FLOOD06420

• County: Costilla
• Stream Name: Rio Grande, Trinchera, Culebra, Costilla Creeks
• Basin: Rio Grande
• Title: Floodplain Information Report
• Date: 3/1/1989
• Prepared For: Costilla County
• Prepared By: CWCB
• Contract/PO #: &&
• Floodplain - Doc Type: Floodplain Report/Masterplan

I I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
II

2.2 Human Settlement

Within Costilla County there are two incorporated
municipalities, the Towns of San Luis and Blanca, as well as
numerous unincorporated settlements. San Luis is the oldest
town in Colorado. having been incorporated in 1651. The whole
area was settled as part of the northward expansion by Spanish
settlers from the Santa Fe/Taos area of what is now northern
New Mexico. They were the first white settlers in the area.
Much evidence of the area's Spanish heritage still remains.

According to the 1960 U.S. Census. the total population of
Costilla County was 3,071. In May, 1966 the Colorado
Department of Local Affairs estimated the county's 1967
population at 3,403. The 1960 Census population for the Town
of Blanca was 252. and for the Town of San Luis it was 642.
State estimates for 1967 population for the two towns were 269
and 954, respectively.

2.3 StudY Reaches

In addition to examlnlng the Rio Grande through Costilla
County, this report examines all three major streams that are
tributary to the Rio Grande (Trinchera Creek, Culebra Creek,
and Costilla Creek), and their subtributaries, from the Sangre
de Cristo Mountains downstream to their confluences with the
Rio Grande (or to the state line in the case of Costilla
Creek). Subtributaries were studied where existing or
projected population concentrations or development activity
warranted delineation. While this study was being prepared,
one area of particular interest was the site of the proposed
gold mining and milling project by Battle Mountain Corporation,
about 3 miles east of San Luis in the Rito Seco basin.
Specific stream reaches, with approximate lengths. are listed
in Table 1.

2.4 Rio Grande Basin

The Rio Grande has its headwaters in the San Juan Mountains
of Hinsdale, Mineral, and San Juan Counties. Elevations in the
western headwaters range as high as 13,895 feet. (The highest
elevation in the entire Rio Grande basin is actually in
Costilla County, at 14.345 feet.) The river then flows
southeasterly into Rio Grande County and then Alamosa County,
where it turns to the south. It enters Costilla County at an
elevation of about 7,520 feet. forming the boundary between
Costilla and Conejos Counties. It leaves Colorado at an
elevation of about 7,475 feet, continuing through Albuquerque

-7-