Arc Hydro Tools Research Articles

Delineation of Drainage Network and Estimation of Total Discharge using Digital Elevation Model (DEM)

The rapid urbanization and the population growth, have increased the demands of fresh water to manage various tasks from domestic to industrial scales. Various man driven sectors such as agriculture, industry and water filtration plants, require fresh water to cater the need of increasing population. Therefore, the management of available fresh water reservoirs is of great importance to save water for a sustainable future “save water save life”. Digital elevation model (DEM) is efficient to extract the drainage network, basin boundaries and to evaluate the volume of fresh water available in study site. We used Arc hydro tools in Arc GIS interface for extraction of drainage network in the study site. Flow direction and accumulation were computed according to Z-value of individual pixel available in the raster grid. A total 127 streams were extracted against 127 catchments. We observed that the catchments bearing steep slopes were incised in comparison to gentle slopes which were mostly eroded. We evaluated the total discharge in cusec using Q=CIA, where the coefficient ‘C’ of rainfall was substituted as 0.76 for each catchment having rocky soil type. The total discharge was estimated as 10871 cusec. GIS tools proved efficient to map watershed in the study site.

Prioritization of W. Alarab Sub-Watersheds (North Jordan) for Conservation Measures Using RS, GIS, and Multi-Criteria Analysis

Soil erosion and high sediment flow are of eminent environmental concern in Wadi Alarab catchment, northern Jordan. The objective of this research is to conduct a prioritization scheme using RS, GIS, and multi-criteria analysis approach based on morphometric analysis, land use/land cover (LULC) change analysis, and soil loss modeling based on RUSLE model factors. ASTER GDEM and Arc GIS were utilized to delineate watersheds and extract the drainage networks using the Arc Hydro tool. Five basic morphometric parameters, five linear and five shape parameters, six LULC classes, and five soil erosion risk classes are applied to prioritize 13 sub-watersheds connected to W. Alarab basin. LANDSAT images were subjected to supervised classification (the Maximum Likelihood Method) to determine land use/cover changes and to establish the LULC map/layer. Soil erosion risk classes were estimated using the RULSE model. RULSE factors (R, K, L, S, C, and P) were calculated in a GIS environment, then multiplied together so as to estimate soil loss (ton·ha-1·yr-1) and to establish a soil erosion risk map for the entire watershed and the thirteen sub-watersheds. A GIS-based integration of the three layers compiled for each criterion reveals that six sub-watersheds (1, 5, 8, 9, 10, and 11) are categorized under low priority. Further, three sub-basins (4, 12, and 13) are fall under moderate priority, and four sub-basins (2, 3, 6, and 7) are designated as of high priority. It is obvious that 53.8% of these sub-basins must be prioritized immediately for soil and conservation measures. The validity of the achieved priority classes was tested statistically using Discriminant Analysis (DA), and the results showed that morphometric parameters, LULC analysis, and soil loss are accepted criteria for prioritization. These results are intended to help decision-makers to prepare reliable soil erosion management plans.

The usefulness of alos-palsar dem data for drainage extraction in semi-arid environments in The Iishana sub-basin

Study regionThe study area is the Iishana sub-basin located in north-central Namibia. The basin is characterised by low-lying interconnected ephemeral drainage networks locally known as Iishana. In the past decade, the basin has experienced frequent droughts and flooding events due to recent weather anomalies possibly enhanced by the sprawling urban development. Study focusAlthough extensive studies have been conducted on water availability in the basin, no attempts have been made to update existing hydrological maps which provide limited information on the impacts of geo-hydrological dynamics in the area. The aim of this study was to test the effectiveness of the Advanced Land Observing Satellite Digital Elevation Model (ALOS DEM) for drainage network extraction. ArcHydro tools were used for drainage feature extraction. Validation of extracted networks was based on field observations and delineated networks from earth observation data and Normalized Difference Wetness Index (NDWI). The accuracy of extracted drainage networks was assessed through visual observation of data overlay and the coefficient of line correspondence (CLC). New hydrological insightsThe resulting drainage networks will be used to update the current hydrographic map of the area which will aid in the development of flood and drought mitigating measures for environmental management. The CLC computed metric obtained a 0.91 match between extracted and delineated drainage networks. The results show that ALOS DEM is capable of extracting drainage networks within the Iishana sub-basin.

