Drainage Network Density Research Articles

Analyzing water level variability in Odisha: insights from multi-year data and spatial analysis

A comprehensive analysis of long-term water level trends is essential for freshwater sustainability. Given that Odisha heavily relies on agriculture, the monitoring and management of groundwater and its fluctuations are imperative for ensuring future sustainability in the state. Here, we analyzed the trend in Groundwater using water level data for a 30-year period (1990–2020) for the entire Odisha region. Moreover, to determine the long term variability, critical zones of future groundwater variability and controlling parameters of the water level change, we used spatio-temporal water level data of 746 locations. Water level rise of coastal districts during post-monsoon (POM), corresponds to the intensity of rainfall received, thus rising, however other districts of Odisha, showing decline in water level during the same season is due to shortage of rainfall, increase in population at a sudden, and over pumping due to industrial activities. Similarly, during pre-monsoon (PRM), water level shows an increasing trend in hard rock terrain of Odisha implying rabi crop irrigation, high density drainage network and lesser population density. Feature selection techniques were used in this study to know the parameters controlling most to this water level fluctuation in the entire Odisha state. Precipitation followed by landuse & landcover, lithology and population density are controlling the most for the long term water level change. Drainage, elevation, lithology and slope are positively related to the water level change while others are negatively related. It is also inferred that the districts like Mayurbhanj, Sundargarh, Keonjhar, Kandhamal, Boudh, Dhenkanal, Gajapati, Koraput and Kalahandi contain most of the high critical zone concerning future availability of groundwater while most of the coastal regions are safe.

Data-driven urban configuration optimization: An XGBoost-based approach for mitigating flood susceptibility and enhancing economic contribution

The indiscriminate evolution of urban configurations aggravates flood vulnerabilities, threatening sustainable urban expansion. Present methodologies fall short in supplying urban planners with flood mitigative strategies centered on urban configuration facets. Leveraging the power of the XGBoost algorithm, this study posits an advanced optimization schema, adroitly balancing the dual objectives of mitigating urban flooding and enhancing economic growth, with minimal disruption to established urban layouts. Shenzhen serves as the investigative ground, where the model displays exceptional accuracy, resilience, and interpretability in predicting Pluvial Flooding Susceptibility (PFS) and Economic Contribution (EC). Model interpretation divulges the profound influence of three-dimensional urban configuration elements, primarily the Building Congestion Degree, on PFS and EC. Pareto solution exploration for multi-objective optimization unveils the ideal urban configuration interval. To minimize PFS while maximizing EC, the research suggests pertinent measures: augmenting vegetation density, regulating the impervious coverage ratio within 50–70%, limiting two- and three-dimensional building density thresholds, and moderately escalating urban drainage network density. Additionally, it encourages a comprehensive appreciation of function-oriented land usage and intrinsic site topographical characteristics to reconcile varied urban development goals during planning. By fusing data-derived insights with multi-objective optimization, this research anticipates influencing urban planning models, thus enhancing decision-making related to urban configuration and fostering flood-resilient, sustainable, and economically prosperous urban habitats.

Integrated GIS and analytic hierarchy process for flood risk assessment in the Dades Wadi watershed (Central High Atlas, Morocco)

Flood risk assessment is crucial for delineating flood hazard zones and formulating effective mitigation strategies. Employing a multi-criteria decision support system, this study focused on assessing a Flood Risk Index (FHI) at the Dades Wadi watershed scale. Seven main flood-causing criteria were broadly selected, namely flow accumulation, distance from hydrographic network, drainage network density, land use, slope, rainfall, and permeability. The relative importance of each criterion prioritized as per their contribution toward flood risk, which were employed a blend of the Analytical Hierarchy Process (AHP) and Geographic Information System (GIS)/Remote Sensing (RS) techniques. The significance of each criterion was determined based on their contribution to flood hazard, and their relative importance was established through an AHP pair-wise comparison matrix. The efficacy of the AHP model was performed with a consistency ratio of 0.08, which indicated that each flood criterion weight is confirmed. Among the flood-causing criteria, the hydrologic flow accumulation factor was identified as the most influential (weight: 3.11), while permeability exhibited the least prominence (weight: 0.58). Approximately 40.36% of the total area, equivalent to around 1319, 89 km2, was concentrated within very high flood-risk zones situated near rivers. In contrast, an area of approximately 399,943 km2 (56.33%) exhibited a low to very low flood risk zone. The validation of the FHI map encompassed the application of the Receiver Operating Characteristic Curve (ROC) technique, revealing an Area Under the Curve (AUC) of 85%.

