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Continuing the Scourges of Mankind Fires Pests Droughts Today----Floods Southwest Flooding

Continuing the Scourges of Mankind Fires Pests Droughts Today----Floods Southwest Flooding --in the desert??? Rain-streamflow cycle Hydrographs Recurrence Interval Three Examples from Tucson “washes” as representative of Southwest. Why Care About Floods?. Fate of Rainfall.

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Continuing the Scourges of Mankind Fires Pests Droughts Today----Floods Southwest Flooding

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  1. Continuing the Scourges of Mankind Fires Pests Droughts Today----Floods Southwest Flooding --in the desert??? • Rain-streamflow cycle • Hydrographs • Recurrence Interval • Three Examples from Tucson “washes” as representative of Southwest

  2. Why Care About Floods?

  3. Fate of Rainfall

  4. 1993 Mississippi Flood

  5. Southwest (Arid) Washes • - • Rather, tend …………. …………………………. • …………………………………… • ------------------------------

  6. 1983 Flood • ------------ • -------------

  7. Measuring Streamflow • - • - • Typical units: --- = - - -

  8. Hydrographs • - • -

  9. SW Streams tend to be flashy: Why? 1: In arid environments: -

  10. SW Streams tend to be flashy: Why? 2: Watershed is small: --

  11. SW Streams tend to be flashy: Why? 3: Steep watersheds:

  12. SW Streams tend to be flashy: Why? 4: Watershed is urbanized:

  13. Flood of 1983 • “It seemed like a flood of biblical proportions” • The numbers tell the story: • -------------------- • --------------------- • --------------------- • -------------------- • --------------------- • ---------------------

  14. Flood of 1983 • Summer of 1983--, • -. • -- • ----

  15. 1993 1983

  16. 1983 Flood Looking S from St Mary’s Bridge. L Oct 2, 1983; R pre-flood

  17. Dodge at Rillito Ina at Stana Cruz

  18. 1983 Flood • North of Tucson • After Rillito joins it, Santa Cruz is not entrenched

  19. 1983 Flood • What happens to structures?

  20. How Much in 1983 Flood?

  21. 1983 flood: 884,900 af • How many years does that “water” Tucson? = ~10 Tucson years

  22. After 1983: • "The rivers themselves moved.” • The real problem wasn't flooding, but erosion. • “If we're going to have flooding rivers, we have got to have something to protect the banks.“ • In the last 20 years at a cost of $112 million • Pima County 78 miles of soil cement bank protection, including 28 miles along the Santa Cruz River • 24 miles on the Rillito • 2 miles on Pantano Wash. • 10 miles of levees, • Purchased 12,000 acres of flood control property and are looking at environmental restoration projects on the Santa Cruz and Rillito.

  23. Bank Reinforcement

  24. Soil Cementing the Rivers • - • - • - • But: • - • -? Doug Shakel, geology professor at Pima Community College calls the county's soil cement project a "channelization effort" and labels what the county has implemented as a "flood guarantee program" that will prevent erosion but aggravate flooding.” (Devine 2003, Tucson Weekly)

  25. Flood of 1993 Rated #2 Weather event of 20th century by Tucson Weather Service January 1993 – ---- • several ----------------------- produced the wettest January on record • ----- • -------” rain fell across the metro between the 5th and 19th.  • Runoff from --------- from the Santa Catalina Mountains added to the flood.  • $60-100 million in damages

  26. 1993 1983

  27. Sabino Canyon is 'forever changed' Record flood that swept through July 31 left the treasured site 'a different place‘Doug Kreutz, Arizona Daily Star Tucson, Arizona | Published: 08.12.2006

  28. Rainfall & runoff in Sabino

  29. July 31/Aug1, 2006 Rainfall totals: Upper Sabino– 8-10” Molino Basin– 5-6” Lower Sabio—2” Sabion Stream Gauge peak: 15,000 cfs http://www.sabinocanyon.arizona.edu/ Rainfall duration less than 5 hours http://www.fs.fed.us/r3/coronado/forest/districts/scrd/2006sabinoflood.shtml http://www.tucsonweekly.com/gbase/Currents/Content?oid=oid%3A97514 http://wwwpaztcn.wr.usgs.gov/Santa_Catalina_Debris_Flows.pdf

  30. Sabino 2006– Damage by?

  31. Sabino 2006 Damage by?

  32. Sabino Canyon 2006 $1 million damage Long-term stream rehab? What about houses? No deaths in this one, but 2 dead 2007, More than 20 in last 20 years

  33. Not All Floods Alike Storm Duration Antecedent Conditions Total discharge Cost Storm Type Season 1983 1993 Sabino Total volume: 1983= 884,900 acre feet

  34. High-magnitude events: ____ • Low-magnitude events: __________ • Recurrence interval: ------------------------------------- • 10-year flood: discharge that has a ______________

  35. Recent Changes • Mean about the same • Variance increasing somewhat • Skew off the charts!

  36. High skew: an extreme event

  37. Determine flood plain of 500-yr flood • Don’t build there

  38. Flood Management • Floods happen, frequently lately • Soil cementing is a debatable strategy, but we’re doing it • Have ample setbacks, at least 500 feet, to avoid flood damage.

  39. How to Know About Paleofloods?

  40. Consider Intro. to Dendro (geos 464/564

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