With the expansion of cities and the construction of roads and highways, land otherwise permeable to water, are increasingly made resistant to rainfall absorption, the reduction of forest lands and pastures, growing at an alarming speed, also adds to the severity of the problem. Therefore, with the increase of impermeable lands in the cities on the one hand and with the decrease of pasture lands in rural areas on the other, floods increase in terms of volume and number. Floods are only natural phenomena and are as old as nature itself. What is unnatural is man, s insistence on occupying flood plains and also his ignorance or forget-fullness regarding their recurrences. Therefore, if natural phenomena are well understood and residents are trained in using such plains, damages and casualties can be reduced drastically. similarly, advanced technology can be employed to stop or reduce the occurrences of such catastrophic but natural phenomena.In this paper, we studied floods and especially floods in province of Esfahan. In the province of Esfahan floods is a one of most natural phenomena.

Mansoon rains, floods and other disaster, all of these started in July 26, 2010. Pakistan was affected by the worse flood in the recent decade.Nearly, one fifth of the entire landmass and more than 20 millions of the population were directly affected in this flood.More than 1.9 millions houses and many infrastructures including transportation system, health facilities and schools were damaged or destroyed.About a quarter of the country’s harvest has been destroyed and the next year’s harvest seems to be threatened too. Estimated Sindh’s agricultural loss is at least US$1 billion which is quite high for a country with low GDP. Much of the cotton crop as one of the major Pakistan’s export has been wiped out. The social and economic effect of this tragedy seems to be already more than all the three recent major natural disasters namely Indian Ocean Tsunami in 2004, Southeast Asian earthquake in 2005 and Haiti earthquake in 2010.

Natural hazards, including floods, are one of the basic problems of rural settlements in Iran. Indigenous knowledge of dealing with floods and coexisting with them has existed in Iran for a long time. In this research, the effectiveness of native methods has been evaluated by examining local methods of dealing with and exploiting flood water resources and comparing them with modern methods in Dashtiari and Chabahar regions. Investigations have been done through library studies, conversations with local people, field observations and data analysis. In these areas, indigenous knowledge is used through the construction of Degaar and Hootak structures for the purpose of exploiting and building Tonpak structures in order to deal with floods and reduce the vulnerability of residential houses. These structures have the same function as check dams, flood spreading structures and dams and construction based on height code in order to reduce vulnerability. According to the investigations and results, the performance of structures based on local knowledge is more suitable in the studied area, and among them, construction on tonpaks for residential houses has created safety against flood inundation. Hotaks have worked very well in the region as a source of flood water storage for villages.

In order to analyze the floods of the Larestan area, the rain days with 0.1 millimeter or more were obtained from the Iranian Meteorological Organization for the 1960-2005 period. First the plenty of rainy days were divided to groups based on their continuation, Then made known the highest region rains during the statistical period, after that assigned the probable rain and return period of torrential Larestan's rains.The result of research showed that:1) The most important cause of happening of Lar floods is intensity and duration of rain and also topography of region.2) The mainly Lar flood way that damage the ancient texture of city is Varband flood way and the new texture of city is Asad strait's flood way.

The main aim of the current paper is to discuss the important effective variables, particularly synoptic patterns, in creating flood in Masoule basin using flood discharge data in Komadoul station during 20 year period (1984-2003). To achieve the aim, daily average and instantaneous maximum of discharge in mentioned station were used. Data accuracy was done using the data for Chomesghal station and technical report from the unexpected events section in the area. In the study period, among the 181 identified flash flood events, 61 events were chosen between years 1996-2003. Then, based on the most effective creator parameters, they were classified into two main groups; events which were due to atmospheric instability and synoptic patterns and those occurred as a result of combination rainfall and short length of main channel. About 51% and 49% of destructive floods in the study area belong to the first and second groups, respectively. Using the synoptic maps of surface level, 700 and 500 HP, and based on the position of cyclone and anticyclone on basin and their movement over the moisture resources, three specified patterns was distinguished. The cyclonic systems come from Mediterranean Sea and Black Sea, while the anti-cyclonic models mainly come from Caspian Sea and rarely from Black Sea. The result of the research also showed that mentioned systems, based on their characteristics or establishment period on the basin, have been made flood with different magnitude. Among the sampled events, 34, 13, and 14 events were adjusted with one, two and three consecutive day rainfall, respectively. From the temporal point of view, distribution of flood shown that most of them were occurred between Sept. and Oct., late winter and early spring.

