County Scientist Reveals Rain Trends: "Not to Scare You, But...."

by Janine Gates
www.janineslittlehollywood.blogspot.com

About 100 community members packed a room at The Olympia Center Monday night to hear about the very latest local hydrological cycles of Thurston County and its climate impacts on the region. The event was sponsored by Olympia Climate Action and the League of Women Voters, with city and county representatives giving presentations.

The discussion had direct relevance to the city of Olympia's update of its Shoreline Management plan, due to the state in September. City staff held a series of public meetings on the shoreline update in February and March.

The city's Planning Commission formed a subcommittee and has been meeting regularly to discuss issues pertinent to the update.

Cari Hornbein, senior city planner, gave the audience an update of the city's shoreline master plan's progress. The city will make a presentation to the city's Planning Commission on Monday, April 19, on "early plan language for their review and contemplation," said Hornbein.

Future planning commission meetings on May 3 and May 17th will also review and discuss sections of the draft Shoreline Master Program. Hornbein said a draft will be available for the public to review in about a month to five weeks. Several Planning Commission members were in the audience as well as Olympia City Councilmember Stephen Buxbaum.

Amy Tousley, Planning Commission vice-chair, gave a presentation on the commission's shoreline master plan sub-committee work thus far and encouraged community dialog. Several in the audience questioned the tight timeframe in which the document needs to be completed.

"It has put us in a crunch," Tousley admitted. "If we don't submit the document to Ecology, what are the ramifications? I don't think we can afford to fail....I am feeling quite pressed."

Thurston County's Hydrogeological Cycles

Nadine Romero, hydrogeologist for Thurston County, gave a well-received Powerpoint presentation featuring the very latest data on rainfall patterns and trends facing Thurston County. Prior to the county, she spent four years with the Squaxin Island Tribe to quantify the region's small rivers, something which hasn't been done in Thurston County since 1948 by the United States Geological Survey (USGS).

"At the county, for the last three years, I've worked on 70 projects per year, ranging from two to 280 hours of hydrologic analyses. We are putting together quite a big puzzle," said Romero.

"We have 14 precipitation stations, eight stream gaging stations, 80 groundwater monitoring wells which monitor at 15 minute and one hour intervals, the daily average flows and water table maps, figuring out their pulse."

The statistics don't lie. Romero explained, in simple lay-language to the captive audience, the graphs and charts that showed how sensitive our rivers are to precipitation, and given change, how the rivers behave.

Using National Oceanic and Atmospheric Administration (NOAA) data from 1948 - 2010 gathered at the Olympia Airport weather station, trends show that springs are getting wetter, summers are getting warmer, winters and autumns are getting drier.

Out of 18,900 daily precipitation events during this timeframe, Romero mapped out the Top 20 daily extreme rain events and discovered more extremes (greater than 3.5 inches per day) in the last decade than in the previous five decades, and notes a three year cycle in the last decade.

The region experiences an average yearly rainfall of 4.33 feet. That's 86.7 billion cubic feet in total yearly rainfall volume. We measure 35 billion cubic feet every year. She shared information on Salmon Creek Basin, Scatter Creek Basin and Scott Lake flooding, and seven years of data on McLane Creek at the Delphi Bridge.


Above: Storm damage at McLane Creek Nature Trail in 2006.

Plotting huge daily and monthly storm data, Romero determines trends such as the six heavy precipitation patterns which leads to various types of flooding. In October, for example, when it rains more than three inches per day; consecutive daily totals of one inch or more for five days; consecutive monthly totals of more than 15 inches per month. In November 2006, we experienced a 19.68 inch rainfall.

Climate Change and Our Shorelines

What all this data means with regard to climate change, according to the University of Washington Climate Impacts Group, is that the average temperature will increase 2.2 degrees by 2020, all seasons will be warmer, sea level rise is expected to reach 22 inches by 2050 and 50 inches by 2100.

Locally, Romero says another significant event could happen sometime between November of 20111 and February of 2012. "These are interesting trends. At the county level, we plan for six inch storms. Not to scare you, but at 2020, 2030, what happens? Are we in for more saturation? " said Romero.

Romero was asked about capturing water in cisterns or rain barrels, clarifying that this excessive rainfall is not necessarily going into our groundwater supply at a time during the year when we need it most. She cited an example in the Tanglewilde subdivision where she went out last December and did soil core samples. The ground, just a few inches below the surface, like many lawns in older subdivisions, was bone-dry.

"It is running off as surface water....We need to save it, manage it, plan for the future, and be innovative," Romero urged.

Romero said she is scheduled to give the Thurston county commissioners a field trip to local rivers with an explanation of her most recent findings on May 3. "I will create a field trip guide and we'll put that online so you can see what we've shown them," Romero promised. Romero says this information is all brand new and will be placed online on the county website by August.

Impressed by the wealth of information just presented, audience member Sherri Goulet asked Tousley if this information should be formally incorporated into Olympia's update of the comprehensive plan and shoreline master plan. Tousley agreed that it should be, saying, "showing our homework justifies the shoreline designations - to defend our work."

Goulet pressed Tousley if there is a plan to formally incorporate the information. "I don't have a plan myself, but I've taken copious notes tonight," she responded.

For more information on the city's Shoreline Management plan process and Comprehensive Plan process, go to www.olympiawa.gov/imagine-olympia.com.