Analisis Identifikasi Jaringan Drainase Permukaan Menggunakan Metode Penghalusan DEM LiDAR Feature-Preserving Dan Edge-Preserving Smoothing (Studi Kasus: Sungai Kedungbener, Kecamatan Kebumen)

Informasi akurat terkait konektivitas hidrologi akan diperlukan dalam aliran permukaan daratan yang terkena dampak bencana alam. Seperti halnya pada wilayah Kecamatan Kebumen yang merupakan daerah dengan tingkat kerawanan banjir tinggi, termasuk di daerah sekitar Sungai Kedungbener. DEM resolusi tinggi yang dihasilkan dari data LiDAR dapat memetakan kondisi permukaan daratan secara akurat, namun memiliki tingkat kekasaran dan kompleksitas yang tinggi. Metode penghalusan feature-preserving dan edge-preserving secara umum dapat menghasilkan smoothed DEM LiDAR yang optimal pada nilai parameter tertentu dalam algoritmanya. DEM LiDAR optimal untuk kedua metode penghalusan (FPDEM-S dan EPDEM-S) ditentukan berdasarkan konsistensi efek penghalusannya pada tiap-tiap parameter algoritma. DEM optimal didapatkan pada parameter kernel size 25-31 piksel; normal difference threshold 20o-25o; iterasi 10 kali (metode feature preserving) dan sigma spasial 1,7-2,3 piksel; sigma range 2,0-10,0 meter (metode edge-preserving). Jaringan drainase yang dihasilkan dari FPDEM-S dan EPDEM-S dapat mengidentifikasi hingga fitur drainase kecil di sekitar sawah dan pemukiman. FPDEM-S dan EPDEM-S memiliki karakteristik morfometri aliran dan watershed yang hampir sama, dengan rasio panjang aliran pada FPDEM-S memiliki konsistensi 7% lebih baik. Kedua DEM menghasilkan karakteristik bentuk watershed oval mendekati sirkular

The Application and Relevancy of Rainfall-Runoff-Inundation (RRI) Model in Indonesia

Abstract: Indonesia has a very large number of watersheds and has a very diverse size. Damage to several watersheds in Indonesia has also occurred and often results in catastrophic floods and droughts that threaten people. The presence of the RRI Model with its capabilities will help contribute to watershed management in order to solve water resource problems. The RRI model is a two-dimensional (2D) model capable of simulating runoff, rainfall, and flood inundation simultaneously. The use of this model in Indonesia has reached 13 times which was compiled based on the number of publications on the application of the RRI model. All of these publications have passed peer-reviewed papers from both journals and conference papers. Applications have been made in several places including the Solo watershed, the Upper Citarum watershed, the Batanghari watershed, and the upstream Brantas watershed. Given the increasing number of problematic watersheds in Indonesia, the use of this model has the prospect and relevancy of being carried out in other watersheds. However, until now, researchers have had challenges in building hydrological models because of the constraints on the availability of climatological and hydrological data in the watershed. Therefore, in addition to improving the data measuring infrastructure in the field, remote sensing techniques are also needed in an effort to generate targeted watershed information. In fact, the effort to utilize remote sensing in generating unmeasurable data in the field has been successfully conducted in several studies.Abstrak: Indonesia memliki jumlah DAS yang sangat banyak dan memiliki ukuran yang sangat beragam. Kerusakan beberapa DAS di Indonesia juga telah terjadi dan sering berakibat bencana banjir dan kekeringan yang mengancam penduduk setempat. Kehadiran Model RRI dengan kemampuannya akan membantu berkontribusi dalam memajemen DAS ataupun dalam usaha untuk menyelesaikan permasalahan sumberdaya air. Model RRI adalah suatu model dua dimensi (2D) yang memiliki kemampuan untuk mensimulasikan limpasan curah hujan dan genangan banjir secara simultan. Penggunaan model RRI ini di Indonesia telah mencapai 13 kali, yang tercatat berdasarkan jumlah publikasi yang terkait dengan aplikasi model RRI. Semua publikasi tersebut telah melewati peer-review baik dari jurnal maupun dari konferensi. Aplikasi telah dilakukan dibeberapa tempat termasuk DAS Solo, DAS Citarum, DAS Batanghari, dan DAS Brantas. Mengingat jumlah DAS yang bermasalah di Indonesia semakin meningkat, maka penggunaan model ini memiliki prospek untuk dilakukan di DAS lain. Namun sampai saat ini, para peneliti memiliki tantangan dalam membangun permodelan hidrologi karena terkendala pada ketersediaan data klimatologi dan hidrologi di dalam DAS. Oleh karena itu, selain peningkatan infrastruktur pengukur data dilapangan dan teknik pengindraan jauh juga diperlukan dalam usaha menyediakan informasi DAS yang ditargetkan. Usaha penggunaan teknik pengindraan jauh dalam menyediakan data yang tidak terukur dilapangan telah sukses dan terbukti dilakukan di beberapa studi

