TFMA’s 2011

‘No Adverse Impact’ Survey of Texas Communities

May 22, 2012ASFPM - San Antonio

Mike Moya, PE – Halff AssociatesBrian Reis, PE – RPS EspeyBrian Wells, PE – MWM Design Group

Purpose is to determine what Texas communities are doing above the minimum FEMA standards

Developed by members of TFMA & ASCE/EWRI

On-line survey from Aug ‘11 to Feb ‘12

Workshop was held Sept. ‘11 at TFMA’s fall conference

Survey Background

3

Activities that could adversely impact another property or community will be allowed only to the extent that the impacts are mitigated or have been accounted for within an adopted community-based plan

NAI defined by ASFPM

4

Principle developedNAI Toolkit Legal Aspects of NAICoastal NAI funded by

NOAA

www.floods.org/

NAI Tools

Physical increases◦ Peak flow rates ◦ Frequency of bank full conditions◦ Stormwater pollution ◦ Sediment transport (aggradation) ◦ Etc.

Physical reductions◦ Base flow ◦ Infiltration◦ Sediment transport (degradation)◦ Etc.

Adverse impacts can result from…

The NFIP Regulations mandate that participating communities adopt and enforce at least the minimum standards of 44 CFR 60.3

Reference: 44 CFR 59.2(c)

Communities may exceed the minimum standards and are encouraged to do so

Reference: 44 CFR 60.1(d)

The Curse of Minimum Standards

When the NFIP was established in 1968, it was decided that minimum development standards would be required for participation

They were considered sufficient to establish a balance between an acceptable level of flood risk versus difficulty in conducting the local program

Goal: Keep the program as simple as possible so more communities will enroll

The Curse of Minimum Standards

Even with the minimum FEMA standards, flood damages in the United States have continued to increase

“No Adverse Impact floodplain management is where the action of one property owner does not adversely impact the rights of other property owners, as measured by increased flood peaks, flood stage, flood velocity, and erosion and sedimentation.”

The Curse of Minimum Standards

The Curse of Minimum Standards

Case Study: San Marcos, Texas

Located between Austin and San Antonio Population 45,000 Home of Texas State University San Marcos River

◦ Popular recreation area◦ Home to several threatened or endangered

species Texas Blind Salamander Fountain Darter Texas Wild Rice

Will be subject to EPA MS 4 regulations

Houston

FW D

SA

Austin

Amarillo

El Paso

Brownsville

Laredo

Site Location

San M

arcos

25-year and 100-year are to be conveyed / contained within ROW or drainage easements

Peak flow shall not cause increased inundation of any building or roadway for the 2-, 5, 10-, 25-, 50- or 100-year storm frequencies.

Fully developed conditions upstream.

Detention is required for the 2- and 25-year frequency storm events.

Drainage / FloodplainDesign Criteria (1 of 2)

Development within the floodplain shall not increase the base flood elevation by more than 1 foot.

Development within the floodway shall not result in any increase in the base flood.

Floodplain alterations shall not create an erosive water velocity (> 6 fps) on- or off- site.

Drainage / FloodplainDesign Criteria (2 of 2)

San Marcos

Water Quality Design Criteria

Limits on impervious cover◦ Slopes (i.e. <15%, 15% to 25%, > 25%)◦ Special areas: Edwards Aquifer, SM River Corridor◦ Additional restrictions: water quality and buffer

zones

Permanent BMPs ◦ Edwards Aquifer - limits increase in TSS to 20% ◦ SM River Corridor - capture first ½ inch

Water Quality Design Criteria

San Marcos Comprehensive Planning◦ In progress◦ Land use suitability analysis◦ Identification of environmental metrics◦ Develop new sustainability standards: detention,

drainage, erosion, sedimentation control, archeological site protection, etc.

◦ Consideration of Habitat Conservation Plan Goals

Habitat Conservation Plan, December 2011◦ Result of the EA Recovery Implementation Program◦ Identifies species and habitat◦ Identifies biological goals◦ Includes ‘take’ coverage◦ Activities required to minimize impacts

Future considerations

USFWS to issue Incidental Take Permit based on HCP

Permittees◦ San Marcos◦ New Braunfels◦ Texas State University◦ Edwards Aquifer Authority ◦ San Antonio Water System (SAWS)

A collaborative, consensus-based stakeholder process.

Plan to protect the federally-listed species affected by the management of the Edwards Aquifer and other activities.

The goals of the HCP include contributing to the recovery of these species.

Edwards Aquifer Recovery Implementation Program (EARIP)

Restoration of Texas Wild-Rice Expanded program of monitoring water

quality Management of recreational use Management of aquatic vegetation and litter Control non-native and predator animal

species A program to register, permit and evaluate

septic systems Reduce impacts of IC through BMPs/LID Etc.

Habitat Conservation Plan (highlights)

Corridor Development CertificateTrinity River Corridor – NCTCOG

The Corridor Development Certificate Process (CDC) affirms local government authority for local floodplain management and establishes a set of Common Regional Criteria and procedures with the goal of minimizing flood risks along the Trinity River Corridor in north central Texas

Corridor Development CertificateTrinity River Corridor

The Corps Regional Environmental Impact Statement Trinity River and Tributaries – 1988 (TREIS) determined that the cumulative impact of allowing individual development projects in the Trinity River floodplain could be both measurable and significant.

