Elizabeth Fassman

Urban Runoff Mitigation by a Permeable Pavement System over Impermeable Soils

The respective runoff from a 200 -m2 permeable pavement test site and an adjacent 850 -m2 conventional asphalt road catchment in Auckland, New Zealand, was monitored concurrently between 2006 and 2008. Despite installation over relatively impermeable subgrade soils, and on an atypically high slope (6.0–7.4%) and active roadway, the overall hydrologic performance of the permeable pavement was exceptional. Measured discharge from the permeable pavement underdrain demonstrated peak flow (81 storms) comparable to or below modeled predevelopment conditions for most storms, regardless of antecedent conditions, including a 10-year, 24-h annual recurrence interval event. For large events (5% exceedance), underdrain discharge volume was comparable to predevelopment conditions, but it was substantially less than asphalt runoff for all events up to approximately 70% exceedance. The distributions of peak flow and volume were statistically different between the asphalt catchment runoff and the permeable pavement under...

Road Runoff Water-Quality Mitigation by Permeable Modular Concrete Pavers

Discharge from a 200  m2 permeable modular concrete paver test section on an atypical 6.0 to 7.4% slope and in an active roadway was monitored concurrently with an adjacent reference conventional asphalt section in Auckland, New Zealand. The permeable modular pavement (PMP) underdrain water quality had consistent total suspended solids (TSS), zinc, and copper event mean concentrations that were statistically less than the reference asphalt runoff. Event mean concentration (EMC) distributions ranged over only a few μg/L, or mg/L from the PMP underdrain versus more than an order of magnitude for some parameters from the reference asphalt. Runoff volume control by the PMP contributed to substantial pollutant mass loading differences despite clay subsurface soils. PMP joint and bedding material were identified as the likely source of most pollutants in the underdrain discharge that might be avoidable with a construction specification for well-washed materials. A properly designed PMP section would likely prov...

Strategies for improving energy saving behaviour in commercial buildings in Malaysia

Purpose – The purpose of this paper is to investigate the level of energy saving behaviour between green and conventional office buildings in Malaysia to determine if people in green buildings perform better energy saving behaviour than people in conventional buildings. The paper specifically focused on use of technology, computer usage and potential energy savings from that use. The paper then examines what strategies are used to encourage energy saving behaviour for building occupants. Design/methodology/approach – Questionnaires were distributed to occupants in the buildings to evaluate the extent of energy saving behaviour practiced, and identify potential strategies to encourage energy saving behaviour. Findings – The findings show better energy saving behaviour practice in green buildings and the paper show why this is the case. The recommended strategies to encourage energy saving behaviour are discussed, and include means of raising education awareness on energy efficiency among the occupants. Thi...

Eliciting Stakeholders’ Preferences for Low-Impact Design Incentives: Conjoint Analysis Approach

AbstractIncentives are considered effective catalysts for influencing human decisions to bring about attitudinal changes in behaviors with negative consequences on the environment. As a result, various forms of incentive instruments are currently being developed and trialed across the globe to promote the uptake of low-impact design (LID) infrastructure to improve storm-water management in the urban environment. Given the complexity of incentive policy design for a paradigm shift toward LID adoption, this study explores stakeholders’ preference for five types of generic LID incentives within the New Zealand context. To address the inertia associated with economic variables in the decision to adopt LID by the development communities, the use of incentives has been widely advocated. This study’s main objective is to measure the level of preference for these LID incentives among its stakeholders. The study will also help reveal the impact of a lack of incentives provision in support of the calls for its use ...

Media Moisture Content to Determine Evapotranspiration from Swales and Bioretention Cells

Average 24-hr dry weather ET was determined for a bioretention cell and a grassed swale near Auckland, New Zealand in the winter, spring, and early summer. As both systems were lined and monitored for outflow, soil moisture content measured during dry periods could be used to costeffectively determine average 24-hr ET. Grassed swale ET ranged from < 0.5 mm/24-hr in winter to ~ 1 mm/24-hr in early summer. Bioretention cell ET was greater, at 1-3 mm/24-hr in winter and 2-3 mm/24-hr in summer. Published climate statistics significantly overestimate grassed swale ET, but are relatively comparable for the bioretention cell. Continuous simulation using a water balance approach would not be suitable for the grassed swale using published data. Grassed swale ET is likely affected by its microclimate more substantially than a bioretention cell, as the former is also influenced by limited moisture storage capacity. Additional work is required to expand the limited data set and investigate interactions of climate parameters’ influence on ET from LID devices.

