Sustainable stormwater management in Sogndal Tewelde Mebrahtu Tesfay Master Thesis in Climate Change Management Department of Environmental Sciences, Faculty of Engineering and Science WESTERN NORWAY UNIVERSITY OF APPLIED SCIENCES Sogndal [May, 2019] I confirm that the work is self-prepared and that references/source references to all sources used in the work are provided, cf. Regulation relating to academic studies and examinations at the Western Norway University of Applied Sciences (HVL), § 10. Sustainable stormwater management in Sogndal Master thesis in Climate Change Management Author: Tewelde Mebrahtu Tesfay Author sign. Tewelde Thesis submitted: Open/confidential thesis Spring 2019 Main Supervisor: Dr.Thorben Dunse Co-supervisors: Ms.Eli Anine Heiberg Keywords: Number of pages: 67 Stormwater, Climate change, Land use + modification, Sustainable stormwater Appendix: 6 management Sogndal, 03.06.2019 Place/Date/year This thesis is a part of the master’s program in Climate Change Management (Planlegging for klimaendringer) at the Department of Environmental Sciences, Faculty of Engineering and Science at the Western Norway University of Applied Sciences. The author(s) is responsible for the methods used, the results that are presented and the conclusions in the thesis. Preface This thesis paper is submitted for the master degree, of climate change management at the Western Norway University of Applied Sciences in Sogndal. The research study was conducted under the supervision of Dr.Thorben Dunse and Ms.Eli Anine Heiberg in the department of environmental sciences, faculty of engineering and science. I would like to thank all the teachers, friends and students at the faculty of Engineering and science and the administration staff in Western Norway University of Applied Science of Sogndal, who helped me in writing this thesis. I would like to give my special thanks to Dr.Thorben Dunse and Ms. Eli Anine Heiberg for their provision of important guidance and investing a lot of time and efforts in supervising my work. Furthermore I would like to thank for Sogndal municipality and especially for engineer Tola Bake and Markus Mohn Werner for data supply of municipal stormwater management system and planning. I would like to thank for my friend Christian, for his helping me to use his GPS and his guiding when I am using the GIS tool. I Abstract Stormwater management is a strategy of handling excess runoff water, which accumulate from precipitation and flow over the surface. There is a need for stormwater management in the northern side of the city of Sogndal, from the lower area of Foss up to the upper areas of Bergi and Tona. The management of stormwater using pipe systems is challenging many cities nowadays because changes in climate conditions and the modifications in land use elements, increase runoff in volume and speed. In addition, those changes affect the ecosystem elements in the sites. The purpose of this project is to analyse the changes made in the land use elements, catchments areas, the volume of runoff discharge from them and finding potential of the site, where it is possible to open the natural streams. For that purpose, a conceptual plan design is developed, which helps minimizing the runoff and increase landscape quality in the same time. Some of the findings of this study indicate that stormwater will be challenging in the future with increasing precipitation levels, due to the modifications that were made in land use elements and capacity of the existing pipes. However, blue- green solution is an alternative treatment for stormwater challenges. It fit to work in cooperation with the other stormwater management solutions and it can give benefits in minimizing runoff challenges, ecosystem improvements and aesthetics. II Sammendrag på norsk Det er behov for overvann håndtering i nordsiden av Sogndal, fra det nedre området Foss opp til de øvre områdene Bergi og Tona på stedet. Overvann håndtering er en strategi for å minimere overskytende avløpsvann, som akkumuleres fra nedbør og strømmer over overflaten. Forvaltningen av overvann som bruker rørsystemer utfordres i mange byer i dag. Fordi endringene i klimaforhold og endringene i arealbruk elementer øker avrenninga i volum og hastighet. I tillegg påvirker disse endringene økosystemelementene på nettstedene. Formålet av dette prosjektet er å analysere enderingene i arealbruk elementene, avløpsområdene, volumet av avløps utslipp fra dere og finne potensialet på stedet der er mulig å åpne de naturlige avløpene. Videre utvikle en konsept planløsning som bidrar til å minimere overvann og kan gi bedre kvalitet av arealbruk. Noen resultat av denne Project viste at overvann vil våre utfordring i fremtiden med økende nedbørs nivå, på grunn av endringene ble gjort i arealbruk elementene og kapasitet av eksisterende rør. Blågrønn løsning er imidlertid en alternativ løsning for å minimere overvann utfordringene. Fordi det passer til å fungere sammen med de andre overvann håndtering løsninger, og de kan gi fordeler ved å minimere avrenninga utfordring, økosystemforbedringer og arealbruk estetikk. III IV Table of contents Preface…………………………………………………………….