historical perspectives on flooding in southern californiaaftf.csusb.edu/documents/history of...

23
Historical Perspectives on Historical Perspectives on flooding in Southern California flooding in Southern California Presentation by: Dr. Kent Schofield Suzie Earp, WRI Historian/Archivist [email protected] (909) 537-7683 Technical Consultants to the Alluvial Fan Task Force Alluvial Fan Task Force Alluvial Fan Task Force Plenary Meeting 1 Plenary Meeting 1

Upload: lethien

Post on 20-May-2018

219 views

Category:

Documents


0 download

TRANSCRIPT

Historical Perspectives on Historical Perspectives on flooding in Southern Californiaflooding in Southern California

Presentation by: Dr. Kent SchofieldSuzie Earp, WRI Historian/[email protected](909) 537-7683Technical Consultants to the Alluvial Fan Task Force

Alluvial Fan Task ForceAlluvial Fan Task ForcePlenary Meeting 1Plenary Meeting 1

MajorMajor PointsPointsHistorical information about flooding is Historical information about flooding is limited with records dating back to limited with records dating back to only the late 1700only the late 1700’’ssHigh total rainfall does not always High total rainfall does not always equal flooding.equal flooding.Periodic flooding is normal.Periodic flooding is normal.Fires make floods worse.Fires make floods worse.Small isolated events floods can cause Small isolated events floods can cause major damage. major damage.

Total yearly Total yearly rainfall does not rainfall does not

always equal always equal major floodingmajor flooding

* Indicates major flood year

Periodic Flooding is normalPeriodic Flooding is normal Southern California Great FloodsSouthern California Great Floods

182518251862186218851885191619161938193819691969198019801998199820052005

Southern California Major FloodsSouthern California Major Floods

1938 Flood, Upland

1938 Flood, Colton

1969, Mojave River

1980, San Bernardino

1980, Ventura

Clearlake, 2005

Fires in watersheds can create Fires in watersheds can create flooding conditionsflooding conditions

Wildfires, 2003, San Bernardino and San Gabriel Mountains

Small isolated events can cause big Small isolated events can cause big problemsproblems

1934, La Canada

Van Nuys, 1952

1978, La Crescenta

Lake Elsinore, 1995

1904, San Bernardino

Notice alluvial fans and natural water ways in the unpopulated valley

2007, San Bernardino

Notice same alluvial fans with much higher population, and burned watershed

SummarySummaryHistorical records indicate that large amounts of rain Historical records indicate that large amounts of rain in a given year do not necessary trigger flooding in a given year do not necessary trigger flooding Historical records suggest that Southern California has Historical records suggest that Southern California has a history of periodic flooding on alluvial fans and a history of periodic flooding on alluvial fans and downstream alluvial floodplains downstream alluvial floodplains Historical records reveal that highHistorical records reveal that high--velocity, debrisvelocity, debris--laden flows on alluvial fans are often triggered by a laden flows on alluvial fans are often triggered by a series of storms following wildfires at higher elevationsseries of storms following wildfires at higher elevationsHistorical records show that serious flooding can also Historical records show that serious flooding can also be triggered by small isolated rain eventsbe triggered by small isolated rain eventsFlooding on fans can cause major damage to Flooding on fans can cause major damage to structures not only on fans but also on downstream structures not only on fans but also on downstream alluvial floodplains.alluvial floodplains.

Recommended reading