Forest Hydrology: The Japanese Experience

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Brooke Daniel
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1 Forest Hydrology: The Japanese Experience Roy C. Sidle Professor of Geography Sustainability Research Centre University of the Sunshine Coast Queensland, Australia

2 FFPRI, Tsukuba, Hokkaido PWRI, Tsukuba Tokushima University FFPRI, Tsukuba University of Tsukuba Niigata University PWRI, Tsukuba Tokushima University Tokyo Kyoto University, DPRI Chiba University Shinshu University Shizuoka University Mie University Kagoshima University Tokyo University Geological Survey of Japan JR Railways Disclaimer this presentation is not comprehensive and highly influenced by my personal affiliations in Japan

What have been some of the driving forces in forest

The inextricable relationship between hydrology and

hydrogeomorphology Ongoing issues of maintaining forest

sediment hazards Flood and sediment hazard assessment and

3 What have been some of the driving forces in forest hydrology research in Japan? The inextricable relationship between hydrology and landslides, giving rise to the new science of hydrogeomorphology Ongoing issues of maintaining forest productivity, whilst protecting against flood and sediment hazards Flood and sediment hazard assessment and control Historical devastation of native forests in granitic areas Need for better management of degraded hinoki forests

4 Research development and progress in forest hydrology & hydrogeomorphology in Japan Early work of Professors Tsukamoto and Okunishi Early development of the variable source area concept Process-based linkages amongst topography, flow pathways, and landslide initiation Hillslope channel interactions Basic concepts of hydrogeomorphology This pioneering research inspired detailed studies in: Geomorphic hollows Suzuki, Kuboto, and others Preferential flow/pipeflow in forested catchments Hydrologic conditions that trigger different types of landslides Landslide debris flow linkages

5 Variable source area concept Increasing Wetness Variable Source Area Concept Based on work of Tsukamoto (1961, 1963); Hewlett & Hibbert (1963, 1967); and Kirkby (1969) Subsurface runoff was considered the dominant process that contributed to stormflow in streams

Saturated overland flow (SOF) Research in an agricultural catchment in Vermont (Dunne and Black, 1970) showed that SOF was the primary source of storm runoff Later work by Tanaka (1982, 1988) in the

6 Saturated overland flow (SOF) Research in an agricultural catchment in Vermont (Dunne and Black, 1970) showed that SOF was the primary source of storm runoff Later work by Tanaka (1982, 1988) in the forested Hachioji Experimental Basin in Japan showed that SOF was discontinuous and accounted for up to only 7% of total storm discharge Nevertheless, riparian areas are important sources of rapid overland flow, but their contribution to runoff depends on their spatial extent findings from Hitachi Ohta Experimental Watershed, Japan

Effect of soil properties and geomorphology on subsurface flow and groundwater response Effects of soil physical properties on shallow groundwater response Tani, Kayane

7 Effect of soil properties and geomorphology on subsurface flow and groundwater response Effects of soil physical properties on shallow groundwater response Tani, Kayane Effect of topography and slope position on shallow groundwater response and storm runoff, particularly hollows Tsukamoto & Ohta, Suzuki, Kubota, Terajima & Moroto, Tsuboyama et al.

expansion of preferential flow pathways Rapid response of hollows after a threshold of water

8 Hydrogeomorphic Concept of Headwater Stormflow Generation Hitachi Ohta Dynamic catchment responses during storms Saturation overland flow in narrow riparian corridor Non-linear expansion of preferential flow pathways Rapid response of hollows after a threshold of water storage Progressive wetting of lower hillslopes by subsurface drainage Strong implications for forest management

Pioneering Research on Macropore/Pipeflow/Preferential Flow Earlier research by Kitahara, Tanaka, Narioka, Tsukamoto and Ohta, & Terajima Kitahara s work is significant as

9 Pioneering Research on Macropore/Pipeflow/Preferential Flow Earlier research by Kitahara, Tanaka, Narioka, Tsukamoto and Ohta, & Terajima Kitahara s work is significant as it some of the first research on: Detailed mapping of macropore systems in the field Studies of hydraulics of macropores Related pipeflow to throughflow at the hillslope scale

Later work on preferential flow/pipeflow in steep forested catchments Uchida showed that several major pipes exuded large amounts of flow during large storms Such large pipes monitored by Kitahara,

10 Later work on preferential flow/pipeflow in steep forested catchments Uchida showed that several major pipes exuded large amounts of flow during large storms Such large pipes monitored by Kitahara, Terajima, and Uchida appear to be intimately connected with the drainage network of hollows i.e. a kind of subsurface channel More recent preferential flow studies (including modeling) by Maruyama, Noguchi, Terajima, Tsutsumi, Kosugi, and Tsuboyama et al. from Uchida et al. (1999)