Approaches to assessment of the total nitrogen and phosphorus inflow into the Neva Bay using the example of the Krasnenkaya River and the Dudergofskiy Channel

There is a necessity for the Baltic Sea environmental protection against toxic contamination and anthropogenic eutrophication. The protection proposes an annual evaluation of the total nitrogen and phosphorus income into the Neva Bay from St. Petersburg. The evaluation takes into account the substances, which inflow into the Neva Bay with water of the Neva River and its spill streams. However, an additional source of the substances is the substances inflow by runoff from watercourses entering Neva Bay. The watercourses do not have monitoring points. There is an additional source of the elements, which is the nonpoint dispersed outflow of the substances from the Neva Bay shore. The paper presents the evaluation methodology of the nitrogen and phosphorus outflow of catchment areas without monitoring points and the methodology verification result. The methodology uses data of analogous watersheds with close spatial structure, drainage network density, and average slope and so on. The methodology includes application of GIStechnologies and cluster analysis. The paper presents some results of the total nitrogen and phosphorus income into the Neva Bay with runoff of two small watercourses.

Identification of sustainable urban settlement sites using interrelationship based multi-influencing factor technique and GIS

Evaluation of a site suitability for sustainable urban settlement growth is crucial. A system for evaluating an interaction between the factors must be established to assure that critical site selection interrelationships are not neglected. To solve this problem, the proposed methodology was evaluated to identify a suitable site for sustainable residential development in Nashik, India. The Geographic information system (GIS)-based multi-influence factor (MIF) approach is used in this study to find ideal locations for future urban settlement. The assessment was based on 11 factors including vegetation, elevation, land use, industry, drainage network, slope, water bodies, road, health services, railway station and population density. The sustainable site suitability was delineated by aggregating all considered factors and their associated MIF weights using the interrelationship between the factors. The results showed that 27.26% of research area was not ideal for settlement development, 16.82% was low suitable, 30.65% was moderately suitable, 16.48% was highly suitable and 8.77% was very highly suitable. Most of the suitable sites were located near the existing habitant area, and major roads. The suitability sites were validated using receiver-operating characteristic (ROC), and area under curve (AUC) value of 0.895 indicated that the model was effective. Sensitivity analysis revealed that the distance from road, drainage network, and health services are the dominant for selecting the optimal location of settlement development in research area. The findings of the delineated ideal areas for the intensive urban settlement development will be helpful to planners and policy makers for sustainable urban growth in the near future.

Urban Floods and Suitability Analysis of Rainwater Harvesting Potential Areas in Lahore City, Pakistan

There is a growing threat of urban flooding, particularly in Pakistan that needs attention and requires effective management strategies. The chief trigger for urban flooding is the rapid and unplanned urbanization in areas where impermeable surface inhibits rainwater diffusion and changes the natural water flow. In many developed countries, a technique of rainwater harvesting is implemented as a sustainable strategy to manage urban stormwater. Most studies and projects chiefly focused on the potential use of the Rainwater harvesting technique for water conservation in arid and semi-arid climates. In the present work, GIS and remote sensing methodologies are utilized for the suitability of rainwater harvesting structures. This study was conducted in Lahore, the second most populated city of Pakistan and the capital of Punjab. Generally, the water harvesting technique depends on topographical areas with water accumulation, where there is an availability of open spaces in the form of green areas and barren lands, rainfall, drainage network density, and rainfall distribution, particularly in the urban environment. The SRTM DEM data were used for finding high water accumulated areas, and the Landsat OLI image is used to retrieve land use information i.e. vacant land and open green spaces, existing drainage network density, and rainfall distribution. All these layers were integrated through AHP to detect the potentially suitable sites for the construction of rainwater harvesting structures. Results concluded 94 suitable sites with categorization from highly to critically suitable for the construction of rainwater harvesting structures in which 6 were highly suitable areas in Data Gunj Bakhsh Town and Ravi Town. Besides, residential areas are having a maximum site suitability percentage, followed by roads, agricultural and open spaces in the area under consideration. Considering the suitable sites, further rainwater harvesting methods can be identified in the study area to alleviate urban flooding and improve the urban environment.

