FLOOD07275 - Laserfiche WebLink

Home Browse Search

2.6 Cule~ra Creek aasin f'rom Garcia downstream, the stream becomes gradually drier due to i7rigation diversions. Settlement is sparse, and obstructIons are limited. This is the least developed of the three major tributaries valleys. The creek joins the Rio Grande in northern New Mexico shortly after leaving Colorado. at an el"v;jtion of about 7.4'15. The Culebra Creek headwaters are in the Sanqre de Cristo Mountains in the middle Of Costilla County as one goes from north to south. The hiqhest elevation is 14,04". The creek flows generJlly to the west, through San Luis and on to the Rio Grande. The elevation at the confluence with the Rio Grande is about 7.480 feet. 2.8 Summary of DrainaQe Areas The Culebra Creek basin is similar to the Trincherd Creek basin in several respects. Narrow and steep mountain streams originate in the Sangre de Cristo Mountains to the east. Occasional roads and bridges comprise the major floodplain development. Where these streams enter the alluvial plain near the western foothills. many small settlements. mostly dating back to the early time of SpaniSh settlement. cluster around the streams. sometimes in the floodplain. In and around San Luis several tributaries gradually join Culebra Creek. Except for a narrow constriction immediately downstream of San Luis. formed by local qeologic features. this transition zone is where the valleys become broader and flatter. Being the most siqnificant urbanized area in Costilla County, it is also where there is the most extensive floodplain encroachment in the county. Table 2 lists total drainage areas. including areas above any reservoirs, at various points on several of the streams in Costilla County. The areas above reservoirs have been specifically called out in footnotes to Table 2. Figure 3 shows the major tributary basins in Costilla County. It does not show the drainage area for the Rio Grande outside of Costilla County. Below San Luis, Culebra Creek flows through agricultural areas unti lit crosses Highway 142 dt San Acacio. There dre some roads. bridges, culverts, and agricultural structures in the floodplain. Although agricultural activity has partially obliterated the channel and substantially reduced flows. the floodplain is still apparent. Below San Acacio the valley is sparsely inhabited. The channel is almost completely obliterated. The Highway 142 crossing acts partly as a dam. contributing to the appearance of a desert valley all the way to the Rio Grande. There are almost no obstructions after San ACdcio. 2.7 Costilla Creek Basin Part of the headwaters of Costilla Creek are in southern CoLorado. and part are in northsrll New Mexico. Headwater elevations are as high as 13.676 feet. The tdbutad.." basically flow south toward Costilla Reservoir. Below that reservoir there is one major mountain stream valley with small tributary valleys. In a big arc, the stream turns toward the northwest. It emerges from the foothills near Costilla. New M'Hc:lCO and Garci.a, Coloril<l.o at an elevation of ahout 7,7<;0 feet, There is the same pattern of urbanization and agricultural uses. with the accompilnying ellcroacll!a..nts. as ~n the other major stredms in the county. \ I I I 1 I I -13- _14_ , ,