Petteri Alho

Determination of aboveground biomass (AGB) requires accurate measurements from individual trees including measurements of height, multiple stem diameters, density of the wood, bark and branches, and dry mass of the needless. These measurements are time-consuming and expensive, and can only be collected in a destructive manner. Terrestrial and airborne laser scanning (TLS / ALS) are promising techniques for measuring the required tree attributes that can be used in the estimation of AGB of the single trees. TLS and ALS produce dense three-dimensional (3D) point clouds that can be used in extraction of various tree attributes. The main objective was to develop and evaluate the accuracy of a combination of ALS and TLS in total AGB modelling. The study also reviews state-of-the-art in laser scanning-based single tree AGB modelling. The use of ALS in the estimation of canopy biomass have been promising, but can be further improved with TLS data. Thus, in the further studies TLS and ALS should be combined to improve the single tree AGB modelling accuracy.

The demand for cost­efficient aboveground biomass (AGB) mapping applications at all forest levels is growing worldwide. Airborne laser scanning (ALS) is a promising mapping technique, due to its capability for measuring three­dimensional vegetation structure. The National Land Survey of Finland (NLS) began collecting ALS data throughout Finland in 2008, and collected dataset has great potential for and a wide variety of possible applications in forestry. The main objective of the study was to evaluate the accuracy of NLS's ALS data in estimation of plot­level AGB and to compare it with existing large­scale forest­mapping techniques, which utilizes satellite imagery and ground plots. The results showed that ALS data can be used to estimate AGB with accuracy of 26.1–38.1%. The accuracy was significantly higher than in MS­NFI which was caused by differences in the RS data utilized To fully utilize the potential of NLS's ALS data, the following questions should be addressed: 1) the optimal amount of training data required for nearest neighbour estimation, 2) calibration of the ALS data caused by leaf­off situations and 3) effect of varying scanning equipment and parameters on the estimation accuracy. The supportive strengths of the nationally available ALS data are the low costs of the data and the need for new more accurate and cost­efficient methods to map and monitor forest AGBs.

Digital twins are part of ongoing digital transformation to test, monitor, and maintain physical environments virtually. The collaboration of smart measurement sensors, advanced communication networks, cloud data storage capacity, and cutting-edge computing techniques has the potential to create a digital twin of a river basin with greater physical, spatial, and temporal scalability. The digital twin is defined as a realistic virtual representation of the physical river basin that aids in improved decision-making through real-time data connectivity, association, and relationship. Because of the continuous bidirectional interactions between virtual and physical entities, the digital twin is unique to the physical river basin. The digital twin has the advantage of adapting to changing real-time river basin characteristics, resulting in increased operational efficiency, better uncertainty quantification, early warning detection, and identification of emergency management. By imagining smart river basin management via the digital twin concept, we are venturing into uncharted territory, with the goal of improving the ecological status of a river basin by balancing environmental and socioeconomic interdependence while minimizing natural resource depletion. This poster provides an overview of the concept, framework, methodology, and challenges involved in developing a digital twin of a river basin. The framework’s six dimensions are river basin, data, modeling, infrastructure, service, and connectivity. The methodology emphasizes the digital twin’s purpose identification, maturity spectrum, workflow architecture, technical core, data layers, model simulations, knowledge creation, and effective application. We discuss the key services provided by the digital twin for the river basin, as well as its future prospects for autonomous control in the physical river basin.

<p>The global climatic change has been projected to affect hydrology, ice-covered flow period and river morphology, including changed sediment transport conditions, in northern high-latitude regions. For understanding the impacts of expected shortening of frozen period on sediment transport, it is needed to understand the present sediment transport conditions in high-latitude northern rivers with annually occurring ice cover. Thus, the aims of this paper are 1) to define the impacts of ice-cover on near-bed flow characteristics during hydrologically varying years, and 2) to analyze the impacts of these mid-winter flow-characteristics on sediment transport potential. The analyzes are based on Acoustic Doppler Current Profiler (ADCP: 2016–21) and Acoustic Doppler Velocimeter (ADV: 2020-21) measurements performed in mid-winter ice-covered conditions of sandy and small (circa 20 m wide) Pulmanki River, Northern Finnish Lapland.</p><p> </p><p>Despite the ice-covered river conditions, there is sediment transport throughout the year. The critical shear velocities of mid-winter conditions were exceeded each winter (2016-21), bedload transport occurred according to bedload measurements, and calculated bed capture rates (Gaeuman and Jacobson [2006] method) indicate transport. Three different situations occurred regarding the sediment transport and near-bed velocity conditions: 1) high measured mid-winter discharges indicate high velocities throughout the meander bend; 2) low measured mid-winter discharges inidate low near-bed velocities throughout the meander bend; 3) winters having intermediate discharges indicate near-bed velocities and sediment transport potential being higher at the upstream inlet and apex sections of the meander bend, but clearly lower downstream of the apex. The confinement by the river ice cover, i.e. bottom-fast ice, explains the velocity variation. The near-bed velocities were the highest at the upstream inlet section of a symmetrical meander bend, where the measurement cross-sections were narrower and shallower. The velocities were the lowest downstream of the apex, where the channel changed from relatively narrow to wider and deeper.</p>