Flood Hazard Index Application in Arid Catchments: Case of the Taguenit Wadi Watershed, Lakhssas, Morocco

During the last decade, climate change has generated extreme rainfall events triggering flash floods in short periods worldwide. The delimitation of flood zones by detailed mapping generally makes it possible to avoid human and economic losses, especially in regions at high risk of flooding. The Taguenit basin, located in southern Morocco, is a particular case. The mapping of the flood zones of this basin by the method of the Flood Hazard Index (FHI) in a GIS geographic information systems environment was based on the multi-criteria analysis, taking into consideration the seven parameters influencing these extreme phenomena, namely rainfall, slope, flow accumulation, drainage network density, distance from rivers, permeability, and land use. Average annual rainfall data for 37 years (1980 to 2016) was used in this study for floodplain mapping. A weight was calculated for each parameter using the Analytical Hierarchy Process (AHP) method. The combination of the maps of the different parameters made it possible to draw up a final map classified into five risk intervals: very high, high, moderate, lower and very lower presenting, respectively, 8.04%, 20.63%, 31.47%, 15.36%, and 24.50% of the area of the basin. The reliability of this method was tested by a Flood susceptibility analysis. The results generated by the Flood Hazard Index (FHI) model are similar to those of previous historical events. Realistic and applicable solutions have been proposed to minimize the impact of these floods as much as possible.

Morphometric analysis for flood flow formation feature identification (on example of Ulaanbaatar agglomeration)

Water flows with significant flow rate feature a high destructive force and can lead to catastrophic consequences. Fluvial processes caused by uneven distribution of rain precipitation over the area pose risks to the developed inland foothill territories. The purpose of this study is to carry out a quantitative morphometric analysis of the territory in order to identify the formation features of flood flows. The analysis and ranking of catchment basins are performed using a basin approach. On the basis of SRTM images and the use of stock cartographic material in the GIS program the authors have built specialized electronic maps that allow to obtain quantitative parameters reflecting the morphometry of the basins under analysis including basin geometry, drainage network and terrain relief. On example of the Ulaanbaatar agglomeration territory it is shown how initial morphometric parameters of basins and watercourses (length, width, area, perimeter, erosion dissection, drainage network density, terrain relief coefficient, Melton coefficient, etc.) form the features of flood flow. For developed territories, the initial data on the catchment basin morphometry constitute the basis for compilation of specialized maps to be used in planning and construction. The combination of morphometric indicators on the territory of the Ulaanbaatar agglomeration indicates that there is possibility of large flood formation and development of dangerous mudstone flows in some catchment basins.

Modeling the Soil Erosion Regulation Ecosystem Services of the Landscape in Polish Catchments

In this study, the soil erosion regulation ecosystem services of the CORINE land use/ land cover types along with soil intrinsic features and geomorphological factors were examined by using the soil erosion data of 327 catchments in Poland, with a mean area of 510 ± 330 km2, applying a multivariate regression modeling approach. The results showed that soil erosion is accelerated by the discontinuous urban fabric (r = 0.224, p ≤ 0.01), by construction sites (r = 0.141, p ≤ 0.05), non-irrigated arable land (r = 0.237, p ≤ 0.01), and is mitigated by coniferous forest (r = −0.322, p ≤ 0.01), the clay ratio (r = −0.652, p ≤ 0.01), and the organic content of the soil (r = −0.622, p ≤ 0.01). The models also indicated that there is a strong relationship between soil erosion and the percentage of land use/land cover types (r2 = [0.62, 0.82, 0.83, 0.74]), i.e., mixed forest, non-irrigated arable land, fruit trees and berry plantations, broad-leaf forest, sport and leisure facilities, construction sites, and mineral extraction sites. The findings show that the soil erosion regulation ecosystem service is sensitive to broadleaf forests, rainfed agriculture, soil water content, terrain slope, drainage network density, annual precipitation, the clay ratio, the soil carbon content, and the degree of sensitivity increases from the broadleaf forest to the soil carbon content.

