2 research outputs found
Physical Model Study of Living Breakwaters: Stability and Ecological Analysis of Green-Grey Hybrid Structure Concept for Climate Change Adaptation
No full textA vast majority (84%) of all countries in the world have coastlines and 80-100% of their population resides within 100 km of the shoreline. Studies show a major growth in population in low-elevation coastal zones and a scenario of rising sea level may force millions of people to relocate. To deal with the increased frequency of extreme events and sea level rise, coastal vegetation (mangroves, salt marches and coral reefs) has been observed to act as an effective natural barrier. Coral reefs are believed to reduce upto 90% of wave energy but increasingly warming oceans and acidification are destroying this barrier by coral bleaching. Apart from a social, ecological and environmental damage, this will also result in an increase in environmental loading on coastal structures. This study focuses on the development of a climate change adaption measure for existing structures on the principles of Sustainability. In order to do so, a representative existing breakwater at Kiberg Norway is chosen. A brief ecology study of the area is conducted and based on economic value and vulnerability, Red King Crabs and Capelin are chosen as target species. A green-grey hybrid structure consisting of an existing breakwater with additional Artificial Reefs (AR) as toe elements is hypothesized to be the suitable solution. However, hydraulic performance of AR is still not understood properly and to utilize them to enhance the stability of existing breakwater may create tension between hydrodynamic and ecological performance. In order to investigate the hydraulic behaviour of hybrid structure, physical model study is conducted. A traditional method of using transmission coefficient to quantify energy dissipation over submerged/non-submerged AR breakwater is not suitable for this hybrid structure. Therefore, stability of existing breakwater is measured in terms of damage level (Ahrens and Cox, 1990) and indirectly by turbulent kinetic energy (Mukaro and Govender, 2013) for 9 plunging and 6 surging wave conditions. Four configurations of experimental setup are finalized with four types of AR units (AR1, AR2, AR3 and AR4) and in total 175 tests are carried out. Behaviour of breaking and non-breaking waves is observed to be different especially over config-3 and config-4. Landward vortex and breaker tongue are not fully developed in config-3 due to depth limited scenario. Additional non-linearities in the flow, due to interaction of incoming and secondary waves, are observed for config-4, which resulted into higher reflection coefficient than other configurations. Behaviour of a hybrid structure can be predicted by Van der Meer stability formulas for plunging and surging waves at lower wave heights. However, higher waves exhibit greater damage reduction and formulas show larger deviations. Results indicate that one row of AR placed as toe, does not reduce much damage (10%). A comparison of all the configurations indicate that config-3 and config-4 show an average damage reduction of 38% and 51% respectively. Critical stability number of config-4 (i.e. 1.45) is lower than of config-1 (i.e. 1.7), indicating that disturbing forces are becoming weaker due to the presence of AR. Residence time of wave on reef is believed to be of much importance and with a 15m reef length a damage reduction upto 45% is observed. Reef porosity is observed to have dependency on placement location and reef length. Ecological performance is predicted to increase by 25% in 10 years of construction. However, differently chosen indicator species might have shown better results. It is concluded from the study that green-grey hybrid structures can be a suitable short-term climate change adaption measure.Coastal and Marine Engineering and Management (CoMEM
Independent and combined effects of improved water, sanitation, and hygiene, and improved complementary feeding, on child stunting and anaemia in rural Zimbabwe: a cluster-randomised trial.
No full textBACKGROUND: Child stunting reduces survival and impairs neurodevelopment. We tested the independent and combined effects of improved water, sanitation, and hygiene (WASH), and improved infant and young child feeding (IYCF) on stunting and anaemia in in Zimbabwe. METHODS: We did a cluster-randomised, community-based, 2 × 2 factorial trial in two rural districts in Zimbabwe. Clusters were defined as the catchment area of between one and four village health workers employed by the Zimbabwe Ministry of Health and Child Care. Women were eligible for inclusion if they permanently lived in clusters and were confirmed pregnant. Clusters were randomly assigned (1:1:1:1) to standard of care (52 clusters), IYCF (20 g of a small-quantity lipid-based nutrient supplement per day from age 6 to 18 months plus complementary feeding counselling; 53 clusters), WASH (construction of a ventilated improved pit latrine, provision of two handwashing stations, liquid soap, chlorine, and play space plus hygiene counselling; 53 clusters), or IYCF plus WASH (53 clusters). A constrained randomisation technique was used to achieve balance across the groups for 14 variables related to geography, demography, water access, and community-level sanitation coverage. Masking of participants and fieldworkers was not possible. The primary outcomes were infant length-for-age Z score and haemoglobin concentrations at 18 months of age among children born to mothers who were HIV negative during pregnancy. These outcomes were analysed in the intention-to-treat population. We estimated the effects of the interventions by comparing the two IYCF groups with the two non-IYCF groups and the two WASH groups with the two non-WASH groups, except for outcomes that had an important statistical interaction between the interventions. This trial is registered with ClinicalTrials.gov, number NCT01824940. FINDINGS: Between Nov 22, 2012, and March 27, 2015, 5280 pregnant women were enrolled from 211 clusters. 3686 children born to HIV-negative mothers were assessed at age 18 months (884 in the standard of care group from 52 clusters, 893 in the IYCF group from 53 clusters, 918 in the WASH group from 53 clusters, and 991 in the IYCF plus WASH group from 51 clusters). In the IYCF intervention groups, the mean length-for-age Z score was 0·16 (95% CI 0·08-0·23) higher and the mean haemoglobin concentration was 2·03 g/L (1·28-2·79) higher than those in the non-IYCF intervention groups. The IYCF intervention reduced the number of stunted children from 620 (35%) of 1792 to 514 (27%) of 1879, and the number of children with anaemia from 245 (13·9%) of 1759 to 193 (10·5%) of 1845. The WASH intervention had no effect on either primary outcome. Neither intervention reduced the prevalence of diarrhoea at 12 or 18 months. No trial-related serious adverse events, and only three trial-related adverse events, were reported. INTERPRETATION: Household-level elementary WASH interventions implemented in rural areas in low-income countries are unlikely to reduce stunting or anaemia and might not reduce diarrhoea. Implementation of these WASH interventions in combination with IYCF interventions is unlikely to reduce stunting or anaemia more than implementation of IYCF alone. FUNDING: Bill & Melinda Gates Foundation, UK Department for International Development, Wellcome Trust, Swiss Development Cooperation, UNICEF, and US National Institutes of Health.The SHINE trial is funded by the Bill & Melinda Gates Foundation (OPP1021542 and OPP113707); UK Department for International Development; Wellcome Trust, UK (093768/Z/10/Z, 108065/Z/15/Z and 203905/Z/16/Z); Swiss Agency for Development and Cooperation; US National Institutes of Health (2R01HD060338-06); and UNICEF (PCA-2017-0002)
