NDRRA Flood Restoration Guideline for Queensland Local

IPWEAQ Page 1 of 34 Revision No. 1.0

NDRRA Flood Restoration Guidelines for Queensland Local Governments

NDRRA Flood Restoration Guidelinefor Queensland Local Governments

Prepared by:

INSTITUTE OF PUBLIC WORKS ENGINEERING AUSTRALIAQUEENSLAND DIVISION INC



Quality Information

Document NDRRA Flood Restoration Guideline for Queensland LocalGovernments

Ref IPWEAQ - NDRRA

Date 3 September 2012Preparedby Michael Kahler

Reviewedby Suzanna Barnes-Gillard

Revision History

Revision RevisionDate Details

Authorised

Name/Position SignatureA 7-September

2012Issued to Qld Members Suzanna Barnes-

Gillard

DISCLAIMEREvery effort and care has been taken by IPWEAQ to verify that the methods and recommendations contained in theseGuidelines are appropriate for Queensland. Notwithstanding these efforts, no warranty or guarantee, express,implied, or statutory is made as to the accuracy, reliability, suitability or results of the methods or recommendations.The authors shall have no liability or responsibility to the user or any other person or entity with respect to any liability,loss or damage caused or alleged to be caused, directly or indirectly, by the adoption and use of the methods andrecommendations of the Guidelines, anticipatory profits, or consequential damages resulting from the use of theGuidelines. Use of the Guidelines requires professional interpretation and judgement. Appropriate procedures andassessment must be applied to suit the particular circumstances under consideration.



TABLE OF CONTENTS1 Introduction ................................................................................................................................ 4

1.1 Purpose................................................................................................................................ 4

2 Funding Eligibility ...................................................................................................................... 4

2.1 NDRRA Funding Categories ................................................................................................. 4

2.2 Complementary Works (ineligible for NDRRA funding) ...................................................... 5

3 Fitness for Purpose Design..................................................................................................... 6

3.1 General ................................................................................................................................ 6

3.2 Safety................................................................................................................................... 7

3.3 Reuse of Existing Materials and Infrastructure ................................................................... 8

3.4 Pavement Structural Design Life ......................................................................................... 8

3.5 Pavement Drainage ............................................................................................................. 9

4 Drainage Infrastructure .......................................................................................................... 10

4.1 Key Drainage Requirements .............................................................................................. 10

5 Safety in Design...................................................................................................................... 10

6 Road Essential Public Assets - Work Types & Funding Eligibility .................................. 12

6.1 Pavements ......................................................................................................................... 12

6.2 Bridges, Drainage Structures and Embankments.............................................................. 13

6.3 Road Geometry ................................................................................................................. 16

6.4 Roadside Furniture and Delineation ................................................................................. 17

7 Improving Resilience and VfM Outcomes........................................................................... 18

7.1 Introduction....................................................................................................................... 18

7.2 Pavements ......................................................................................................................... 18

7.2.1 ExistingMoisture Conditions ......................................................................................... 18

7.2.2 Design Approach ........................................................................................................... 19

7.2.3 Non-flooded Pavements (Saturation Damage) ............................................................. 19

7.3 Flooded Pavements ........................................................................................................... 20

7.4 Surfacing of Unsealed Roads ............................................................................................. 22

7.5 Drainage Infrastructure ..................................................................................................... 22

7.5.1 Design Approach ........................................................................................................... 22

7.6 Bridge Approaches, Abutments and Piers......................................................................... 23

a) Pavements ........................................................................................................................... 27

b) Bridges, Drainage Structures and Embankments .......................................................... 29

c) Road Geometry................................................................................................................... 33

d) Roadside Furniture and Delineation ................................................................................ 34



Overview1 Introduction1.1 PurposeBased on feedback from IPWEAQ members and senior Queensland Reconstruction

Authority (QldRA) officers, there is a need to provide additional information to assist local

government practitioners in determining “eligible” flood restoration works and “fit for

purpose“ design treatments. As a result, IPWEAQ has prepared this guideline to assist its

members and improve the level of confidence and consistency around flood restoration

submissions. The guideline provides a general approach only and does not attempt to

define specific design treatments. The guidelines apply to road and drainage restoration

works and focus on “eligibility” considerations and determination of a “fit for purpose” design

treatment. Whilst the guidelines have been based on previous flood restoration experience

and engagement with QldRA during their preparation, they are not a QldRA document.

This guideline is to be read in conjunction with the QldRA “Submission Guide V3 for NDRRA

Applicants” (currently under review by QldRA) and focuses on NDRRA Category B funding.

This guideline also provides additional information on the selection of design treatments for

restoration works which are likely to be deemed “fit for purpose” and considered an

appropriate level of response treatment for flood damage.

It is anticipated that the guideline will be updated when the QldRA ceases to exist in

February 2013 and a new “approving authority” is created within one or more of the State

Government departments.

2 Funding Eligibility2.1 NDRRA Funding CategoriesThere are two funding categories under NDRRA for local government flood restoration

works:

x Restoration – This funding is for the restoration of essential public assets, following

an eligible disaster event, to pre-disaster standard/level of service, in accordance

with current engineering standards and requirements and building codes and

guidelines, while maintaining the same asset class and/or immunity level.

x Betterment - In rare cases “betterment” of an asset can be eligible for NDRRA

funding. Relatively few local government assets will meet the eligibility criteria



under the Federal NDRRA guidelines as detailed below. The level of effort to

prepare the business case and approval process (which requires consideration by

State Cabinet, approval and referral to the Federal Secretary for consideration) is

very onerous. The following criteria must be met for proposed “betterment” works

to be eligible for NDRRA funding:

o the asset is an essential public asset; and

o the State Cabinet informs the Federal Secretary of its decision to restore the

asset to a more disaster-resilient standard, and of its reasons for doing so; and

o the Federal Secretary is satisfied with the cost effectiveness of the proposal;

and

o the Federal Secretary is satisfied that the increased disaster-resilience of the

asset will mitigate the impact of future natural disasters.

2.2 Complementary Works (ineligible for NDRRA funding)This work is the component of work which is additional to the work required to reinstate an

essential public asset to its pre-event standard. Typically it involves additional works which

will increase the service standard of an essential public asset to that which existed pre-

event. Examples include constructing a two lane road where the flood damaged section

was single lane, increasing seal widths, pavement widths, extending the extent of works

beyond the flood damaged area, increasing flood immunity through changing vertical

alignment, increasing culvert capacity.

