Streamgages Measure Drought, Earthquake Impacts on Water plus 1 more

[USGS Newsroom <oc_web@xxxxxxxx>]

Title: USGS Newsroom

Streamgages Measure Drought, Earthquake Impacts on Water plus 1 more

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Streamgages Measure Drought, Earthquake Impacts on Water

Posted: 16 Sep 2014 11:00 AM PDT

Summary: While the national streamflow database is documenting evidence of California’s historic drought, the database is also confirming another recently seen hydrologic phenomenon: earthquake-induced increases in streamflow

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Contact Information:

Laurel  Rogers ( Phone: 619-980-6527 ); Leslie  Gordon ( Phone: 650-329-4006 );

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Hydrograph showing stream flow in cubic feet per second on USGS streamgage on Sonoma Creek near Agua Caliente, from about August 23 - September 13, 2014. The sharp rise starting on August 24 reflects an increased streamflow due to the South Napa Earthquake. (High resolution image)

Hydrograph showing stream flow in cubic feet per second on USGS streamgage on Sonoma Creek near Agua Caliente, from April 1 - mid-September, 2014. The steady decline in streamflow reflects current drought conditions in California. The sharp decrease and increase aroundAugust 1 is a regional trend, reflecting an upstream irrigation diversion.The sharp rise starting on August 24 reflects an increased streamflow due to the South Napa Earthquake. (High resolution image)

Hydrograph showing an increase of gage-height in feet (.01 increments) at the Sonoma Creek at Agua Caliente gage, in the early morning of August 24, 2014. The sharp rise in water level between 4:15 - 4:30 a.m. reflects an increased streamflow due to the South Napa Earthquake an hour earlier. (High resolution image)

SACRAMENTO, Calif. — While the national streamflow database is documenting evidence of California’s historic drought, the database is also confirming another recently seen hydrologic phenomenon: earthquake-induced increases in streamflow.

Rivers and streams across California are flowing at record lows. Streamflow data from 182 U.S. Geological Survey streamgages in California with at least 30 years of record, currently show that 62 percent of streamgages are recording flows less 25 percent of normal, and 44 percent are recording flows less than 10 percent of normal. At several streamgage sites, scientists have had to extend measurement scales and rating formulas that help calculate accurate streamflow, because of record low water flows.

Hydrograph showing an increase of gage-height in feet (.01 increments) at the Sonoma Creek at Agua Caliente gage, in the early morning of August 24, 2014. The sharp rise in water level between 4:15 - 4:30 a.m. reflects an increased streamflow due to the South Napa Earthquake an hour earlier. (High resolution image)

Meanwhile, in the aftermath of the August 24 magnitude 6.0 South Napa Earthquake in California, water has begun to flow again in some previously-dry surrounding creeks, rivers and streams prompting many nearby residents to scratch their heads.

Hydrogeologic responses to earthquakes have been known by scientists for decades. In the case of the South Napa Earthquake, the discharge of springs and groundwater to some streams has increased. Based on experience in previous earthquakes, stream and spring flows are expected to decline again over the next several months, assuming that the Napa region does not get significant rainfall over that time period.

Post-earthquake changes in streamflow were recorded at a USGS streamgage on Sonoma Creek, near the city of Sonoma where measured increases in streamflow began after 4:15 a.m. on August 24, about an hour after the earthquake occurred. Streamflow has increased intermittently since the earthquake from 0.1 cubic feet per second to nearly 3 cfs on September 12. The median historical streamflow for this time period is about 0.5 cfs. Scientists theorize that this increase in streamflow is due to groundwater flow entering the river, and the intermittent nature of the streamflow is due to the non-uniform release of groundwater across the basin. 

Related Links and Resources

• U.S. Drought Monitor.
• WaterWatch.
• The California Drought
• Hydrologic responses to earthquakes, USGS Fact Sheet 096-03, “Earthquakes—Rattling the Earth’s Plumbing System.”
• Current information for streamflow along the Sonoma Creek at Agua Caliente.
• Information about the August 24 South Napa Earthquake.

Getting Out of Harm's Way: Evacuation from Tsunamis

Posted: 16 Sep 2014 09:30 AM PDT

Summary: Scientists at the U.S. Geological Survey have developed a new mapping tool, the Pedestrian Evacuation Analyst, for use by researchers and emergency managers to estimate how long it would take for someone to travel on foot out of a tsunami-hazard zone

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Contact Information:

Leslie  Gordon ( Phone: 650-329-4006 );

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MENLO PARK, Calif. — Scientists at the U.S. Geological Survey have developed a new mapping tool, the Pedestrian Evacuation Analyst, for use by researchers and emergency managers to estimate how long it would take for someone to travel on foot out of a tsunami-hazard zone. The GIS software extension, released this week, allows the user to create maps showing travel times out of hazard zones and to determine the number of people that may or may not have enough time to evacuate. The maps take into account the elevation changes and the different types of land cover that a person would encounter along the way.

Maps of travel time can be used by emergency managers and community planners to identify where to focus evacuation training and tsunami education. The tool can also be used to examine the potential benefits of vertical evacuation structures, which are buildings or berms designed to provide a local high ground in low-lying areas of the hazard zone. 

The Pedestrian Evacuation Analyst software can assist communities with tsunami planning by answering questions such as:

• How long could it take for people to evacuate out of tsunami-hazard zones?
• Will people have enough time to evacuate before the first tsunami waves arrive?
• If people don’t have enough time to evacuate, then where could vertical-evacuation refuges provide high ground?
• How do you compare the benefits of multiple sites for potential vertical-evacuation refuges?

“The tool can be used to provide valuable decision support for tsunami evacuation planning and vertical evacuation siting, which is just in the beginning stages in the U.S. Pacific Northwest,” said Jeanne Jones, USGS geographer who led the development of the software tool.  The tool has enabled USGS researchers to better understand various aspects of community vulnerability to tsunamis, including community comparisons based on evacuation times, vertical-evacuation decision support, the impact of post-tsunami recovery decisions, and the evacuation challenges posed by different types of tsunami threats.

The software tool can be downloaded online, and the complete users guide, “The pedestrian evacuation analyst—Geographic information systems software for modeling hazard evacuation potential” is also available online.

A graph comparing pedestrian evacuation time estimate for Ocean Shores and Aberdeen, WA. (high resolution image)

Landcover map (left) and pedestrian evacuation time estimate map (right) Ocean Shores, WA. (high resolution image)