Assessment of morphometric and hypsometric study for watershed development using spatial technology – a case study of Wardha river basin in Maharashtra, India

ABSTRACT The assessable results of the Wardha river basin are essential for the behaviour of the drainage and river network and to know its geology, slope and geo-hydrological condition. The Wardha river basin is covered by 1730.85 sq. km2 with dendritic and sub-dentric drainage patterns. This study area is delineated into nine sub-watersheds from digital elevation model data using Arc hydro tools. The morphometric characters were observed to understand the drainage and watershed characteristics and its impact on groundwater resources for the occurrence of bifurcation ratio that shows very high runoff and low infiltration of groundwater recharge at the basaltic terrain rocks. Slope and topographic maps may be used for groundwater development; theses maps can be used for suitable well points and artificial and ground water recharge sites at the Wardha river basin. The slope values were inversely proportional to infiltration and it has led to the hypsometric analysis using Arc GIS 10.3 software. In this study, different types of morphometric characteristics were measured using computations of linear and areal aspect using geospatial technology domain. The total streams order (3509) has been identified from digital elevation model data. The data show that large numbers of stream are present in this area for scope of water harvesting structures and these play a main role in groundwater development and controlling soil erosion factors. In this study, various morphometric parameter were calculated using mathematical equation and spatial data for understanding of surface runoff, slope, watershed characteristics and watershed condition. Hypsometric investigation has been generally used to reveal the steps of geomorphic growth or land forms. The hypsometric integral value shows nine sub-watersheds observed which shows the mature stage at the Wardha river basin. The hypsometric analysis results have been calculated for watershed and groundwater development. During the study, bifurcation ratio values such as 2.5–4.25 suggest morphological and the basic control for watershed management and drainage network analysis in the area, while drainage density and fine drainage texture suggest its high runoff in basin. The drainage basin characteristics have been made for the assessment of many linear factors such as stream order, stream number, stream length, stream length ratio, bifurcation ratio, drainage density, texture ratio, and stream frequency) and Channel index (Ci) Valley index (Vi), Rho coefficient (q) and Basin Area. All these results may be useful for watershed development programme in the semi-arid area and most influence of basaltic hard rock areas.

Estimation Curve Numbers using GIS and Hec-GeoHMS Model

Recently, the development and application of the hydrological models based on Geographical Information System (GIS) has increased around the world. One of the most important applications of GIS is mapping the Curve Number (CN) of a catchment. In this research, three softwares, such as an ArcView GIS 9.3 with ArcInfo, Arc Hydro Tool and Geospatial Hydrologic Modeling Extension (Hec-GeoHMS) model for ArcView GIS 9.3, were used to calculate CN of (19210 ha) Salt Creek watershed (SC) which is located in Osage County, Oklahoma, USA. Multi layers were combined and examined using the Environmental Systems Research Institute (ESRI) ArcMap 2009. These layers are soil layer (Soil Survey Geographic SSURGO), 30 m x 30 m resolution of Digital Elevation Model (DEM), land use layer (LU), “Look–Up tables” and other layers resulted from running the software. Curve Number which expresses a catchment’s response to a storm event has been estimated in this study to each land parcel based on LU layer and soil layer within each parcel. The results showed that a CN of 100 (dark Blue) means surface water. The high curve numbers (100 -81) (Blue and light Blue) corresponding to urbanized areas means high runoff and low infiltration; whereas low curve numbers (77- 58) (Brown and light Brown) corresponding to the forested area means low runoff and high infiltration. Four classes of land cover have been identified; these are surface water, medium residential, forest and agriculture.

