American River Basin flooding targeted by the HydroMet Testbed project
Sacramento and Blue Canyon precipitation during the first part of HMT06.
The city of Sacramento, CA, has been battling the threat of flooding ever since it was founded at the convergence of the American and Sacramento Rivers during the Gold Rush in 1849. The city continues to expand within the floodplain, and much of the current population lives behind levees. A close-call came as recently as 1997 when a storm struck the American River Basin, causing the Sacramento River to peak within a half a foot of the record level set in 1986. Sacramento was spared only because the fury of the storm was centered 40 miles north, but nearby towns flooded when levees failed.
The flood-vulnerable American River Basin was targeted this winter by the HydroMet Testbed (HMT) research project. The project team tested and improved streamflow models and learned what is required to make better predictions of where, when, and how much rain will fall. The HMT ran from December 1, 2005 through March 1, 2006, and involved the NOAA National Weather Service (NWS) and several NOAA/OAR labs including the NOAA Earth Systems Research Laboratory (ESRL)/Physical Science Division (formerly the Environmental Technology Laboratory), the NOAA ESRL/Global Systems Division (formerly Forecast Systems Laboratory), and NSSL.
NSSL provided one of its SMART-Radars to supplement the coverage of the X-Band polarimetric radar, provided by ESRL/ PSD. Their goal was to see how the quantitative precipitation estimation (QPE) coverage provided by the national WSR-88D network could improve. The SMART-R site was in the small town of Foresthill, CA, at an elevation near 3000 feet. Based on a 48-hour forecast of rain over the basin, a two-person team deployed from NSSL to operate the radar during the storm. At the conclusion of the rain event the team returned to NSSL to await the next storm.
The ESRL/PSD transportable X-Band polarimetric radar was placed in Auburn, CA, northeast of Sacramento and about 27 km from the SMART-R. These sites were carefully chosen to provide excellent low-level coverage of the basin as well as to allow for some dual-Doppler analyses for selected cases. The data from both radars will eventually be input to NSSL's national radar mosaic system (Q2) in order to compute QPE over the basin. Detailed intercomparison with rain gages in the basin will provide a metric for evaluating improvements to QPE.
By December
2005, the American River Basin had already received more than 42 inches of
precipitation, three times the climatological average for the month. These
early-season storms caused flooding on nearby watersheds including the Russian,
Napa, and Sacramento Rivers in California. Interstate 80 between Reno and Sacramento
was closed for a time due to debris flow. These examples illustrate why flood
data research is critical. The HMT team will use proof-of-concept results to
enhance NOAA's
current observing and modeling capabilities and improve predictions of location,
timing, and amounts of rainfall.