<p>A competence center of the water sector for boreal and subarctic catchment, river and lake environments was highly needed, as impacts of climate change on river basins, adaptation, and resilience request detailed analysis of the behavior of river basins under extreme conditions. This further demands detailed measurements in time and space of morphological, hydrological, and biological variables. A consortium of private and public institutions in Finland have been formed to establish a Sustainable Freshwater Competence Centre to support detailed monitoring, research, development of new techniques and equipment innovation.</p><p>The complete venture structure includes a network of public and private institutions that supports measurement the development of instruments; a research infrastructure, composed of eight sites (three supersites), and the development of digital solutions, such as digital twins and data transfer, to generate cost-effective monitoring and model river connectivity, hydrological processes, as well as nutrient and carbon loads from different land use in multi scale river basins.</p><p>Hydro-RDI-Network was inaugurated in 2021 to serve as the first Finnish competence center of the water sector. It aims to improve and implement river and catchment measurement, mapping, modelling approaches, and innovation. The Hydro-RI-Platform research infrastructure (2022 onwards) will facilitate solving environmental issues (e.g. erosion, flooding, water quality) of these fragile boreal and subarctic freshwater environments. A pool of unique instruments for bathymetric, hydrological, hydraulic, morphodynamic and water quality measurements, with a variety of autonomous under- and above-water sensor platforms, a mobile field laboratory facility, and a data sharing platform are developed to study essential scientific questions in present and future hydrology.</p><p>Green-Digi-Basin (2022 onwards) aims to develop state-of-the-art understanding on green and digital transform in river basin and provide new tools and integrated modelling approaches for sustainable water resource management to assess impacts of nature-based solutions (e.g. peatland restoration, wetland and gypsum treatment) and land use changes through boreal-subarctic river basins. These will be done by utilizing remote sensing technologies, laser scanning high-resolution water quality and flow sensors, river basin 3D-mapping and geospatial analyses. Online data transfer systems, automatic data analysis will serve processed data to modelling software such as national wide river basin model WSFS-VEMALA to develop digital twins for river basin management.</p><p>The holistic concept of the Sustainable Freshwater Competence Centre in Finland will create a broad and reliable source of hydrologic monitoring, research, development, and innovation to support the adaptation of the hydrology of the Baltic Region to climate change.</p>

<p>Macro-turbulent flows during ice-covered and open-channel conditions, and their impacts on the total sediment transport, have not been studied widely in northern rivers. Previous studies have detected these processes, for example, only at the inlet area of one meander bend, or only during low discharge conditions. Thus, for understanding their impacts on the total sediment transport, it is needed to detect these macro-turbulent flow structures from a variety of cold region rivers, from multiple years, and also from a variety of different flow magnitude conditions. The pulses of high flow velocities related to these macro-turbulent structures may be important for determining the seasonal total sediment amount transported to the arctic ocean.</p><p> </p><p>The aim is 1) to detect the macro-turbulent flow in a meandering river at ice-covered low flow condition, and compare it to both high and low magnitude open-channel flow conditions. 2) Within a meander bend, the macro-turbulent flow will be compared between its inlet, apex and outlet sections. 3) The shear forces will be analyzed to detect the effects of macro-turbulent flow on potential sediment transport and channel development. The analyses are based on 5–10 minutes long moving boat Acoustic Doppler Current Profiler (ADCP) measurements from a meandering sub-arctic river. The measurements have been done in February and May during 2016–2019, and in September during 2016-2018. The preliminary results of this study are presented. The hypothesis is that the sediment transport potential of a sub-arctic river could be higher during all seasons than previously expected due to the pulses of high velocities related to macro-turbulent flow structures.</p>

