LIDAR topography of mountainous Federal lands in the Cascades and
Olympics

T Sisson, C Gardner, D Ramsey, VHZ

**Statement of problem** -- Existing digital topography covering the
Cascade and Olympic Mountains has an effective resolution of 30 m.
Diverse geologic, biologic, and water resources investigations in the
Western Region would be advanced by acquiring LIDAR topographic data,
typically with a resolution of 1 m laterally and 0.05 m vertically.
Although collecting such data over all western Federal lands might be
prohibitively expensive, a targeted effort on the mountainous portions
of the Cascades and Olympics would produce multiple immediate benefits
(see relevance and impact).

Objectives -- Facilitate hazards, climate change, and biological
investigations by producing detailed digital topographic data for
mountainous Federal lands in the Cascades and Olympics.

# Work strategy -- LIDAR is now a mature, commercially available surveying technology costing \$0.67 to \$0.86 per acre for at least 4 laser-pulse returns/m^2^. Edifices and flood/lahar prone drainages of the major volcanoes of the Cascades encompass 2.3 million acres and would cost \$1.5 - \$2 million to survey. Olympic and North Cascades National Parks are large, and consultation with the National Park Service could narrow efforts to highest priority areas. For example, the non-volcanic Mt. Olympus massif encompasses 170,000 acres and would cost ca. \$130,000 to survey. Overall, high-resolution LIDAR surveys over the higher portions of Federal lands in the Cascades and Olympics and their major drainages might cost \$2 - \$3 million. Following verification of accuracy and resolution, the data would be made available to researchers, land managers, and the general public. The Puget Sound LIDAR Consortium can provide quality assurance and a contracting mechanism. 

**Relevance and impact:** *Climate change* - The Cascades and Olympics
contain most of the glaciers in the contiguous United States (Mts.
Shasta, Hood, Rainier, Adams, Baker, Glacier Peak, the North Cascades,
and the Mt. Olympus massif). High-resolution LIDAR topography would
produce a snapshot of ice surface elevation and extent, establishing a
precise regional baseline for monitoring changes in ice volume, thus
quantifying one of the most apparent effects of climate change.
Bare-earth LIDAR topography is also a base for measuring snow
thicknesses by regional aerial winter surveys.

*Paleoclimates and neotectonics* - The ability of LIDAR to image the
bare ground surface precisely in forested areas enables studies of past
climatic events, particularly Holocene ice advances that left neoglacial
moraines (five Holocene ice advances at Mount Rainier), and can reveal
subtle neotectonic features (fault scarps) and landslides.

*Flood hazards* - Due to high erosion and sediment transport rates,
rivers draining most of the glaciated regions are aggrading, enhancing
the frequency and extent of flooding. High-resolution topography would
improve the accuracy of flood inundation modeling and quantification of
aggradation rates, among others.

*Volcano hazards --* High-resolution topography and imagery are
important for monitoring changes in volcano edifice shape, but also by
enabling detailed field studies of volcanic deposits and quantitative
predictions of the paths of lahars, lava flows, and landslides.

*Biological resources* -- Vegetation is rapidly colonizing recently
deglaciated areas throughout the Cascades and Olympics. LIDAR can show
vegetation extents and heights that, coupled with other images, provide
a baseline for measuring ecosystem changes.

# Partnerships - Results would be of use to Federal land managers, mainly in the National Park and Forest Services, and also to state geological surveys. The National Park Service currently seeks funding for a detailed LIDAR survey of Mount Rainier National Park to respond to \$30 million in damage from flooding in Nov. 2006. LIDAR surveys would complement the Department of Agriculture's \~\$110 million per year NAIP program producing 1-meter resolution color aerial orthoimages of the entire United States.