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1

Comparison of depression removal methods implemented in open-source software

Šamanović Sanja, Markovinović Danko, Cetl Vlado, Đurin Bojan

GIS Odyssey Journal

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2022

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Vol. 2, no. 1

85--97

EN

Modern tools for hydrological analysis are based on data derived from DEM. Hydrological methods that create a stream network by overland flow simulation require to remove depression (pit or sink) on DEM first. Depression occurs when a cell or group of cells is surrounded by adjacent cells at higher altitudes. Even though their removal creates an incorrect DEM, it is common practice to remove all topographic depressions (real, artificial, or combined) not to interrupt the creation of stream networks. There are two basic methods of depression removal: the filling method and the carving or breaching. Combined methods contain good characteristics of both procedures. GIS software includes a depression removal algorithm within its hydrological analysis module. The paper investigates which methods are implemented within individual open-source software SAGA and GRASS. A comparison of DEM before and after depression removal for each method is given. The methods were tested on a DEM, resolution 5x5 meter for a hilly area intersected by a significant number of watercourses.

2

Analiza przestrzennego układu sieci dróg i cieków w gminie wiejskiej

Fiedler M., Antkowiak M., Sojka M.

Inżynieria Ekologiczna

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2014

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Nr 39

51--61

PL

Drogi i związana z nimi infrastruktura mogą znacząco oddziaływać na stan środowiska. Sieć drogowa wpływa na wielkość spływów powierzchniowych i może prowadzić do zmian w obiegu wody w środowisku. Zwiększenie wielkości terenów nieprzepuszczalnych wpływa na zmniejszenie infiltracji i zdolności retencyjnych, co powoduje, że w okresach roztopów oraz opadów burzowych punkty łączne sieci dróg i cieków stanowią dodatkowe źródło wody dopływającej do cieków. Prowadzi to do zwiększenia fal wezbraniowych oraz przyspiesza czas ich wystąpienia. W pracy przedstawiono metodę pozwalającą na określenie obszarów szczególnie narażonych na zwiększony dopływ wód powierzchniowych do cieków. Do analizy wykorzystano takie parametry jak: gęstość sieci cieków, gęstość sieci drogowej, rozkład punktów łącznych obu sieci oraz długość cieków w odległości mniejszej niż 100 m od dróg. Wyniki badań wykazały liczne występowanie punktów łącznych wynikające z dość dużej gęstości zarówno sieci drogowej, jak i sieci cieków. Analizowany obszar wykazuje równocześnie dużą zmienność możliwości wpływu dróg na przepływy w ciekach. Tereny o najwyższym zagrożeniu zajmują prawie 25% powierzchni całkowitej i powinny podlegać szczegółowej analizie w kontekście zagospodarowania przestrzeni.

EN

Roads and infrastructure strongly influenced on the environment. Therefore an effect of road network on hydrological conditions of watershed should be taken into account. Road networks have an effect on surface water flow and lead to direct and indirect changes of water circulation in the environment. Road networks appear to have increased contribution of impermeable areas and decreased infiltration and retention capabilities. This effect in increasing of flood waves peak and also expedite time to their occurrence. During storms or snow melting junctions of road and stream networks could be additional sources of water flowing directly from road surface or from ditch to the stream. In the paper we describe method which could help to find areas with high interaction between road networks and stream networks. Examined area of Kleszczewo community was divided into grid which consist of 92 square cells of 1 km side size. For each cell we described the interaction of roadand stream networks. The generalized factor take into account density of stream network, density of road network, number of junctions of both networks and length of roads closer than 100 m from streams in each cell. Calculated values of the factor allow to distinct three classes of interaction possibilities. Results of investigation showed that the community area has big density of stream network, as well as road network what effect in numerous junction points. The majority of junctions occur between streams and field roads. Analyzed area show great variability in possibility of interaction between road network and stream network occurrence. Areas with highest possibility of such interaction took almost 25% of total area. Such places could effect in higher direct storm water flow into streams, and in consequence higher flood peaks.

3

Kinematic model of solute transport in stream networks: example with phosphate retention in Morsa Watershed, Norway

Wörman A., Klove B., Wachniew P.

Archives of Hydro-Engineering and Environmental Mechanics

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2004

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Vol. 51, nr 1

41-53

EN

A theoretical description of reactive solute transport in a network of stream channels is derived by convoluting unit solutions based on a physical representation of transport and topographical information of the distributions of solute load as well as pathways. The theory is applied to a generic analysis of the phosphate export in Morsa watershed due to the load from 620 individual households with a local wastewater treatment. Essential factors for the phosphate export is filtering of the water in stream-bed sediments through a distribution of hyporheic flow paths of various lengths. This generic study indicates that a significant portion of phosphate is retained in the hyporheic zones for a long time. The 90\% recovery time following a hypothetical remediation action in the households is expected to be in the order of one decade.