An Assessment Of The Impact Of Dem Interpolation Technique, Resolution, And Terrain Type On The Extraction Of Drainage Network

This research used points extracted from high-resolution DEMs (1m) to investigate the impact of resolution, interpolation method and topography on the accuracy of drainage network extraction. The investigation was conducted by evaluating the accuracy of the estimations of streams length, streams number, drainage density, and the Longitudinal Root Mean Square Error (LRMSE) of the extracted drainage networks from different DEMs interpolated using Topo to raster, Natural Neighbor (NN), kriging and IDW interpolation methods at 5, 10, 15 and 20m resolutions over moderate, steep, and gentle slope terrain. Each evaluation conducted yielded a different result, but the accuracy of the streams length estimation for most of the DEMs at all the sites increases with an increase in streams order. The total lengths of all the streams of each of the extracted networks at gentle and steep slope sites are shorter than those of the corresponding reference networks though, 15 and 20m kriging and IDW DEMs created longer streams at the moderate slope site. IDW DEMs have proven reliable for streams length estimation while Topo to raster 5, 10, and 15m for streams number estimation. In general, N.N. extracted networks are the only networks that show consistency in the streams length and number estimations, drainage density estimation as well as in LRMSE and DEM RMSE computation at all the resolutions and for all the sites. Therefore, the accuracy of N.N. DEMs and their derivatives do not rapidly change with change in resolution, especially between 5 and 20m at all (steep, gentle and moderate) terrain types

Impact of DEM Resolution and Spatial Scale: Analysis of Influence Factors and Parameters on Physically Based Distributed Model

Physically based distributed hydrological models were used to describe small-scale hydrological information in detail. However, the sensitivity of the model to spatially varied parameters and inputs limits the accuracy for application. In this paper, relevant influence factors and sensitive parameters were analyzed to solve this problem. First, a set of digital elevation model (DEM) resolutions and channel thresholds were generated to extract the hydrological influence factors. Second, a numerical relationship between sensitive parameters and influence factors was established to define parameters reasonably. Next, the topographic index (TI) was computed to study the similarity. At last, simulation results were analyzed in two different ways: (1) to observe the change regularity of influence factors and sensitive parameters through the variation of DEM resolutions and channel thresholds and (2) to compare the simulation accuracy of the nested catchment, particularly in the subcatchments and interior grids. Increasing the grid size from 250 m to 1000 m, the TI increased from 9.08 to 11.16 and the Nash-Sutcliffe efficiency (NSE) decreased from 0.77 to 0.75. Utilizing the parameters calculated by the established relationship, the simulation results show the same NSE in the outlet and a better NSE in the simple subcatchment than the calculated interior grids

Vertical accuracy assessment of improvised global digital elevation models (MERIT, NASADEM, EarthEnv) using GNSS and airborne IFSAR DEM

During the last decades, freely available GDEMs, such as ASTER, SRTM, and AW3D30, have been widely used in many applications such as for environmental, spatial analysis, research in geomorphology, hydrology, etc. However, these available GDEMs suffer from various limitations. In order to enhance the quality and accuracy of GDEMs, several GDEMs have been merged or reprocessed using a more rigorous method to develop new GDEMs. The advent of these new improvised GDEMs has advanced their applications. Unfortunately, there are very limited studies that focus on the comprehensive and systematic evaluation of the quality of improvised GDEM. Therefore, this study examines the vertical accuracy of three freely available improvised GDEMs (MERIT, NASA, and EarthEnv GDEMs) over the northern region of Peninsular Malaysia using 7757 GNSS points and two reference model, i.e., TanDEM-X DEM 12m resolution and local airborne IFSAR DEM 5m resolution. The accuracy assessments have been performed over three different land covers (urban, non-forest, and forest areas) to evaluate the impact of different land covers on the GDEM's accuracy. Since SRTM DEM is the primary data input in the improvised GDEM, this GDEM is also considered to identify the performance of the new improvised GDEMs. Comparison with GNSS points shows that the accuracy of MERIT DEMs outperforms SRTM DEM and other GDEMs with RMSE of ±2.668m, followed by NASA (±3.656m), SRTM (±5.666m), and EarthEnv (±5.948m). The vertical accuracy of DEM varies with different land cover conditions. Comparison with TanDEM-X and IFSAR DEM shows that all tested GDEMs' accuracy is high over a nonforest area, followed by urban area, and worse over forest area. Overall, the tested GDEM shows only a slight improvement compared to the SRTM. However, these results will help users in selecting the optimum DEM for any applicatio