INTRODUCTION: Since the presence or absence of various hazards in a geographical context is a relative matter, the resilience of cities to natural hazards is one of the important issues in urban planning and management, therefore, the objective of the present study is to assess the vulnerability of Konarak city to hazards caused by urban floods. METHODS: In this descriptive-analytical study, field survey and a researcher-made questionnaire were used to collect data. The statistical population of the research included citizens living in Konarak city, 380 of whom were selected using the Cochran formula using a simple random sampling method. The data were analyzed with GIS software. FINDINGS: According to the findings, the vulnerability of Konarak city to floods was assessed in terms of physical-infrastructural, social, economic, and institutional indicators in all neighborhoods. In the neighborhoods of Kalk Bazar, Surg, and Kohiyan, the physical-infrastructure index was higher than the average, which indicates the unfavorable condition of these neighborhoods in terms of physical conditions, socially, the lowest average was for Nazarabad and Surg neighborhoods, also, economically, the lowest average was for Nazarabad, Surg, and Baluchan neighborhoods, and institutionally, the lowest average was for Nazarabad, Surg, and Kohiyan neighborhoods. CONCLUSION: The results showed that neighborhoods of Nazarabad, Surg, Baluchan, and Kohiyan have a very unfavorable situation in terms of environmental vulnerability, respectively, while neighborhoods of Zargaran, Kalk Bazar, and Saheli Markazi have a relatively more favorable situation.

IntroductionThe importance of heavy rainfall and its consequences have caused this phenomenon to be of special importance in environmental planning and water resources management. Using statistical methods and the discharge data of the Dez river, the heavy floods of this river were extracted to identify the effective factors in their creation. Among all systems leading to heavy rains, the Sudanian system has been the main factor of moisture advection in the lower layer of the troposphere with its expansion to the north and northeast. Due to its thermal characteristics, this system has been prone to receive considerable moisture from the surrounding warm seas. This system has provided the necessary conditions for the creation of surface instabilities in most transitional systems independently and in a smaller number in the integrated state with the Mediterranean system. In the investigation of the middle layer of the troposphere in all the systems that led to the floods of 1993 and 2005, it was observed that the anticyclone cell of Arabia was established over the Arabian and Oman seas and the east of the Arabian Peninsula by moving eastward. In this situation, a very deep trough has formed in the west of Iran, and the southern end of the trough has extended to southern Sudan and northern Ethiopia. The eastward movement of high pressure in Arabia and the significant southward expansion of the Mediterranean trough and the formation of a low-altitude center over Iraq is the most suitable pattern for the heavy cloud rains in the basin. Materials and MethodsIn terms of geographic location, the Dez basin is limited between 48°10' to 50°21' east longitude and 31°34' to 33°7' north latitude. The studied area is a part of the Dez river basin, which is located almost in the middle part to the end part. After the Karun branch of one of the largest and longest Dez rivers, Dez is formed from two main branches named Caesar and Bakhtiari, and after leaving the mountainous region north of Andimeshk and Dezful, it enters the plain of Khuzestan. For comprehensive and accurate interpretation of pressure systems and assessment of their environmental effects on the earth, the maps of the earth's surface and level of 500 hPa are very efficient. In most cases, the wind direction and temperature distribution at the 500 hPa level are completely affected by the topographic arrangement of the geopotential height at the 500 hPa level. Geopotential height maps are one of the most important and efficient atmospheric maps in synoptic analysis and interpretation. Heavy rains on representative days are analyzed, interpreted, and explained. Two statistical and synoptic methods were used for a more detailed investigation of the synoptic situation of heavy rains in the Dez river basin. In the statistical part, factor analysis, which is one of the widely used statistical methods in climatology, was used, and in the synoptic part, maps of different atmospheric levels were extracted and analyzed using Gardes software for the specified days. To determine the members of each group, the correlation of the scores of each factor with the sea level pressure map in the time period (1964-2020) was calculated, and the members of each group were determined. To determine the representative days, the correlation of the SLP maps of the days of each group was used, and the day that had a high correlation with more days was selected as the representative day. To perform factor analysis, the elements of the database were transferred from the Excel environment to the S-Plus2008 software environment, and then by performing various inferential analysis calculations, the most suitable method was selected to identify the main and effective factors. Results and DiscussionAs can be seen, the heavy rains of 2013 lasted for 6 days, and the system of 2011 lasted for 7 days. Of course, as mentioned, in some systems, days before or after the end of the activity period of the main system, scattered rains, even with high intensity, have been recorded in some stations. But these scattered rains are considered local rains. The highest peak flow rate of 8556 m3 belongs to the system in February 2013. This system has lasted for 4 days. It took 31 hours to reach the peak of the flood. ConclusionIn the investigation of the middle layer of the troposphere in all the systems that led to the floods of 1993 and 2005, it was observed that the Arabian anticyclone has been established over the Arabian and Oman seas and the east of the Arabian Peninsula by moving eastward. In this situation, a very deep trough has formed in the west of Iran, and the southern end of the trough has extended to southern Sudan and northern Ethiopia. Therefore, the eastward displacement of the high pressure in Arabia and the significant southward expansion of the Mediterranean trough, and the formation of a low-altitude center cut over Iraq is the most suitable pattern for heavy cloud precipitation in the Dez basin. The peak discharge of floods with a delay of 12 to 24 hours from the day of peak rainfall has created a very intense discharge system. So, the floods of 2005 with a peak discharge of 8556 m3 s-1 and the flood of 1993 with a peak discharge of 4022 m3 s-1, while they were very heavy floods, there were two study periods.