Complementary Works may also apply where the extent of restoration works is increased

beyond the minimum required to reinstate the flood damaged asset to pre-event standard.

A common example is the use of half or full pavement width treatments rather than isolated

failure repair to rectify flood damage. Where half or full width treatments can be undertaken

at a cost equal to or lesser than isolated failure repairs the works will typically be fully

recoverable under NDRRA and provide a superior VfM outcome. Where the costs of this

approach are well above the costs to reinstate the isolated failures resulting from flood

damage the difference in the cost of the two treatments will likely be determined as

complementary works by QldRA.

When undertaking NDRRA works there may be opportunities to combine and coordinate the

works with the ordinary capital works program to provide increased efficiencies and

economies of scale. Cost control and reporting systems need to be established to ensure a

clear demarcation between the scope and cost of NDRRA and non-NDRRA works where

this occurs. Reactive and scheduled maintenance program activities need to be coordinated



and recorded where works occur on assets where planned NDRRA works are proposed. In

some instances, early works can be undertaken to make sections safe and these works

incorporated into the permanent restoration works. Where the time period between the

interim works and final reconstruction works is not excessive and the interim works can be

demonstrated to reduce the cost of the final restoration works the costs of interim works may

be recoverable under NDRRA. A good example of this approach is the undertaking of

isolated failure repair on pavements where the interim failure repairs are incorporated into

the pavement of the permanent restoration works.

Opportunities to collaborate with neighboring local goverenments also undertaking NDRRA

works should be investigated as the efficiencies and benefits can sometimes be achieved

through the pooling of in-house resources and knowledge, and through economies of scale

by increasing the scope of restoration works tendered and increasing the level of market

interest and contractor capability.

3 Fitness for Purpose Design3.1 GeneralWhen designing flood restoration works engineers are faced with a number of challenges.

These include but are not limited to:-

x The pre-event design standards of damaged essential public assets do not align with

current engineering standards.

x Saturated subgrades and associated low subgrade strength require additional design

treatments such as subgrade stabilization, subsoil drainage, placement of geo-

fabric.

x Changing traffic conditions such as increased traffic volume and increased

percentage of heavy vehicles. In some instances this may result in a change in the

road function and design cross section for proposed restoration works.

x Inadequate surface water drainage due to deficiencies in existing longitudinal

drainage and cross drainage on damaged road sections

x Constraints on using cost effective treatments such as in-situ stabilization due to

deficiencies in the existing pavement materials and/or lack of availability of cost

effective new pavement materials which meet current engineering specifications.

x An absence of a consistent and clearly defined road hierarchy and associated design

standards for all road types within the LG region.

x The absence of hydrographic studies to define the catchment characteristics and



define design flow for culverts and floodways.

x The need for additional design elements to improve asset resilience which may be

considered complementary works by QldRA if they were not present prior to the

event. Typical examples of treatment to improve resilience and VfM include raising

the vertical alignment of roads, addition of subsoil drainage, and construction of

cutoff walls, wingwalls and scour protection on drainage structures.

When considering proposed design treatments for restoration works QldRA have a strong

focus on scope, VfM and the appropriateness of the proposed design treatment. As the

costs of “eligible” works for Councils are fully recoverable under NDRRA guidelines the

physical footprint of the damage identified in the submission compared to that of the final

restoration works is closely monitored by QldRA. Similarly the pre-event condition and

“service standard” of the asset are considered and compared to the proposed restoration

treatment by QldRA to determine whether the proposed treatment is an appropriate level of

response and fit for purpose.

All design is a compromise between the ideal and what is fit for purpose and affordable.

Relevant engineering experience, professional judgment, and an understanding of the

technical fundamentals, principles and safety aspects of design criteria and practices is

necessary when making tradeoffs between competing priorities. Importantly, restoration

solutions must not create any increase in safety risk than existed prior to the declared

natural disaster events.

In reality, with constrained budgets, application of the guidelines to the extensively damaged

and aged network requires compromises and some residual performance risks will remain. It

is expected that experienced practitioners will apply the guidelines to deliver fit for purpose

outcomes within approved QldRA funding and Council budget allocations for complementary

works.

3.2 SafetyAs a minimum, the existing level of safety prior to the flood event is to be maintained.

Restoration works on essential public assets to achieve the pre event safety conditions are

eligible for NDRRA funding. Where current engineering standards require additional safety

measures to be incorporated in the design, LG’s may be required to contribute funding for

the costs over and above reinstatement costs to pre-event standard. Alternate safety

treatments which comply with current engineering standards and enable and improvement in

safety levels to the pre-event standard for a similar cost will generally be eligible for full

NDRRA funding.



In some instances a road safety audit may be warranted. If a road safety audit identifies a

more costly and extensive design solution than the pre-event conditions a complementary

works funding contribution from the Council will likely be required for the additional cost

component. If complementary works funding is not available, the design solution may

warrant consideration by Council in future capital program budgets. Where the works cannot

be implemented due to budget constraints, interim safety treatments should be considered

such as speed management measures.

3.3 Reuse of Existing Materials and InfrastructureReuse of existing materials and infrastructure is actively encouraged in the program (e.g.

paving materials, traffic signs, guardrails, stormwater pipes and culverts etc). The decision

to reuse materials and infrastructure is to be made by an experienced practitioner by

considering factors such as likely residual life, risk of failure and compliance with current day

standards etc.

3.4 Pavement Structural Design LifeWhen selecting a pavement design life Council staff must be cognizant of the pre-event

condition of the asset and the design standard. In many cases the asset condition prior to

the flood event will have deteriorated significantly from the time of its creation. This is clearly

evident on road sections where the extent of road immediately adjacent to flood damage

sections is poor and approaching the end of its useful life. Where flood damaged assets

exhibited significant deterioration prior to the flood event and/or where the design standard

of the asset did not closely align with current engineering standards, QldRA may not fund

the cost of renewal of the asset to current engineering design standards. To be fully eligible

for NDRRA funding the pavement design adopted must take into consideration the pre-event

condition of the asset. For example, the design for a pavement under current engineering

standards may require a 20 year design life to be used. The restoration of the asset to this

standard will often result in a pavement significantly deeper than the adjacent undamaged

pavement sections and a significant improvement of the asset useful life when compared to

the pre-event condition. A compromise approach needs to be adopted to ensure the

pavement design life adopted achieves a reasonable engineering and VfM solution.

