Dimitrios Myronidis

An Integration of Statistics Temporal Methods to Track the Effect of Drought in a Shallow Mediterranean Lake

During the last decades, a progressive decrease of water level in shallow Mediterranean lakes was recorded. This contribution tried to identify whether the rapid decrease of the Lake Doiran (N. Greece) water level was associated with drought phenomena. Drought characteristics over the study area were revealed by employing the Standardized Precipitation Index (SPI) in different time scales. Negative trends of the SPI drought index were recognized by using the Mann-Kendall non parametric test, which suggested that drought conditions were intensified through time. The impact of the intense drought phenomena to the lake’s water level became evident by employing the Pearson correlation coefficient. A year ahead forecast of future drought conditions was achieved by training a hybrid ARIMA/ANN model. The predicted results indicated that mild drought conditions should be anticipated in the future and the water level would further drop as well.

Streamflow and Hydrological Drought Trend Analysis and Forecasting in Cyprus

The persistent water shortage in Cyprus has been alleviated by importing freshwater from neighbouring countries, and severe droughts have been met with financial reimbursement from the EU at least twice. The goal of this research is to investigate and perform short-term forecasting of both streamflow and hydrological drought trends over the island. Eleven hydrometric stations with a 34-year common record length of the mean daily discharge from 10/1979 to 09/2013 are used for this purpose, with the relevant upstream catchments considered to represent pristine conditions. The Streamflow Drought Index (SDI) successfully captures the hydrological drought conditions over the island, and the performance of the index is validated based on both the historic drought archives and results from other drought indices for the island. The Mann–Kendall (M-K) test reveals that the annual and seasonal time series of the discharge volumes always illustrate a decreasing but insignificant trend at a significance level of a = 0.05; additionally, the decrease per decade in the average annual streamflow volume based on Sen’s slope statistic is approximately −9.4%. The M-K test on the SDI reveals that drought conditions intensified with time. Ten autoregressive integrated moving average (ARIMA) models are built and used to forecast the mean monthly streamflow values with moderate accuracy; the best ARIMA forecast model in each catchment is derived by comparing two model-performance statistical measures for the different (p,d,q) model parameters. The predicted discharge values are processed by the SDI-3 index, revealing that non-drought conditions are expected in most catchments in the upcoming three months, although mild-drought conditions are anticipated for catchments 7, 8 and 9.

Post-Evaluation of Flood Hazards Induced by Former Artificial Interventions along a Coastal Mediterranean Settlement

AbstractInappropriate artificial activities can escalate the frequency, the intensity, and the magnitude of floods and aggravate their aftermath. Additionally, urban sprawl is responsible for increasing the manifestation of flood events in coastal areas. In this study, the effects of diachronically formulated artificial stream-channel modifications and registered urban expansion on flood hazards were quantified. Initially, land-use changes were monitored over time and a detailed field topographic survey was performed. The peak discharge for a 50-year return period storm event was found to be equal to 42.3  m3/s, as computed by the rational method. A steady flow analysis with a mixed flow regime was then performed so as to compute the water velocity and surface runoff elevation at 49 discrete cross sections for the years of 1945, 1981, and 2009, whereas the inundation extent was found equal to 12,208, 10,519, and 9,530  m2 for the same years by implementing another model. Although the water level and inund...

Utilising 3D solid modelling tools for simplified designing of a small concrete gravity dam

Small concrete gravity dams play a dominant role in controlling the sediment production and flood phenomena at torrential streams. Since 1931, the Greek Forest Service has established hundreds dams of such type in the mountain regions all over the country with practically zero failures. The objective of this article is to illustrate a 3D solid modelling procedure which could be employed on different computer aid design software so as to accomplish a simplified designing of a small concrete gravity dam with structural height and length of 4.2m and 13.14m respectively based on the Greek Forest Service guidelines. Furthermore, the material quantities, which are necessary for the dams construction, are easily calculated by using the same techniques. The concrete and excavation volumes, which are necessary for the dams construction, are estimated to 75.43m³ and 27.42m³ respectively. Although the dam designing guidelines may differ among countries, the reader can easily utilise 3D solid modelling tools and modify the gravity dam design according to its country standards.