English

Ethiopia is constantly affected by shortage of water for rain-fed agriculture, mainly because of lack of proper water resources utilization and management practices. For the efficient use of available surface water resources with balanced attention to maximize economic, social, and environmental benefits, it is necessary to have effective integrated water resources assessments and planning. Beles River Basin is one of the most potential river basins in Ethiopia, which is the main tributary for upper Blue Nile River Basin and accounting 14,200 km2. In order to supplement planning and development of this area, a detailed characterization of the basin is important. The main objective of this study is to process and determine different terrain processing parameters and morphology by using Arc-Hydro tools in Arc-GIS for generating different data for the basin. Therefore, it has been observed from this study that the drainage density is higher in relatively elevated areas especially when the weathered section is thick or when the pattern of structures crossing the rocks is higher. Direction of flow of these rivers is controlled by the topography. The highlands (maximum 2729 m above sea level) from where the streams flow are general humid and rugged and the surrounding lowlands (minimum 458 m above sea level) in which the streams flow, are mostly arid and relatively flat. These topographic differences induce rapid run off, low retention in soil layers and soil erosion on the highlands. Considering a 30 × 30 m drainage area, 62 catchments, eight flow directions with 128 flow grids have been identified in the basin. The delineated watersheds were Gilgel Beles with 617.56 km2, Upper Main Beles with 2866.05 km2 and Lower Main Beles with 6613.84 km2. Therefore, the watershed external boundary is determined to be 10,097.45 km2. Important basin information, like slope and contour lines has been determined through spatial analysis and the result indicated that about 52.8 % of slope was found to be relatively suitable for agricultural soil and water management options in Beles River Basin. In the future, it would be advisable to consider emerging issues in water resource measures like GIS modeling with Remote Sensing data for effective and efficient water resource management when there is limited and lack of data.   Key words: River basin, Arc-Hydro, Arc-GIS, Degital Elevation Model (DEM).

Hydrological Modeling in A Semi-Arid Region Using HEC-HMS

In this study, the Hydrologic Engineering Centre's Hydrologic Modeling System (HEC-HMS) model was employed to simulate runoff in the semi-arid region of northwestern China, specifically the Hailiutu watershed. The Hydrologic Engineering Centre's Geospatial Hydrologic Modeling Extension (HEC-GeoHMS) was used in conjunction with ArcHydro tools in an ArcMap geographical information system (GIS) environment to create input files of the catchment physical characteristics for the HMS model. The model was calibrated for the time period of 1978-1992. The results showed that the model systematically underestimated winter and spring hydrographs as well as a few summer flows. This was due to the discrepancy between the nonlinear rainfall-runoff response in the watershed and the linear structure of the Soil Moisture Accounting (SMA) model used. Also, the results pointed out that, due to data unavailability on hydraulic engineering in the Hailiutu watershed, the model faced challenges in simulating runoff properly and therefore could not be validated. Ultimately, the model's general performance in simulating runoff in the Hailiutu watershed was found unsatisfactory.

Assessing the impact of arid area urbanization on flash floods using GIS, remote sensing, and HEC-HMS rainfall–runoff modeling

This study uses an integrated approach, bringing together geographic information system (GIS), remote sensing, and rainfall–runoff modeling, to assess the urbanization impact on flash floods in arid areas. Runoff modeling was carried out as a function of the catchment characteristics and the maximum daily rainfall parameters. Land-use types were extracted from the supervised classification of SPOT-5 (2010) and Landsat-8 (2015) satellite images and were validated during field checks. Catchment morphometric characteristics were carried out using the correlated Topaz and Arc-Hydro tools. Maximum floods of the catchment were evaluated by coupling GIS and remote sensing with Hydrologic Engineering Center–Hydrologic Modeling System (HEC-HMS) hydrologic modeling. Peak discharges were estimated, and the abstraction losses were computed for different return periods. The model results were calibrated according to actual runoff event. The research shows that rapid urbanization adversely affects hydrological processes, since the sprawl on the alluvial channels is significant. This reduces infiltration into the underlying alluvium and increases runoff, leading to higher flood peaks and volumes even for short duration low intensity rainfall. To retain a considerable amount of water and sediments in these arid areas, construction of small dams at the fingertip channels at the outlet of the lower order sub-basins is recommended.

Low-Carbon Watershed Management: Potential of Greenhouse Gas Reductions from Wastewater Treatment in Rural Vietnam.

Currently in many cities and rural areas of Vietnam, wastewater is discharged to the environment without any treatment, which emits considerable amount of greenhouse gas (GHG), particularly methane. In this study, four GHG emission scenarios were examined, as well as the baseline scenario, in order to verify the potential of GHG reduction from domestic wastewater with adequate treatment facilities. The ArcGIS and ArcHydro tools were employed to visualize and analyze GHG emissions resulting from discharge of untreated wastewater, in rural areas of Vu Gia Thu Bon river basin, Vietnam. By applying the current IPCC guidelines for GHG emissions, we found that a reduction of GHG emissions can be achieved through treatment of domestic wastewater in the studied area. Compared with baseline scenario, a maximum 16% of total GHG emissions can be reduced, in which 30% of households existing latrines are substituted by Japanese Johkasou technology and other 20% of domestic wastewater is treated by conventional activated sludge.