USE OF LIDAR-DERIVED TERRAIN AND VEGETATION INFORMATION IN A DECIDUOUS FOREST IN KENTUCKY

The use of Light Detection and Ranging (LiDAR) information is gaining popularity, however its use has been limited in deciduous forests. This thesis describes two studies using LiDAR data in an Eastern Kentucky deciduous forest. The first study quantifies vertical error of LiDAR derived digital elevation models (DEMs) which describe the forests terrain. The study uses a new method which eliminates Global Positioning System (GPS) error. The study found that slope and slope variability both significantly affect DEM error and should be taken in to account when using LiDAR derived DEMs. The second study uses LiDAR derived forest vegetation and terrain metrics to predict terrestrial Plethodontid salamander abundance across the forest. This study used night time visual encounter surveys coupled with zero-inflation modeling to predict salamander abundance based on environmental covariates. We focused on two salamander species, Plethodon glutinosus and Plethodon kentucki. Our methods produced two different best fit models for the two species. Plethodon glutinosus included vegetation height standard deviation and water flow accumulation covariates, while Plethodon kentucki included only canopy cover as a covariate. These methods are applicable to many different species and can be very useful for focusing management efforts and understanding species distributions across the landscape

Supraglacial drainage efficiency of the Greenland Ice Sheet estimated from remote sensing and climate models

Supraglacial stream/river catchments drain large volumes of surface meltwater off the southwestern Greenland Ice Sheet (GrIS) surface. Previous studies note a strong seasonal evolution of their drainage density (Dd), a classic measure of drainage efficiency defined as open channel length per unit catchment area, but a direct correlation between Dd and surface meltwater runoff (R) has not been established. We use 27 high-resolution (∼0.5 m) satellite images to map seasonally evolving Dd for four GrIS supraglacial catchments, with elevations ranging from 1100 m to 1700 m. We find a positive linear correlation (r2 = 0.70, p<0.01) between Dd and simulations of runoff production from two climate models (MAR v3.11 and MERRA-2). Applying this R-Dd empirical relationship to climate model output enables parameterization of spatial and temporal changes in supraglacial drainage efficiency continuously throughout the melt season, although temporal and spatial skewness of Dd observations likely affects the application of this R-Dd relationship on crevasse fields and snow/firn surfaces. Incorporating this information into a simple surface routing model finds that high runoff leads to earlier, larger diurnal peaks of runoff transport on the ice surface, owing to increased Dd. This effect progressively declines from low (∼1100 m) to high (∼1700 m) elevation, causing a roughly order-of-magnitude reduction in diurnal runoff variability at the highest elevations relative to standard climate model output. Combining intermittent satellite Dd mapping with climate model output thus promises to improve characterization of supraglacial drainage efficiency to the benefit of supraglacial meltwater routing and subglacial hydrology models

Modeling the spatial and temporal trends of water quality in boreal managed watersheds