Background and Objectives: Investigation of the basin floods in most cases is only based on flood peak trend analysis using conventional parametric or non-parametric (ordinary linear regression (OLR), Mann-Kendall, Sen) tests. In addition to the primary restrictions, these methods usually are provided to estimate the conditional mean or median and do not consider different quantiles while assessing the appropriate domain of conditional quantiles leads to a very good understanding of trend pattern. The objective of this study is using quantile regression (QR) to estimate the time trend (conditional quantiles) of flood variables including peak, volume and duration that result in better understanding of variables of annual maximum floods (AMF).Materials and Methods: In the first step, AMF time series of Taleh-Zang hydrometry station located in southwestern Iran was considered and the time series of AMF peak flow, volume and duration were extracted.In the next step, trend analysis of AMF variables time series performed using OLR and their efficiency were investigated using fitting precision criteria, statistical significant test and residuals analysis. Then, QR lines were estimated for AMF variables trend analysis considering (0.05-0.95 with 0.01 steps) and their fitting precision criteria and statistical significant test were determined. Considering selected quantiles0.05, 0.15, 0.25, 0.35, 0.45, 0.55, 0.65, 0.75, 0.85 and 0.95 QR lines were plotted for AMF variables.Results: The OLR results indicated positive trends for AMF variables but complementary analysis showed that this method cannot be a suitable analysis for AMF variables trend analysis in this research. The QR application resulted in wide range of line slopes in comparison with OLR method. For all three variables 15% of estimated line slopes using QR were more than their estimation by OLR. Investigation of QR lines indicated statistical significant regression lines of AMF volume were related to upper bound quantiles while for AMF peak and duration were related to quantiles mid bound plus upper bound and there were a few acceptable QR lines for lower bound for all three variables so that for AMF peak, volume and duration 59%, 31% and 73% of QR lines were statistical significant considering 0.05 significance level. The fitting precisions of QR lines of upper and mid bounds were more than lower bound.Conclusion: The quantile regression can be used without affecting the limitations of conventional methods for AMF variables trend analysis to access a wider range of applied trend analysis. Also there are certain differences between AMF variables trend slopes (especially for upper bound quantiles) in comparison with those estimated with OLR therefore the OLR method could not be a useful tool for trend assessment of extreme events. The results show trend of extreme flood variables are significantly more than those estimated by OLR and in other words the OLR led to underestimation of AMF variables increasing trend slope.Moreover, multiple variables flood trend analysis using QR revealed that considering significant trends for three flood variables, the flood potential risk are significantly more than those estimated using single variable analysis.

Natural debris floods travel in straight and meandering courses. The flow behaviour greatly depends on the volume fractions of solid and fluid, as well as on their dynamic interactions with the channel geometry. For the quasi three-dimensional simulations of flow dynamics and mass transport of these floods through meandering and straight channels, we employ a two-phase debris flow model to carry out simulations for debris floods within straight and sine-generated meandering channels of different amplitudes. The results for different sinuous meandering paths are compared with that in the straight one in terms of phase velocity, downslope advection and dispersion, depths of the maxima, deposition of mass, position of front and rear parts of the solid and fluid phases, and also the flow dynamics out of the conduits. The results reveal the slowing of the flow and increase of momentary deposition of the mixture mass in the vicinity of the bends along with the increasing sinuosity. The numerical experiments are useful to better understand the dynamics of debris floods down meandering channels as seen in the natural paths of the rivers as well as already existing channels like episodic rivers in hilly regions. The results can be extended to propose some appropriate mitigation strategies.

Floods are one of the natural hazards that cause a lot of damage in cities. Resilience is one of the ways to reduce the effects of natural hazards. In this study, the material resilience of Isfahan against urban floods was investigated. First, Gis layers of 15 areas of Isfahan city and materials were prepared and the problems of each area were extracted. Then factor analysis was performed on them and the factors affecting the materials were identified. The relevant questionnaire was completed by 35 experts to assess material problems and related tests were performed on them. According to the results, a total of 4 factors explain more than 90% of the variance of the data. The first factor with 50.51% was called slope correction, the second factor with 18.45% was called material reopening, the third factor with 13.14% was called material cleaning, and the fourth factor with 8.2% was named as dredging. The results of t-test showed that according to the average of community 3 in all three social, physical and managerial-institutional criteria, the material situation of Isfahan is at a desirable level. In the community of 5, all three material criteria of Isfahan are far from the desired conditions. Considering that the materials of regions 15, 6, 12 and 10 have the least problems, respectively, it can be said that these regions have the highest resilience and the materials of regions 9, 8, 1 and 13 have the most problems. They have the least resilience.