Alteration of Surface Water Hydrology by Opencast Mining in the Raniganj Coalfield Area, India

Surface excavation and overburden dumping in the Raniganj Coalfield have defaced the natural topography and impacted the hydrology. Excavation and dumping of overburden within the channels has obstructed streamflow and altered water availability in the lower parts of small catchment basins. The surface drainage paths of ephemeral channels and flow accumulation by channel networks was estimated from digital elevation remote sensing images using Arc Hydro Tools of Arc GIS software. The runoff from small basins was estimated using the US Soil Conservation Service Curve Number method and initial abstractions (depression storage) were estimated from CARTOSAT DEM satellite images using GIS techniques. In the studied area, 129 depressions (abandoned and working mines) were identified within 53 small basins over an area of more than 24 km2. The excavated areas arrest surface runoff, leading to degradation of downstream channels.

MORPHOMETRIC ANALYSIS OF THE BASIN LOW MIDDLE SÃO FRANCISCO RIVER

This study aimed to generate the components for morphometric analysis of the watershed of the São Francisco River Lower Basin from geoprocessing and remote sensing surface. SRTM data were used for preparation of digital elevation model (DEM), elements such as flow accumulation, flow direction, flow length and others were obtained by processing ArcHydro tool of ArcGIS 9.3 software. The results showed that the São Francisco River Low middle Basin has a total area of 110.446,0 km ² and a perimeter of 3.834,8 km, the drainage network is moderately branched having a total length of 22.283,6 km with a main course of 720 km, the basin showed a more elongated shape, with a density of less than 0.2 km/km2 drainage as well as low-density area, the predominant class of slope is the floodplain type and plan to undulated represented about 90% of the total area the basin. Classes roofing composed of arborel and shrubby Caatinga, shrubby low Caatinga and Grasslands dominate the landscape occupying an area of 60.385,7; 18.998,5 and 22.737,5 km2, respectively. Different landforms were identified in the watershed based on SRTM (DEM) data with 90 m spatial resolution. GIS techniques were thus characterized by high precision mapping and measurement of morphometric indices and revealed themselves as a tool with great potential for watershed management.

Morphometric Characteristics and the Relation of Stream Orders to Hydraulic Parameters of River Goro: An Ephemeral River in Dire-dawa, Ethiopia

Major morphometric parameters of Goro watershed were derived from Aster Global Digital Elevation Model (GDEM) using ArcGIS10.1 extension, Arc Hydro Tool 2.0 in order to characterize it quantitatively. The study also assessed the relation of stream orders to selected channel hydraulic parameters (width, depth, channel bed slope, velocity and discharge) at bankfull flow condition. Channel geometry data and grain size samples collected from 14 representative cross-sections used as input to compute hydraulic parameters using equations appropriate for ungauged streams. The analysis of morphometric parameters indicate that pattern of stream networks is less controlled by structural condition though the area is situated in the rim of the great east African rift valley; and its geomorphic development is at late youth stage. Though hydraulic components of the channel do have a positive relation with stream orders, only channel cross-section area and discharge well related to stream orders (each increased at the rate of 0.86 and 1 on average with R 2 of 0.92 and 0.8 respectively with increasing in stream orders). However, depth, velocity and bed slope of the channel are less explained by stream order, which may indicate us these hydraulic parameters are rather affected by other local channel factors.

Basin Division Method for TIN-based DEM with Face-Node-Edge Flow Mode

The basin serving as a basic unit is of great importance for flood inundation and other hydrological fields. Most existing basin division methods have been proposed for a raster-based DEM and used in some hydrological software, such as the ArcHydro tool and the RiverTool. Unfortunately, raster has some limitations when compared to TIN; specifically, it cannot depict real ground water flow accurately and reasonably. Referring to the natural law of gravity, which dictates water flowing from high to low areas, we present a Face-Node-Edge (FNE) flow mode for TIN-based DEM. The FNE flow mode assumes the water on each triangle facet flows to its lowest node initially. The water on the lowest node then flows along the steepest edge to its neighbour node; the flow continues until the neighbour nodes' elevations are higher than its own. Meanwhile, upstream triangles pass their flow flags to the downstream triangles along the flow path. After that we can generate basins according to the flags. The case studies demonstrate that the proposed FNE flow mode and basin division method for TIN-based DEM are correct, which can provide more reasonable basin division results than raster, e.g., the ArcHydro tool.