Land use changes have altered natural hydrological pathways and biogeochemical cycling of carbon, nitrogen and phosphorus, among other elements, affecting the quality of aquatic ecosystems such as rivers, lakes and coastal areas. In this dissertation, the spatial and temporal trends of water quality variation in Finnish managed watersheds was studied by applying methods of multivariate statistics, time-series analysis, ecohydrological modeling and high-resolution geospatial data. The results show the complex effects of current land use, particularly agriculture, on stream water quality. New emerging trends of nutrient concentrations and loads were detected in the time-series analysis, such as an increase in the concentrations and loads of dissolved reactive phosphorus and total nitrogen, and a decrease in suspended sediment concentration in streams. This might be linked to the current erosion reduction strategy of land management for water protection. An ecohydrological modeling assessment showed an increasing downstream nutrient export from agricultural watershed under climate change scenarios. The modeling results also showed a potential nutrient export reduction by restoring potential biogeochemical hotspot areas - wet areas or areas prone to water saturation. These areas can function as nutrient sinks and enhance the watershed resiliency. High-resolution geospatial data allowed easier and more accurate mapping of wet areas as well as the extracting of their hydraulic characteristics. However, the ecohydrological models involved several sources of uncertainties, which need to be carefully addressed with extensive observational data, expert knowledge of model parameter definitions, proper modeling unit selection and empirical knowledge of the functioning of the studied watershed system. The results of this dissertation highlight the importance of combined methods for watershed management research, and the proper identification of the biophysical processes in the modeling of non-point pollutant sources; this can in turn lead to an efficient water protection measure, and restoring biogeochemical hotspot areas within the watershed.Vedenlaadun alueellisten ja ajallisten vaihteluiden mallintaminen viileän vyöhykkeen valuma-alueilla. Maankäytön muutokset ovat vaikuttaneet luonnollisiin hydrologisiin prosesseihin sekä hiilen, typen ja fosforin biogeokemiallisiin kiertoihin. Nämä puolestaan vaikuttavat vesiekosysteemien tilaan joissa, järvissä ja rannikkoalueella. Väitöstutkimuksessa tutkittiin vedenlaadun alueellisia ja ajallisia muutoksia suomalaisessa maaseutumaisemassa käyttäen monimuuttujamenetelmiä, aikasarja-analyysejä, ekohydrologista mallinnusta ja erotuskyvyltään tarkkoja paikkatietoaineistoja. Tulokset todentavat maatalouteen kytkeytyvien maankäytön piirteiden kompleksisia vaikutuksia jokivesien laatuun. Aikasarja-analyysit osoittivat myös aiemmin tuntemattomia trendejä jokivesien ravinteiden määrissä ja pitoisuuksissa, esimerkkeinä liuenneen reaktiivisen fosforin määrän ja pitoisuuden lisääntyminen sekä sedimenttisuspension väheneminen; molemmat eroosion vähentämiseen tähtäävien vesiensuojelutoimien seurauksena. Ekohydrologinen mallinnus osoitti myös sen, että ravinteiden huuhtoutuminen maatalousvaltaisilla valuma-alueilla lisääntyy ilmastonmuutoksen seurauksena. Tulokset kannustavat biogeokemiallisten avainalueiden, kuten kosteikkojen ja vettä keräävien painanteiden kunnostamiseen, jolloin ravinteiden huuhtoutuminen vähenee. Ravinnenieluina toimiessaan ne voivat myös parantaa valumaalueen ekologista kestävyyttä ja palautumiskykyä. Tutkimuksessa osoitettiin myös erotuskyvyltään tarkkojen paikkatietoaineistojen hyödyllisyys avainalueiden kartoituksessa ja alueiden hydrologisten ominaisuuksien tunnistamisessa. Ekohydrologiseen mallinnukseen sisältyy toisaalta myös epävarmuustekijöitä, joihin tulisi paneutua vielä kattavammin hyödyntäen asiantuntijatietoa parametrien täsmentämisessä, määrittämällä tarkennettuja mallinnusyksiköitä tai hyödyntäen empiirisiä tutkimustietoja valuma-alueen toiminnasta. Väitöstutkimus osoittaa myös sen, miten erilaisten tutkimusmenetelmien yhdistely vahvistaa valuma-aluetarkastelua ja siihen liittyen erilaisten biofysikaalisten prosessien ymmärtämistä ja keskeisten päästölähteiden mallintamista. Näin muodoin yhdistelmämenetelmien käyttö tukee entistä tehokkaampien vesiensuojelutoimien kehittämistä ja valumaalueiden biogeokemiallisten avainalueiden kunnostamistaModelado de las tendencias temporales y espaciales de la calidad del agua en cuencas hidrográficas boreales manejados. El cambio del uso del suelo ha alterado los procesos hidrológicos naturales y los ciclos biogeoquímicos del carbono, el nitrógeno y el fósforo, entre otros elementos, afectando directamente la calidad de los ecosistemas acuáticos como los ríos, lagos y zonas costeras. En esta disertación, las tendencias espaciales y temporales de la variación de la calidad del agua en cuencas hidrográficas finlandesas se estudiaron mediante la aplicación de métodos de estadística multivariante, análisis de series de tiempo, modelos ecohidrológicos y datos geoespaciales de alta resolución. Los resultados muestran los efectos complejos del uso actual del suelo, particularmente la agricultura, en la calidad del agua de los ríos y corrientes. Se detectaron nuevas tendencias emergentes de concentraciones y cargas de nutrientes en el análisis de series temporales, como un aumento en la concentración y carga del fósforo disuelto reactive y nitrógeno total, y una disminución en la concentración de sedimentos en suspensión en los ríos y corrientes. Esto podría estar vinculado a la estrategia actual de manejo del suelo, orientado a la reducción de la erosión para la protección del agua. Una evaluación a través de modelización ecohidrológica mostró un aumento de la exportación de nutrientes aguas abajo de la cuenca agrícola bajo escenarios de cambio climático. Los resultados de la modelización también mostraron una posible reducción de la exportación de nutrientes mediante la restauración de posibles zonas críticas biogeoquímicas: áreas húmedas o áreas propensas a la saturación de agua. Estas áreas pueden funcionar como sumideros de nutrientes y mejorar la resiliencia de la cuenca. Los datos geoespaciales de alta resolución permitieron un fácil y más preciso cartografiado de las áreas húmedas, así como la extracción de sus características hidráulicas. Sin embargo, los modelos ecohidrológicos involucraron varias fuentes de incertidumbre, que deben abordarse cuidadosamente con bastantes datos de observación, conocimiento experto de las definiciones de los parámetros del modelo, selección adecuada de la unidad de modelado y conocimiento empírico del funcionamiento del sistema de la cuenca estudiada. Los resultados de esta disertación destacan la importancia de los métodos combinados para la investigación de gestión de cuencas hidrográficas y la identificación adecuada de los procesos biofísicos en la modelización de fuentes contaminantes difusas; esto a su vez puede conducir a una medidaeficiente de protección del agua, y restauración de áreas claves de alta función biogeoquímica dentro de la cuenca