Urban Floods and Suitability Analysis of Rainwater Harvesting Potential Areas in Lahore City, Pakistan

There is a growing threat of urban flooding, particularly in Pakistan that needs attention and requireseffective management strategies. The chief trigger for urban flooding is the rapid and unplanned urbanization in areaswhere impermeable surface inhibits rainwater diffusion and changes the natural water flow. In many developedcountries, a technique of rainwater harvesting is implemented as a sustainable strategy to manage urban stormwater.Most studies and projects chiefly focused on the potential use of the Rainwater harvesting technique for waterconservation in arid and semi-arid climates. In the present work, GIS and remote sensing methodologies are utilized forthe suitability of rainwater harvesting structures. This study was conducted in Lahore, the second most populated cityof Pakistan and the capital of Punjab. Generally, the water harvesting technique depends on topographical areas withwater accumulation, where there is an availability of open spaces in the form of green areas and barren lands, rainfall,drainage network density, and rainfall distribution, particularly in the urban environment. The SRTM DEM data wereused for finding high water accumulated areas, and the Landsat OLI image is used to retrieve land use information i.e.vacant land and open green spaces, existing drainage network density, and rainfall distribution. All these layers wereintegrated through AHP to detect the potentially suitable sites for the construction of rainwater harvesting structures.Results concluded 94 suitable sites with categorization from highly to critically suitable for the construction ofrainwater harvesting structures in which 6 were highly suitable areas in Data Gunj Bakhsh Town and Ravi Town.Besides, residential areas are having a maximum site suitability percentage, followed by roads, agricultural and openspaces in the area under consideration. Considering the suitable sites, further rainwater harvesting methods can beidentified in the study area to alleviate urban flooding and improve the urban environment.

Poverty and Physical Geographic Factors: An Empirical Analysis of Sichuan Province Using the GWR Model

Given the complexity of the poverty problem, efforts and policies aiming at reducing poverty should be tailored to local conditions, including cultural, economic, social, and geographic aspects. Taking the Sichuan Province of China as the study area, this paper explores the impact of physical geographic factors on poverty using the Ordinary Least Squares (OLS) Regression and the Geographically Weighted Regression (GWR) models at the county level. In total, 28 factors classified in seven groups were considered as variables, including terrain (relief degree of the land surface, altitude, and slope); vegetation (forest coverage rate); water (drainage network density); climate (temperature, annual average rainfall); and natural disaster (landslide, debris flow, and torrential flood). The 28 variables were then tested using correlations and regressions. A total of six physical variables remained significant for the OLS and GWR models. The results showed that the local GWR model was superior to the OLS regression model and, hence, more suitable for explaining the associations between the poverty rate and physical geographic features in Sichuan.

Spatial and temporal aspects of high streamflow periods within the Danube drainage basin in Bulgaria

High flow events are the main prerequisites for floods with negative social and environmental consequences. Their study under uncertain and changing climate gives informative knowledge for further management decisions. This paper seeks to analyze the spatio-temporal parameters of high flow periods within the Danube drainage basin in Bulgaria. Three characteristics of the hazard phenomena: time of occurring, frequency and duration are investigated. The analysis is based on daily discharge data collected from 20 gauging stations for the period 2000–2005. The surplus water quantities are identified by the Threshold level method using fixed values – Q25 and Q5, derived from the flow duration curve. Results show a concentration of the high flow periods during the spring hydrological season, with an average duration up to six weeks. The calculations establish positive correlations between the duration of high flow, the altitude of catchments, and the density of drainage network. The resulting information can serve as a support for the development of preliminary flood risk assessments in the Danube River Basin.

