Guide - The Flood Observatory - University of Colorado Boulder

Guide to the Surface Water Record
Brakenridge, G.R. and Kettner, A.J., 2013, “Guide to the Surface Water
Record”, Dartmouth Flood Observatory, University of Colorado, Boulder, CO,
• This is a guide for interpreting and using the maps and other
data provided by the Record.
• It also provides some interesting examples of surface water
variability, as observed and measured through this remote
sensing technology.
The Surface Water Record is a collection of online map displays, each measuring 10 deg long. x
10 deg lat., accessed by clicking on one of the map sheets illustrated above in the Dartmouth
Flood Observatory home page: These also provide links
to GIS data supporting the displays.
This 20 year long effort, led by Bob Brakenridge, has been sustained by grants and contracts
from NASA, the European Commission, the World Bank, and other sources, and by Dartmouth
College and the University of Colorado. Version 3 will be fully automated.
In the version 3 Record, the reference water is
unchanging. It is the NASA Space Shuttle
SRTM mission (90 m) SWBD data, February
11-23, 2000. All of the maps presented here
are from version 3, and they each show
MODIS-sensed water on particular dates in
April, 2013 compared to the SWBD water.
Map Symbology
Large areas of purple are now dry land (but were
water in 2000). Very small areas of purple (<.25 km
wide) are water bodies mapped by SWBD, but are
too small to be mapped by MODIS.
Dark blue is current surface water, imaged by both
MODIS and by SWBD (not flooding). Bright blue is
flooding: expanded water areas mapped by MODIS
compared to SWBD.
Elephant Butte Reservoir and surrounding
areas, New Mexico, showing droughtcaused reduced surface water.
Very light blue-gray is all previous flooding imaged
and mapped by the Dartmouth Flood Observatory.
Flooding (bright blue) along the extensive
floodplain of the Lower Mississippi River,
USA, April, 2013.
Also shown is normal water (dark blue) and
maximum observed flood extent (light
1)Only modest flooding is occurring as of
this map date; flooding is contained within
previously mapped limits.
2)Progressive mapping of flooding over the
years has delineated “the floodplain”.
3)Narrow purple areas are water bodies
mapped in the SWBD at higher spatial
resolution (not discernable by MODIS).
Large reservoir status near Oxford,
Mississippi, USA, April, 2013. From
north to south, the Sardis, Enid,
and Grenada reservoirs are shown.
Shrinkage of Sardis surface water
extent compared to February 2000
is shown in purple.
Light blue-gray is maximum water
extent so far imaged. All of the
reservoirs extended far upstream
during past intervals of wet
conditions and flooding.
Many wetlands around the world are being monitored by the Record. For
example, “The country’s largest interior marsh, Cheyenne Bottoms,
Kansas, is the top shorebird staging area in the continental United States,
a resting and refueling area for more than half of all shorebirds that
migrate east of the Rockies. That includes 90% of North America’s
population of Wilson’s phalarope, long-billed dowitcher, white-rumped
sandpiper, Baird’s sandpiper, and stilt sandpiper… “
“Named a "Wetland of International Importance" by the Ramsar
Convention on Wetlands, Cheyenne Bottoms is threatened by conversion
to agriculture and diminishing water supply.”
April 2013, MODIS surface water status (completely dry): a small cropped
subscene from the Record map sheet. Light blue-gray is the maximum water
extent observed by MODIS (May 12, 2007); now dry land. Purple is water imaged
in February 2000 (SWBD data), now also dry land.
Cheyenne Bottoms, June 18, 2010 (“average summer”).
Landsat image from
Cheyenne Bottoms, July 17, 2012 (severe drought, “driest and second-hottest summer on
record. Dry conditions continued into early April, 2013
The MODIS-derived record of
flooding in the northern Mississippi
River Embayment, southcentral USA
(light blue-gray).
Heavy rains fill rivers entering this
large river alluvial plain from the
west; the flooding flows southward
for long distances before joining the
Mississippi. The map shows not
only future flood hazard, but the
large scale flood drainage network.
At this map update, in April, 2013,
“normal” flow conditions prevail
(bright blue areas are very limited).
Subscene from:
Status of Lake Marion, South
Carolina, between Sumter and
At time of this map update, in April,
2013, the reservoir extended past
the February 2000 reference water
(extension shown as bright blue
areas), but flood water has not
reached the maximum extent
previously mapped (light blue gray)
Bright blue fringes around other
reservoirs indicate that they also
are high.
Subscene from:
Status of Indus River, Pakistan, in
April 2013 (dark and bright blue
colors) compared to past flooding
(light blue-gray).
The catastrophic flood of 2010
breached levees in the northern
portion of this scene; much of the
flood water flowed far to the west,
inundating lower terrain bordering
the broad alluvial ridge occupied by
the river.
Subscene from:
See also Syvitski, J.P.M. and Brakenridge,
G.R., 2013, “Causation and avoidance of
catastrophic flooding along the Indus River,
Pakistan”. GSA Today, v. 23, p. 4-10.
Upstream Indus River and
The Chasma reservoir on
the upper Indus is now
extended past its February
2000 state.
Narrow bright blue strips
along the Indus channel
indicates channel change
compared to February 2000.
Also shown is the maximum
flooding observed (light
blue-gray): important
information for flood hazard
Sistan Lake (large purple area): an
ephemeral water body in the arid
lands along the Afghanistan/Iran
The lake is dry in this April, 2013 map.
