village of patch, nm, feasibility study village of patch case study seattle environmen tal planning...

VILLAGE OF PATCH, NM, FEASIBILITY STUDY

Village of Patch

Case Study

Seattle Environmental Planning

ClassJune, 2009

US Army Corps of EngineersAlbuquerque District

1HO #s 2 & 2aCh 1 Module 2

Patch,

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Study Authority

Authority

“ The Secretary of the Army is hereby authorized directed to cause surveys for flood control and allied purposes, including channel and major drainage improvements to be made under the direction of the Chief of Engineers, in drainage areas of the United States and its territorial possessions, which include the localities specifically named in this section”…Patch, NM

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The study is located in Patch, NM. The purpose of the feasibility study is to determine Federal interest and optimize a flood damage reduction/ecosystem restoration plan for the city of Patch. Structures and roadways have been impacted by flows from the surrounding mountains, significantly flooding the community twice in the last 15 years. Flooding originates from two sources-Spring Canyon and Placitas Arroyo. Initial investigations determined that there is a likely Federal interest in constructing flood control projects in the area, the most probable alternatives being a small dam at Spring Canyon. Repeated flooding limits fishery populations.

Regional Setting

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Drainage Area



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Patch, New Mexico


Floodplains



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Patch


Flood History:

• The Village of Patch experienced significant Flood events in 1988, 2002 and 2006.

• FEMA and Corps’ analyses determined Spring Canyon is a flood threat to the Village of Hatch.

•The entire Village of Patch lies within a 100-year Floodplain



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Flood Potential:

• Spring Canyon channel capacity is 1,300 CFX (100-year flow is-1% chance event-estimated at 2,600 CFS)

• Estimated average annualized flood damages of $10.1 million from Spring Canyon



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Existing and Likely Future Without-Project Conditions

• Physical Setting

17.2 square mile watershed draining from the south flowing north into the Rio Grande

An upstream detention structure controls 15.4 square miles of the basin

Elevation in the drainage drops from 6,000 ft to 4,030 ft

Flooding events in 1988, 1992 and 2006 left three feet of water in the street



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• Physical Setting (continued)

Once flows enter the village there is no clear drainage pathway into the Rio Grande; floodwaters remain in place until evaporated.

The Village storm drainage system is sized for a 5-year event. Sediment renders the system largely inoperable during larger events



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•Social and Economic Conditions

2004 population of 10,661

1284 single residential structures within the 1% event floodplain

187 commercial structures within the 1% event floodplain

127 public structures within the 1% event floodplain

10 apartment within the 1% event floodplain



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• Social and Economic Conditions (continued)

Median income for a household: $21,200

Many seasonal inhabitants

“Chile capitol of the world”

172 homes with flood insurance



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More Information• Non-damaging Channel Capacity

• 10,300 cubic feet per second (cfs)

• 100-year flow

20,600 cfs

• Flood Damages

Estimated average annualized flood damages $10.1 Mil

Federal Disaster Area in 2006



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More Information• Biological Communities

Southern cottonwood-willow riparian forest occurs in Spring Creek Watershed. Salt Cedar dominates Placitas Arroyo. The forest provides canopy cover needed for sensitive nesting birds.



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More Information• Other Environmental Issues

10 lower-income apartment complex occurs in close proximity to the channel confluence of Spring Creek & Placitas Arroyo.

New Mexico's Air Quality reviews imply that the high ozone levels in the northwest and southern parts of the state are part of a regional problem.



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VILLAGE OF PATCH, NM, FEASIBILITY STUDYCULTURAL RESOURCES

– During a site visit, black-on-white pottery fragments, burnt plant remains and long bones were observed eroding out of the river banks some 10 feet below the current floodplain.

– Another 2 feet below, a hard clay band was observed in the river bank profile in Placitas Arroyo.

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Plans Studied in Detail• No Action Plan• Non-Structural (Flood

Warning)• Channel Improvements• Flood Detention

o Upper Basin Structureo Lower Basin Structure



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Project Alternatives• No Action Plan• Non-Structural (flood warning)• Non-Structural (raising/flood walls)• Non-Structural (buyouts/relocation)• Channel Improvements• Flood Detention

o Upper Basin Structureo Lower Basin Structure



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Impact Comparison of Alternative Plans

Resource Area No Action Non Structural

NED Dam Channel Improvements

Land Use Farmland No Change to the Existing Condition

Some Change to the Existing Condition

Minimal impact to agricultural land

use due to location of structure.

High; Project located along agricultural

lands.

Transportation Existing Condition Minor Impact Temporary during Construction

High; numerous road crossings and reroutes.

Noise Existing Condition Existing Condition Temporary Temporary

Air Quality Existing Condition Existing Condition Temporary Temporary

Water Quality Existing Condition Improved Temporary Temporary

Settling Basin Existing Condition Existing Condition Hydrologic change Hydrologic Change

Vegetation/Wildlife Existing Condition Improved Minor Impact High

Cultural Resources Existing Condition Existing Condition Minor Impact Minor Impact

Visual Resources Existing Condition High Minor Impact High 19

Recommended PlanLocally Preferred Plan

100-yr (1% Event) Dam in Lower Basin

Features of the Locally Preferred Plan include• Earth fill Dam approximately 14,000 ft. in length• Concrete spillway 200 ft. in length• Height of approximately 20 ft.• Outlet Conduit• 300 Acre-Foot Sediment pool• 151 Acre-Foot Water Storage pool



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Patch

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village of patch, nm, feasibility study village of patch case study seattle environmen tal planning...

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