“Flood monitoring and mapping for Emergency Response in San Antonio-Texas”

Part I

by

Silvana Alcoz

Source photo http://www.hdrinc.com/information/

Term Project - CE 394K - GIS in Water Resources

0 10 205 Kilometers ¯

Lower Salado Creek

Upper Salado Creek

Lower Leon Creek

Elm Creek

Medina River

Medio Creek

Culebra Creek

Upper Leon Creek

Martinez Creek

Calaveras Creek

Lower San Antonio River

NW LOOP 1604

Upper San Antonio River

SE LOOP 410

§̈¦35

Area under study:

Rosillo Creek – Lower Salado Creek watershed

Center for Research in Water Resources:Model Integration Framework for Floodplain Mapping

Which is the land use in Rosillo Creek basin?

Source orthophotos: TNRIS

http://www.tnris.state.tx.us

• Census boundaries: ESRI’s Geography Network: Census 2000 Tiger/Line DataThis census boundaries are just boundaries, do not have census demographic data associatedCoordinate system: decimal degrees

http://www.esri.com/data/download/census2000_tigerline

Level of census geography chosen: block groups

• Census database tables: US Census Bureau, will be joined to the census geographic areas SF1 data is the basic information of the Census, we will be able to join it to the boundary through a common field called STFID

http://factfinder.census.gov

Obtaining data from the Census 2000

0 10 205 Kilometers

0-25%

25.01%-50%

50.01%-75%

75.01%-100% ¯

Hispanics as a proportion of total populationof each census blockgroup

Population under 5 as a proportion of total population of each census blockgroup

0-5%

5.01%-10%

10.01%-15%

15.01%-20%

20.01%-25%0 10 205 Kilometers ¯

0-7%

7.01%-14%

14.01%-21%

21.01%-36%

36.01%-100%0 10 205 Kilometers ¯

Percentage of house units that are rented occupied

To characterize the basin:

1. Geodatabase - Center for Research in Water Resources: Model Integration Framework for Floodplain Mapping (Projected Coordinate System: Lambert_Conformal_Conic (feet))

It includes:2 storm events

– Hydroresponse unit– Time series tables- Basin- Hydroedge, Hydrojunctions, Hydronetwork

No information on how the basin and network had been obtained

2. New Geodatabase– National Elevation Dataset: DEM grid– National Hydrography Dataset to obtain the surface water drainage network (nhd coverage)

Both datasets are in geographic coordinates -> Projection chosen: UTM zone 14N (meters)

ArcToolbox->projection->project wizard (coverages, grids)

Cell size of projected DEM grid: 30m

Seamless dataset of the USA

NED:

• user specifies geographic extent• horizontal locations are referenced in decimal degrees of latitude and longitude• a consistent grid spacing of 1-arc-second (approximately 30 meters) is used• Elevation units are standardized to decimal meters• The horizontal datum for NED is the North American Datum of 1983 (NAD 83)• the vertical datum is the North American Vertical Datum of 1988 (NAVD 88). 40

http://seamless.usgs.gov/viewer.htm

HUC: 12100301

Upper San Antonio

West Coordinate = -98.64886855615 East Coordinate = -98.2209294179 North Coordinate = 29.73515182874 South Coordinate = 29.14713602515

nhd coverage has line, polygon, and node topology

National Hydrography Dataset

http://nhd.usgs.gov/data.html

Threshold to generate stream: 2000 cells

Flow accumulation at the outlet is 86,235 cells, each cell is 30mX30m, so the total area of the basin is 77.6115 square km

nhd_route.rch

generated_drainage_line

generated_catchment

0 4 82 Kilometers ¯

Drainage density of the river network generated = (55951.65-14.93)/77611500= 0.000721 Drainage density of NHD river network = (36883.37)/77611500 = 0.000475

Results from ArcHydro Terrain Processing:

Degree of agreement with input vector stream

From 5m clipped contours with Rosillo Creek basin:

Min. elevation: 155 metersMax. elevation: 265 meters

nhd_route.rch

generated_drainage_line

generated_catchment

0 4 82 Kilometers ¯

Joining precipitation data to the generated catchment

hydroresponse unit and time series table don’t have any field in common with the catchment feature class to be joined.

Then, spatial join, joining the attributes of features by their location, with the objective to get the storm event spatially aggregated by the catchment.

Intersection feature class: catchment and hydroresponse unit - 62 records each one with both attributes

Temporal layer: intersection feature class and time series table

Microsoft access and ArcMap data manipulation to assign rain to catchments,First accumulating rain per area, then per HydroID

inches per hour

0.000000

0.000001 - 0.105100

0.105101 - 0.185400

0.185401 - 0.263800

0.263801 - 0.319700

0.319701 - 0.400400

0.400401 - 0.624400

0.624401 - 0.770500

0.770501 - 0.939000

0.939001 - 2.050400

Event:

20-hour Storm: 01 Jul 2002 at 04:00 through 01 Jul 2002 at 24:00

Variable: precipitation, inches per hour

Animation of storm event over Rosillo Creek Basin using extension for ArcMap called the Tracking Analyst:

0 4 82 Kilometers ¯

Accumulated volume of water in cubic meters

501,662 - 1,111,797

1,111,798 - 2,744,519

2,744,520 - 6,316,588

6,316,589 - 11,119,905

11,119,906 - 16,896,844

Use of ArcHydro tool “accumulate” based on NextDownID field, to accumulate the incremental volume of rain water for each catchment downstream

Average depth of rainfall during the storm over the whole Rosillo creek basin:

217 mm

Accumulated volume at outlet: 16,896,844 cubic meters

Total area of Rosillo Creek basin: 77,612,399 square meters

Continues: Part II

Acknowledegment:

• Dr. David Maidment • Oscar Robayo, PhD student