U.S. Department of the Interior

U.S. Geological Survey

Fact Sheet 2016–3097

March 2017

The Upper Mississippi River System—

The Upper Mississippi River System (UMRS), the navigable part of the Upper Mississippi and Illinois Rivers, is a diverse 

ecosystem that contains river channels, tributaries, shallow-water wetlands, backwater lakes, and flood-plain forests. Approximately 

10,000 years of geologic and hydrographic history exist within the UMRS. Because it maintains crucial wildlife and fish habitats, the 

dynamic ecosystems of the Upper Mississippi River Basin and its tributaries are contingent on the adjacent flood plains and water-level 

fluctuations of the Mississippi River. Separate data for flood-plain elevation (lidar) and riverbed elevation (bathymetry) were collected 

on the UMRS by the U.S. Army Corps of Engineers’ (USACE) Upper Mississippi River Restoration (UMRR) Program (fig. 1). Using 

the two elevation datasets, the U.S. Geological Survey (USGS) Upper Midwest Environmental Sciences Center (UMESC) developed a 

systemic topobathy dataset.

What is Topobathy?

Topobathy is a seamless surface model that contains 

terrestrial and riverbed elevation. The terrestrial elevation 

is a product of airborne lidar, Light Detection and Ranging, 

converted to digital elevation models (DEMs). Lidar is a pulsed 

laser remote sensing method used to measure the surface of the 

Earth. Bathymetry, a water depth measurement collected using 

hydroacoustics, is used to calculate riverbed elevation. To create 

a seamless topobathy dataset, lidar and bathymetry datasets are 

combined (fig. 2).

What Data Were Used to Generate Topobathy?

From 2007 to 2011, the UMRR Program acquired a onemeter resolution, bluff-to-bluff lidar acquisition of the UMRS. 

Additional lidar data from Minnesota, Missouri, and Illinois, 

as well as further data from the USGS and the USACE, were 

used to supplement remaining parts of the UMRS. The lidar 

derivatives consist of one-meter DEMs, one-meter hillshades, 

and half-meter contours. Lidar processing was completed in 

2015 on all lidar derivatives.

In addition to the lidar data, the UMESC and the UMRR 

Long Term Resource Monitoring (LTRM) element have 

administered the collection, handling, and serving of UMRS 

bathymetric data since 1989. The collection of systemic UMRS 

bathymetry data was completed in 2010 and is essential for the 

calculation of riverbed elevation. When water-surface elevations 

at select flow conditions are applied to bathymetry, water depth 

is converted to riverbed elevation. Other benefits of bathymetric 

data include monitoring ecology of the river, analyzing 

sedimentation, assessing possible impacts of hydrodynamic 

changes, and modeling vegetation distribution.

How Can Topobathy be Used?

Researchers, scientists, local and Federal governments, 

and private companies are focusing on topobathy data as a vital 

and innovative elevation dataset. For the UMRS, topobathy is a 

crucial data layer for understanding, monitoring, and restoring 

the flood plain and river ecosystem (fig. 3). Topobathy data 

may be applied to flood-plain and fluvial geospatial models, 

research projects, resource monitoring, and mapping. Until 

recently, hydrodynamic models have been limited to predictions 

in low-water conditions; but now, hydrodynamic models can 

be developed under multiple flow conditions when using a 

topobathy dataset.

A Decision Support System has been developed at UMESC 

to utilize topobathy data—the Connectivity and Inundation 

tool. The Connectivity and Inundation tool generates spatial 

data layers that summarize hydrologic conditions over a user 

specified date range. The produced data layers help to examine 

the cumulative effects of irregular water flow and depth.

Topobathy offers the ability to predict nearshore 

elevations. Nearshore areas are nearly impossible to measure 

because airborne lidar does not penetrate turbid waters or thick 

vegetation and because of shallow conditions, bathymetric 

surveys by boat cannot reach shorelines. These two limitations 

cause a slight data gap to exist along river shorelines. 

Fortunately, when creating a topobathy dataset, interpolation of 

elevation between the bathymetry survey and shoreline lidar will 

generate a predictive representation of unnavigable nearshore 

areas. The UMRS topobathy dataset will provide managers and 

researchers with a continuous elevation dataset of nearshore 

areas that previously has not been available. This is information 

that may be important when assessing the impacts of water-level 

management on critical flood-plain transition zones (fig. 4).

ISSN 2327-6916 (print) ISSN 2327-6932 (online)

https://doi.org/10.3133/fs20163097
IOWA

ILLINOIS

MINNESOTA

MISSOURI

WISCONSIN

Base from U.S. Census Bureau-TIGER, 1990

and U.S. Geological Survey digital data, 1999, 

Albers projection, North American Datum of 1983

96° 92° 88°

46°

42°

38°

Mississippi 

River

Illinois River

0 100 200 KILOMETERS

0 100 200 MILES

Long Term Resource Monitoring study 

 area

Upper Mississippi River Restoration 

 Program study area

Upper Mississippi River System Basin

Illinois

Iowa

Minnesota

Missouri

Wisconsin

EXPLANATION

Figure 1. The Upper Mississippi River System (UMRS) and the Upper Mississippi River Restoration (UMRR) Program area, where topobathy 

data are available. The area is located in five Midwestern States: Minnesota, Wisconsin, Iowa, Illinois, and Missouri. Topobathy is a valuable 

dataset used by flood-plain managers, scientists, Federal and State agencies, and other researchers as a tool to understand river ecosystems, 

landscape modeling, habitat restoration planning, and research amongst flood-plain communities.
Bathymetry Lidar Topobathy

Figure 2. Datasets combined to develop the seamless topobathy coverage.

Figure 3. Topobathy surface of Mississippi River Navigation Pool 8 south of La Crosse, Wisconsin. This three-dimensional image 

provides a visual representation of a braided channel and backwater complex.
Figure 4. A topobathy, three-dimensional view of the U.S. Army Corps of Engineers’ restoration project of Weaver Bottoms, south of 

Weaver, Minnesota, on Mississippi River Navigation Pool 5.

What is the Future of Topobathy?

Topobathy is one of the fastest growing geospatial products 

related to benthic habitats, nearshore habitats, and flood plains. 

Topobathy lidar, a high-resolution sensor consisting of green 

waveform lasers, is an advanced and powerful technology. 

An advantage of topobathy lidar is that terrestrial and aquatic 

conditions may be measured on the same day using only one 

sensor, which results in the reduction of acquisition cost. 

Topobathy lidar does have limitations such as limited penetration 

into turbid or thickly vegetated waters, depth restrictions, and 

weather conditions. The UMRS is generally too turbid for 

current topobathy lidar technology; hydroacoustics are presently 

the most effective technology to measure bathymetry in the 

UMRS to determine riverbed elevation. As airborne topobathy 

lidar technology advances, topobathy of the entire UMRS 

may eventually be acquired using only airborne collected data. 

Currently, a plan is being developed to replace outdated lidar and 

bathymetry datasets that make up parts of the UMRS topobathy. 

Lidar and topobathy data are publicly available at

http://www.umesc.usgs.gov/data_library/topobathy.html.

For more information contact:

USGS Upper Midwest Environmental Sciences Center

2630 Fanta Reed Road

La Crosse, WI 54603

Jayme M. Stone, 608-781-6290, jmstone@usgs.gov

Jenny L. Hanson, 608-781-6372, jhanson@usgs.gov

Stephanie R. Sattler, 608-781-6272, ssattler@usgs.gov