Quantification of in-channel large wood recruitment through a 3-D probabilistic approach

Large wood (LW) is a relevant factor in physical, chemical, environmental and biological aspects of low order mountain streams system. LW recruitment, in turn, is affected by many physical processes, such as debris flows, shallow landslides, bank erosion, snow- and wind throw, and increases the potential hazard for downstream human population and infrastructures during intense flood events. In spite of that, the LW recruitment quantification and the modelling of related processes are receiving attention only since few years ago, with particular reference to hillslope instabilities which are the dominant source of LW recruitment in mountainous terrains at regional scale. Actually, models based on the infinite slope approach, commonly adopted for slope stability analysis, can be used for estimating probable LW volume and for identifying the most hazardous areas of wood input, transport and deposition. Such models, however, generally request a robust calibration on landslide inventory and tend to overestimate unstable areas and then LW recruitment volumes. On this background, this work proposes a new LW estimation procedure which combines the forest stand characteristics of the entire catchment and a three-dimensional probabilistic slope stability model. The slope stability model overcomes the limits of the infinite slope approach and considers the spatial variability and uncertainty of the model input parameters through a Monte Carlo analysis. The forest stands characteristics allow including the root reinforcement into the stability model as stochastic input parameter, and provide the necessary information to evaluate the forest wood volume prone to be recruited as LW and its position on the hillslopes. The procedure was tested on a small mountainous headwater catchment in the Eastern Italian Alps, covered with pasture and coniferous forest and prone to shallow landslide and debris flow phenomena, especially during the late spring and the early autumn. The results showed how the proposed procedure is very promising. In fact, the estimated LW volume is comparable with the one measured by field surveys. As the procedure used data commonly available, it is of great interest as a tool for forest planning and management, and to predict the effects of forest alterations, both of natural and of anthropic origin (e.g. diseases, fire, clear-cutting or clearing), as well as helping in-channel wood retention structures positioning

The vegetation of a mountain area of the Scalve Valley (Southern Alps) twenty years after environmental restoration work

The restoration of highly natural areas, such as mountain territories, is a very important issue for those involved in land management and nature conservation. This study reports data provided by the analysis of the vegetation of an area of the Scalve Valley (Lombardy, Italy) which underwent environmental restoration and soil stabilization work using soil bioengineering techniques following a landslide that occurred in 1992. Data on the vegetation, acquired by performing several phytosociological relev\ue9s (inside and outside the area) according to the Braun-Blanquet method (1964), were used to analyze the floristic and ecological characteristics of the plant communities currently present in the area. The Ecological Index of Maturity (EIM) (Giupponi et al. 2015) was applied in order to assess the level of disturbance to which the various plant communities are currently subject. The EIM is the result of the elaboration of flora and vegetation indices proposed by Taffetani & Rismondo (2009) and Rismondo et al. (2011) for the evaluation of the functionality of agro-ecosystems, and provides values ranging from 0 (high disturbance of vegetation) to 9 (undisturbed vegetation). Results showed that, in the study area, there are some plant communities typical of forest margins, some typical of less evolved soils, and others with a high proportion of exotic species that were introduced in 1995 (at the end of slope stabilization work), when a mixture of commercial seed was sown. The results obtained calculating the EIM showed the presence of high disturbance for the plant communities with high percentages of exotic species and for those on unstable soils

A Customized GIS-based Model for Stormwater Mitigation by LID Controls

The effects of urbanization on hydrology, water quality, habitats, as well as ecological and environmental compartments, represent issues of primary importance for multiple agencies at the national, regional and local levels. In the context of the SMART-GREEN project, funded by Fondazione Cariplo and currently in progress, a new tool called SMARTGREEN plugin is under development in a desktop GIS framework. The software will provide: 1) a user friendly interface to help analysts in the hydrologic-hydraulic modelling of urban watersheds and drainage networks through the model MOBIDIC-U, with the possibility of considering Low Impact Development (LID) solutions, 2) a set of tools to easily import information from existing databases, 3) a set of tools to check the database quality, highlight missing or incorrect data, and suggest possible fixes automatically, 4) an easy and faster way to speed up the analysis of the results. In this work, we show the main functionalities of the plugin through a basic test case. The software aims at supporting water service management companies in planning LID implementation in urban areas

Water balance of rice plots under three different cultivation methods : First season results

In the last years rice cultivation methods have been the object of an intense research activity aiming to implement new irrigation methods in addition to traditional flooding, in order to reduce water use. This change has concerned also the traditional paddy-rice territories of the north-west of Italy, where rice has been traditionally cultivated as flooded and where paddy fields are a strong landscape landmark and represent a central feature in the Italian and European network for nature protection. The new techniques introduced in these territories consist in a dry seeding followed by field flooding after about one month (third-fourth leaf), and in a full aerobic cultivation with intermittent irrigations, similarly to standard irrigated crops. This paper presents the results obtained after the first year of a monitoring activity carried out at the Ente Nazionale Risi Experimental Station of Castello d\u2019Agogna-Mortara (PV, Italy), where the main terms of water balance have been measured or estimated during the whole crop season. Because there is a substantial lack of data concerning the water balance related to the new water management techniques, the data are of wide interest despite this study covered only one season. The results here presented show that dry seeding-delayed flooding method required a rather similar amount of water respect to the traditional flooding method (2200 mm and 2491 mm, respectively), whereas the aerobic technique required one order of magnitude less water (298 mm), also due to the very shallow depth of the surface aquifer. Since evapotranspiration was nearly the same for the three methods (578 mm, 555 mm, and 464 mm, respectively for traditional flooded, dry seeding-delayed flooding and aerobic methods), percolation was very high in the case of the two flooded methods and very limited in the case of the aerobic cultivation with intermittent irrigations. These results suggest that, if the aerobic cultivation of rice represents a highly effective water-saving technique at the field scale, at the same time if applied on a large scale in traditional paddy areas, as the north-west of Italy, it could be a potential threat for groundwater dynamics, due to the dramatic decrease of groundwater recharge, and in general for traditional landscape conservation and nature protection

