FLOOD11631 ‎(2)‎

• County: Costilla
• Community: Costilla County
• Stream Name: Rio Grande, Trinchera Creek, Culebra Creek, Costi
• Basin: Rio Grande
• Title: Floodplain Information Report - Costilla County
• Date: 3/1/1989
• Prepared For: Costilla County, CWCB
• Floodplain - Doc Type: Floodplain Report/Masterplan

and on to Texas. From the vicinity of E1 Paso it forms thp
border between Texas and Mexico. The flow that remains a~ter
irrigation diversions and reservoir storage enters the Gul£ of
Mexico near Brownsville, Texas.
The Rio Grande is large enough that it is well defined
throughout the county. At the north end of the county, as it
flows south from Alamosa County, the river is broader and
flatter with a very wide floodplain, on the order of two or
three miles wide. Then in a stream di.stance of about two or
three miles the floodplain narrows substantially, to a width of
about 500 feet. Further south, the valley turns into a canyon
that is about 80 feet deep as the river enters N~w Mexico. On
the Rio Grande there are a few buildings in the morthern part
of the county. Otherwise, to the south, very widely spaced
bridges are the only obstruction.
2.5 Trinchera Creek Basin
Trinchera Creek originates in the Sangre de Cristo
Mountains of northern Costilla County. Elevations are as h.iqh
as 14,345 feet. It flows generally to the west and southwest.
At its confluence with the Rio Grande the elevation is about
7,500 f~et.
In the eastern part of the Trinchera Creek basin stream.s
are narrow and steep. Development in the floodplain has
consisted primarily of roads and bridges. ln Fort Garlan@ and
a few miles to the west several tributaries gradually joim
Trinchera Creek to fotm a single major drainage. As Trinchera
Creek and its tributaries emerge from the foothills of the
Sangre de Cristo Mountains onto the alluvial plaan of the
eastern San Luis Valley, the individual stream valleys become
broader and flatter.
Urbanization, mostly in and around Fort Garland, and
agricultural uses have led to streets, roads. houses,
commercial facilities, agricultural buildings and facilities,
and irrigation structures in and adjacent to Trinchera Creek
and its tributaries. This is the area where there is the most
extensive encraachment into the floodplain of Tri.nchera Creek
and its tributaries.
F'inally, in the western part of the Trincher~ Creek basin,
the single creek flow through agricultural areas or currently
undeveloped areas. The main channel and side channels are
poorly defined, and sometimes human activity has obliterated
them. Aside from highways, roads, bridges, and culverts, there
are few obstructions.
-12-