WETLAND FLOOD WATER RETENTION ESTIMATION USING A 3-DIMENSIONAL GIS MODEL

James Handley1 and Cynthia Berlin1, 2 
1Center for Geographic Information Science, University of Wisconsin-La Crosse, 
La Crosse, WI 54601. 3 River Studies Center, University of Wisconsin-La Crosse, 
La Crosse, WI 54601.

This research examines the utility of estimating surface flood water retention 
by wetlands through the use of remotely-sensed data, digital topographic data, 
and a 3-dimensional GIS model.  The study focused on a small urban wetland, the 
La Crosse River Marsh, in the Upper Mississippi River System.  The April 2001 
Mississippi River flood provided an excellent opportunity for developing the 
model, since Landsat ETM imagery and 1:24,000-scale aerial photography were 
available for the day the flood peaked in the study area.  The model was 
evaluated using the photographs and images separately, and the statistical 
comparisons were made for estimation results.  An aerial photograph and ETM 
image of non-flood conditions were used to provide baselines for the model. 
Digital topographic data were used to derive a digital elevation model, which 
provided the basis for depth and water volume measures. The aerial photographs 
and pan-enhanced ETM images were interpreted to identify water and non-water 
surface cover, and used to derive the surface spatial extent of inundation.   
This data was then combined with the DEM to produce estimates of surface flood 
water retention.

Key words:  Flooding, GIS modeling, wetlands, Landsat, aerial photography.