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The improvement relates to the calculation of the variation of flow time in each cell, due to the velocity variance, regarding the uneven distribution of rainfall over time. This model also incorporated the rainfall losses by using the curve number methodology Soil Conservation Service [ 73 ]. This model was named time variant spatially distributed direct hydrograph.

At the end of the decade, Van der Knijff et al. As flood management became more and more important due to climate change and other environmental and human factors, many researchers pointed their work toward these issues. In this frame, Rozalis et al. Also in , Kourgialas et al.

In the year that followed, Paiva et al. Furthermore, Fugura et al. Kia et al. Sarhadi et al. Despite the significant volume of previous research, the publication list in this topic is still increasing. Lopez—Vicente et al. Paiva et al. Tehrany et al. Another published novel idea of the year was that of Formetta et al. Furthermore, among the published papers of , the integration of RS and GIS occupies a rather special place, with the most influential works on this topic. Chen et al. Finally, Fiorillo et al. Both research works couple GIS and hydrological modeling.

In conclusion, from the references presented above, it can be easily deduced that hydrological modeling occupies a distinguished place in environmental modeling and research. The development and application of this coupling is expected to flourish the following years in scientific research. As mentioned earlier, GIS-based hydrological analysis has a very wide variety of applications in natural events and natural disasters. This part of the chapter intends to highlight the contribution of GIS in hydrological analysis and simulation by presenting an empirical analysis.

The basic aim of this simulation is to estimate the peak flood discharge, derived by an extreme rainfall event, as well as the critical time to reach this peak right after the rainfall peak. In order to do that, a synthetic Unit Hydrograph UH is obtained by estimating the time-area curve. The curve histogram of time-area shows the spatiotemporal relationship during time at which water flows within the basin. This curve can be expressed with a reclassification of time concentration at specific time intervals.

These time periods are distinguished by isochrones. These are the lines within the catchment where runoff has the same travel time to reach the outlet of the basin. According to the theory of the UH, the duration of the flood is the same for any given amount of active rainfall duration, while the ordinates of the hydrograph on the joint duration time base flood is directly proportional to the amount of rain Chow et al.

Thus, the discharge at the outlet of the basin is resulting from the superposition addition of instantaneous UH produced by active rain at each time step. UHs in hydrological practice are exported with numerical techniques from observed hydrographs. Many scientists have used GIS technology in order to construct rainfall-runoff model for UH attainment [ 13 , 21 , 63 , 72 ].

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In order to estimate the magnitude of a flood, a routing model was designed in a GIS context [ 63 , 72 , 90 , 91 ]. The choice of the specific model was based mainly on its ability to be created entirely in a GIS environment. Accordingly, this model is very flexible to changes and connection with other models. Also, it is expandable, and it can be easily used in different areas. The basic concept of the simulation is the runoff analysis in a GIS environment given a specific storm.

The initiate data which is needed for this simulation is. The model can incorporate various types of rainfall data. More specifically, data derived by rainfall stations can be used. In this case, the use of them depends on the number of meteorological gauge stations. So, for example, if there is only one rainfall station in the river basin i. The distribution of rainfall is used after the modeling to construct the flood hydrograph. This simulation is taking into account only the time distribution of the rainfall time modeling. If the study area has more than one meteorological gauge stations, then the best way to handle all the rainfall data is to proceed to the tessellation of the data, e.

In this way, the simulation is taking into account, besides time, the spatial context of the rainfall distribution semispatiotemporal modeling. Nowadays, the use of radar for record rainfall, or the use of data that are provided by Atmospheric Simulation Model, has provided the ability to incorporate in the hydrological modeling both the spatial and temporal variation of rainfall spatiotemporal modeling.

In each case, the best way to simplify the hydrological modeling is to modify the total rainfall in terms of the part of rainfall which finally becomes surface runoff excess rainfall. This data can be extracted from Atmospheric Simulation the rainfall grid values can be only the excess rainfall.

Otherwise, techniques such as Curve Numbers CN can be established in order to be used as a layer in the process of simulation [ 72 ]. The digital elevation models have been used, during the last decades along with the development of GIS, in order to derive hydrological and hydro-geomorphological properties such as streams, basins, flow direction, flow accumulation, flow length, and stream order. Nowadays, the development in satellite technology provides very high accuracy for remotely sensed data in terms of landscape topography.

Alternatively, data generated from digitization of topographic maps can be used after applying the suitable algorithms in order to create a DEM, e. This specific algorithm produces a coherent grid which maintains the integrity of the topography [ 94 ]. The cell size of a DEM largely determines the accuracy of the analysis that is carried out each time.

The methodology which is presented in this paradigm is actually based on the estimation of concentration time in order to construct a layer of isochrones. Accordingly, calculations were carried out for flow time within the basin, both for channel and overland flow. In order to discrete these two types of water flow, a suitable threshold on flow accumulation must be selected.