For example in lieu of a 20 year design life a 10 year design life may be adopted on sealed

roads which recognizes pre-event deterioration of the asset and results in a more

“proportional” design treatment being selected. QldRA has recently advised that, based on

submission data received from across the State, pavement depths up to 300mm are

considered typical. This can often be achieved through treatments such as insitu

stabilization and on lower order roads with reasonable subgrade strength and low traffic



volumes. There are significant advantages in terms of risk exposure to weather, cost, time

of construction and material reuse where box out and replacement of materials can be

avoided by using an effective design treatment using in-situ materials.

On roads with poor subgrade strength and/or high traffic volumes pavement depths in

excess of 300mm will likely be required even when adopting a 10 year pavement design life.

Subsequently the maximum 300mm pavement depth requirement should be used as a

guide. Individual sealed pavement design depths will likely fall above or below this depth

depending on the road function, subgrade properties, local design factors, traffic loading etc.

The treatment adopted should reflect that of Council’s “standard practice” for reconstruction

on the same standard of road in non flood-affected areas.

For higher order roads in the network which were in good condition prior to the event and

exhibit pavements that reflect current engineering standards, the same design standard

should be adopted for any restoration work (for example 20 year pavement design life) as

this will reflect the pre-event asset standard.

Where a design life is adopted that provides a significantly greater strength and residual life

to that exhibited by the asset prior to the flood event, a complementary works funding

contribution will likely be required from the Council. The complementary funding component

will apply the portion of the works which QldRA deems to be of a higher standard to the pre-

event standard. For example, if a 20 year design life was adopted and QldRA considers a 10

year design life more appropriately reflects restoration to the pre-event standard, then only

costs to construct the pavement with a 10 year design life will be eligible, with the balance

costs associated with the 20 year design standard to be covered by the Council as

complementary works.

3.5 Pavement DrainageWhere there is evidence of failure due to water infiltration associated with the declared flood

event, a drainage blanket should be considered. For example, if the pavement in a cutting

has failed due to water infiltration from below, the installation of a drainage blanket may be

warranted. Such a failure may also occur where kerb and channel was constructed without

subsoil drains, subsoil drains are not functioning correctly or table drains are inadequate.

Where possible the invert of table drains should be at least 200mm below the top of

subgrade or bottom of a drainage blanket. If kerb/kerb and channel with subsoil drains exists

then consideration should be given to replacing the existing drainage system with table

drains.



Detailed early discussions with QldRA are recommended to establish the scope and funding

eligibility of pavement drainage treatments.

4 Drainage Infrastructure4.1 Key Drainage RequirementsWhere drainage assets have been destroyed or suffered damage from the declared flood

event, proposed NDRRA restoration works should aim to reinstate the drainage system to its

pre-event immunity level using current engineering standards. With respect to road

drainage, this pre-event standard is the original design standard (e.g. 1 in 10 year immunity)

or service level of the drainage system. Simply replacing culverts with ‘like for like’ may not

give the same hydraulic performance / capability as originally designed. This can be a result

of changes in design standards since the asset was created (e.g. QUDM vs. AR&R),

changes to the catchment characteristics, and/or alteration of the catchment and terrain by

the flooding. These factors should be considered when determining if ‘like for like’

replacement is appropriate.

It is recommended that the original design and its intent be reviewed and understood to

ensure that design work properly reinstates the drainage system to at least match original

performance criteria. Council may wish to improve the flood immunity of drainage structures

to the pre-event standard in some instances due to current or future road function or service

level requirements. Where this is warranted Council will need to allocate complementary

funds to cover the additional cost component of the design which is over and above the

costs to reinstate to the pre-event service standard.

5 Safety in DesignWhere detailed design is required for NDRRA restoration works, Councils need to consider

the new legal obligations for designers of road infrastructure introduced in Queensland on

1July 2007 under amendments to the Workplace Health and Safety Act 1995 (the "Act").

Since 2003, designers have had an obligation to design a structure that is intended to be

used as a workplace that is without risk to the persons when it is being used for the purpose

for which it was designed (s34B). The Act has been amended to include designers as one of

the several duty holders responsible for health and safety in the workplace.

Workplace Health and Safety should be considered for three groups of people:

x Those who use the road system for their livelihood (truck drivers, taxi drivers, bus

drivers, tourist operators) and the safety of this group cannot be separated from



that of the driving population as a whole;

x Enforcement - Police, Transport Inspectors; and

x Those who build maintain and operate: construction workers, maintenance workers,

traffic response crews, emergency services and their supervisors

Some significant hazards faced by the third group include:

x Working close to moving traffic

x Working at height

x Working on slopes

x Working in confined spaces

x Working with specialist materials

Safety in Design requires a more rigorous and documented design processes that uses a

risk management approach in consideration of construction, operation, and maintenance

requirements and should be applied to the design of all public infrastructure assets.



6 Road Essential Public Assets - Work Types & FundingEligibility

6.1 Pavements

Table 1 Pavement Work Types and Funding Eligibility

Type PavementWork Type Eligible NDRRA Works Complementary Works

GravelResheets

Where gravel material has beenremoved as a result of concentratedsurface runoff or sheet flow; or wheregravel has been saturated as a resultof inundation or prolonged rainfallassociated with the declared event andgravel strength significantly reducedcausing rutting and poor roadformation. Reform or resheet inaccordance with Council’s designstandard. The works should berepresentative of the Council's usualpractice. Typically a 100mm to150mm compacted gravel resheetdepth is supported by QldRA. Theadopted depth of gravel resheets willbe dependent on gravel properties andthe standard practice/design standardapplied by the Council for resheetsworks.

Improvement workscomponent where theroad formation issignificantly improvedthrough widening orraising of verticalalignment. Additionalresheet depth whereresheet depth is greaterthan the pre-existingstandard and/or currentstandard practice of theCouncil.