Rill network development on loessial hillslopes in China

AbstractRill network development not only potentially affects hillslope and drainage network evolution, but also causes severe soil degradation. However, the studies on rill network development remain inconclusive. This study aimed to investigate the temporal and spatial development of hillslope rill networks and their characteristics based on rainfall simulations and field observations. A soil pan (10.0 m long × 3.0 m wide × 0.5 m deep) on a 20° slope was applied three successive simulated rains at two intensities of 50 and 100 mm h–1. The field observations were performed on two bare hillslope runoff plots (10.0 m long × 3.0 m wide) at 20°. Three typical erosive natural rainfall events were observed in the field, and rills were measured in detail, similar to the laboratory rainfall simulation. The results indicated that with increases in rainfall events, the rill network morphology varied from incipient formation to the maximum drainage network density. Four rill network development indicators (rill distribution density, distance between rills, rill bifurcation number, and confluence point number) exhibited different changes over time and space. Among the four indicators, the rill bifurcation number was the best indicator for describing rill network development. Rill flow energy increased and decreased cyclically on a slope ranging between ~3 and 4 m. Moreover, rill networks on loessial hillslopes generally evolved into dendritic rather than parallel forms. The development characteristics of the rill network were relatively similar between the laboratory simulation and natural field conditions. Over time, rill erosion control measures become increasingly difficult to implement as the rill network develops. The morphology of eroding rills evolved over time and space, which led to corresponding rill network development. Further study should quantify the impacts of rill network development on soil degradation and land development. © 2020 John Wiley & Sons, Ltd.

РОЗРАХУНКОВІ ХАРАКТЕРИСТИКИ СЕРЕДНЬОГО РІЧНОГО СТОКУ ВОДИ ПРАВОБЕРЕЖНОЇ ТА ЛІВОБЕРЕЖНОЇ ЧАСТИН БАСЕЙНУ Р. ДНІСТЕР ДО М. ЗАЛІЩИКИ

The Dniester River is the second longest and most watery river in Ukraine, which is characterized by heterogeneity and diversity of conditions for the formation of water flow, both in terms of its length and numerous tributaries. The right-bank and left-bank parts of the Dniester River basin are quite different in terms of physical and geographical conditions, drainage network density, water regime and river water content. The object of the study is the average annual water flow of the rivers of the Dniester River basin, the subject is its calculated characteristics of different probabilities of exceeding. The purpose of the study is to analyze, systematize, generalize and compare the calculated characteristics of the average annual water flow of rivers of the right-bank and left-bank parts of the Dniester basin. Input data is based on the average annual river water discharge from 50 stream flow measuring stations in the Dniester River basin (to Zalishchyky). The data bank was formed from the beginning of observations until 2016. 89% of 28 right-bank stream flow measuring stations have a continuous series of more than 50 years, and 86% of 22 left-bank stream flow measuring stations have a continuous series of observations of more than 50 years. As for the catchment areas of rivers in the closing areas, the right bank is dominated by small ones – 64% of 28 stations have an area of less than 500 km2 and 25% – from 500 to 1,000 km2. 37% of 22 stations on the left bank have a catchment area of less than 500 km2 and 41% – from 500 to 1,000 km2. According to statistical criteria, the series of observations of the average annual river water discharge in both parts were mainly homogeneous and representative. Analytical distribution curves were calculated by the method of moments, as the coefficients of variation do not exceed 0.50. Generalization and comparison of the calculated characteristics of the average annual water flow of different probabilities of exceeding the rivers of the right-bank and left-bank parts of the Dniester basin have shown that the smallest scatter of certain analytical ordinates is observed for the probability of exceeding 50%, the transition coefficients from the norm are close to 1. The greatest spread of variation of ordinates is observed at extreme probabilities of excess of distributions, that is 0,01 % and 99 %. Analysis of the ranges of variability of transition coefficients from the norm of average annual water consumption has shown that the intensity of their change in the region of rare probabilities (0.01, 0.1, 1 %%) on the left bank is more significant than on the right bank of the Dniester basin. As for low-water supplies (95, 97, 99 %%), their ranges of variability coincide in both studied parts.