This can be done by several iterations until the stream layer reflect reality. Hence, the two types of flow are separated, and it also results in drainage network determination and mapping. As mentioned before, the topography of the land surface expressed by a DEM is one of the most fundamental elements for this simulation. Thus, DEM construction and analysis is the first step in order to execute the current rainfall-runoff model.

Short communication SOILPAR 2.00: software to estimate soil hydrological parameters and functions

There are various derivatives from the hydrological analysis of a DEM such as the slope surface analysis , flow direction, flow accumulation, and flow length hydrological analysis. If the rainfall comes from only one meteorological station, R is actually a number which represents the amount of rainfall throughout the duration of the event.

If the rainfall comes from several gauge stations, R is a grid layer which corresponds to closest gauge station. Lastly, if the rainfall comes from several grid layers which represent the spatiotemporal distribution of the rain, the discharge within the channel must be calculated as many times as the number of the separate grids. Then, these grids are added to give the total discharge within the river network.

K is a coefficient that is determined after the calibration of the model and corrects the simulation errors of slope and n. Measurements of real discharge Q are very helpful and highly desirable in order to calibrate the model. The combination of the above two types of velocities provides the final velocity, since the final velocity is calculated for each cell off the basin using conditional algorithms.

All the above equations can be calculated with the use of map algebra in a GIS software package. Map Algebra is a language that defines a syntax for combining map themes by applying mathematical operations and analytical functions to create new map themes. Finally, in order to estimate the flow time and isochrones i. The time-area unit hydrograph theory, as it known, inaugurates a specific association between the travel time T and a part of the upper catchment that may contribute runoff during this travel time T. The area which is closest to the catchment outlet will contribute to the runoff hydrograph sooner than the other areas which are on the catchment boundary.

This method indicates that the catchment is divided into areas of approximately travel time isochrones. These lines of equal travel time are known as isochrones. Hence, the time-area histogram is actually converted to a hydrograph. For this reason, the amount of water that falls onto each time zone is calculated.

The next step is the calculation of the total volume for each palm of water discharge that reaches the outlet of the basin. The final step is the reduction of each volume to time, which is actually the calculation of the discharge. By plotting these values of discharges against time the synthetic UH is constructed. This UH reveals two vital values of the flood hydrographs which are the critical time and the maximum peak value of the discharge.

This methodology attempts to analyze the physical processes of a rainfall event in a hypothetical study area. Thus, a rainfall-runoff model is used for estimating the spatially distributed synthetic UH for the outlet of the catchment. The form of the model-derived synthetic UH for the outlet of the basin can be used in a variety of cases. There are two crucial values derived from a UH, the critical time time difference between peak rainfall and maximum discharge and the peak value of the discharge.

Hydrological transport model

The development of such hydrographs can be used for extreme rainfall magnitudes in order to design constructions such as bridges and roads. Also, UH can be used in order to extrapolate flood flow records based on rainfall records and for the development of flood forecasting and warning systems. Additionally, each UH shows the response of the catchment-study area, i. The empirical modeling described earlier has also some limitations. It undertakes uniform distribution of rainfall over the catchment and uniform intensity during the duration of rainfall excess in case of rainfall data from rain gauge stations.

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In practice, these conditions are not satisfied during a real storm event. Under specific situations of nonuniform aerial scattering and disparity of intensity, UH, still, can be used if the spatial distribution is constant between different flood events. In addition, in some cases, when the rainfall data comes from meteorological stations, the catchment size levies a superior limit on the pertinency of the UH implementation due to rainfall distribution.

In this case, a very big river basin needs to be tackled as the sum of smaller subcatchments. Thus, this obligation noises for an assortment of flood events of so slight a period which would generally yield a strong and approximately unchanging effective rainfall. Also it would yield a distinct single peak of hydrograph of short time base.

UHs that are having the same time base are unswervingly relative to the total amount of runoff given by each hydrograph linearity. Usually, in hydrological modeling and especially in modeling of flash floods, there are some definite assumptions. For instance, the effects of evapotranspiration, as well as the synergy between the aquifer and the rivers, are ignored. This could also be overlooked due to the fact that the amount of evapotranspiration during the time, in which the flood occurs, is insignificant when compared to other fluxes such as infiltration. Furthermore, the effect of the aquifer-river synergy is commonly disregarded due to the response time of overland flow versus the flow within the channel.

Similarly, effects of the rest of hydrological procedures such as interception and depression storage are also ignored. The introduction of GIS technology led researchers to develop data processing automations and to produce reliable simulation models. They appreciate the standing and welfares of such a technology that empower them to evaluate data, contend with complications, generate instinctive visualization approaches, and make conclusions with a higher effectiveness.

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The objective of this chapter was to present the extended history of GIS modeling and to converse the modern observes in terms of integration of GIS with the hydrological modeling, and also to discuss the problems, the assumption, and the limitations of GIS-based hydrological models. Generally, four different approaches have been widely proposed and used in terms of integrating GIS with the hydrological modeling.

These are a embedding GIS-like functionalities into hydrological modeling software, b embedding hydrological modeling into GIS software, c loose coupling add-on , and d tight coupling which actually is to customize applications into a GIS software [ 95 ]. Therefore, these models can be used as tools for policy makers in order to take decisions for the construction of artificial dams i.

