Geology topics
Publications and source records attributed to Karl G. Johnson.
This report provides hydrologic and hydraulic information related to the flood of September 16, 1975 in the Guayanilla Valley. The information presented is a compilation of data recovered by the U.S. Geological Survey, and information provided by the residents in the study area.
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Severe flooding throughout St. Croix, United States Virgin Islands occurred on October 8, 1977. A tropical storm moving across the island produced as much as 16 inches of precipitation. The most affected areas were near Frederiksted, Mon Bijou, and the Airport. The peak discharge of River Gut near the Airport was about 11,400 cubic feet per second. The water depth in some urban areas exceeded 4.0 feet. Flood maps and flood profiles show the inundated areas near Frederiksted, Mon Bijou and the Airport.
This report provides a record of the flood of September 16, 1975, and associated hydrologic data. These data can be used in making rational decisions in formulating effective flood-plain regulations that would minimize flood problems in the Tallaboa Valley. The Tallaboa Valley (fig. 1) lies on the southwestern coast of Puerto Rico about 12 km (7.5 mi) west of the city of Ponce. The climate is semiarid with a mean annual precipitation of about 1,020 mm (40 in). It is a relatively small valley which until the late fifties was dedicated mainly to the product ion of sugarcane. Since then, the economy started changing from agriculture to industry. At present the lower part of the valley is completely industrialized. The upper part of the valley is used for agriculture--mostly as pastureland. The reach from Highway 132 downstream to the new Highway 2 is mainly agricultural with a few scattered communities. The lower part of the valley that includes the area from the Highway 2 bridge to the mouth is covered with heavy industry concerned with the refinement of oil, and associated industries. The continuous growth of industry and consequently of the urban area of Peñuelas has encouraged growth onto the flood plain. The study area is subject to flooding by the Rio Tallaboa and the Rio Guayanes, its main tributary. The Rio Guayanes is the- cause of flooding in the urban area of Penuelas, encompassing the reach from the northern edge of town downstream to Highway 132 where it joins the Rio Tallaboa. Data are generally referred to in SI (International System) units followed by corresponding inch-pound units in parentheses. The SI units.may be converted to inch-pound units by multiplying the units given by the factors shown.
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