1 Pavementpatching(Caseexample 3)

Where isolated pavement failuresoccur as a result of the declared floodevent. The design treatment adoptedfor the failure options analysis toidentify the most cost effective andsuitable treatment type. Failure repairdepths and materials are consistentwith a adjacent pavement and LGpractice. Design life of failure repairstreatment does not exceed 10 years.

If a higher-order treatmenttype is chosen, e.g. half roadwidth or full width repairs theadditional cost of the treat-ment will be complementaryworks, unless the cost of thehigher-order treatment can bedemonstrated to be equal toor lesser than the isolatedpavement repair costs andthus achieves a superior VfMoutcome.

2 Part-widthpavementrehabilitation

Where there is consistent damagealong a segment/s of the pavementcross section. The pavement designselected takes into account the pre-event pavement depth and type andprovides a similar performanceoutcome. The pavement depthproposed is not greater than the pre-event pavement depth. A pavementdesign life is adopted which takes intoaccount the pre-event assetdeterioration. If the pavement depth

If full-width pavementrehabilitation is chosen, theadditional cost above the partwidth repair will becomplementary funding.

The additional cost of astronger pavement (e.g. onewith a higher design life thanthe original asset or adjacentundamaged road sections)will be complementary



Type PavementWork Type Eligible NDRRA Works Complementary Works

required is greater than the pre-existing depth as a result of very poorsubgrade strength resulting fromsaturation all measures have beenimplemented to reduce costs andprovide a cost effective designtreatment.

funding.

3 Full-widthpavementrehabilitation(Caseexample 2)

Where there is damage across the fullwidth of the carriageway as a result ofthe declared flood event and anappropriate pavement design isadopted. The pavement designselected takes into account the pre-event pavement depth and type andprovides a similar performanceoutcome. The pavement depthproposed is not greater than the pre-event pavement depth. A pavementdesign life is adopted which takes intoaccount the pre-event assetdeterioration. If the pavement depthrequired is greater than the pre-existing depth as a result of very poorsubgrade strength resulting fromsaturation all measures have beenimplemented to reduce costs andprovide a cost effective designtreatment.

The additional cost of astronger pavement (e.g. onewith a higher design life thanthe pre event asset).

6.2 Bridges, Drainage Structures and Embankments

Table 2 Bridge, Culvert and Embankment Damage Types and Funding Eligibility

TypeBridge orDrainageStructure

Damage TypeEligible NDRRA works Complementary Works

1 Bridges orculvertsdestroyed as aresult of thedeclared event

Full replacement of structure anddamaged approaches andpavement based on currenthydraulic conditions using pre-event performance criteria (ARI).The proposed design and costestimate must take intoconsideration the pre-eventcondition of the asset.

Providing increased width tomatch a final visioncarriage-way width of theapproach roadways (if thesewidths are greater).Increasing immunity – e.g.upgrading drainage to caterfor a higher ARI to meet thedesired current or futureservice standard. Replacinga significantly deterioratedasset near the end of itsremaining useful life with anew asset may necessitate





the allocation of Councilcomplementary works fundsfor a portion of the projectcosts. Detailed discussionswith QldRA to determineeligibility and scope arerecommended prior tofinalization of design inthese instances.

2 Abutmentprotectiondestroyed ordamaged

Replacement with similar or moreresilient materials to currentdesign criteria

The additional cost ofproviding materials moreexpensive than specified bycurrent design criteria

3 Pier that hassunk or lostload capacitydue to scour

Underpinning and/orreinstatement of axial and/ormoment load capacity pier

4 Damagedbridge barrier

Replacement to existing or currentengineering standards

Extra cost of bridge deckstrengthening

Cost of realignment ofbridge approach barriers tocurrent engineeringrequirements

5 Damagedbattersincludingdamagedfloodwayprotection

Reinstatement of existing wheredamage is minorProvision of additional resiliencewhere damage is significantincluding flattening batters whereappropriate if the works candemonstrate a VfM outcome.

Cost of resumptions orenvironmental offsets

6 Damagedpavements onFloodways

Reinstatement to pre-eventstandard. Reinstatement usingmore resilient materials to currentengineering standards provided aVfM outcome can be demon-strated (i.e. improved resilience forrelatively low additional cost of likefor like replacement).

Increased cross drainage/under drainage beneathfloodway. Increased costcomponent of replacingsealed granular pavementthrough floodway withreinforced concretestructure.

7 Cross Drainage Reinstatement using existingmaterials where pipes or culvertsare not damaged. Replacementwith new pipes or culverts tocurrent engineering standards.The design standard/serviceabilitystandard of cross drainage is thesame as the pre-event level (e.g.remains at a 1 in 5 year designARI for serviceability).

Costs associated withincreasing the hydrauliccapacity and servicestandard (e.g. 1 in 10 yeardesign storm, where pre-event serviceability 1 in 5year design storm). Costsassociated with theextension of culverts toenable road widening orfuture widening.





8 Large culvertdamaged

Replacement with new bridgestructure at a similar cost toreinstatement of like with like.Reinstatement with alternatedesign solution which providesimproved value-for-money andincreased resilience for noincrease or minor increase in costthan like for like replacement.

Where an alternate andhigher order design solutionis adopted the cost on andabove like with likereinstatement will requirecomplementary funding.

9 Scouredlongitudinaldrains

Reinstatement of existing V- drain.

Replacement with trapezoidaldrain if costs are equivalent toreinstatement of existing V- drain.

Additional cost oftrapezoidal drain over thereinstatement of V-drain

10 Damage to endwalls and scouraround struct-urally unsuitableculvert (doesnot satisfycurrentengineeringstandards)

Reinstatement of end walls andscour protection

Supply and installation ofnew (structurally adequate)culvert components



6.3 Road Geometry

Table 3 Geometric Issues and Funding Eligibility

Type Geometric Issue Eligible NDRRA works Complementary Works

1 Seal width of two-lane,two-way rural road

Formation widening andprovision of seal widths inaccordance with currentengineering standard for thesame service standard.

Formation widening toachieve a width greaterthan the currentengineering standard forthe pre-event servicestandard.

5 Opportunities tofacilitate future linkdevelopment stages,e.g. provision for cyclepaths

None, unless no additional costis involved.

Additional width to providefuture cycle paths / widershoulders.

