Cultivating alternative spaces – Zagreb’s community gardens in transition: From socialist to post-socialist perspective

This paper provides an in-depth analysis of community gardens in a (post)socialist setting during a time of key changes in their perception and management. Community gardens in Zagreb emerged in two specific economic and socio-cultural contexts and a diachronous approach to the study of urban gardens offers a unique insight into differences and similarities reflecting and contrasting those periods. Semi-structured interviews and non-participatory observation were employed. Results show that community gardens in Zagreb are multilayered places which satisfy diverse needs of the urban residents, including home grown food, socializing, recreation, contact with the nature, and supplementation for low pensions. They can also be seen as examples of heterotopias or alternative spaces during both examined periods. In the socialist period they were secluded, private, pseudo-rural places in a semi-authoritarian, communal, and (supposedly) urban and industrial society. In post-socialist Zagreb, characterized by an uncontrolled and unplanned spatial context reliant on neoliberal market-oriented principles, social insensitivity and exclusion, the new gardens are depicted as beacons of communal involvement, grassroots movements, and the ability of citizens to stand together and make their voices heard.     

Hydrogeochemical stratification of the unconfined Samobor aquifer (Zagreb,Croatia)

In the western part of the city of Zagreb, Croatia, hydrogeochemical and isotopic investigations of the Samobor aquifer were carried out with the aim of determining the differences in hydrogeochemical characteristics at increasing aquifer depths. The aquifer comprises 40-m thick gravelly–sandy deposits, with lenses and interlayers of silt and clay. The analyses have proven that with increasing aquifer depth, there are decreases in groundwater temperature and the values of electrical conductivity and increases in the sodium, iron and manganese concentrations. The δ¹³C distribution shows an evident increase in biogenic carbon concentrations with increasing aquifer depth. The measured specific ¹⁴C activities showed that the deeper part of the aquifer is characterized by slow water exchange, while the shallower part is influenced by current recharge, although the pumping wells located on the well-field downstream penetrate the aquifer fully. A direct exchange of water from the Sava River and groundwater occurs in the near vicinity of the river. This exchange weakens further away, while the difference in hydrogeochemical characteristics between the Sava River water and groundwater increases.     

Changes in flow conveyance and implication for flood protection,Sava River,Zagreb

A low‐lying part of the Croatian capital, Zagreb, is exposed to flood risk from the Sava River. The biggest flood to data, with catastrophic consequences, occurred on 26 November 1964. To protect Zagreb from the Sava River floods, a flood control system was built and set in operation at the end of 1978. The Sava River's flood response changed over time as a result of this constructed system, as well as other anthropogenic and natural influences. The series of maximum annual Sava River stages and discharges measured at the Zagreb gauging station from 1926 to 2004 were analysed. Hydrological methods were used in order to assess Zagreb safety from the Sava River floods in the new conditions. This paper detects changes in high water occurrence in the Sava River near Zagreb. Long‐term stages and linear trends in discharges were examined. A simple technique for the conversion of stages to actual river channel morphology conditions was used. The technique presented in this paper enabled the recalculation of flood probabilities. It is stressed that for a complete understanding of floods, an examination should include the study of parameters of both maximum stages and maximum discharges. Copyright © 2007 John Wiley & Sons, Ltd.     

Amplification of strong ground motion in the city of Zagreb, Croatia, estimated by computation of synthetic seismograms

A hybrid technique consisting of modal summation and subsequent finite differences modelling is applied for the computation of synthetic accelerograms along a profile crossing the city of Zagreb, the capital of Croatia. Assuming the source geometry is known, the amplification properties of the underlying soil may be determined by comparison of synthetics and their response spectra computed for a bedrock model with the ones obtained under the assumption of a realistic laterally varying local model. The peak ground acceleration is larger by a factor of up to 3.5 than the value obtained for the bedrock model. The amplification of the response spectra is most prominent for frequencies below 2 Hz, and increases sharply to the SW from the mapped fault running through the centre of the city.     

Linear Amplification of Horizontal Strong Ground Motion in Zagreb (Croatia) for a Realistic Range of Scaled Point Sources

— The linear amplification of the larger horizontal component of strong ground motion along a selected profile in the city of Zagreb is estimated by examining the synthetic waveforms corresponding to a suite of 16 realistically chosen scaled point sources. The accelerograms, computed for the average bedrock model by modal summation, are propagated through local laterally heterogeneous anelastic models by the finite-difference algorithm. The ratio of peak ground acceleration (PGA) and of the response spectra (RS), obtained by using local and bedrock models, define the PGA and RS amplification AMP(PGA) and AMP(RS), respectively. Even variations of the order of commonly observed uncertainties of only dip and rake angles of the causative fault show that both AMP(PGA) and AMP(RS) vary at some sites by more than a factor of two. It follows that, especially for strongly laterally heterogeneous structures, local effects must be determined for each of the relevant sources considering all associated uncertainties as completely as possible. Such a conclusion certainly holds for the case of the microzonation of Zagreb, where the local geology is quite complex, and the seismicity is not confined to a single seismic source zone.