Matthias Huttenlau

Continuous monitoring of snowpack dynamics in alpine terrain by aboveground neutron sensing

The characteristics of an aboveground cosmic-ray neutron sensor (CRNS) are evaluated for monitoring a mountain snowpack in the Austrian Alps from March 2014 to June 2016. Neutron counts were compared to continuous point-scale snow depth (SD) and snow-water-equivalent (SWE) measurements from an automatic weather station with a maximum SWE of 600 mm (April 2014). Several spatially distributed Terrestrial Laser Scanning (TLS)-based SD and SWE maps were additionally used. A strong nonlinear correlation is found for both SD and SWE. The representative footprint of the CRNS is in the range of 230–270 m. In contrast to previous studies suggesting signal saturation at around 100 mm of SWE, no complete signal saturation was observed. These results imply that CRNS could be transferred into an unprecedented method for continuous detection of spatially averaged SD and SWE for alpine snowpacks, though with sensitivity decreasing with increasing SWE. While initially different functions were found for accumulation and melting season conditions, this could be resolved by accounting for a limited measurement depth. This depth limit is in the range of 200 mm of SWE for dense snowpacks with high liquid water contents and associated snow density values around 450 kg m−3 and above. In contrast to prior studies with shallow snowpacks, interannual transferability of the results is very high regardless of presnowfall soil moisture conditions. This underlines the unexpectedly high potential of CRNS to close the gap between point-scale measurements, hydrological models, and remote sensing of the cryosphere in alpine terrain.

Temporal development of flood risk considering settlement dynamics and local flood protection measures on catchment scale: an Austrian case study

ABSTRACT With respect to urban development a common practice is to exclude flood-prone areas from further construction for flood safety reasons. Granting exemptions when local flood safety measures are applied is a topic of continued debate. The Ottnager-Redl/Upper Austria case study investigates various future settlement scenarios with or without local flood protection measures (LFPM). In accordance with the legal situation in the Federal Province of Upper Austria, construction permits require flood safety up to a 100-year flood level plus 20 cm. Estimations of potential flood damage in the catchment’s residential areas are based on damage functions used to describe the structural vulnerability at an object level. Impacts are simulated with a distributed hydrological and a 2D-hydraulic model, which incorporate future settlement dynamics. In addition to linking losses to return periods, the cumulative damages within design periods are estimated using a Monte-Carlo modelling framework. Event-based and cumulative losses increase with the different settlement scenarios. The LFPM tested visibly reduce the cumulative losses as they are triggered by high-frequency/low-impact events. Considering single events, the positive effects of LFPM, specifically flexible flood barriers, generally vanish when they exceed the design level. Thus, the increased flood risk due to intensified settlement in the flood-prone area cannot be compensated by LFPM.

A Probabilistic Framework for Risk Analysis of Widespread Flood Events: A Proof‐of‐Concept Study

This article presents a flood risk analysis model that considers the spatially heterogeneous nature of flood events. The basic concept of this approach is to generate a large sample of flood events that can be regarded as temporal extrapolation of flood events. These are combined with cumulative flood impact indicators, such as building damages, to finally derive time series of damages for risk estimation. Therefore, a multivariate modeling procedure that is able to take into account the spatial characteristics of flooding, the regionalization method top-kriging, and three different impact indicators are combined in a model chain. Eventually, the expected annual flood impact (e.g., expected annual damages) and the flood impact associated with a low probability of occurrence are determined for a study area. The risk model has the potential to augment the understanding of flood risk in a region and thereby contribute to enhanced risk management of, for example, risk analysts and policymakers or insurance companies. The modeling framework was successfully applied in a proof-of-concept exercise in Vorarlberg (Austria). The results of the case study show that risk analysis has to be based on spatially heterogeneous flood events in order to estimate flood risk adequately.

Analysis of the loss probability relation on a community level: a contribution to a comprehensive flood risk assessment

Flood risk management is an appropriate method to understand and mitigate the consequences of flooding which regularly causes significant losses to property and human lives. Therefore, the analysis of flood risk is a key issue. Within this risk analysis, direct tangible damages are important flood hazard impact indicators. This paper shows an approach of how to assess the potential direct monetary damages in a mountain meso-scale study area (Austrian Province of Vorarlberg). The approach comprises the following key components: (i) asset pooling and its monetary assessment, (ii) exposure analysis, and (iii) susceptibility analysis. By applying this method, loss probability relations reflecting the potential direct monetary damages of flood events with a return period of 30 yrs, 100 yrs and 300 yrs were derived for all flood exposed communities in the study area. The results illustrate the possible uncertainties that are inherent in the procedure of assessing direct monetary damages. By highlighting this significant variability, it is a valuable contribution to a

Sources of uncertainty in a probabilistic flood risk model

Flood risk models capture a variety of processes and are associated with large uncertainties. In this paper, the uncertainties due to alternative model assumptions are analysed for various components of a probabilistic flood risk model in the study area of Vorarlberg (Austria). The effect of different model assumptions for five aspects is compared to a reference simulation. This includes: (I, II) the selection of two model thresholds controlling the generation of large sets of possible flood events; (III) the selection of a distribution function for the flood frequency analysis; (IV) the building representation and water level derivation for the exposure analysis and (V) the selection of an appropriate damage function. The analysis shows that each of the tested aspects has the potential to alter the modelling results considerably. The results range from a factor of 1.2 to 3, from the lowest to highest value, whereby the selection of the damage function has the largest effect on the overall modelling results.

Risk-based damage potential and loss estimation of earthquake scenarios in the moderate endangered Austrian Federal Province of Tyrol

Although geophysical hazards like earthquakes can lead to tremendous losses, they are often neglected or not considered in risk analyses within an Alpine context. However, lately and especially in the framework of multi-risk analyses, earthquake risk studies are being increasingly implemented within an Alpine relation too. The presented study was conducted to quantitatively estimate potential consequences of earthquake events in the Austrian Province of Tyrol. The methodological study framework integrates the general risk components (i) hazard, (ii) elements at risk, and (iii) vulnerability. They are considered on a regional scale, accepting pragmatic approaches with simplified procedures and assumptions. Scenarios for different potential epicentres were calculated based on two different macroseismic hazard maps derived from punctual ground motion values of the building code and microzonation studies. The maps take into account the design event definitions of existing building code and a, thereupon based, simple and mono-causal Maximum Credible Earthquake assumption. Corresponding elements at risk and damage potentials were identified and potential losses were estimated under consideration of different vulnerability approaches. It can be shown that most scenarios based on the design event definition of the Austrian and European building codes, respectively have the potential of building and inventory losses solely of some hundred million up to approximately €4 billion. Additional, building and inventory losses of maximum credible events can lead to losses of more than €7 billion merely in connection with the primary earthquake event neglecting all other cascading effects.