6 Opportunities toupgrade single laneroads to two lane roads

None, unless no additional costis involved.

Works to extend the widthof seal and any necessarypavement upgrades

7 Geometric elements notlisted above that do notmeet the current designstandards e.g. clearzone widths, horizontaland vertical alignments,sight distance,intersection turntreatments

None, unless work can becompleted for no extra cost

Any work undertaken toimprove the substandardgeometric parameter

8 Improvements to anidentified crash history

Low cost mitigating treatments Higher cost Improvements

9 Missing links - roadsections less than 1kmin length remainingbetween two NDRRAfunded sections thatrequire significantpavement works.

None Any improvements toundamaged sections.

10 Undertake road surveyincluding Mobile LaserScanning

None



6.4 Roadside Furniture and Delineation

Table 4 Roadside Furniture and Delineation Funding Eligibility

Type Damage sustained Eligible NDRRA works Complementary Works

1 Flood damagedroadside safetybarrier

Reinstate to current standards up tothe existing length

Extensions required to satisfycurrent engineeringrequirements

2 Pavementdamage requiringnew seals andline-marking

A line-marking design that iscompliant with the TMR Manual ofUniform Traffic Control Devices(MUTCD).

Additional line-marking abovethat required by the TMRMUTCD.

3 Flood damagedsigns

Flood damaged signs to be replacedwith new signs as per the TMRMUTCD. Additional low cost devicesto manage road safety risks can beimplemented.

Required signs that did notexist pre-event. Implementa-tion of higher cost safetytreatments to mitigate risksidentified in recent or existingroad safety audits.



7 Improving Resilience and VfM Outcomes7.1 IntroductionResilience is the ability to absorb a disaster event and return the community to acceptable

operating conditions. A major objective of Councils and QldRA is to improve the resilience of

Queensland’s road and transport infrastructure so that it will not suffer the same magnitude

of damage as that experienced in recent events.

Works likely to contribute to network resilience are those that:

x improve the network’s ability to survive future similar flooding events by reducing the

extent of damage

x reduce the work and/or time required for the network to be recovered to unrestricted

usage following a future event without improving its flood immunity

Examples are pavement structural improvement, shoulder sealing, resurfacing, slope

stability work, floodway improvements, drainage and structures scour protection, and

drainage scour protection.

Designers must consider improving the resilience of their projects by:

x identifying all infrastructure that has been damaged

x unless unaffordable, designing infrastructure at all damaged sites with an improved

tolerance to damage.

Whole-of-life cost considerations can be used to support what improvements to resilience

should be incorporated into proposed designs however detailed early discussions with

QldRA are recommended. Depending on the demonstrated need, scope and costs of the

proposed works to provide improved resilience may be funded or part funded under NDRRA

or need to be fully funded by Council as complementary works.

This section provides information on improving the resilience of road and transport

infrastructure.

7.2 Pavements7.2.1 ExistingMoisture ConditionsReconstruction works will have to contend with above average, wet ground conditions for

some time following any flood event. Feedback from local government engineers across the

State have shown that a significant number of bridges and culverts still had water flowing

through them or ponding beneath them at the time restoration works commenced. Similarly,

a significant number of table drains were holding water and seepages were still active in cut



faces and adjacent gullies. Evidence suggests that six months after the declared event

water tables were still high and adjacent pavements vulnerable with areas of distress

continuing to grow at an accelerated rate under traffic.

It is difficult to forecast how long the high water tables remain. Even average rainfall over the

six to nine months after an event may continue to top-up aquifers and sustain high water

tables in some areas.

The pavement design solutions developed will need to allow for these existing moisture

conditions. Detailed early discussions with QldRA are recommended around the proposed

design treatment where pavement saturation is the primary cause of failure. Pavement

saturation damage continues to be a complex and somewhat controversial issue for

Councils, QldRA and EMA.

7.2.2 Design ApproachThe design of pavement repair solutions needs to address contributory causes. To simply

reinstate or replace proven vulnerable pavement materials with the same quality or

characteristics will not improve resilience. Contributory causes are identified through

relevant testing and investigatory techniques.

The best pavement solution will be the one that provides the lowest whole-of-life cost when

taking into account factors such as initial construction cost, on-going maintenance costs,

repair and/or rehabilitation costs and frequency and period of inundation to be expected. In

the selection of appropriate solutions, designers should carefully consider whether increased

resilience can be economically achieved without changing the service standard of the asset.

Where improved resilience can only be achieved through a change of service standard of

the asset a complementary works funding contribution from the Council will likely be

required. In many instances Councils will not have the available funding to improve the

resilience of the asset and a reinstatement to pre-event standard and resilience levels will be

the only option.

In determining a design treatment it is important to address contributory cause/s of failure.

For example, it may be a better outcome to obtain NDRRA funding for improving pavement

drainage along with the provision of a new seal, rather than to provide a completely new

pavement without addressing contributory causes and no improvement of resilience.

7.2.3 Non-flooded Pavements (Saturation Damage)The guidance in this section applies to pavements that are not inundated for significant

periods of time but have suffered saturation damage due to moisture ingress as a result of



the abnormally prolonged rainfall periods associated with the declared event. These

pavements are often on grade/s with adjacent longitudinal drains.

Examples of improved resilience for non-flooded pavements are as follows:

x Reducing the pavement’s moisture susceptibility

x Providing sealed shoulders to provide extra distance between the outer wheel path

and the zone of influence of inundation i.e. eliminate unsealed shoulders

x Modifying/stabilising pavements utilising cementitious or bituminous stabilising

agents to reduce the moisture sensitivity of the in-situ pavement materials

x Overlay or substitution of existing pavement materials with new bound materials e.g.

asphalt or bitumen bound base materials

x Improving pavement drainage (where damage has occurred)

x Reinstating table drains

x Cleaning subsoil drains and culverts

x Repairing surface cracks (not eligible for NDRRA funding)

x Adding a geotextile seal

x Adding a drainage blanket

If there is evidence of pavement distress from water infiltrating from below the pavement in

cuttings, or there is evidence that the water table is sometimes within or above the

pavement, consideration should be given to the installation of deep longitudinal cut-off

drains or use of drainage blankets on top of the subgrade in cuttings.