Corridor Development CertificateTrinity River Corridor – NCTCOGCorps of Engineers Record of Decision (1988)

No rise in the 100-year or SPF elevation for the proposed condition will be allowed.

The maximum allowable loss in storage capacity for the 100-year (0%) and SPF (5%)

Alterations in the floodplain may not create or increase an erosive water velocity on or off-site.”

Corridor Development CertificateTrinity River Corridor – NCTCOG

Trinity River Steering Committee, facilitated by the NCTCOG. Statement of Principles for Common

Permit Criteria (January 1988) Resolution for a Joint Trinity River Corridor

Development Certificate Process (December 1988)

Regional Policy Position on the Trinity River Corridor (January 1989).

First edition May 1991

Corridor Development CertificateTrinity River Corridor – NCTCOG

Common Regional Criteria No increase in the 100-year flood water

surface elevation (within 0.04 feet) and no significant increase in the Standard Project Flood water surface elevation

A maximum allowable decrease of valley storage in the 100-year flood and Standard Project Flood discharges of 0.0% and 5.0%, respectively

No creation, or significant increase, in erosive water velocity on-site or off-site

Corridor Development CertificateTrinity River Corridor – NCTCOGBenefits Common Regional Criteria Hydrologic modeling based on year 2050

Upper Trinity River watershed development Hydraulic model incorporating CDC permitted

floodplain development U.S. Army Corps of Engineers technical review Regional review and comment Guarantee of local control of floodplain

development decisions

Questions1. What standards apply to quantify adverse impacts?2. What is considered to be an insignificant impact?3. What mitigation measures are required?4. Which storm events are regulated?5. What physical / chemical properties are regulated?6. What specific challenges have you encountered?

50 participants Communities varied in size

NAI Survey of Texas Communities

What standards apply to quantify adverse impacts?

18.0%

72.0%

60.0%

68.0%

0% 25% 50% 75% 100%

Other

Floodplain Elevations

Peak Flows

NFIP Standards

50 respondents

Yes

Yes

Yes

Velocity and TSS

No Policy

No increase allowed in Zone AE

No rise in floodway

Peak: 0 cfs – 10 cfs or 0% - 2%

Elevation: 0 ft. – 1.0 ft

What is considered to be an insignificant impact?

1 foot rise

no rise

0 cfs

0.00 feet

16.7%

20.8%

58.3%

39.6%

50.0%

16.7%

87.5%

0% 25% 50% 75% 100%

Other

Fee in Lieu

Regional Detention

Valley Storage

DS Channel Improvements

On-Site Retention

On-Site Detention

48 respondents

What mitigation measures are required?

n/a

2.0%

8.0%

4.0%

0.0%

18.0%

40.0%

46.0%

12.0%

36.0%

100.0%

0% 25% 50% 75% 100%

Other

PMF

500-year

250-year

100-year

50-year

25-year

10-year

5-year

2-year

Which storm events are regulated?

50 respondents

n/a

7.7%

43.8%

30.8%

10.3%

12.8%

64.1%

46.2%

0% 25% 50% 75% 100%

Other

Wetlands/Riparian Zones

Sediment Transport

Infiltration / GW recharge

Base Flow

Stream Erosion

Water Quality

What physical / chemical properties are regulated?

39 respondents

TSS

velocity

HCP

n/a

Educating developers, engineers, and politicians Retention / Detention standards Using preliminary data to regulate New FEMA flood maps Conflicting regulations of adjacent

communities/districts Defining “significant” impacts to upstream and

downstream properties Lack of enforcement Consistency in Engineering methodologies Regulating multiple storm frequency events

Specific challenges your community has encountered

Diane Calhoun TFMA Rob Connell FEMA Region VI W. H. Espey AAWRE, President-Elect Nefi Garza City of San Antonio Steve Gonzales ASCE - San Antonio Steve Graham San Antonio River Authority John Hewitt TFMA Assistant Workshop Coordinator Romin Khavari City of Grand Prairie Melinda Luna TX Section EWRI, Chair Sharon Mattox Vinson & Elkins, LLP Sam Riley Medlock ASPFM Mike Moya TFMA Workshop Coordinator (Halff Assoc.) Michael Newman City of Temple Brian Reis TFMA Workshop Coordinator (RPS Espey) Roy Sedwick TFMA Brian Wells TFMA Assistant Workshop Coordinator

Thanks to our contributors

Oct. 17-18, 1998

20-30 inches

31 deaths

$750 million in damages

San Marcos River Corridor

San Marcos, Hays County, Texas

EQ Recharge Zone

San Marcos

24 hoursThrall 39” 1921Alvin 50” 1979Medina 30” 1978

6 hoursNew Braunfels 15” 1972

4 hoursOdem 30” 1984

3 hoursD’Hanis 18” 1935

1 hoursNew Braunfels10” 1972

Texas Meteorology