Forest Investment Account

Abstract of FII Project R02-15

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Testing Current Watershed Assessment Procedures

Author(s): Alila, Younes (University of British Columbia)
Subject: Hydrology
Series: Forest Investment Account (FIA) - Forest Science Program


This project concerns hydrologic simulation research with the Distributed Hydrology Soil Vegetation Model (DHSVM) at three paired watershed experimental sites (Redfish Creek, Upper Penticton Creek and Carnation Creek) to evaluate streamflow responses to forestry activities across biogeoclimatic zones in British Columbia through a long-term statistical-deterministic analysis.
Penticton Creek model development in 2002/2003 has highlighted that care must be taken to ensure proper conceptualization of the forest radiation balance if the model is used to simulate the effects of logging on peak flows. The Penticton Creek DHSVM model is able to reproduce the large array of field data collected at this site with reasonable accuracy. This suggests that the model will provide a reliable tool for assessing potential impacts of forest management in the region. Carnation Creek model development has highlighted that preferential hillslope runoff must be properly accounted for in models of humid forested watersheds, particularly when such models are used to evaluate the effect of forestry activities on small versus large return period peak flows.
Simulation results for the rainfall-dominated Carnation Creek site indicate that percentage effects of harvesting and roads decrease as peak flow event size increases and thus concur with conclusions drawn by Thomas and Megahan while contradicting those of Jones and Grant. On the other hand, findings for the snowmelt-dominated Redfish Creek and Penticton Creek watersheds suggest that the entire population of peak discharges may be shifted upward by timber harvesting, highlighting possible linkages between hydro-climatology and the response of small versus large return peak flow events to forestry activities.
Simulation experiments for Carnation Creek have helped clarify linkages between responses of small versus large return period peak flows to harvesting and roads and the underlying physical processes controlling these responses. This provides a significant advance over previous statistical data analysis work that cannot highlight these linkages.
Extension for 2002/2003 was achieved through: (1) Scientific publications. (2) Lectures. (3) Directed studies. (4) Conference and other presentations. The overriding plan of this multi-year project is to provide a set of recommendations with regard to Watershed Assessment Procedure (WAP) guidelines and to develop a decision-support tool for end-users such as resource practitioners, forest licensees, conservation authorities, the consulting industry and other organizations that utilize the WAP and are engaged in the management of BCs forest resources. We are on track to deliver the proposed decisionsupport tool by 2005/2006. To test WAP guidelines and develop the decision-support tool we need to establish a database of simulations that considers a wide range of operational management scenarios under contrasting hydro-climatic conditions at Redfish Creek, Penticton Creek and Carnation Creek. Next year we intend to establish that database and our immediate objective for 2003/2004 therefore is to explore streamflow responses to a large spectrum of operational forest management scenarios at the three experimental sites. This research is the subject of a proposal that was submitted to FII by team leader Alila: 'Assessing Streamflow Responses to Forestry Activities across Biogeoclimatic Zones in British Columbia', with reference to request for proposals FII RFP FR2003/04.

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Updated August 26, 2005 

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