Hydrologic Topology

1
Hydrologic Topology Francisco Olivera, Ph.D.,
P.E. Assistant Professor (folivera_at_civilmail.tam
u.edu) Srikanth Koka Graduate Research
Assistant (srikanth_at_tamu.edu) Texas AM
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
410,932
974
1,885(2)
2013
Little Rock
9,881
2662
Omaha
2675
824,543
1,274(2)
12,433
Paducah
1819
1496
513,680
20,090
3715(3)
St.Louis
3627
1710
1,790,860
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