Thus, rainfall-runoff models together with the GIS technology are used as integrated systems of assessing potential impacts for various rainfall events. Hence, the GIS technology has the capability to postprocess the results which are obtaining from a model and sublimate them into policy. Licensee IntechOpen. This chapter is distributed under the terms of the Creative Commons Attribution 3. Help us write another book on this subject and reach those readers. Login to your personal dashboard for more detailed statistics on your publications.

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  • Edited by Dr. Mamun Habib. We are IntechOpen, the world's leading publisher of Open Access books. Built by scientists, for scientists. Our readership spans scientists, professors, researchers, librarians, and students, as well as business professionals. Downloaded: Abstract Water resource management and catchment analysis are crucial aspects of the twenty-first century in hydrological and environmental sciences. Keywords hydrological modeling GIS hydrology unit hydrograph floods.

    The most common module is a subroutine for calculation of surface runoff, allowing variation in land use type, topography , soil type, vegetative cover , precipitation and land management practice such as the application rate of a fertilizer. The concept of hydrological modeling can be extended to other environments such as the oceans , but most commonly and in this article the subject of a river watershed is generally implied.

    In , T. Mulvany was probably the first investigator to use mathematical modeling in a stream hydrology context, although there was no chemistry involved. Imbeau had conceived an event model to relate runoff to peak rainfall, again still with no chemistry. Physically based models sometimes known as deterministic, comprehensive or process-based models try to represent the physical processes observed in the real world. Typically, such models contain representations of surface runoff, subsurface flow, evapotranspiration, and channel flow, but they can be far more complicated. Army Corps of Engineers in for reservoir management on the main stem of the Missouri River".

    This, [5] and other early work that dealt with the River Nile [6] [7] and the Columbia River [8] are discussed, in a wider context, in a book published by the Harvard Water Resources Seminar, that contains the sentence just quoted. Flow and transport processes are represented by either finite difference representations of partial differential equations or by derived empirical equations. The following principal submodels are involved:.

    This model can analyze effects of land use and climate changes upon in-stream water quality, with consideration of groundwater interactions. However, not all of these models have a chemistry component. Army Corps of Engineers districts and larger consulting companies to compute flow, water levels, distributed erosion, and sediment delivery in complex engineering designs. A distributed nutrient and contaminant fate and transport component is undergoing testing. Evapotranspiration, inundation, infiltration, and snowmelt modeling capabilities are included. Applications include civil infrastructure operations and maintenance, stormwater prediction and emergency management, soil moisture monitoring, land use planning, water quality monitoring, and others.

    These models based on data are black box systems, using mathematical and statistical concepts to link a certain input for instance rainfall to the model output for instance runoff. Commonly used techniques are regression , transfer functions , neural networks and system identification. These models are known as stochastic hydrology models. Data based models have been used within hydrology to simulate the rainfall-runoff relationship, represent the impacts of antecedent moisture and perform real-time control on systems.

    A key component of a hydrological transport model is the surface runoff element, which allows assessment of sediment, fertilizer , pesticide and other chemical contaminants.

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    Building on the work of Horton, the unit hydrograph theory was developed by Dooge in In the early s the U. An example of these efforts was developed at the Southeast Water Laboratory, [19] one of the first attempts to calibrate a surface runoff model with field data for a variety of chemical contaminants.

    The attention given to surface runoff contaminant models has not matched the emphasis on pure hydrology models, in spite of their role in the generation of stream loading contaminant data. In the United States the EPA has had difficulty interpreting [20] diverse proprietary contaminant models and has to develop its own models more often than conventional resource agencies, who, focused on flood forecasting, have had more of a centroid of common basin models. Liden applied the HBV model to estimate the riverine transport of three different substances, nitrogen , phosphorus and suspended sediment [21] in four different countries: Sweden , Estonia , Bolivia and Zimbabwe.

    The relation between internal hydrological model variables and nutrient transport was assessed. A model for nitrogen sources was developed and analysed in comparison with a statistical method. A model for suspended sediment transport in tropical and semi-arid regions was developed and tested.

    It was shown that riverine total nitrogen could be well simulated in the Nordic climate and riverine suspended sediment load could be estimated fairly well in tropical and semi-arid climates. The HBV model for material transport generally estimated material transport loads well. The main conclusion of the study was that the HBV model can be used to predict material transport on the scale of the drainage basin during stationary conditions, but cannot be easily generalised to areas not specifically calibrated.

    In a different work, Castanedo et al. The model [23] satisfactorily predicted nutrient, sediment and dissolved oxygen parameters in the river. The DSSAM Model is constructed to allow dynamic decay of most pollutants; for example, total nitrogen and phosphorus are allowed to be consumed by benthic algae in each time step, and the algal communities are given a separate population dynamic in each river reach e. Regarding stormwater runoff in Washoe County , the specific elements within a new xeriscape ordinance were analyzed for efficacy using the model.