DEM Derived Floodplain Maps

Home Projects Publications Links Contact	DEM Derived Alluvial Flood Plain Maps and Orthoimagery of Honduras and Guatemala These maps show alluvial floodplain deposits that were derived by geomorphic processing of a 30-meter resolution digital elevation model (DEM) overlain upon a USGS digital orthophoto derived from aerial photography for selected municipalites in Honduras and Guatemala. The data shown on these maps were collected after Hurricane Mitch, which affected Central America in 1998, and were designed to assist municipal governments in hazard preparedness and planning. Geomorphic processing of DEMs analyzes the derivatives of digital elevation data such as elevation, slope, and curvature to derive landform units. The alluvial floodplain deposits shown in this map were primarily derived by applying a compound topographic index (CTI) to a 30-meter DEM. The CTI is a function of both the slope and the upstream contributing area and can easily be derived from a DEM. The implementation of CTI using a DEM can be shown as: CTI = ln ( A / tan (beta) ) where A = upstream area calculated as (flow accumulation + 1 ) * (pixel area in m2) and beta is the slope expressed in radians. The CTI was reclassified to display only alluvial plain and recent alluvial deposits and overlain on top of the orthophotography of the area. The resultant maps provide a basis for land-use planning and for hazard mitigation near or within the floodplain for areas that do not have available LIDAR floodplain models. The contours were digitized from 1:50,000 scale topographic maps by the Instituto Geográfico Nacional of Guatemala. Data have not been altered to match the field checked orthophotos and may be less accurate than the orthophoto imagery. Each of the maps included in this section are saved as Adobe Acrobat PDF documents. To view these maps you will need Adobe Reader to view this file. Download a copy of the latest version of Adobe Reader for free. These maps are fairly large in size, approximately 45MB, and may take a while to load on some computers. For quicker viewing, right click on the map or the link and click "Save Target as," to save the map to your computer. Maps of municipalities in Honduras DEM Derived Alluvial Floodplain Deposits and Digital Orthophoto of Campamento, Honduras DEM Derived Alluvial Floodplain Deposits and Digital Orthophoto of Guiamaca, Honduras Maps of municipalities in Guatemala DEM Derived Alluvial Floodplain Deposits and Digital Orthophoto of Los Amates, Guatemala DEM Derived Alluvial Floodplain Deposits and Digital Orthophoto of Morales, Guatemala DEM Derived Alluvial Floodplain Deposits and Digital Orthophoto of Puerto Barrios, Guatemala DEM Derived Alluvial Floodplain Deposits and Digital Orthophoto of Zacapas, Guatemala	LIDAR Derived 50-Year Flood-Inundation Maps and Orthophotography Landslide Hazard Maps

DEM Derived Alluvial Flood Plain Maps and Orthoimagery of Honduras and Guatemala

These maps show alluvial floodplain deposits that were derived by geomorphic processing of a 30-meter resolution digital elevation model (DEM) overlain upon a USGS digital orthophoto derived from aerial photography for selected municipalites in Honduras and Guatemala. The data shown on these maps were collected after Hurricane Mitch, which affected Central America in 1998, and were designed to assist municipal governments in hazard preparedness and planning.

Geomorphic processing of DEMs analyzes the derivatives of digital elevation data such as elevation, slope, and curvature to derive landform units. The alluvial floodplain deposits shown in this map were primarily derived by applying a compound topographic index (CTI) to a 30-meter DEM. The CTI is a function of both the slope and the upstream contributing area and can easily be derived from a DEM. The implementation of CTI using a DEM can be shown as:

CTI = ln ( A / tan (beta) )

where A = upstream area calculated as (flow accumulation + 1 ) * (pixel area in m2)
and beta is the slope expressed in radians.

The CTI was reclassified to display only alluvial plain and recent alluvial deposits and overlain on top of the orthophotography of the area. The resultant maps provide a basis for land-use planning and for hazard mitigation near or within the floodplain for areas that do not have available LIDAR floodplain models.

The contours were digitized from 1:50,000 scale topographic maps by the Instituto Geográfico Nacional of Guatemala. Data have not been altered to match the field checked orthophotos and may be less accurate than the orthophoto imagery.

Each of the maps included in this section are saved as Adobe Acrobat PDF documents. To view these maps you will need Adobe Reader to view this file. Download a copy of the latest version of Adobe Reader for free.

These maps are fairly large in size, approximately 45MB, and may take a while to load on some computers. For quicker viewing, right click on the map or the link and click "Save Target as," to save the map to your computer.

Maps of municipalities in Honduras

DEM Derived Alluvial Floodplain Deposits and Digital Orthophoto of Campamento, Honduras

DEM Derived Alluvial Floodplain Deposits and Digital Orthophoto of Guiamaca, Honduras

Maps of municipalities in Guatemala

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