There are no author-identified significant results in this report

Baker, V. R.

Holz, R. K.

Hulke, S. D.

English

NASA Technical Reports Server

"Made available varWr NASA sponsorshMp
'n the interest of early and wide d:s- E 7. 4 - 1 0. 3'8 9
seilination of Earth Resources Survey
Program information and without liability
for any use made thereot."
A HYDROGEOMORPHIC APPROACH TO EVALUATING
FLOOD POTENTIAL IN CENTRAL TEXAS FROM
ORBITAL AND SUBORBITAL REMOTE SENSING IMAGERY
by.
Victor R. Baker, Robert K. Holz and Steven D. Hulke
Central Texas is subject to flooding of extraordinary magni- " =
tude, particularly in the frequency range of 10-50 years. Assuming
that stream network geometry has been adjusted to these floods, quan-
titative drainage network analysis can be used to relate stream mor-
phology to potential flood discharge. Stream network geometrics were
digitized from Skylab S-190B imagery, high-altitude and low-altitude
aerial photographs, and large scale topographic maps. The digitized 4 Wdata were then used to generate significant hydrogeomorphic paramet- -
ers with The W. A. T. E. R. System, a computer program for watershed ,
analysis developed at the Universities of Toronto and Purdue. A ten-
tative model for flood potential evaluation was established by relating
known peak discharge measurements to corresponding drainage basin ,
areas, basin shapes, drainage densities, total stream lengths, and
frequencies of first order streams for given rainfall intensity factors. P1 0
Locally, this model provides a more accurate basis for extrapolating o )
hydrologic data than does conVentional regional flood frequency analysis. 5 ,
A critical factor in comparing the hydrogeomorphic utility of
the various imagery formats is their ability to resolve the smallest un- o --
branched stream segments in a drainage network. Resolution is illus- =
trated by the following results from analysis of the upper Bee Creek K -. 4
basin (1. 81 mi2 ) near Austin, Texas: o
Low -Altitude Skylab
Source: Topographic Map Aerial Photography S-190B 1 2
Scale: .1:24,000 1:22, 200 1:172, 000 - < a o
Apparent No. of 82 55 26First Order Streams:
Bifurcation Ratio: 4. 56 3. 93 5.02
Mean Length of First 0. 33 0.133 0.15
Order Streams (miles): :. ,
1 Work supported in part by the National Aeronautics and Space Admin-
istration Contract No. NAS 9-13312.
https://ntrs.nasa.gov/search.jsp?R=19740010885 2020-03-23T11:39:48+00:00Z
A second critical factor is the ability of various imagery formats
to most accurately depict current land-use factors in the drainage basin
that may be of significance in affecting flood magnitudes. Urban hydro-
logic studies in the region have shown that land-use factors alone can
increase peak flood discharge by as much as 300%, all other hydrologic
facotrs held constant. Continuous orbital monitoring holds the promise
for the most accurate depiction of hydrologically significant land-use
factors, particularly in areas of rapid change like the Highland Lakes
region of central Texas.
An important by-product of hydrogeomorphic analysis is the
production of data useful in related regional hydrologic studies of run-
off and base flow. This information includes: 1) wavelength of valley
and channel meanders; 2) distribution, type and density of vegetation;.
3) distribution of exposed bedrock and caliche; 4) estimation of relief
as aided locally by the contour-like character of resistant limestone
units; and 5) distribution of roads, fence lines, drainage ditches, and
other human disruptions of the natural drainage geometry.


A hydrogeomorphic approach to evaluating flood potential in central Texas from orbital and suborbital remote sensing imagery

Abstract

Similar works

Full text

Available Versions

NASA Technical Reports Server