Fwd: Soil Erosion
Kurt and group....
I have read US Geological Survey reports that indicate the Delta soils have
(or had) a very high peat content (drained marshes as you noted), similar
to conditions described by someone in an earlier message for another area.
The organics in the soil oxidize and break down rapidly with the constant
tilling, as well as the burn-over, and the soil thus... vaporizes....
Unfortunately for the local farmers, it appears the dikes that protect
these areas from the surrounding waterways were themselves constructed of
the same peaty soil and are very fragile (one report suggested that they do
not have much resistance against heavy water pressure during a flood, but
it is also easy for muskrats and other burrowing animals to dig through and
create leaks). There is a recurring debate about whether the value of the
area's agricultural product is worth the cost of continued repair and
renewal of the dike system. Particularly as the areas if flooded would
have great environmental value as fish and waterfowl habitat and for
recreation, and would serve as flood retention basins as well. A massive
new public investment will be needed to renew the dike system if these
farmlands are to be preserved. I have not heard whether the issue has been
resolved; it is difficult to bring change when there are entrenched
ownership interests and political leverage. As part of a study of the
impacts of a possible rise in the level of the ocean, one of the earlier
USGS reports diagramed the potential flooding zone of the area. Even with
sea level as at present, as I recall the possible flooded area (based on
land elevation) would be surprisingly large, extending up toward Sacramento
and down close to Stockton.
Larry Aull
Marin, across the Golden Gate from San Franciso
////////////////////////////////
>From: K1MIZE@aol.com
>Date: Mon, 27 Sep 1999 04:07:30 EDT
>Subject: Soil Erosion
>To: medit-plants@ucdavis.edu
>X-Mailer: AOL 4.0 for Windows sub 214
>Reply-To: K1MIZE@aol.com
>Sender: owner-medit-plants@ucdavis.edu
>
>In a message dated 9/25/99 3:11:47 AM EST, theryans@xtra.co.nz writes:
>
><< It sounds to me as though farmers in those "islands" are well overdue
> for a change of basic technique in preparing their soil. >>
>
>Moira:
>
>Most of the agricultural islands in the Sacramento/San Joaquin Delta region
>are actually reclaimed freshwater swamplands, protected by high levees. Due
>to wind erosion and subsidence, many of them are now well below sea level
>(Stockton, where I live, is only 12 feet above sea level), and it's rather
>disorienting to be driving along a levee road with a river on one side
>perhaps five feet below the level of the road, and a vast stretch of
>agricultural land on the other side that is clearly 20 feet below the level
>of the river! We have had a number of disastrous levee breaks in recent
>years that have flooded large tracts of land. One interesting proposal I've
>heard recently is the idea of purposely flooding some of the low-lying
>>islands for use as reservoirs. It is still a controversial idea, and it
>remains to be seen if anything will come of it.
>
>Kurt
