Use BASINS to simulate hydrology of past El Niño storm events: ⫠1977/78: Significant ... Use BASINS Climate Assessment Tool (CAT) to forecast similar storm.
NASA Ames Research Center Climate Change Effects and Adaptation Research: Hind- and Forecasting Flood Risk of NASA Ames Research Center using the BASINS Model Katherine Pitts (San Jose State University), Ariana Gonzales (California State Polytechnic University, Pomona) Advisors: Max Loewenstein Ph.D., Laura Iraci Ph.D., Cristina Milesi Ph.D.; Mentor: J. W. Skiles Ph.D. Background
Methodology
NASA Ames Research Center (ARC), located at the southern end of San Francisco Bay (see Figure 1), is at increased risk of flooding under future climate change scenarios.
Used BASINS, which is coupled with the HSPF (Hydrological Simulation Program – Fortran) model, and a Geographic Information Systems (GIS) interface, to model hydrology of NASA Ames Collected historical meteorological data from NCDC (National Climate Data Center), CIMIS (California Irrigation Management Information System), NSRDB (National Solar Radiation Database)
Sea level rise, accompanied with tidal action, storm surges, and local erosion, may cause inundation if levee heights are not increased (see Figure 2).
Figure 1: (above) Study Area- NASA Ames located in South San Francisco Bay
An example of this is the 1997/98 El Niño season when many buildings, underground vaults, and basements were flooded, and levees were damaged. During this 1997/98 flooding event, NASA Ames and Moffett field experienced some of these flooding damages (see Figures 3 and 4).
July 13 and 16, 2010: 14 locations around NASA Ames Research Center To validate National Geodetic Survey (NGS) Benchmarks and NASA Arc Medallions, we used two Garmin GPS units.
Collected high resolution GIS layers from the United States Geological Survey (USGS), Santa Clara Valley Water District, the Pacific Institute, and NASA staff
The units and a Silva Compass clinometer were also used to verify the heights of the levees surrounding the SWRP.
Combined GIS layers to define study area (see Figure 5) and determined significant hydrologic features within the study area (see Figure 6)
Also, possible changes in storm frequency and intensity, as well as land use changes, could cause inland flooding by fresh water.
Figure 2: (above) Potential inundation at NASA Ames if levees fail.
Field Work
Figure 12: Points measured around SWRP using GPS units and clinometer
Used GPS to verify elevation heights at 14 points along the Storm Water Retention Pond (SWRP) (see Figure 12)
Figure 6: (left) Important hydrological features at NASA Ames Research Center. NASA Ames is divided into eastern and western drainage systems.
Formatted meteorological data using WDMUtil to data in correct format for HSPF model to run Used BASINS CAT to simulate future storm events
Results
(Above, left) Garmin GPS units and NGS Benchmark C887; (Above, right) Team calculating levee height with clinometer Figure 5: (above) Local NASA Ames watershed as defined for use in the BASINS model; water features shown in blue are the main sources for watershed’s drainage to the San Francisco Bay.
(Right) Emergency pump from SWRP to Stevens Creek; (Far right) Settling Basin located at 2.13 meters above mean sea level; (Bottom Right) The team discussing the possible inundation of the levees
Table 1: Summary of observed precipitation and modeled streamflow for hindcasted years.
• Western drainage area (see Figure 6) pump capacity: 10 cfs • Eastern drainage area capacity: 49 cfs
Hindcast 1997/98
Rain Season Total Total Rain Max hourly (Nov - April) Precipitation (in) Days precipitation (in) 1977/78 1992/93 1997/98
24.64 19.37 24.51
71 68 91
0.338 0.36 0.71
Mean Daily Flow (cfs)
Max Daily Flow (cfs)
8.6133 8.7864 13.021
88.434 84.816 253.63
Figure 13: (Left) Graphed comparison of levee height measurements with given values from DEM and LiDAR. We found that the clinometer measurements were very close to the DEM and LiDAR measurements and that the GPS units were subject to poor satellite accuracy in altitude measurements.
Figure 8: (Left) Graph of total seasonal precipitation in inches vs. total number of seasonal rain days. 1977/78, 1992/93, and 1997/98 are El Niño storm events and are highlighted in red. Figure 3: (left) NASA Ames Golf Course during 1997/98 flooding event
The season in the graph is defined as November through April.
Figure 4: (right) View of flooded runway after 1997/98 flooding event
El Niño Characterized by warmer than normal sea surface temperatures in the equatorial eastern Pacific, El Niño brings above average rainfall to the study area and coastal California.
Figure 7: (above, left) Observed hourly precipitation (in); (above, right) modeled daily mean streamflow (cfs) for 1997/98
Discussion and Conclusions Our model results show that as temperature increases, mean daily flow decreases. Also as change in precipitation increases, mean daily flow also increases. Increasing storm intensity increases mean daily flow, but not as much as it would from increasing all precipitation as a whole. However, this does not mean that more intense storms are less of a threat than overall increased precipitation. If an increased storm event has a volume of precipitation such that the SWRP is filled and starts to overflow, but the pumps cannot pump out water as fast as water is flowing in from the storm, then inland flooding can occur. The model results also show that increasing urban land will increase the flow, but only slightly. Also, changing urban lands to wetlands decreases the flow, but this is probably due to water having less land to be run off of.
1997/98 had 24.51 inches of rain and 91 rain days, making it one of the rainiest El Niño years on record.
Forecast 1997/98
This increased rainfall can lead to increased risk of flooding. The top right graph depicts the mean sea surface temperatures for a normal winter.
Future Work Use the TOPS (Terrestrial Observation and Prediction System) model as well as BASINS
The graph on the bottom right depicts the monthly mean sea surface temperature and its anomalies for the 1997/98 El Niño.
RMS= 0.342
Project Goals RMS= 1.949
Use BASINS to simulate hydrology of past El Niño storm events: 1977/78: Significant precipitation, but no flooding at NASA ARC 1992/93: Significant precipitation, but no flooding at NASA ARC 1997/98: Significant precipitation, with flooding at NASA ARC Determine thresholds for which flooding at NASA Ames could occur Use BASINS Climate Assessment Tool (CAT) to forecast similar storm events under projected climate scenarios
Figure 9: Modeled daily mean flow (cfs) when temperatures are increased from 0 to 10°F and precipitation is changed from 85% to 115% of normal for 1997/98.
Figure 10: Modeled daily mean flow (cfs) when temperatures are increased from 0 to 10°F and storm intensities are increased by taking the top 10% of rain events over 0.1 inches and amplifying up to a 10% increase in precipitation volume.
Figure 11: . (Top, left) Modeled daily mean flow when land cover is changed to simulate a sea level rise of 18” by taking 307.5 acres from urban land and turning it into wetlands, and (bottom, left) difference of changed daily mean flow from original modeled flow. (Top, right) Modeled daily mean flow when land cover is changed by taking 20% from agriculture and range land and turning it into urban land, and (bottom, right) difference of changed daily mean flow from original modeled flow
Split up watershed in BASINS to calculate for East and West Drainage Systems separately Incorporate the pipes and drainage system of NASA ARC into BASINS for more accurate flow results Team up with Environmental Management Division, who are working with the Army Corps of Engineers on a feasibility study to increase levees Share results with NASA ARC master planners, who can then adapt new procedures for future developments with awareness of anticipated climate change effects