Understanding dynamic preferential flow network behavior

measurements of macropore flow Tracer tests Linking

3 5 4 7 6 Studies by Tsuboyama, Noguchi, Hosoda & Sidle

11 Understanding dynamic preferential flow network behavior at the hillslope scale Staining tests Hydrometric measurements of macropore flow Tracer tests Linking findings to hillslope scale 1 Self-organizing behavior Studies by Tsuboyama, Noguchi, Hosoda & Sidle in Hitachi Ohta Experimental Watershed 8 Top soil Mineral soil Bed rock

12 Influence of catchment geology on runoff generation Early work by Shimizu showed catchment lithology strongly affected runoff response: Sedimentary basins: most flashy (variable) runoff Volcanic basins: more stable Granitic basins: most stable runoff

much more common in granitic catchments, yielding greater runoff during storms compared to shale catchments Springs were more

13 Comparison of discharge and drainage density from shale and granite forest catchments (Onda et al.) K1 Type B talus Type A talus Shale catchments had lower drainage density than granite catchments Lateral subsurface stormflow is much more common in granitic catchments, yielding greater runoff during storms compared to shale catchments Springs were more common in shale catchments & occurred at K6 higher elevations due to the dominance of vertical subsurface recharge Yotagiri watershed (Granite) Koshibu watershed (Shale)

14 Distinguishes between effects of forest management/removal and land degradation Degradation at Tanakmi Mtn. began as early as the 7 th Century with culling of large trees to build temples Thresholds (tipping-points) differ for different lithologies from Tani et al., 2012 Hydro. Process.

Other significant contributions from Japanese scientists to forest hydrology Tracer investigations to separate recession flow of hydrographs Using temperature under a snow cover to separate the

15 Other significant contributions from Japanese scientists to forest hydrology Tracer investigations to separate recession flow of hydrographs Using temperature under a snow cover to separate the runoff into surface and subsurface flow Natural isotope tracers to identify storm runoff sources and residence times Using Si, DOC, etc. to assess rain-runoff lags & bedrock seepage The importance of slope position on subsurface water accretion in zero-order basins and slopes Unsaturated zone phenomena related to rapid water table response to rain Hillslope response to rainfall storm runoff Contributors include: Ohte, Katsuyama, Asano, Kabeya, Uchida, Tsuboyama, Kubota, Tsujimura, Haga, Fujimoto, Muraoko, Hirata, Kobayashi, Terajima, Tanaka, Kayane, Kaihotsu, Tani, Kosugi...

16 The long-term experimental catchment studies in Japan Mie University Experimental Forest Takaragawa Experimental Watershed Strengths generally overcome weaknesses, especially when nested studies are conducted Hitachi Ohta Experimental Watershed

What are some management issues related to forest hydrology that urgently need to be addressed

Cumulative land use effects we know little about these effects on runoff and water quality How

17 What are some management issues related to forest hydrology that urgently need to be addressed in Japan? Cumulative land use effects we know little about these effects on runoff and water quality How are upstream impacts translated downstream? - i.e., scaling issues Forest roads/trails and their affect on hydrology? (and at what scales?) Long-term investigations related to thinning of plantations Incorporating forest management practices into parsimonious models Effects of forest management practices on hydrogeomorphic processes that influence landslidedebris flow linkages

A few parting observations: When I first came to Japan in 1991, a big impression was that forest hydrologists were engaged in detailed process-based investigations and were not so quick to jump onto

18 A few parting observations: When I first came to Japan in 1991, a big impression was that forest hydrologists were engaged in detailed process-based investigations and were not so quick to jump onto bandwagons of new politically-driven research coming out of US or Europe. While this is changing, good process-based research needs to continue and must be applied at larger spatial scales and longer temporal scales and in models. We need to develop fundamental knowledge about why processes change with scale not just using statistical approaches This is a big challenge for the next generation of forest hydrologists & without this field-based knowledge it will be difficult to improve on existing models & we will be stuck in the same old cycle of small scale process understanding vs. large scale empirical hydrology predictions

19 Acknowledging some of the younger Japanese talent that I have had the pleasure of working with in my career

20 Domo arigato gozaimasu

Hillslope Hydrology Q 1 Q Understand hillslope runoff processes. 2. Understand the contribution of groundwater to storm runoff.

Hillslope Hydrology Q 1 Q Understand hillslope runoff processes. 2. Understand the contribution of groundwater to storm runoff. Objectives Hillslope Hydrology Streams are the conduits of the surface and subsurface runoff generated in watersheds. SW-GW interaction needs to be understood from the watershed perspective. During a storm