framework

- Flow Relationships

Reaches

Drains

Full NHD

slide7

Why build the Value-Added Attributes?

  • Keep the best of both Reaches and Drains, while eliminating the disadvantages of each.
  • Fast and Efficient methods for traversing the stream network.
  • Provide a time-tested modeling framework.
stream order
Stream Order

Measure of the position of a stream (defined as the segment between successive tributaries) within the hierarchy of the drainage network. It is the basis for quantitative analysis of the network.

“A Dictionary of Earth Sciences,” Oxford University Press 1999

Techniques:

Strahler, Shreve, Horton

strahler stream order
Strahler Stream Order

The smallest permanent streams are called "first order". Two first order streams join to form a larger, second order stream; two second order streams join to form a third order, and so on. Smaller streams entering a higher-ordered stream do not change its order number.

Strahler 1964

1

1

2

1

1

2

1

2

3

arbolate sum
Arbolate Sum

The sum of all segment lengths that flow to the downstream end of a segment.

4/4

5/5

3.5/12.5

4.5/4.5

2.5/2.5

5.1/22.1

2.2/2.2

2/6.7

1.9/30.7

path length
Path Length

The distance from the downstream end of a segment to the network termination point.

4/10.5

5/10.5

3.5/7.0

4.5/7.0

2.5/3.9

5.1/1.9

2.2/3.9

2/1.9

1.9/0.0

start flag terminal flag
Start Flag & Terminal Flag

Start Flag designates headwater features.

Terminal Flag designates a feature that terminates the network

(A feature that flows to Atlantic Ocean, Pacific Ocean, Gulf

of Mexico, A Great Lake, Canada, Mexico, or the ground.)

divergence flag
Divergence Flag

A flag which defines the major and minor branches of a flow split (divergence).

0

0

1

0

2

1

2

0

drain stream level
Drain Stream Level

Stream level provides the information necessary to determine the main path upstream of each confluence.

  • Flow Volume
  • Stream Name
  • Arbolate Sum

2

1

1

2

2

1

3

2

1

downstream level
Downstream Level

2/1

1/1

1/1

2/1

2/2

1/1

3/2

2/1

1

hydrologic sequence identifier
Hydrologic Sequence Identifier

A nationally unique sequence number that places the stream segments in hydrologic sequence.

  • Descending sequence =

upstream to downstream

  • Ascending sequence =

downstream to upstream.

8

9

7

6

3

5

4

2

1

level path identifier
Level Path Identifier

The hydrologic sequence identifier of the most downstream segment on the same level path.

2/8/8

1/9/1

1/7/1

2/6/6

2/3/2

1/5/1

3/4/4

2/2/2

1/1/1

terminal identifier
Terminal Identifier

The hydrologic sequence identifier for the terminal segment to which this segment flows.

8/1

9/1

7/1

6/1

3/1

5/1

4/1

2/1

1/1

from node to node
From node/To node

10

9

A set of nationally unique identifiers for the node endpoints of the segments. These ids are independent of the node ids in the .NAT table of NHD workspaces.

8

7

5

6

3

4

2

1

thinning attribute
Thinning Attribute

An ordinal value designed to allow selection of progressively more dense networks. The least dense network is obtained by selecting Thinner=1.

thinning attribute29
Thinning Attribute
  • Provide a control for improving performance in large area displays especially in Web applications.
  • Assist in the correction of NHD density shifts.
  • Provide appropriately dense stream networks for National and regional application.
how are the vaas computed
How are the VAAs Computed?
  • For each Catalog Unit/Sub-basin:
    • Move Reach Attributes to Drains
    • Move Reach Measures to Drains.
    • Compute Drain Flow Relationships based on Reach Flow Relationships and Drain Topology
  • Run 3 National Passes
    • Process CUs downstream to upstream

(Start and Terminal Flags, Divergence Flag, Arbolate Sum)

    • Processing CUs upstream to downstream

(Drain Level, D/S Level, Hydrologic Sequence ID, Level

Path ID, Terminal ID, Path Length, F/T Nodes, Thinner)

    • Processing CUs downstream to upstream

(Stream Order)

importance of the vaas
Importance of the VAAs
  • Establish the integrity of the network
  • Easy answers to network questions
  • Faster and simpler network navigation
  • Four ways to navigate the network
    • Fast, sequential routing
    • Simple SQL queries
    • Link Node routing
    • Flow Table navigation
  • Provide some commonly used attributes
questions
Questions?

Cindy McKayLDM@Horizon-Systems.com