A tailored green-approach for managing CSOS in high density urban areas

This study was aimed at providing evidence about the possibility to adopt low-cost \u201cgreen-approaches\u201d for mitigating peak flow, volume and pollution loads of CSO in areas where high density of urbanization occur. In particular, the proposed approach exploits detention, infiltration and self-depuration capacities of natural systems already existing in peri-urban areas, in order to achieve a tailored solution that is suited to the specific context. The findings presented in this work show that combining first-flush tank (FFT) with a constructed wetland system (CW) and finally managing the flows in the receiving water body (RWB) about 90% of pollutant load abatement can be achieved. Therefore, the system can be simultaneously designed to pursue flood risk reduction (abatement of flow peak) and improvement of receiving water quality objectives. Moreover, each component of the proposed system has some peculiarities. For example, CW performs a dual function, i.e. on one hand it cuts the peak of flow thanks to its storage capacity, while on the other hand it reduces the volume thanks to its infiltration capacity. This features are most important especially in the context of \u201chydraulic-hydrologic\u201d invariance measures (that are becoming more and more present at local scale) where the reduction of peak discharge has necessarily to be accompanied by a reduction of volumes. Further improvements can be obtained through the control of flow in the RWB aimed to maintaining a correct ratio between upstream accumulation and downstream flow control according (i) the variability of flow in input to the RWB and (ii) the downstream canal hydraulic capacity. Flow control can be achieved by installing smart gates that operate automatically based on flow sensors and software-based actuators. Finally, the additional ecosystem services that can be provided by the green components of the system combined with the relatively low-cost of the interventions make the approach particularly attractive for small municipalities where large investments are seldom possible

Exploring the performances of a new integrated approach of grey, green and blue infrastructures for combined sewer overflows remediation in high-density urban areas

Most sewage collection systems designed between 19th and early to mid-20th century use single-pipe systems that collect both sewage and urban runoff from streets, roofs and other impervious surfaces. This type of collection system is referred to as a combined sewer system. During storms, the flow capacity of the sewers may be exceeded and the overflow discharged into a receiving water body (RWB) through spillways without any control and remediation. Combined sewer overflows (CSOs) may, therefore, produce serious water pollution and flooding problems in downstream RWBs. Methodologies for a rational management of CSOs quantity and quality share many commonalities, and these two aspects should be considered together in order to maximize benefits and promote local distributed actions, especially in high urban density areas where the space availability for the construction of CSO storage tanks is often a limiting factor. In this paper, a novel strategy to control downstream flow propagation of a CSO as well as to improve its quality is tested on a real case study in the area of the metropolitan city of Milan. The approach is based on the combination of grey, green and blue infrastructures and exploits the integrated storage and self-depuration capacities of a first-flush tank, a constructed wetland and a natural stream to obtain admissible flow rates and adequate water quality in the RWB. The results, evaluated through a modelling framework based on simplified equations of water and pollutants dynamics, show excellent performances for the integrated system, both in terms of flow control and pollution mitigation. The pollution, using biological oxygen demand concentration as a proxy of the whole load, was decreased by more than 90% and downstream flooding situations were avoided, despite the spillway was not regulated. Concerning the economic point of view, from a rough estimate of the costs, the system allows reducing the investment of 30 to 50% in respect to the traditional CSO controls based solely on flow detention tanks. The proposed approach, as well as the modelling framework for its effective implementation, appear strongly scalable in different world contexts and aim to fill the gap between urban and rural environments in the management of stormwater and CSOs, promoting the involvement of the water managers, the irrigation-reclamation agencies and regional authorities

Soil and water bioengineering: practice and research needs for reconciling natural hazard control and ecological restoration

Soil and water bioengineering is a technology that encourages scientists and practitioners to combine their knowledge and skills in the management of ecosystems with a common goal to maximize benefits to both man and the natural environment. It involves techniques that use plants as living building materials, for: (i) natural hazard control (e.g., soil erosion, torrential floods and landslides) and (ii) ecological restoration or nature-based re-introduction of species on degraded lands, river embankments, and disturbed environments. For a bioengineering project to be successful, engineers are required to highlight all the potential benefits and ecosystem services by documenting the technical, ecological, economic and social values. The novel approaches used by bioengineers raise questions for researchers and necessitate innovation from practitioners to design bioengineering concepts and techniques. Our objective in this paper, therefore, is to highlight the practice and research needs in soil and water bioengineering for reconciling natural hazard control and ecological restoration. Firstly, we review the definition and development of bioengineering technology, while stressing issues concerning the design, implementation, and monitoring of bioengineering actions. Secondly, we highlight the need to reconcile natural hazard control and ecological restoration by posing novel practice and research questions