Permeable Pavement Performance over 3 Years of Monitoring

A 200 m2 permeable pavement test site was installed along Birkdale Road on Aucklands North Shore. Data from the permeable pavement section and an adjacent conventional asphalt section were collected concurrently in 2006 and 2008. Despite installation on an atypical high slope (6.5–6.8%), relatively impermeable subsoils, and active roadway, overall system performance was exceptional. For the 81 complete storms monitored for hydrology, peak flow, runoff timing and volume compared well to predevelopment conditions. A catchment designed on an LID (low impact development) basis of controlling frequently occurring events would be well served using permeable pavement. Additional hydrologic control may be needed for design storms greater than 5-yr ARI. Water quality characterization for 4–17 storms (depending on pollutant type) was comparable to or better than typical end-of-pipe devices for TSS, PSD, total and recoverable Cu and Zn, and dissolved Cu and Zn. The permeable pavement discharge water quality had consistent event mean concentrations which were statistically lower than the conventional asphalt. Pollutant removal efficiencies are presented. A properly designed permeable pavement section would likely provide adequate treatment for an expanded source area. Permeable pavements should be given strong consideration as an LID at-source control.

Permeable Pavement Performance for Use in Active Roadways in Auckland, New Zealand

A field monitoring study of an interlocking block permeable pavement system was initiated in Auckland, New Zealand to assess performance in achieving LID goals. Automatic sampling and continuous hydrologic monitoring occurred for one year on an active carriageway and bus lane. Concurrent testing of a conventional asphalt surface and the permeable pavement system indicate that on average, the permeable system delays the onset of runoff by 2.4 hrs (40 events), and decreases peak flow by 83% (18 events). Peak flow during a 10-yr event was reduced by 70%. Clay subsoils prevent volume control. While flows exceed modelled predevelopment conditions, the permeable system contributes significantly to overall hydrologic control. Water quality sampling (6 storms) indicates that the permeable system discharges lower pollutant mass by 58 ±15% for TSS, 58% ±10% and 71±10% for total and dissolved Cu, respectively, and 86 ±8% and 96 ±2% for total and dissolved Zn, respectively. Differences between asphalt surface and permeable system EMCs are statistically evident. Permeable system pollutant discharge is less than or comparable to effluent from most BMPs reported by the International Stormwater BMP Database. Incorporating hydrologic routing in the design process would likely further increase hydrologic and water quality control. Surface infiltration testing for four permeable pavement sites is used to assess maintenance needs. The primary study site shows no loss in permeability and all tests achieve at least the 1200 mm/hr design objective. Other sites showed that fines and leaf litter can reduce permeability by an order of magnitude or more.

Quantifying Evapotranspiration Rates for New Zealand Green Roofs

Green roofs are an emerging storm-water management tool that has predominantly been analyzed for runoff volume reduction and peak flow mitigation. Little research has been completed on evapotranspiration ET in green roofs. Sedum mexicanum Mexican stonecrop and Disphyma australe New Zealand iceplant in a New Zealand designed, pumice- and zeolite-based substrate were analyzed to determine daily and hourly ET rates under both water-abundant and drought-stressed conditions. Water loss, and thus storage recovery of the substrate, was greatest in the first 9 days. Transpiration T by S. mexicanum contributed up to 48% of total ET 2.19 mm/day and D. australe contributed up to 47% of total ET 2.21 mm/day. After the initial rate of rapid water loss, plants conserved water and ET was not significantly different from evaporation E from unplanted substrate. S. mexicanum had a greater ability to conserve water and thus a greater longevity of life than D. australe under harsh drought conditions.

Stormwater mitigation by living roofs in Auckland, New Zealand.

Living roof technology is emerging as a low impact development method for stormwater management suitable for retrofit in densely developed urban centres. This paper presents results of field monitoring of a 235 m 2 extensive living roof suitable for retrofit installation in Auckland, New Zealand (NZ), to quantify the extent of stormwater control. Comparison in stormwater control is made between living roofs with three different substrate types at two different depths in a side-by-side comparison. No statistically significant differences in runoff response were found between the three substrate types tested. There was no statistically significant additional stormwater benefit found when increasing plot depth from 50–70mm. The overall cumulative retention efficiency of the UoA living roof was 71.6% over the period of 23 October 2008 to 22 October 2009, where 1137.2 mm of rainfall was received. On an individual event basis, the living roof retained a median of 83.6% of rainfall received, with a median peak flow reduction per event of 93.2%. Living roof response cannot be linked to one factor alone; multiple parameters such as rain depth, rain intensity, climatic variables and antecedent dry days all play a role in influencing hydrologic response.