Franco Montalto

Phragmites australis invasion and expansion in tidal wetlands: Interactions among salinity, sulfide, and hydrology

Through their physiological effects on ion, oxygen, and carbon balance, respectively, salinity, sulfide, and prolonged flooding combine to constrain the invasion and spread ofPhragmites in tidal wetlands. Initial sites of vigorous invasion by seed germination and growth from rhizome fragments appear limited to sections of marsh where salinity is <10‰, sulfide concentrations are less than 0.1 mM, and flooding frequency is less than 10%. In polyhaline tidal wetlands the invasion sites include the upland fringe and some high marsh creek banks. The zones of potential invasion tend to be larger in marshes occupying lower-salinity portions of estuaries and in marshes that have been altered hydrologically. Owing to clonal integration and a positive feedback loop of growth-induced modification of edaphic soil conditions, however, a greater total area of wetland is susceptible toPhragmites expansion away from sites of establishment. Mature clones have been reported growing in different marshes with salinity up to 45‰, sulfide concentration up to 1.75 mM, and flooding frequency up to 100%. ForPhragmites establishment and expansion in tidal marshes, windows of opportunity open with microtopographic enhancement of subsurface drainage patterns, marsh-wide depression of flooding and salinity regimes, and variation in sea level driven by global warming and lunar nodal cycles. To avoidPhragmites monocultures, tidal wetland creation, restoration, and management must be considered within the context of these different scales of plant-environment interaction.

Life cycle implications of urban green infrastructure

Low Impact Development (LID) is part of a new paradigm in urban water management that aims to decentralize water storage and movement functions within urban watersheds. LID strategies can restore ecosystem functions and reduce runoff loadings to municipal water pollution control facilities (WPCF). This research examines the avoided energy and greenhouse gas (GHG) emissions of select LID strategies using life cycle assessment (LCA) and a stochastic urban watershed model. We estimate annual energy savings and avoided GHG emissions of 7.3 GJ and 0.4 metric tons, respectively, for a LID strategy implemented in a neighborhood in New York City. Annual savings are small compared to the energy and GHG intensity of the LID materials, resulting in slow environmental payback times. This preliminary analysis suggests that if implemented throughout an urban watershed, LID strategies may have important energy cost savings to WPCF, and can make progress towards reducing their carbon footprint.

Observed and Modeled Performances of Prototype Green Roof Test Plots Subjected to Simulated Low- and High-Intensity Precipitations in a Laboratory Experiment

With continued urbanization pressure, regulators and developers alike are increasingly looking to new forms of green infrastructure and low-impact development technologies as a means of appropriately integrating built infrastructure into the landscape. This paper describes the results of a series of experiments designed to simulate the hydrologic performance of green roofs under variable precipitation conditions. The experiments were designed in order to test performance under both steady, low-intensity rainfall, as well as under short duration, high-intensity rainfall conditions. A control membrane roof and prototype green roofs of 2.5-, 6.3-, 10.1-cm depths were subjected to simulated precipitation in a laboratory setting. The green roofs delayed, prolonged, and reduced the peak rates of green roof discharge to 22–70% that of a standard roof surface, with greater percent reductions associated with deeper roofs. Negligible discharge was observed from all of the prototypes during the first 10 min of simul...

Using Life Cycle Assessment to Evaluate Green and Grey Combined Sewer Overflow Control Strategies

Decentralized approaches to managing urban stormwater are gaining increased attention within the contexts of urban sustainability, climate change adaptation, and as a means of reducing combined sewer overflows (CSOs). This study applied a life cycle assessment (LCA) to comparing the environmental efficiency of three means of equivalently reducing CSOs to the Bronx River (Bronx, NY, USA). Strategy 1 featured decentralized green infrastructure technologies, while “grey” strategies 2 and 3 detained, and detained and treated, respectively, excess flows at the end of pipe. We estimated greenhouse gas emissions (in metric tons of carbon dioxide equivalents [t CO‐eq]) over the construction, operation, and maintenance phases, including energy consumed at the wastewater treatment plant (WWTP), carbon sequestered, and shading provided by vegetation (in the case of the green approach) over a 50‐year analysis period. The study area comprised the entire drainage area contributing to New York State permitted CSO discharge points associated with the Hunts Point WWTP. The analysis was performed using a hybrid of process and economic input‐output (EIO) LCA methods. The decentralized green strategy outperformed the two grey strategies in terms of this set of environmental metrics. The net emissions of the green strategy over 50 years was 19,000 t CO‐eq, whereas the grey strategies emitted 85,000 t CO‐eq (detention) and 400,000 t CO‐eq (detention and treatment). These results were significantly influenced by the emissions associated with the operation and maintenance activities required for strategies 2 and 3, and the carbon sequestered and shading provided by the vegetation in strategy 1, and suggest that watershed managers who seek to reduce CSOs and reduce carbon footprints would opt for the green approach.