Hamun lake, the small water body to
the south of Zabol, is full.
Episodes of flooding were previously
mapped in the area. They are
recorded by dated GIS files in the
Record’s “Surface Water Archive”;
here all files are merged as light bluegray.
Status of Rana Pratap Sagar
(top) and Gandhi Sagar (bottom)
India, in April, 2013
The northern lake today matches
its February, 2000 extent. The
southern lake is much extended,
and drains into the former. Thus,
the two-reservoir system
exhibits much greater combined
water storage in April, 2013 than
that in February 2000.
Mahanadi River delta, India.
This portion of the Record map
sheet shows extensive
flooding in the recent past;
both upstream along the
Mahanadi, above Cuttack, and
also in the delta and other
shoreline (in some cases, from
tropical storm surges)
On the day of map update, in
April 2013, no significant
flooding was occurring.
Salandi Reservoir northwest of
Kuparj is mapped as purple
(dry). It may fill again during
the wet season. Sedimentation
has greatly reduced the
storage capacity of this
Monitoring of lakes in Tanzania.
Lake Natron, at the border with
Kenya, is full; Lake Eyasi, to the
southwest, is lower than in
February 2000 (note purple area
marking new dry land). Much
smaller Lake Kitangiri further to the
southwest is much expanded. To
the south, Lake Sulunga to the
south is much reduced. Numerical
area values can be obtained from
the GIS files.
No surface water is imaged and mapped by MODIS
in this northern India, April, 2013 Record subscene
(but note channel changes of the Ganges, in bright
blue). During the summer monsoon, flood water
will once again be observed, and its maximum
extent can then be compared to previous
monsoons. Each year, some of the light gray-blue
areas are reoccupied by water.
In the online Record, the black dot (#52) is
clickable and provides river discharge
measurements, 1998-present (next slide)
In 2008, a breach of the east levee of the Kosi
River, upper part of this subscene, allowed flood
water to spill out over large areas of Bihar (light
blue-gray), causing 250 fatalities and displacing 3
million. This river avulsion is recorded for posterity
in the Surface Water Record map sheet, and in
more detail.
The 1998present daily
discharge time
series (bottom
plot) and the
most recent
part of same
record (upper
plot) at river
site 52 on the
Kosi River.
Note the large
(but not flood
of record)
with the levee
breach in 2008.
In 2011, abundant rainfall upstream of
Bangkok, Thailand, filled floodplains
and reservoirs, and over several weeks
time flooding eventually reached
Bangkok (light blue-gray). As for the
previous slide, this portion of the
relevant Surface Water Record map
sheet shows little surface water in April,
2013, but provides a guide to past and
future monsoon season flooding.
Complete 10 degree map sheet for a
portion of the northern central USA and
Canada, in April, 2013.
Light blue-gray maps previous flooding
along the Red River valley (northern portion
of map) and, far to the south, in Iowa.
Permanent water mapped by both the
SWBD and MODIS is shown as the western
portions of Lake Superior (upper center
right). Bright blue shows current spring
flooding in the wetlands and agricultural
areas of southern Minnesota.
In northern Minnesota and southern
Canada,extensive purple areas are icecovered lakes (mapped as dry land). The
maps record the spring thaw each year as
this water transitions from purple to blue.
Accessing Surface Water Record Data
The maps and associated GIS data provide current surface water extent and the observed
recent history of changes (since DFO began mapping floods, in 1993, but with most data
commencing in yr 2000). Surface water expansions and contractions are both illustrated.
Mapped water expansions may be short-term, from inland flooding or storm surges. Or
long-term, from post-2000 reservoir construction and increases in rice agriculture or
aquaculture. Reductions in surface water may also be short-term, from drought
conditions, or long term (some shrinking wetlands).
The Record maps provide some but not all of the information contained in the GIS files.
The GIS files can be analyzed further: to search for particular floods, to examine seasonal
patterns, or to show other features of surface water variability, and at various map scales
and projections.
The most-recent observed water is accumulated as 14 daily water files: to remove nearly
all cloud obscuration. Thus, today's map includes 14 days of data. Following are the links
to GIS data directories; these are also provided at the page for each individual map sheet.
In 2013, DFO is transferring many GIS files in its holdings to these public locations.
Located here (change upper left corner degree coordinates as appropriate) is access to the
archived long term record for each map sheet. The GIS file names include their associated
dates. Choose appropriate dates to retrieve surface water changes during particular floods
or droughts. Or retrieve the yearly .ppt slide compilation, when available, from that
directory, and scroll through time.
In April 2013, automated updating is being implemented. This uses .shp (and associated
files) named "current" in the MODISlance_2wkpro directory:
Theses .shp files are 14 day accumulations.
Located here is access to the automated daily .shp file GIS record (record commences in
2011). Choose map sheet directory and appropriate dates to retrieve surface water changes
during particular floods or droughts. The end user can also accumulate files over any
chosen interval. DFO uses only the three day .shp file product, commencing January 1,
2013, as the two day .shp files include abundant cloud shadow noise for some map sheets.
See also NRT Global MODIS Flood Mapping from NASA
and technical information about the Record, including hints for importing the maps
into GIS
With citation of the source, this “Guidebook” and all map displays and associated GIS
data can be further distributed and used under the Creative Commons Attribution 3.0
Unported License:
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