<p>Light detection and ranging (lidar) has become an essential tool in mapping and change detection in different environments over the last 20 years. Laser scanners capture point clouds to create accurate digital snapshots of their surroundings. These snapshots tell about the structural information in the scene and can be readily returned to again and again to detect and measure any changes with multi-temporal measurements. However, multitemporal measurements cannot typically resolve the change events nor can they resolve more high frequency dynamics that happen on daily or weekly basis in the scene. Also, lidar systems operate still mainly with single wavelength limiting their usability in classification tasks. First multi- and hyperspectral systems have been already demonstrated, but have yet to break through in wider usage. Finnish Geospatial Research Institute (FGI) has been prototyping with different 3D measurement systems for the last 10 years to improve multitemporal mapping (4D) solutions. The prototypes include both hyperspectral and long-term multi- and hypertemporal lidar systems, and their combinations in static and mobile configurations. FGI started early on to experiment with hyperspectral laser sources (2007) and successfully demonstrated the first hyperspectral laser scanner prototype in 2012. The system was later used in detecting intraday vegetation dynamics in 2015. Multitemporal multispectral ALS measurements have been conducted since 2015 in Evo and in Espoolahti. The first long-term multitemporal studies with FGI mapping platforms were started with ALS to monitor changes in forests (1998) and built environment (2001) and with mobile laser scanning in studying the erosion of an arctic river basin (2008) annually.  Multitemporal ALS studies with vegetation started in 1998 in Kalkkinen and in 2007 in Evo followed with bi-temporal studies with TLS. Test Site Evo has been acquired with ALS. In 2020, Evo test site was granted Academy of Finland Research Infrastructure (RI) status. The RI will collect a 30-year-long time series with annual measurements using various laser scanning sensors for investigating single tree growth processes, forest dynamics, understanding cyclic forest while having variation at diurnal and annual scales and forest monitoring technologies. Vegetation dynamics monitoring was extended in 2020, when FGI started set up a permanent TLS measurement station in a boreal forest. The TLS station accurately detects structural changes of hundreds of tree crowns around it. The experiment aims to detect the changes of phenological state the trees and further link them with the environmental parameter variation. 4D measurements have successfully demonstrated their potential in extending the information available from laser scanning systems. To improve the usage of these novel information, automated pre-filtering of the vast data amounts already at sensor level will be imperative. Different lidar platforms can operate throughout the spatial scale from millimeter precision all way to national coverage. Thus, development of new scalable lidar RIs open new possibilities to complement already existing infrastructures.</p>

Even within a relatively small area like Finland the effects of climate change on floods can be non-uniform due to differences in climate and watershed characteristics. The overall picture of the changes in flood hazard in Finland with consistent methods and scenarios has been missing since the European scale assessments have been contradictory and not reliable on small scale (Lehner

Oppaassa käydään läpi yleispiirteisen tulvavaarakartoituksen laatimisprosessi yleisellä, ohjelmariippumattomalla tasolla. Oppaassa esitellään myös aiheeseen liittyvää terminologiaa ja taustoja. Suomen ympäristökeskuksesta on saatavilla erillinen tekninen osio työn teknisen puolen toteuttamista varten. Tulvavaarakartta kuvaa tulvan peittävyyden ja vaaran asteen karttapohjalla tietyllä todennäköisyydellä. Vaaran asteena käytetään yleensä vesisyvyyttä. Tulvavaarakartat laaditaan ainakin keskimäärin kerran 100 vuodessa ja kerran 250 vuodessa toistuville suurtulville. Oppaassa on vertailtu tilastollisten menetelmien, vesistömallien ja virtausmallien käyttöä virtaamien ja vedenkorkeuksien määrittämisessä sekä kerrottu myös muista määritysmenetelmistä. Oppaan laatimistyössä arvioitiin erityyppisten tietoaineistojen käyttökelpoisuutta ja kustannuksia, vertailtiin erilaisia mallinnustekniikoita sekä laadittiin havainnollisia kuvia ja kaavioita tulvavaarakartoituksen työvaiheista. Oppaassa on myös esitetty määritelmiä ja suosituksia eri tulvavaarakartoitusmenetelmistä ja niiden tarkkuuksista. Yleispiirteinen tulvavaarakartta määritettiin työssä kustannustehokkaasti edullisesti saatavilla olevista lähtötiedoista tulvariskiin suhteutetulla tarkkuudella tuotetuksi tulvavaarakartaksi. Sitä käytetään yleiskaava- ja maakuntakaavatasolla. Maanpinnan topografian kuvaava korkeusmalli tehdään edullisesti saatavilla olevasta korkeusaineistosta, kuten Maanmittauslaitoksen ja kuntien korkeusaineistoista tai näiden yhdistelmästä. Korkeusmallin tarkkuus huomioidaan esitysmittakaavassa ja kartan yleistysasteessa

ABSTRACT We evaluated the accuracy and efficiency of airborne (ALS), terrestrial (TLS) and mobile laser-scanning (MLS) methods that can be utilized in urban tree mapping and monitoring. In the field, 438 urban trees located in park and forested environments were measured and mapped from our study area located in Seurasaari, Helsinki, Finland. A field reference was collected, using a tree map created manually from TLS data. The tree detection rate and location accuracy were evaluated, using automatic or semiautomatic ALS individual tree detection (ALSITDauto or ALSITDvisual) and manual or automatic measurements of TLS and MLS (TLSauto, MLSauto, MLSmanual, MLSsemi). Our results showed that the best methods for tree detection were TLSauto and MLSmanual, which detected 73.29% and 79.22% of the reference trees, respectively. The location accuracies (RMSE) varied between 0.44 m and 1.57 m; the methods listed from the most accurate to most inaccurate were MLSsemi, TLSauto, MLSmanual, MLSauto, ALSITDauto and ALSITDvisual. We conclude that the accuracies of TLS and ALS were applicable for operational urban tree mapping in heterogeneous park forests. MLSmanual shows high potential but manual measurements are not feasible in operational tree mapping. Challenges that should be solved in further studies include ALSITDauto oversegmentation as well as MLSauto processing methodologies and data collection for tree detection.