Designers will need to be conscious of any risks in providing for the increased resilience. For

example, stabilised pavements are more prone to fatigue, unless there is adequate depth of

pavement to resist this.

7.3 Flooded PavementsThe guidance in this section applies to pavements that are inundated for a significant period

of time. These pavements are often at low points located around major cross drains or in flat

terrain.

Pavements are at their most vulnerable when subjected to traffic loading at high moisture

conditions. The longer a pavement is flooded the more likely it is that its moisture content

will increase. Pavements do not dry out quickly, so the longer the combination of traffic

loading and high moisture content continues the larger the loss of service life is likely to be.



This is particularly the case for unbound granular pavements.

With the probable exception of concrete pavements, all pavements will suffer loss of service

life if the pavement structure, including the subgrade, is trafficked when above its designed

operating moisture range. Non-concrete pavements may provide an acceptable level of

resilience (or performance) if restrictions on traffic loading are applied over several weeks

and months after periods of inundation. However, this may not meet community

expectations and will be very difficult to administer.

It is recommended that priority be given to providing a high level of resilience on the higher-

order roads. This may be more easily justified on higher-order roads with higher traffic

volumes, particularly if shorter lengths of inundation and stable subgrades apply.

Where, due to whole-of-life cost considerations and/or budget and/or resource constraints,

non-concrete pavements, particularly unbound granular are considered in areas subject to

inundation, local knowledge and experience is required to determine how long a particular

pavement material could be inundated without significant loss of service. Load restrictions

may have to be applied until deflection analysis indicates there are no signs of weakness,

particularly in the outer wheel path.

Examples of improved resilience for pavements subject to flooding are as follows. Please

note that the level of improvement gained under some of these treatments is not certain. In

these cases, local knowledge and experience is required to determine their suitability.

x Reducing the pavement’s moisture susceptibility

x Providing increased flood protection on the downstream side of floodways to resist

embankment batter erosion that if left unprotected will result in damage to

pavement seals and materials

x Providing more under-drainage for waterways (including floodways), where there is a

history of recurrent damage to seals and pavement materials when over-topped

due to high velocity flows or long period of inundation

x Installing concrete pavements on floodways (including approaches)

x Installing concrete pavements on approaches to low-level bridges



7.4 Surfacing of Unsealed RoadsFor unsealed roads, there may be economic benefits of sealing:

x road sections that flood (e.g. floodways)

x steeper sections of roadway that are prone to scour

x sections where there is a loss of traction and damage under traffic when wet.

Sealing these sections of roadway could be done in association with sealing of other

sections to improve factors such as safety (e.g. sealing sections comprising tighter

horizontal curves). The latter is funded under Complementary Works.

7.5 Drainage Infrastructure7.5.1 Design ApproachConsideration should be given to providing more resilient drainage solutions where damage

has occurred, particularly if the damage has occurred often. Whole of life cost considera-

tions can be used to determine whether a more resilient drainage solution is justified.

Increased resilience to overtopping can be provided through three broad strategies: -

increased capacity, reduced difference in head, and scour protection.

The risk of scour to drainage structures, embankments and pavements is reduced as more

floodwater is channeled under the road. There are also direct safety and economic benefits

from minimising the time during which water lies across road carriageways. In many cases a

nominal increase in pipe size can be achieved at a low incremental cost to greatly improve

under-road capacity/performance.

On some floodways, the risk of scour is reduced if the road surface is at the same level as

the ground / base channel – minimising ‘damming’ effects, and resulting in less armouring

protection being required. However, there will still be some uplift pressure on the pavement

and possible scouring from pooling if there is a high upstream velocity. Obviously this

solution requires a full or partially ‘boxed’ pavement below the natural surface that needs to

be specifically designed to operate in saturated conditions, at least during normal wet

seasons.

This strategy will not be possible if the pavement is to be raised or high embankments

already exist.

If it is not possible to improve resilience through the previous strategies, then ‘armament’

protection against scouring should be considered.



In many instances, protection from scouring will be the only practical option. For example, if

a road is on a floodplain and provision of increased culvert capacity (i.e. under-flow capacity)

is too costly then designing for overtopping will be required. In this case, protection against

scouring of the embankment may be the only practical treatment that will improve the

resilience of that section.

Downstream embankments at culverts and bridges are more likely to scour from over-

topping than upstream embankments and will usually require scour protection. However,

upstream embankment protection should also be considered on a case-by-case basis. At

bridge sites, spill-though abutments may be undermined. Similarly at culvert locations,

overtopping can result in removal of material supporting the culvert.

7.6 Bridge Approaches, Abutments and PiersAddressing contributory causes of damage to bridge approaches, abutments and piers

requires an investigation to establish factors such as:

x the magnitude of the event

x whether the original assumed ‘design immunity’ for that bridge was meant to cope

with such an event

x how well the bridge has performed

x what is now required for the bridge to perform as originally intended

x whether complementary works are required to improve on the bridge’s original

‘design immunity’.

It is recommended heavy duty scour protection is incorporated in all instances where

scouring has occurred at abutments and piers.

For bridges, batter protection on the downstream side of the road embankment shall extend

along each carriageway past the abutment (in both directions) for a distance three times the

height of the road embankment, but not less than 10 metres.



Attachment A

Examples of Typical Food Damage – Road Assets

Figure 1 Pavement Breakouts Figure 2 Pavement Crocodile Cracking

Figure 3 Pavement Potholing Figure 4 Pavement Rutting



Figure 5 Pavement Stress Cracking Figure 6 Lifting / Loss of Bitumen Seal

Figure 7 Flushing of Bitumen Seal in WheelPaths

Figure 8 Unsealed Shoulder Scouring

Figure 9 Flood Debris to be Removed Figure 10 Scouring of Bridge Structures



Figure 11 Scouring / Loss of Culvert Inlet /Outlet Structures and Protection Works

Figure 12 Scouring / Loss of Gravel SheetingMaterial

Figure 13 Damage to Floodway Structures Figure 14 Slope Failure & Instability

Figure 15 Embankment Slump



Attachment B

Case Examples – Road Drainage & Bridge Assets

a) Pavements

x The ‘inner’ and ‘outer’ wheel paths in both traffic lanes of a section of two-lane

carriageway has been damaged over the full length of a road section by the

declared rainfall / flooding event.

