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Coastal & Marine Geology Program > Coastal Classification Mapping Project > Open File Report 2006-1133

Coastal Classification Atlas

South Texas Coastal Classification Maps - Mansfield Channel to the Rio Grande

USGS Open File Report 2006-1133

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 percentages of the 68.3-km-long segment of coast between Mansfield Channel and the Rio Grande are presented for each classification unit in Table 2. Eighty nine percent of this coastal segment is undeveloped, but where it is developed, the development is mostly moderate to high density (Table 2). Single-family homes, that were predominant in the 1950s and 1960s, represent less than 1% of the shore. Multi-family units, such as high-rise condominiums and hotels, represent 4% of the shore. Only 4% of the shore is classified as parks, which includes both state and county parks. About 50% of the shore has high continuous dunes and discontinuous dunes cover an additional 24% of the shore. Because the dunes are mainly continuous, complete overwash occurs only along 7% of the shore (Table 2). Eighty one percent of the shore is characterized by natural beaches more than 30 m wide; wide maintained beaches account for another 12% of the shore. Because the beaches are wide and mostly undeveloped, there is little need for shoreline stabilization structures. Only about 8% of the shore is influenced by hard structures (Table 2); the most extensive structures are walls built in the backbeach of South Padre Island to protect the condominiums and hotels.

Table 2. Lengths of shore and percentages for the classification units mapped between Mansfield Channel and the Rio Grande. Total length of this coastal segment is about 68.3 km.
Category Classification Length (km) Percent Pie Chart
Overwash No overwash 63.7 93 Overwash pie chart - overwash 93%, no overwash 7%
Overwash 4.6 7
Dunes Absent 16.3 24 Dune Presence pie chart - absent 24%, continuous 50%, discontinuous 24%, overwash terrace 2%
Continuous 34.0 50
Discontinuous 16.7 24
Overwash terrace 1.2 2
Beach width > 30 m natural 55.3 81 Beach width pie chart - greater than 30 meters natural 81%; greater than 30 meters maintained 12%, less than 30 meters natual 6%, less than 30 meters maintained 1%
> 30 m maintained 8.2 12
< 30 m natural 4.2 6
< 30 m maintained 0.6 1
Structures No structure 62.6 92 Structures pie chart - no structure 92%, wall 8%
Wall 5.7 8
Development Density Undeveloped 60.6 89 Density of development pie chart - undevelopled 89%, low density 3%, moderate density 2%, high density 6%
Low density 2.0 3
Moderate density 1.2 2
High density 4.5 6
Dwelling Type No dwelling 59.0 86 Dwelling type pie chart - no dwelling 86%, single family 1%, mixed 4%, multi-unit 4%, park 4%
Single family 0.4 1
Mixed 3.0 4
Multi-unit 3.0 4
Park 3.0 4

Coastal & Marine Geology Program > Coastal Classification Mapping Project > Open File Report 2006-1133

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