Hydrologic Topology
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Transcript of Hydrologic Topology
Hydrologic Topology 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 System
Mean Annual Precipitation
Downstream Flow Length
Weighted Drainage Area
Upstream Trace
Longest Flow Path
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.
252-526 mm/year
527-801 mm/year
802 – 1076 mm/year
1077-1351 mm/year
1352-1626 mm/year
0-1000 Km
1000-2000 Km 2000-3000 Km 3000-4000 Km 4000-5242 Km
CityName
UpstreamFlow
Length(Km)
DownstreamFlow
Length(Km)
Drainage Area
(Km2)
AnnualMeanFlow
(m3/sec)
2013
2662
1819
3627
5337
410,932Little Rock
Omaha
Paducah
St.Louis
New Orleans
974
2675
1496
1710
2013
824,543
513,680
1,790,860
3,196,680
9,881
12,433
20,090
37,469
85,914
1,885(2)
1,274(2)
3715(3)
6,601(2)
16,772(4)
0 – 10 106 mm Km2/year10 – 100 106 mm Km2/year
100 – 500 106 mm Km2/year
500 – 1000 106 mm Km2/year
1000 – 2711 106 mm Km2/year
Network Topologic and Geometric Parameters
PotentialMeanFlow
(m3/sec)(1)
(1) Potential Mean Flow (m3/sec) = Weighted Drainage Area (mm Km2/year) , (2) Value for 1999, (3) Value for 2000, (4) Value for 1995
Mississippi River Climate & Hydrology ConferenceMay 13 – 17, 2002New Orleans, LA
31,555
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.