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## PowerPoint Slideshow about ' Hydrologic Topology' - beau-dixon

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Francisco Olivera, Ph.D., P.E. – Assistant Professor ([email protected])

Srikanth Koka – Graduate Research Assistant ([email protected])

Texas A&M University – Department of Civil Engineering - College Station, Texas

Mississippi River Climate & Hydrology Conference

May 13 – 17, 2002

New Orleans, LA

Network Topologic and

Geometric Parameters

Overview

Due to the inherent spatial complexity of large hydrologic systems, for modeling purposes, rather than applying lumped models to represent entire basins, it is better to subdivide them into elementary flow elements organized as networks by virtue of their topologic relations. Likewise, each element should have different hydrologic properties to account for the terrain spatial variability and different hydrologic behavior to account for the different flow processes.

Hydrologic topology is the relation of the flow elements of a system to one another, so that each of them "knows" which other elements are upstream and which are downstream. Establishing the hydrologic topology is fundamental for flow routing as well as for tracking constituent particles transported by water.

Use of vector data, as opposed to raster data, has the advantage that each element represents a real-world flow element and, consequently, sets a better ground for physically-based modeling, not to mention that overall it is more accurate and better suited for modeling large study areas.

Mississippi River System

Downstream Flow Length

Upstream Trace

Upstream

Flow

Length

(Km)

Downstream

Flow

Length

(Km)

Potential

Mean

Flow

(m3/sec)(1)

Drainage

Area

(Km2)

Annual

Mean

Flow

(m3/sec)

City

Name

974

410,932

1,885(2)

Little Rock

2013

9,881

Omaha

2662

2675

824,543

1,274(2)

12,433

Paducah

1819

1496

513,680

20,090

3715(3)

St.Louis

1,790,860

3627

1710

37,469

6,601(2)

New Orleans

5337

2013

3,196,680

85,914

16,772(4)

0-1000 Km

1000-2000 Km

(1) Potential Mean Flow (m3/sec) = Weighted Drainage Area (mm Km2/year) , (2) Value for 1999, (3) Value for 2000, (4) Value for 1995

2000-3000 Km

31,555

3000-4000 Km

4000-5242 Km

Hydrologic Topology GIS Tools

For every point of the network, the tools:

- Identify upstream and downstream streams and watersheds.
- Determine upstream flow length and weighted upstream flow length to the farthest headwater.
- Determine downstream flow length and weighted downstream flow length to the outlet.
- Determine drainage area and weighted drainage area.
- Trace upstream and downstream for user-defined points of the network.
- Identify the longest flow path of the system.

Mean Annual Precipitation

Longest Flow Path

Weighted Drainage Area

527-801 mm/year

0 – 10 106 mm Km2/year

252-526 mm/year

10 – 100 106 mm Km2/year

802 – 1076 mm/year

100 – 500 106 mm Km2/year

1077-1351 mm/year

500 – 1000 106 mm Km2/year

1352-1626 mm/year

1000 – 2711 106 mm Km2/year

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