Watershed modeling using arc hydro based on DEMs: a case study in Jackpine watershed

Raster-based digital elevation models (DEMs) play an important role in distributed hydrologic modeling supported by geographic information systems (GIS). In this study, DEMs and stream network data were used to model the Jackpine Watershed in Ontario, Canada, using Arc Hydro Tools. The modeling results include stream network and catchment delineation. The effects of the DEM reconditioning process and the stream threshold value on the modeling accuracy were examined through three simulations. The accuracy was discussed by overlying the actual and simulated maps, as well as by comparing stream densities, network lengths and numbers of streams, catchment area, and number of catchments. Other possible methods to improve the watershed modeling were also discussed. It is concluded that Arc Hydro is capable of performing watershed modeling with satisfactory performance. It is shown that DEM reconditioning can improve the accuracy of watershed modeling. It is also implied that lower stream threshold value can not only lead to a more detailed stream network but also enhance the accuracy of catchment delineation.

Multifractal analysis applied to the study of the accuracy of DEM-based stream derivation

A correct description of river network morphology is very important when it is used to study different features of a river's morphology as well as phenomena related to it, such as erosion, nitrogen retention or sediment pollution. In recent years, different algorithms have been developed to extract drainage networks directly from Digital Elevation Models. In this paper, the suitability of ArcHydro extension, developed for ArcGIS Desktop and based on the D8 algorithm to generate river networks has been studied by using multifractal analysis. The river networks generated by ArcHydro tools were compared to those provided by photogrammetric restitution for different flow accumulation threshold values. One limitation of the D8 algorithm in order to generate the most appropriate river networks is the correct choice of the flow accumulation threshold value. Multifractal analysis has shown itself to be an efficient approach to determine the most suitable flow accumulation threshold values. Moreover, this approach has allowed characterizing the morphology of river networks and testing the quality of ArcHydro results. According to the multifractal spectra, the main difference between the networks considered here is the lesser stream density with a low channel order detected for ArcHydro results compared to photogrammetric restitution. In addition, the relationship between ruggedness number for the largest contributing area and fractal dimensions in each study area has been explored. The use of multifractal analysis has been extended to drainage network simulation going beyond the descriptive aim of previous works.

Flash flood hazard mapping based on quantitative hydrology, geomorphology and GIS techniques (case study of Wadi Al Lith, Saudi Arabia)

Flash floods are considered as catastrophic phenomena possessing major hazardous threat to the coastal cities, towns, villages and infrastructures. This study deals with the evaluation of flash flood hazard in the ungauged Wadi Al Lith basin depending on detailed morphometric characteristics of Al Lith basin and its sub-basins. For the detailed study, ASTER data were used for preparing digital elevation model (DEM), and geographical information system (GIS) was used in the evaluation of linear, areal and relief aspects of morphometric parameters. The major parameters such as watershed boundary, flow accumulation, flow direction, flow length and stream ordering are prepared using the ArcHydro Tool. Surface Tool in ArcGIS-10 software, and ASTER (DEM) was used to create different thematic maps such as DEM, contour, slope aspect and hill shade maps. Twenty-five morphometric parameters were measured, calculated and interlinked to produce nine effective parameters for evaluation of the flash flood hazard degree of the study area. Based on nine morphometric parameters which affect the hydrologic behaviour of the Wadi, by influence on time of concentration which has a direct influence on flooding prone area. The flash flood hazard of the Al Lith basin and its sub-basins was identified and classified into three groups (high, medium and low hazard degree). The study provides details on the flash flood-prone area (Wadi Al Lith) and the mitigation measures. This study also helps to plan rainwater harvesting and watershed management in the flash flood alert zones.

