Summary of Alternatives Comparison

The two final CSRM alternatives were evaluated for performance against the criteria established by policy and the original study objectives

Federal Principles & Guidelines established four criteria for evaluation of water resources projects. These are completeness, effectiveness, efficiency, and acceptability. These criteria and their definitions are listed below. Alternatives

considered in the study were evaluated to confirm that they meet minimum subjective standards of these criteria to qualify for further consideration and comparison with other plans.

Completeness

Completeness is defined as the “extent to which an alternative provides and accounts for all features, investments, and/or other actions necessary to realize the planned effects, including any necessary actions by others”. It does not necessarily mean that alternative actions need to be large in scope or scale. Does the plan include all the necessary parts and actions to produce the desired results?

Effectiveness

Effectiveness is defined as the “extent to which an alternative alleviates the specified problems and achieves the specified opportunities.” Does the plan meet the objectives?

How does the plan address constraints?

Efficiency

Efficiency is the extent to which an alternative plan is a cost-effective means of alleviating the specified problems and realizing the specified opportunities. Does the plan minimize costs? Is it cost effective? Does it provide net benefits?

Acceptability

Acceptability is defined as “the viability and appropriateness of an alternative from the perspective of the Nation’s general public and consistency with existing Federal laws, authorities, and public policies. It does not include local or regional preferences for particular solutions or political expediency.” Is the plan acceptable and compatible with laws and policies?

Table 31 - Alternative A and D2 Evaluation Against Applicable Criteria

Criteria /Metric Coastal Barrier Plan Bay Rim Plan

P&G

This plan includes layered

features that address risk over a broad region and perform as a system.

This plan includes features that features that address risk in a more concentrated landward alignment adjacent to development and

This plan addresses coastal risk in the broadest region, enclosing the more coastal landforms within the system.

This plan addresses coastal risk in a smaller sub region of the study area.

Efficiency Is the plan cost-effective?

Both plans achieve net benefits Both plans achieve net benefits

Acceptability Is the plan acceptable and compatible with laws and policies?

This plan includes broad

communities rather than concede to SLC losses over time in

coastal barrier communities.

Primary feature, the storm surge barrier, can meet mitigation requirements for potential

impacts, but generates concern among the public and agencies.

This plan concedes that coastal barrier communities may be sacrificed to SLC over time. Levee or wall along bay rim generates concern among the public and agencies about community disruption and impacts, and creates some unacceptable risk without redundancy in the case of design exceedance.

NED

RISK REDUCTION

Criteria /Metric Coastal Barrier Plan Bay Rim Plan

Redundancy • System provides redundant

• features, with coastal alignment and maintain the bay as a

“release valve” to contain water if design is exceeded

• Redundancy increases reliability over time

This system places features within close proximity to assets and people, providing less redundancy.

Robustness

RED Economic activity • Sustains coastal region for

tourism, fisheries and related industries

• Sustains support infrastructure-childcare, shopping, services in areas that house regional workforce

• Preserves medical campus

Concedes coastal barrier region over time to SLC damages to natural and business resources

EQ

Air Temporary impacts from

emissions during construction

Temporary impacts from emissions during

construction

Noise Temporary impacts from pile

driving, construction equipment to species and humans for a longer duration than Bay Rim

Temporary impacts from pile driving, construction

equipment to species and humans

Water Quality Small changes to tidal amplitude from the storm surge barrier will impact salinity in Galveston Bay

Avoids salinity impacts of gate closure, does not avoid impacts of storm surge over land and into bay

Species or Habitat More mitigation for in-water construction from Storm Surge Gate construction and operation

Less potential impact to species from in-water construction

Criteria /Metric Coastal Barrier Plan Bay Rim Plan

Cultural and Historic Resources

• Preserves historical architecture on Galveston Island

• Sustains culturally significant recreation

Concedes coastal barrier lands to eventual SLC risks, risking loss of cultural

resources Community Cohesion Maintains viability for broader

region of communities facing storm risk or SLC

• Concedes to SLC and storm damage for outer

communities which will face disinvestment over time

• May alter community identity and cohesion with bay area structures creating

subregions that are “in” or

“out” of the system.

Recreation • Maintains bay and Gulf as separate habitats over time

• Renourishes and maintains beach resources along coastal barrier system

System may sacrifice exterior regions under RSLC.

Life Safety

PAR losses Smaller population exposed to flood risk and displaced following storms

Larger population exposed to flood risk and displaced following storm events and eventually retreated from barrier island system Life Safety • System reduces surge risks

while not exacerbating risks during high-precipitation events

• Larger community afforded risk reduction by placing system at the broadest extent

System places features adjacent to communities which may not reduce all risks when coastal storms coincide with high-

precipitation events

Several broad performance comparisons can be made:

Higher net benefits: Under all RSLR Scenarios and cost ranges, Alternative A still obtains the highest net benefits.

Lower residual risk: Alternative A is set farther away from the developed areas of the study area and therefore has a lower residual risk in the event of extreme overtopping

events.

Greater flexibility and greater focus on critical infrastructure: Alternative A takes a systems approach when reviewing the regions larger system context. Similar to the Multiple Lines of Defense approach it builds upon existing projects and other proposed recommendation yet to be built (Figure 47).

Figure 47 - Linked ER and CSRM in the Upper Coast with existing and large scale projects