The reconstruction of the full carriageway width to pre-event service standard (i.e.using full-width pavement rehabilitation) for that section is ELIGIBLE for NDRRAfunding.

x There are isolated patches / areas of a road that have been damaged by the declared flood

event.

The reconstruction of the patches and the seal required (initial primer seal and follow-upoverlapping seal) for those areas are ELIGIBLE for NDRRA funding. Any additional sealprovided to the remainder of the undamaged pavement is INELIGIBLE for NDRRA funding.(Note: seal texture differences and age and condition of remaining seal need to be takeninto account when considering the need for a full-width seal).

x A review of the treatment options for restoration works over a section of damaged

pavement identifies full-width reconstruction of the pavement can be completed at a similar

cost of isolated failure repairs due to economies of scale, more cost effective treatment

type (e.g. in situ stabilization) improved constructability etc. The full-width restoration is

adopted in lieu of the isolated failure repair (patch work) approach for the road section.

The costs of full width restoration of the road section will be ELIGIBLE for NDRRA fundingprovided that the Council can demonstrate the cost of full-width restoration is less than orequal to the cost of isolated failure repairs over the subject road section. The adoptedapproach will result in a higher VfM outcome and improved resilience.



If the costs of the full-width restoration of the section are significantly higher than the costof repair of the individual flood damage failures, the additional cost of full width treatmentis INELIGIBLE for NDRRA funding and a complementary funding contribution will berequired.

x The current engineering standard for a damaged pavement requires a 20 year design life

to be adopted. A full depth reconstruction of the pavement will be required as alternate

treatments such as insitu stabilsation have been deemed inappropriate due to factors such

as loss of original pavement material, unsuitable material type, low subgrade strength etc.

The use of a 20 year design life will result in a pavement depth significantly deeper than

the pre-event pavement and adjacent pavement. The pavement damaged as a result of

the flood event was approximately 50% through its useful life at the time of the event.

In recognition of the adjacent pavement depth and condition, a 10 year design life is

adopted in lieu of 20 year by the Council. A design option analysis is carried out to confirm

that the pavement design adopted is the most cost effective treatment type.

The costs of the full depth reconstruction to the lesser pavement design life of 10 years willbe ELIGIBLE for NDRRA funding provided the Council demonstrates this reflects the pre-event condition of the pavement and the road function and the treatment option adoptedprovides the best VfM outcome.

If a 20 year design life is adopted by the Council, the additional costs above a 10 yeardesign treatment will be INELIGIBLE for NDRRA funding and a complementary fundingcontribution will be required.



b) Bridges, Drainage Structures and Embankments

x The end pipe of a 450mm diameter culvert along with the end wall has been separated

from the remainder of the culvert as a result of the flood waters. This has resulted in the

exposure of the remainder of the culvert as well as scour to the embankment. The

remainder of the culvert is structurally unsuitable as a result of the age of the culvert.

As the end cell/pipe, headwall and embankment was impacted by the flood event then onlythis work (reinstatement of the existing pipe, headwall, embankment and pavement) isELIGIBLE for reconstruction. But the unsuitable culvert has to be replaced. The cost ofsupply and installation of the new culvert components to the site is INELIGIBLE for fundingunder NDDRA and must be replaced under complementary works funding.

x The entire length of a 2 cell 375mm diameter culvert has been damaged as a result of

flood waters. The original 2 cell 375mm diameter culvert was designed to Q20 flood

immunity. A hydraulic assessment has been undertaken subsequent to the flood event and

as a result of a change in the local catchment (not caused by the flood event) the

assessment finds that to provide the same Q20 flood immunity an additional cell (3 cells in

total) is required to be constructed to comply with the current engineering standards.

As the 3 cell culvert provides the pre-disaster standard / flood immunity and is proposed to beconstructed in accordance with the current engineering standards then the replacement of all3 x cells of the culvert is ELIGIBLE for funding.

x The entire length of a 2 cell 450mm diameter culvert has been damaged as a result of

flood waters. The original 2 cell 450mm diameter culvert was designed to Q5 flood

immunity. The current engineering standard for this location stipulates that Q10 flood

immunity shall be provided. This flood immunity increase results in an additional cell (3

cells in total) is required to be constructed to comply with the current engineering

standards.

As the 3 cell culvert provides improved pre-disaster standard flood immunity and isproposed to be constructed in accordance with the current engineering standards then onlythe replacement of 2 cells of the culvert is ELIGIBLE for funding. If 3 cells are to be installedthe additional 1 cell is INELIGIBLE for NDRRA funding.



x A timber bridge has been made structurally unsound by the recent flood event and is

required to be replaced.

It is current Council policy to replace timber bridges with concrete due to the shortage ofappropriate structural timber materials and the superior whole of life cost effectiveness ofconcrete bridges. The cost of the replacement of the concrete bridge providing the sameimmunity level and with no changes in height is ELIGIBLE for NDRRA funding. If the spanneeds to be increased because the banks have been eroded by the event then the cost oflengthening the bridge is also ELIGIBLE for NDRRA funding.

x A concrete bridge has been made structurally unsound by the recent flood event.

The cost of repairs to the damaged bridge is ELIGIBLE for NDRRA funding. If a newbridge is proposed, the additional cost above the repairs to the existing bridge and anycost of increasing the flood immunity and consequent cost of reconstruction of the roadapproaches is INELIGIBLE for NDRRA funding.

x The barriers on a bridge have been damaged due to overtopping and debris impact. After

appropriate investigations and analysis, a decision is made to replace the barriers to current

engineering standards, which requires the bridge barriers to provide increased traffic impact

capacity. Also, realignment of the bridge approach barriers is required. Because impact

loading increases the loading on the bridge deck there is a consequential need to increase

the deck load capacity along both edges of the deck.

The cost of replacement of the damaged bridge barrier to the current engineeringstandards is ELIGIBLE for NDRRA funding. The cost of increasing the bridge deckcapacity and alignment of the bridge approach barriers as a consequence is INELIGIBLEfor NDRRA funding. (Note, had the decision been made to delay the upgrading of thebarriers to current engineering standards and to replace the barrier to the pre-eventstandard then replacement to that standard would have been ELIGIBLE for NDRRAfunding.)



x A bridge has been badly damaged and a decision is made to replace it. Investigation

show it was originally designed to Q20 flood immunity and the current vision standard for

the road link is Q50 flood immunity.

