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Coastal & Marine Geology Program > Coastal Classification Mapping Project > Open File Report 2005-1370

Coastal Classification Atlas

Southeast Texas Coastal Classification Maps - Sabine Pass to the Colorado River

USGS Open File Report 2005-1370

Robert A. Morton, Russell L. Peterson

Report Home Maps Overview Mapping Methods Coastal Classifications Geologic Setting Coastal Processes Coastal Vulnerability Classification Summary References

Classification Summary

The coastal classification maps provide a basis for establishing the lengths of shore that have a particular morphological characteristic or urban attribute. Such information is relevant for local and state governments for planning that involves the amount of shore that is developed versus undeveloped, or the amount of parkland held in the public trust. Also, there is interest regarding the amount of shore that is affected by engineering structures, referred to as armoring or hardening of the shore. Environmental-protection and resource-management issues such as these require quantitative data that can be derived from the classification maps.

The shore lengths and equivalent percents of the 242.6-km-long segment of coast between Sabine Pass and the Colorado River are presented for each classification unit in Table 2. Seventy-four percent of this coastal segment is undeveloped and where it is developed, such as on Bolivar Peninsula, Galveston Island, and near Freeport, the development is mostly low to moderate density. High-density development is restricted to Galveston Island. Single-family homes are much more common than multi-family units, such as high-rise condominiums and hotels, and 7% of the shore is classified as parks. Dunes are not well developed along most of this shore and continuous or discontinuous dunes are only present on 35% and 7% of the shore, respectively. An overwash terrace is present along 51% of the shore and zones of complete storm overwash represent about 2% of the shore. The overwash zones are located along the Brazos River delta and in the Cedar Lakes area. Low artificial dunes have been constructed on Galveston Island that in its natural erosional state would have been classified as overwash terrace. Fifty-four percent of the shore is characterized by narrow beaches less than 30 m wide. Because the beaches are commonly used for recreation, about 40% of the shore is regularly maintained by some type of beach raking or scraping. About 21% of the shore is influenced by hard structures. Most of the structures are walls, riprap revetments, or geotubes built in the backbeach area. The engineering structures are concentrated in the developed areas, with the most structures concentrated on Galveston Island where the massive seawall, groins, and riprap line the shore. The most recent attempts to stabilize the shore with structures have involved placement of geotubes on Bolivar Peninsula, Galveston Island, and the north end of Follets Island (Fig. 10).

Table 2. Lengths of shore and percentages for the classification units mapped between Sabine Pass and the Colorado River. Total length of this coastal segment is about 242.6 km.
Category Classification Length (km) Percent Pie Chart
Overwash Overwash 3.9 2 Overwash pie chart - overwash 2%, no overwash 98%
Closed inlet 0.0 0
New inlet 0.0 0
No overwash 238.6 98
Dunes Absent 16.5 7 Dune Presence pie chart - absent 7%, discontinuous 7%, continuous 35%, overwash terrace 51%, overwash terrace with ridge less than 1%, artificial dune less than 1%
Continuous 85.8 35
Discontinuous 15.8 7
Overwash terrace 122.7 51
Other 1.8 <1
Beach width > 30 m natural 30.0 12 Beach width pie chart - greater than 30 meters maintained 33%; greater than 30 meters natural 12%, less than 30 maintained 7%, less than 30 meters natural 47%
> 30 m maintained 80.6 33
< 30 m natural 144.1 47
< 30 m maintained 17.9 7
Structures No structure 191.0 79 Structures pie chart - multiple structures 5%, no structure 79%, geotube 4%, riprap 6%, wall 6%
Wall 14.6 6
Riprap 14.5 6
Geotube 9.1 4
Multiple structures 13.5 5
Development Density Low density 24.3 10 Density of development pie chart - high density 5%, moderate density 11%, low density 10%, undeveloped 74%
Moderate density 26.9 11
High density 11.9 5
Dwelling Type Single family 44.8 18 Dwelling type pie chart - single family 18%, multi-unit 3%, mixed 2%, park 7%, industrial/commercial undifferentiated less than 1%, no dwelling 70%
Mixed 3.9 2
Multi-unit 7.2 3
Park 16.3 7

Coastal & Marine Geology Program > Coastal Classification Mapping Project > Open File Report 2005-1370

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