Application of satellite image processing and GIS-Spatial modeling for mapping urban areas prone to flash floods in Qena governorate, Egypt

Flash floods in Egypt are considered frequent meteorological natural hazards. Qena is one of the most Egyptian governorates prone to flash floods. Various flash floods events hit Qena from 1954 till 2016. Flash floods occurred in Qena on 28th October 2016 inundated houses and roads, generated losses in lives, damages to private and public property. The intensive rainfall coupled with the rapid urban expansion in Qena and along the Nile Valley could worsen the situation. Despite, the destructive impacts of the flash floods in Qena, flash floods can be used as a valuable source of fresh water as the study area is classified as an arid zone and characterized with the fresh-water shortage. Integration of remotely sensed data with the Analytical Hierarchy Process and Geographic Information Systems spatial modeling presented valuable analysis techniques in this study. The present study focused on mapping the spatial distribution of flash floods vulnerability in Qena's urban areas. Ten indicators were used to analyze the flood floods namely; rainfall, soil, geology, slope, elevation, flow direction, drainage network, land cover, total population, and population density. The results revealed that Qena, Qus, Naqadah, and Dishna urban districts are the most vulnerable to flash floods and located in the very high zone with 25.3%, 14.9%, 12.3%, and 9.8% respectively. The total population situated at very high and high vulnerability zone reached represents 7.66% and 43.36% of the total population. The obtained results considered crucial information for decision-makers for future effective flash floods hazards mitigation, assessment management, planning, and sustainable development.

Caracterização morfométrica das bacias hidrográficas inseridas no município de Rio Verde, Goiás, como ferramenta ao planejamento urbano e agrícola

A caracterização morfométrica das bacias hidrográficas propicia a uma rápida avaliação dos mananciais e seus respectivos potenciais de degradação. Assim, com este trabalho objetivou-se fazer a caracterização morfométrica das bacias inseridas no município de Rio Verde, Goiás, como ferramenta ao planejamento e urbano e agrícola. Foram analisadas nove bacias hidrográficas dentro do município de Rio Verde. As bacias com maior potencial a grandes enchentes foram as que possuem forma circular sendo a maior parte destas ocupadas por áreas agricultáveis, o que pode comprometer a economia local. As variáveis morfométricas servirão para planejamentos futuros e gestão ambiental regional, assim como para a previsão de enchentes em áreas urbanas e agrícolas.

Patterns of Urban Housing Shape Dengue Distribution in Singapore at Neighborhood and Country Scales.

Dengue is the most important human arboviral disease in Singapore. We classified residential areas into low‐rise and high‐rise housing and investigated the influence of urban drainage on the distribution of dengue incidence and outdoor breeding at neighborhood and country scales. In Geylang area (August 2014 to August 2015), dengue incidence was higher in a subarea of low‐rise housing compared to high‐rise one, averaging 26.7 (standard error, SE = 4.83) versus 2.43 (SE = 0.67) per 1,000 people. Outdoor breeding drains of Aedes aegypti have clustered in the low‐rise housing subarea. The pupal density per population was higher in the low‐rise blocks versus high‐rise ones, 246 (SE = 69.08) and 35.4 (SE = 25.49) per 1,000 people, respectively. The density of urban drainage network in the low‐rise blocks is double that in the high‐rise ones, averaging 0.05 (SE = 0.0032) versus 0.025 (SE = 0.00245) per meter. Further, a holistic analysis at a country‐scale has confirmed the role of urban hydrology in shaping dengue distribution in Singapore. Dengue incidence (2013–2015) is proportional to the fractions of the area (or population) of low‐rise housing. The drainage density in low‐rise housing is 4 times that corresponding estimate in high‐rise areas, 2.59 and 0.68 per meter, respectively. Public housing in agglomerations of high‐rise buildings could have a positive impact on dengue if this urban planning comes at the expense of low‐rise housing. City planners in endemic regions should consider the density of drainage networks for both the prevention of flooding and the breeding of mosquitoes.