…………………………..I Abstract……………………………………………………..…………………………….....II Samandrag på norsk………………………………………………………………....................III Table of contents………………………………………………………………………...…...V 1. Introduction…………………………………………………………..………………..…..8 1.1 Stormwater management in urban area………..………………………………….....8 1.1.2 Effects of climate change……………………………….…………….……....…9 1.1.3 Catchment charactrestics………………………………………..…………...…11 1.1.4 Runoff characteristics…………………………………………………….…….12 1.1.5 Challenges of stormwater management's pipe systems ………………………..13 1.1.6 Sustainable stormwater management with urban infrastructures ……………...14 2. Study site and Methods ……………………………………………….…………….…16 2.1 Study site northern side of Sogndal city……………………………………......…16 2.1.1 Intensity of precipitation ……………………………………..……………….19 2.2 Method…………………………….………………………………………………22 2.2.1 Hydrological analysis in(GIS)……………………………..………………..…22 2.2.1.2 Soil Infiltration ability……………………………..……………………….24 2.2.1.3 Land use elements …………………………………… ………………......24 2.2.1.4 Municipal stormwater management systems………………………..….….24 2.2.2 AutoCAD……………………………..………………………………………25 2.2.3 Field work ……………………………………..………………..…………….25 2.2.4 Rational method …………………………………………...…….……………25 2.2.4.1 Runoff coefficient ………………………………………………………….26 2.2.4.2 Time of concentration …………………………………………………...…27 2.2.4.3 Climate factor………………………………………………….……………27 2.2.5 Manning equation………………………………………………..………… 27 3. Results……………………………………………………………………………………29 V 3.1 Land use categories of the study site ………………………..…………………..29 3.2 Soil infiltration ability of the study site …………………………………….…...30 3.3 Study site natural catchments and their characterstics ……………………….....32 3.3.1 Stormwater discharge from the natural catchments ………………………...34 3.4 Municipal stormwater management systems and modified catchments ………...35 3.4.1 characterstics of the modified catchments……………………. ………….....39 3.4.2 Stormwater discharge from the modified catchments ………………...……..40 3.4.3 Total runoff from the modified catchments and the capacity of the pipes on their outlets…………………………………………….....………………………………………..42 3.5 Stormwater management plan of the study sites…………………………..……..43 3.5.1 Existing situation of Foss and Fosshaugane………………….……………....44 3.5.1..1 Buildings……………………………..……………………………….......45 3.5.1.2 Roads……………………………………………………….………….…46 3.5.1.3 Parkings ……………………………………….…………………………47 3.5.2 The planning situation………………………………….……………………..48 3.5.3 Principal plan for opening existing pipes………………….…………………49 3.5.3.1 Areal zone 1……………………………………….…………………..…51 3.5.3.2 Areal zone 2………………………………………….…………………..53 3.5.3.3 Areal zone 3……………………………………….……………………..54 3.5.3.4 Areal zone 4 ………………………………….………………………….56 3.5.3.5 Areal zone 5……………………………………….……………………..57 3.5.3.6 Areal zone 6…………………….………………………………………..59 4. Discussion……………………………………………………………………………...60 4.1 Results interpretation……………………………………………………………….60 4.2 Uncertainties and limitations of input data…………………………….……..….…61 4.3 Uncertainties and limitations of the methods……………………………….……...62 4.4 recommendation…………………………………….……………………………...63 5. Conclusion……………………………………………………………………………..63 6. References…………………………………………………………………………..…65 VI 7. Appendix………………………………………………………………………………68 VII 1. Introduction 1.1 Stormwater management in urban area Stormwater is the excess water that flows over the surface. It accumulates from precipitation during rain and snow melt events. Stormwater management is the effort to handle the excess runoff (Nie, Skallebakke, Campisano, & Marsalek, 2013) using different systems, such as Green infrastructure (GI) practices (Zhang & Chui, 2018), Low Impact Development (LID), and Water Sensitive Urban Design (WSUD), while also taking into consideration the future climate change (Roy et al., 2008). Stormwater is influenced and reshaped by precipitation, types of land use, density of buildings, snow melting and topography (Nie et al., 2013). Climate change, compacted urbanization, increased fraction of impermeable surface, are escalating the challenges of stormwater in most urban areas (Nie, Øyen, Groven, & Aall, 2011). Climate change is manifested in both temperature and precipitation. The changes in precipitation will increase the rainfall level in many monsoon regions across the world (Eckstein, Paisley, Burchi, Curlier, & Stephan, 2010). The expected changes of climate variables in Norway are summarized