Sediment Dynamics and Channel Connectivity on Hillslopes

The pattern, magnitude, and frequency of hillslope erosion and deposition are spatially varied under the influence of micro-topography and channel geometry. This research investigates the interrelationships between erosion/deposition, micro-topography, and channel connectivity on a hillslope in Loudon, Tennessee using the centimeter (cm) level temporal Digital Elevation Models collected using laser scanning. This research addressed (1) the effect of spatial resolution on the erosion/deposition quantification, and rill delineation; (2) the influences of micro-topographic factors (e.g. slope, roughness, aspect) on erosion and deposition; (3) the relationship between the structural connectivity -- depressions and confluence of rills -- and the sedimentological connectivity. I conducted (1) visual and quantitative assessments for the erosion and deposition, and the revised automated proximity and conformity analysis for the rill network; (2) quantile regression for micro-topographic factors using segmented rill basins; and (3) cross-correlation analysis using erosion and deposition series along the channels.Overall, rills are sedimentologically more dynamic than the interrill areas. A larger grid size reduces the detectable changes in both areal and volumetric quantities, and also decreases the total length and number of rills. The offset between delineated rills and the reference increases with larger grid sizes. A larger rill basin has higher erosion and deposition with the magnitude of erosion greater than deposition. The slope has a positive influence on erosion and a negative one on deposition; roughness has a positive influence on deposition and a negative one on erosion. Areas that are more north-facing experience higher erosion and lower deposition. Rill length explains 46% of the variability for erosion and 24% for deposition. The depressions are associated with higher erosion in the downslope direction. The correlations between the erosion and the confluence are positive; the correlation between the deposition and the sink is positive. Overall, the influence of structural connectivity on the sedimentological connectivity is within 25 cm in both upstream and downstream directions. This research contributes to the understanding in how the sediment movement on hillslopes is governed by topographic variations and channel connectivity, and future work may explore hillslope channels at broader geographical and temporal scales

What is the Effect of LiDAR-Derived DEM Resolution on Large-Scale Watershed Model Results?

This paper examines the effect of raster cell size on hydrographic feature extraction and hydrological modeling using LiDAR derived DEMs. LiDAR datasets for three experimental watersheds were converted to DEMs at various cell sizes. Watershed boundaries and stream networks were delineated from each DEM and were compared to reference data. Hydrological simulations were conducted and the outputs were compared. Smaller cell size DEMs consistently resulted in less difference between DEM-delineated features and reference data. However, minor differences been found between streamflow simulations resulted for a lumped watershed model run at daily simulations aggregated at an annual average. These findings indicate that while higher resolution DEM grids may result in more accurate representation of terrain characteristics, such variations do not necessarily improve watershed scale simulation modeling. Hence the additional expense of generating high resolution DEM\u27s for the purpose of watershed modeling at daily or longer time steps may not be warranted