Integrating Valuation Methods to Recognize Green Infrastructure's Multiple Benefits

Reducing the negative impacts of storm water is gaining priority in United States communities’ efforts to develop more sustainably and to comply with Clean Water Act requirements. Nationwide, communities may need to invest hundreds of billions of dollars in coming decades to meet clean water goals, assuming expansion and repair of conventional infrastructure (US EPA 2002). These projections include

Applicability of Classical Predictive Equations for the Estimation of Evapotranspiration from Urban Green Spaces: Green Roof Results

54.8 billion for combined sewer overflow (CSO) control, and another nine billion dollars for storm water management programs (US EPA 2008a). The Clean Water Act’s regulatory requirements, along with perennial budget struggles facing many municipalities, are driving cities and utilities to identify and choose the most costeffective approaches to storm water management.

The link between hydrology and restoration of tidal marshes in the New York/New Jersey estuary

Green roofs and other urban green spaces can provide a variety of valuable benefits linked to evaporative processes, including storm-water management, reduction of urban heat island, and carbon sequestration. Accurate and representative estimation of urban evapo- transpiration (ET) is a necessary tool for predicting such benefits. However, many common ET estimation procedures were developed for agricultural applications, and thus carry inherent assumptions that may not be applicable to urban green spaces, including green roofs. The objective of this paper is to evaluate the performance of two combination methods for the prediction of ET from a green roof. Two ETestimation methodologies were compared, using on-site and regionally available data sets for daily time steps, to weighing lysimeter measurements of actual ET at a green roof site in the Bronx, New York. Regionally available estimates of potential ET did not accurately predict lysimeter measured actual ETon 30 nonconsecutive, non-water-limited days in months from September through December. Over the same period, the ASCE Standardized Reference Evapotranspiration Equation performed well in predicting actual ETwith an RMSD of only 0.03 mmd −1 . Additionally, the ET equation for short reference types, using on-site climatic data and coupled with a variation of the Thornthwaite-Mather approximation, which accounts for variable media moisture conditions, gave reasonable predictions of actual evapo- transpiration for 89 days analyzed (representing months from June through January) with an aggregate underestimation of 10.1%. However, this method was highly sensitive to input parameters, specifically media field capacity. Further on-site data collection is necessary to fully evaluate the performance of the equations over different seasons at this location, and monitoring of supplementary urban green spaces and green infrastructure sites will also lend further insights regarding urban evapotranspiration. DOI: 10.1061/(ASCE)HE.1943-5584.0000572.

Decentralised green infrastructure: the importance of stakeholder behaviour in determining spatial and temporal outcomes

The objectives of this paper are to summarize existing knowledge on the hydrologic characteristics of tidal marshes in the New York/New Jersey (NY/NJ) Estuary, to document the extensive linkages between hydrology and tidal marsh function, to underline their importance in designing restoration projects, and to identify research needs in this area. Hydrologic processes are responsible for the evolution, inter- and intra- marsh variability, and functional value of tidal marshes. Hydrology also controls the movement of materials and organisms between estuaries, wetlands, uplands, and the atmosphere. The importance of hydrology to tidal marsh function is widely recognized by the scientific community. Hydrologic research in tidal wetlands of the NY/NJ Estuary, however, is lacking. Anthropogenic development activities have resulted in drastic losses of tidal wetland value, and restoration is now finally a priority in many of the region’s natural resource management plans. The success of tidal marsh restoration efforts depends on how appropriately hydrologic factors and their interdependencies are recognized and incorporated into design; yet, little guidance about how best to restore tidal marsh hydrology is available. There is a need to document better the hydrologic characteristics of existing and historical tidal wetlands, to improve hydrologic modeling capabilities, and to accompany other ecological investigations in tidal marshes with hydrologic documentation.

Mapping the Design Process for Urban Ecology Researchers

The traditional approaches to resolving urban stormwater problems include costly expansion of collections systems and/or creation of in-line storage and treatment capacity. An emerging ‘green’ infrastructure (GI) approach would instead reduce runoff sources. An agent-based model is used to explore the spatiotemporal emergence of rain gardens and green roofs in Point Breeze, a 175 ha neighbourhood in South Philadelphia, PA, under two different scenarios. In the first, household GI adoption rules consider only economic self-interest and the physical compatibility of each GI technology with lot characteristics. In the second scenario, the adoption rules are enhanced based on insights into the possible behaviour of property owners, as intuited by the designers/authors over a two-year period using a variety of empirical methods. In Scenario 2, relevant knowledge and perceptions are transferred to household decision-makers through social networks, and exposure to GI is assumed to diffuse GI innovation. The two scenarios differ in the temporal rate of GI adoption in the neighbourhood at large (greater in Scenario 1), as well as in the spatial influence of early adopters in Scenario 2, underscoring the importance of stakeholder decisions in the ultimate the effectiveness of watershed-scale GI programs.

Development and Calibration of a High Resolution SWMM Model for Simulating the Effects of LID Retrofits on the Outflow Hydrograph of a Dense Urban Watershed

The integration of research into the design process is an opportunity to build ecologically informed urban design solutions. To date, designers have traditionally relied on environmental consultants to provide the best available science; however, serious gaps in our understanding of urban ecosystems remain. To evaluate ecosystem processes and services for sustainable urban design and to further advance our understanding of social-ecological processes within the urban context, we need to integrate primary research into the urban design process. In this article, we develop a road map for such a synthesis. Supporting our proposals by case studies, we identify strategic entry points at which urban ecology researchers can integrate their work into the design process.