Assessing Flood Hazard at River Basin Scale: Comparison between HECRAS-WMS and Flood Hazard Index (FHI) Methods Applied to El Maleh Basin, Morocco

The cartography of floods by two different approaches enabled us to determine the limits and the advantages of each one of them. This cartography has been applied to the El Maleh basin situated in the South-East of Morocco. The HEC-RAS approach consists of a combination of the surface hydrologic model and the digital terrain model data. This combination allows thereafter the mapping of the flood zones by the use of the WMS software. Thus it can predict the probability occurrence of floods at various frequency times and determine the intensity of the flood (depth and velocity of flood water) inside the El Maleh river by using the existing hydrological data. Otherwise FHI method approach introduces a multi-criteria index to assess flood risk areas in a regional scale. Six parameters (flow accumulation, distance from drainage network, drainage network density, slope, land use, and geology) were used in this last method. The relative importance of each parameter for the occurrence and severity of flood has been connected to weight values. These values are calculated following an Analytical Hierarchy Process: AHP, a method originally developed for the solution of Operational Research problems. According to their weight values, information of the different parameters is superimposed, resulting to flood risk mapping. The use of the WMS model allowed us to accurately map the flood risk areas with precisely flood heights in different levels. However, this method is only applicable for a small portion of the basin located downstream of the hydrological station. Otherwise, the FHI method allows it to map the entire basin but without giving an indication of the water levels reached by floods. One method does not exclude the other since both approaches provide important information for flood risk assessment.

Landslide susceptibility mapping using AHP method and GIS in the peninsula of Tangier (Rif-northern morocco)

The peninsula of Tangier (Northern Morocco) is submitted to a significant number of landslides each year due to its lithological, structural and morphological complexity; which cause a lot of damage to the road network and other related infrastructure. The main objective of this study is to create a landslide indexed susceptibility map of Tangier peninsula, by using AHP (Analytical Hierarchical Processes) model to calculate each factor’s weight. The work is made via GIS by using an ArcGIS AHP extension. In the current research, First of all, the four main types of landslides were identified and mapped from existing documents, works and new data which came from either remote sensing or fieldwork. Lithology, land use, slope, hypsometry, exposure, fault density and drainage network density were used as main parameters controlling the occurrence of the selected landslides. Then, afterward, each parameter is classified into a number of significant classes based on their relative influence on gravitational movement genesis. The validity of the susceptibility zoning map which is obtained through linear summation of indexed maps was tested and cross-checked by inventoried and studied landslides. The obtained landslide susceptibility map constitutes a powerful decision-making tool in land-use planning, i.e. New highways, secondary highways, railways, etc. within the national development program in the Northern provinces. It is a necessary step for the landslides hazard assessment in the Tangier peninsula in northern Morocco.

Parameters Estimation of Synthetic Unit Hydrograph Model Using Multiple Linear and Non-linear Regressions

The use of synthetic unit hydrograph model (SUH) is remain popular used to transform rainfall into run off for water resources development. The typical feature of this model is that the main equation represents the shape of the curve expressed by the relationship between time and discharge. In addition, the SUH model is also expressed in three parameters i.e. peak time (TP), peak discharge (QP), and base time (TB), representing the hydrograph curve equation. In general, SUH model is developed based on morphometry parameters of watershed, especially watershed area (A), main river length (L) and main river slope (S). Another approach in hydrograph modelling is based on the fractal characteristics of watershed. This study aims to develop a synthetic unit hydrograph model based on a combination of morphometry and fractal characteristics of watersheds. The three model parameters (TP, QP and TB) were predicted using multiple linear regression and compared with multiple nonlinear regression. The results of the analysis show that the two methods showed excellent performance. The estimation of SUH parameters using linear regression resulted peak time equation (TP) as function of river length (L), ratio of river length (RL) and density of drainage network (D) with determination coefficient of 99.8%, a base time equation (TB) as the function of watershed area (A) and river slope (S) with determination coefficient of 98.2%. Using multiple non linear regression, estimation of SUH parameters formulated peak time equation (TP) as function of river length (L), ratio of river length (RL) and ratio of watershed area (RA) with determination coefficient of 99.9%, a base time equation (TB) as the function of watershed area (A) and ratio of watershed area (RA) with determination coefficient of 97.9%. Peak discharge equation (QP) is stated as a function of peak time and a simple single curve equation derived from Gamma Distribution Equation.