Automated extraction of watershed boundary and drainage network from SRTM and comparison with Survey of India toposheet

The recent development of digital representation has stimulated the development of automatic extraction of topographic and hydrologic information from digital elevation model input, using geographic information system (GIS) and hydrologic models that integrate multiple databases within a minimal time. The objective of this investigation is to compare the drainage extracted from Shuttle Radar Topography Mission (SRTM) data with the drainage digitized from topographic data (1:50,000) and also to draw attention to the functions of an add-on tool in ArcGIS 9.2 (Arc Hydro v.2) of Kuttiyadi River basin. The analysis reveals that the watershed extracted from the SRTM digital elevation model (DEM) (90 m resolution) is having an area of 668 km2 and that from toposheet is 676 km2. The river mouth in the drainage network from the SRTM DEM is found to be shifted to the northern side from where it actually exists. The drainage network from SRTM DEM at stream threshold 15 (0.0002 % of maximum flow accumulation) is delivering best results than the other threshold value in comparison with the drainage pattern derived from toposheets. The study reveals the importance, reliability, and quaintness of drainage network and watershed derived from the SRTM using the Arc Hydro Tool, an extension for Environmental Systems Research Institute ArcGIS. The advantage of the Arc Hydro Tool is that it would help a novice with little GIS knowledge to run the model to obtain watershed and drainage network.

Calculation of average skidding distance on sloping terrain with GIS tools

To determine skidding productivity and costs for skidding operation, it is necessary to estimate real skidding route and to calculate average skidding distance. This study was intended to expose how the real average skidding distance was to be calculated and which operation process was to be followed up for harvesting units/blocks having irregular shapes as three dimensions. Compartments, harvesting stands, were divided into sub-compartment polygons called harvesting blocks with respect to transport borders determined according to road location, stream flow, and topographic structure of mountainous terrain. To calculate average skidding distance based on surface length between the most suitable existing road segments and centroids of the polygons, a selective process was followed. In this study, vector and raster Geographic Information System (GIS) tools were used. To compare with other approaches and evaluate of the calculus algorithm, various skidding distance determination strategy were improved and applied on the same test area. In this study, spatial analyses have been made for 17 compartments selected from Pamucak Forest Planning Unit of Isparta Forest Region, in Southern of Turkey. According to the results the mean difference between real average skidding distance (ASDR) and shortest average skidding distance (ASDS) was found amount 24 meters for the test area. It has been considered that the ASDR amount calculated in this study is too close to real skidding distance used for harvesting operations. Keywords: Average skidding distance, Transport boundary, GIS, ArcHydro tool

Accuracy Analysis of Multisource DEMs on Extracted River Networks and Drainage Basin by Arc Hydro Tools: A Case Study of Taoerhe River Basin

本文简要分析了HYDRO1K、SRTM3-2、ASTER GDEM 3种数据源基本特征,对数据的水平空间分辨率、现势性、覆盖范围、误差来源进行了比较;阐述了Arc Hydro Tools提取数字河网、划分流域及子流域方法的关键步骤;并以洮儿河流域为研究对象,分析了有(无)河网辅助条件下,3种初始DEM在不同地貌类型中数字河网提取、流域及子流域划分的准确度。研究结果表明:(1)无河网辅助条件下,中山、低山-丘陵地区用三种DEM提取的数字河网与实际均比较吻合;平原地区HYDRO1K提取的主河道与真实主河道相似性较高,而SRTM3-2、ASTERGDEM均出现较大偏差,ASTER GDEM偏差更大;3种DEM提取的流域边界与实际流域边界存在一定的偏差;(2)有河网辅助的条件下,经过河网与流域边界校正后,3种DEM在中山、低山-丘陵地区提取的数字河网,以及平原地区提取的主河道与真实河网与主河道相似性很高,SRTM3-2、ASTER GDEM提取的数字河网改善明显;3组DEM提取的流域边界与实际流域边界较为接近,其中,HYDRO1K提取的流域边界与实际边界基本吻合。

Automated Watershed Evaluation of Flat Terrain

Catchment area and watershed delineation is a common task in hydrology. The determination of the catchment is still as a challenge considered being crucial key issues particular in flat terrains. Three concepts could be briefly identified through: the manual delineation of a catchment based on a topographic map with contour lines which is a difficult task for flat terrains, by combination of field survey or evaluation of satellite images. The present research is focus on evaluating the possibility to delineate catchments from flat and arid areas by means of DTM avoiding hard techniques like river burning or other manual hydrological DTM corrections. Three GIS packages were used (Arc Hydrotools, TNTmips and RiverTools) within two DEM: the 90 m and 30 m SRTM in addition to the ASTER 30 m, the application sample presented by western Iraq desert—Ubaiydh wadi. A brief review is given how the delineation algorithms have been developed since the 1980’s. Where result shows that automated watershed analysis of flat terrains is cannot be done without manual evaluation and correction either by using several seeding points or river burning technique.