FLOOD09579

• County: Statewide
• Community: Dallas, Texas
• Basin: Statewide
• Title: Effects of Urbanization on Floods in the Dallas Texas Metropolitan Area
• Date: 1/1/1974
• Prepared By: USGS, City of Dallas
• Floodplain - Doc Type: Educational/Technical/Reference Information

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ILLUSTRATIONS

Page

Map of Texas showing the location of the Dallas
metropolitan area................................... 4
Schematic diagram of the hydrologic model............. 6
Map showing locations of drainage basins, stream-
gaging stations, and rain gages..................... 9
Scatter diagram of observed and computed peak
discharges in the control basins.................... 17
Scatter diagram of observed and computed peak
discharges in the noncontrol basins................. 18
Flood-frequency curves for six gaging stations
based on simulated peak discharges for 1914-70...... 33
Flood-frequency curves for eight gaging stations
based on simulated peak discharges for 1914-70...... 34
Nomograph showing the relation between flood
frequency, drainage area, and a coefficient of
imperviousness. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 43
Comparison showing the effects of urbanization
on the 50-year peak discharges in Dallas and
Houston. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 46
Graph showing the relation of effective impervious
area to the ratio of urban runoff to rural runoff... 48

TABLES

Identification and definition of the parameters
used in the digi tal modeL.......................... 7
Drainage area, percentage of impervious area, and
topographic characteristics of drainage basins
in the Dallas metropolitan area..................... 11
Zoning categories and average percentage of
impervious area..................................... 12
Stream-gaging stations and rain gages in the
Dallas metropolitan area............................ 14
Stream-gaging stations, rain gages, rain-gage
grouping, and rainfall-weighting methods used
in the basins modeled............................... 15
Storm-rainfall and discharge data for Dallas.......... 19
Storms for which peak discharges were computed
from the hydrologic model........................... 35
Summary of simulated peak-discharge data.............. 36
Station flood-frequency characteristics computed
from simulated peak discharges...................... 40
Regional flood-frequency equations.................... 44
Annual rainfall and runoff in selected basins

1962-70. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 49

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