Flood Damage Map

Runoff Management Features and USGS Indirect Discharge Sites

Digital Elevation Model

Soils Data


Hydrography- Streams, Perennial Lakes and Canals

Composite Land-Surface Hydrology

USGS- Spring Creek Channel Cross-Sections (Courtesy of USGS)

HEC-2 (HEC-RAS) Input Deck for Spring Creek

SWMM Model Input Deck (not yet available)

METADATA (Data on Data)

The geospatially-referenced data available for downloading on this page are stored in UTM coordinates, Zone 16, using the Clark 1866 reference geoid.  These maps were written using the GRASS Geographic Information System (GIS).  The format of ASCII GRASS maps is explained on the Baylor University website.

Flood Damage Map

    The following image was scanned from a map of damaged areas developed by the City of Fort Collins, Geographic Information Systems Department.  The Spring Creek Watershed boundary is drawn approximately to illustrate the region considered.  The legend shows the type of damages incurred within the watershed during the flood.  This image also details the location of the detention pond that was designed to attenuate the 1% probability storm.


Runoff Management Features and USGS Indirect Discharge Measurement Sites in the Spring Creek Watershed

The figure below shows some of the salient features of the watershed, including lateral canals that cross Spring Creek, details of the large detention basin,  and points were the Colorado District of the USGS performed indirect discharge estimates (in grey, numbered rectangles).


Digital Elevation Model

We first went to the US Geological Survey to obtain a digital elevation model (DEM) of the Spring Creek watershed.  We discovered to our delight that the data for the Spring Creek watershed are available  30m horizontal resolution.  These data were contained on two USGS quadrangles, namely the Fort Collins and Horsetooth quads.  We ordered the data and anxiously awaited its arrival.

Upon arrival, we used the public-domain GRASS Geographic Information System (GIS) to merge these two quadrangles into a seamless DEM of the watershed.  After completing this straightforward step, we displayed the resultant digital elevation model and saw the following (with the Spring Creek boundary vector overlaid):

Merged USGS Fort Collins and Horsetooth DEM Quads

In the above image, the elevation of the DEM elevation increases from yellow to cyan.    If you look carefully at this image, you will notice two things.  First, this is a very noisy DEM.  Notice the spotty nature of the elevations.  Secondly, you will notice a vertical line in the lower left-hand corner of the DEM.  This line  corresponds to the location of the boundary between the Fort Collins (eastern) and Horsetooth (western) quads.  The line only appears in the lower (southern) portion of this image, but this is an artifact of the color map used in the image.  To further examine the difference, the same DEM is displayed below using a different color scale.

As you can see in the above two images, this abrupt change in elevation extends alont the entire boundary between the Fort Collins and Horsetooth 30m DEM quadrangles.  The magnitude of the error across the boundary of the two quadrangles varies between 2 and 15 m (6.6 and 49.2 ft).   This error is unacceptable for detailed hydrologic analysis, so we went back to square 1.

In the end, we decided to construct our own digital elevation model.  We found that the elevation contours on the Fort Collins and Horsetooth paper quadrangles lined up quite well at their common boundary.   Creation of our own DEM was a two-step process.  First, we digitized the contours from both maps.  Second, we used the GRASS s.surf.tps algorithm to generate a continuous surface.  The resulting digital elevation model is shown in the figure below, with the original vector contours overlaid on the surface.  The contour interval is 10 ft (3.04m).

Shift-click here to download this map.  This map is a floating-point ASCII GRASS GIS map, with elevation in meters.  The format of ASCII GRASS maps is defined here.

Soils Data

Soils data were obtained from the USDA Natural Resources Conservation Service (NRCS- formerly SCS) county soil survey for Larimer County, Colorado.  The distinct soil classes were digitized, and converted from vectors into a 30 m raster map using GRASS.  This map was reclassified into Rawls and Brakensiek (1983) soil textural classifications:

The soil textural classifications corresponding to the above map are:
Soil type
Percent coverage
Sandy loam
light green
dark green
Silt loam
Clay loam
silty clay
water (perennial lake)

Land-Use/Land-Cover Data

The image below shows  digitized land-use/land-cover (LULC) vectors overlaid on the final digital elevation model of the Spring Creek Watershed.  Each of the polygons in the LULC data layer has distinct attributes.  These attributes were obtained from the GIS Department in the City of Fort Collins.

The LULC attributes were assigned to the 30 m raster elements within the watershed boundary.  The resulting raster map appears in the following figure.

Notice the one-to-one correspondence of the above colored regions in the raster map (bottom) to the vector map (top).  Each of the colors in the raster map correspond to a distinctive LULC classification.  For instance, pasture appears as blue, perrenial lakes are pink, suburban LULC is orange, etc.

Shift-click here to download this integer GRASS ASCII map.  The format of ASCII GRASS maps is defined here.

Hydrography- Streams, Lakes and Canals

The following image shows vector hydrographic data (blue) and the vector Spring Creek watershed boundary (black).  Spring Creek runs from the southwest corner of the watershed, towards the east-northeast.  There are numerous small irrigation canals crossing the watershed from north-northwest to south-southeast.  The capacity of these irrigation canals is quite small because of their small cross-section and slope.  Therefore, their impact on the flooding was minor.

Composite Land-Surface Hydrologic Characteristics

A number of factors affect the hydrologic behavior of the land surface.  The three dominant factors are the land-use, land-cover, and soil texture.  The map below shows a composite soil saturated hydraulic conductivity map.

The following saturated hydraulic conductivity values were assigned to the categories shown in the above map:

Color Description Percent Coverage Sat. Hydr. Conductivity (cm/h)
yellow impervious areas 23 0.0
green Clay loam 21 0.20
cyan Silt loam 3 0.34
blue Loam 42 0.6
red Sandy Loam 11 1.0

Shift-click here to download this map.  This map is a floating-point ASCII GRASS GIS map.  The format of ASCII GRASS maps is defined here.

Spring Creek Channel Cross-Sections
(provided by Colorado District, US Geological Survey)

The following Microsoft Excel (8.0) files contain detailed cross-section surveys at 10 points that had a significant effect or established control on the flood discharges.  Not all of the cross-sections are in Spring Creek.

Shift-click to download each file you want.

 Fairbrooke. Channel     (Spring Creek watershed)
 Clearview Channel       Clearview channel downstream from Taft Hill Road (CSU Campus watershed)
 Dorset Drive                   (Spring Creek watershed)
 Fossil Creek                    at S. Lemay Avenue (Fossil Creek watershed)
 Hill Pond Subdivision     Spring Creek downstream from Shields Street
 Plum.xls                            Plum channel upstream from Taft Hill Road
 Riverside Ave.                Spring Creek at Union Pacific RR Bridge (downstream indirect discharge site)
 Railroad Embankment  Spring Creek detention pond was formed by this railroad embankment, near College Ave.
 Shields St.                         Spring Creek main channel just downstream from Shields Street.
 Wallenburg Drive           Spring Creek downstream from Shields Street.

HEC-2 (HEC-RAS) Input Deck (provided by the City of Fort Collins)

 Springm.dat   Shift-click to download.

Data Links

CSU Radar data http://olympic.atmos.colostate.edu/
Doppler http://www.hmsweather.com/doppler.htm

Atmospheric CSU http://olympic.atmos.colostate.edu/flood97.html