Microtopography and Surface Water Detention

Upland Microtopography and Implications to Surface Water Detention in Maine

Abstract: A notable characteristic of Maine’s forested landscape is the microtopography caused by a combination of factors related to surficial geology and tree fall. These features are often on the scale of single meters wide and decimeters to a meter in depth, appearing as “puddles” in the landscape during intense or high magnitude precipitation events. The surface water detention provided by the depressions can be substantial at the scale of a watershed and measurably affect runoff rates in low order streams. Generalized ranges for surface water storage capacity have been summarized in textbooks for varied landscape conditions, but little is known about how microtopography and related detention varies in Maine’s dominant physiographic settings defined by slope, surficial geology, and land cover conditions. With the increasing availability of high resolution elevation data, it has become possible to remotely evaluate the extent of these depressions and quantify the total upland storage capacity they may represent.

In this poster we describe and quantify microtopography in several Maine settings using measurements of hillslope terrain ruggedness and depression volume. We then relate the distribution of microtopography to variations in landform and land use conditions. The implications of spatial and temporal patterns of storage to runoff generation and habitat are then considered. For our analysis, we use LiDAR data in several Maine watersheds: Webhannet River in Wells; Darling Marine Center campus in Walpole; two streams on Marsh Island in Orono; Cromwell Brook on Mount Desert Island; and our sole inland watershed on Lead Mountain in East Hancock.