The cost of replacement of the damaged bridge to the existing flood immunity isELIGIBLE for NDRRA funding. The cost of raising the bridge to achieve Q50 floodimmunity and consequent cost of reconstruction of the road approaches isINELIGIBLE for NDRRA funding.

x A bridge and abutments have been damaged and a decision is made to improve its

resilience in similar future events. Investigations show it was originally designed to Q50

flood immunity and the actual flood event in the catchment was analysed and found to be

a Q40 event.

The cost of repair of the damaged bridge and abutments to existing Q50 floodimmunity and commensurate resilience is ELIGIBLE for NDRRA funding.

x A large culvert has been made structurally unsound by a recent flood event and the entire

culvert is required to be replaced. Following an assessment of the replacement options it

has been determined that a bridge structure will provide the best VfM outcome.

Providing the new concrete bridge provides the same immunity level, the cost of thereplacement bridge would be ELIGIBLE for NDDRA funding. If the new bridge isproviding a greater immunity level, the additional cost to provide this improved immunitywould be INELIGIBLE for NDRRA funding.

x A section of road on embankment in a flood plain area continues to have the pavement and

seal damaged when the road is inundated by a flood event. The existing batter treatments

comprise natural vegetation at some locations and rock pitching at others. The current

engineering standard for sections of such road which are flood affected on a regular basis is

a form of concrete batter/margin installed on the embankment.

As the proposed works are in accordance with current engineering standards and the pre-disaster level of immunity is not being improved, then the cost of the additional concretebatter / margin is ELIGIBLE for NDRRA funding.



x A section of V-drain adjacent to the road in flat terrain has been scoured as a result of a

flood event and is contributing to the saturation and damage of the adjacent pavement.

The current engineering standard requires a trapezoidal drain be provided in this instance.

The cost of constructing the trapezoidal drain in this location is equivalent to the cost of

repairing the V-drain.

In this case, the cost of constructing the trapezoidal drain is ELIGIBLE for NDRRAfunding. However, if the cost of constructing the trapezoidal drain was more thanrepairing the V-drain, the additional cost would be INELIGIBLE for NDRRA funding.

x A section of batter has eroded as a result of a flood event. This batter had some grass

cover and natural vegetation on the slop prior to the disaster.

The cost of reinstating the grass and vegetation to a similar density as the pre-disasterstandard is ELIGIBLE for NDRRA Funding.

x A section of batter has eroded as a result of a flood event. To comply with the current

engineering standards the batter slope needs to be flattened. There is some vegetation

that needs to be removed at the bottom of the batter to accommodate this batter

flattening. There is a vegetation offset required as a result of the removal of this

vegetation.

The cost of flattening the batter and removal of vegetation to comply with the currentengineering standards is ELIGIBLE for NDRRA Funding. The cost of the environmentaloffset as a result of the clearing of the vegetation is INELIGIBLE as it is considered aconsequential cost.



c) Road Geometryx Full-width pavement rehabilitation (including a structural overlay) is being undertaken on

an existing 9.5m wide carriageway. Current engineering standards indicate that the

absolute minimum carriageway width is the interim seal width and a value of 10m applies

for this road.

The public asset is being retained to the pre-disaster standard (i.e. 2 lanes + shoulder). Asthe current engineering standard is 10m then this width of reconstruction is ELIGIBLE forNDRRA funding.

x This example is the same as the previous, except the road has a significant crash

history. The vision seal width is 11m. It is proposed to restore the asset to the vision seal

width of 11m due to the added safety benefits than can be achieved.

The public asset is being retained to the pre-disaster standard (i.e. 2 lanes + shoulder). Asthe current engineering standard (interim seal width) is 10m then this width ofreconstruction is ELIGIBLE for NDRRA funding. The additional cost of 11m seal andpavement width is INELIGIBLE for NDRRA Funding.

x As a result of a decision to provide additional pavement width to satisfy interim seal width

requirements, there is a requirement to widen embankments, lengthen culverts and to

relocate ancillary elements (i.e. signs, re-alignment of drains, re-alignment of turning

lanes and kerb & channel) to comply with current engineering standards.

As embankment widening, culvert extensions and the relocation of ancillary elements is aresult of complying with current engineering standards and maintains the pre-disasterstandard/level of service then the re-use and repositioning of these ancillary elementswould be ELIGIBLE for NDRRA funding. Existing signs deemed unsuitable for reuseshould be replaced and the cost of replacement is INELIGIBLE for NDRRA funding.

x Part-width pavement rehabilitation (involving boxing out of the outer wheel paths and

shoulders – no overlay) is being undertaken on an existing 10m wide carriageway.

Current engineering standards indicate that the general minimum carriageway width is

equal to the interim seal width of 10m. A vision seal width of 11m applies to this road.



The public asset is being retained to the pre-disaster standard (i.e. 2 lanes + shoulder). Asthe current engineering standard (interim seal width) is 10m then this width ofreconstruction is ELIGIBLE for NDRRA funding. However, it must be determined whetheror not this solution offers value-for-money as it involves sliver widening. It may be better toeither adopt the existing width without formation widening or to widen to the vision sealwidth. Any additional cost of providing an 11m carriageway over a 10m carriageway isINELIGIBLE for NDRRA funding.

x A single lane road is damaged to the full formation width of 8m. The road includes a

current seal width of 4m.

The reconstruction of the full formation is ELIGIBLE for NDRRA Funding. The seal width isalso ELIGIBLE to be replaced to the current engineering standard for a single land road.

d) Roadside Furniture and Delineation

x A section of Xm guardrail has been damaged by a recent flood event. In order to repair the

guardrail to current engineering standards the section of guardrail that is required to be

replaced is (X + Y) m.

The cost of the replacement of the Xm of guardrail is ELIGIBLE for NDRRA funding. Thecost of replacement of Ym of guardrail is INELIGIBLE for NDRRA funding. Where a sectionof guardrail has been damaged and the entire guardrail has to be replaced as compatibleguardrail cannot be sourced ELIGIBILITY only applies to the equivalent value of the sectionand not the entire guardrail.

Documents

NDRRA Flood Restoration Guideline for Queensland Local