Internet Archaeol. 16. Phillips. Topography

2.1 Topography

This region is very dramatic topographically, with a flat coastal plain, rising only 2m above mean sea level at the Hikutaia Stream junction which is 15km inland, and hills rising steeply to the east and west (Fig. 3). As spring tides commonly reach 1.5-1.8m a.s.l. much of the land was frequently subjected to flooding until flood protection measures were constructed in 1914. Although there were many natural resources available to Māori (fibre plants, timber, fruits and firewood, birds, shellfish, fish and eels) and the rivers formed natural transport routes to other regions, it was a rather demanding environment for occupation (Phillips 2000a). Yet within this setting there were pockets of slightly elevated ground that provided drier conditions for settlement and better-drained soils for cultivation. These were mainly located upstream from the Hikutaia Stream junction, although an important exception was the natural sub-fossil shellbanks marking a former coastline.

A series of environmental changes have been detected. The first since human settlement in Aotearoa (circa 800 BP) must have been the Kaharoa eruption around AD 1314±12 (Lowe et al. 2002). Large amounts of volcanic ash blanketed the ground over a wide area, covering the vegetation and clogging the streams, a process that may have opened up the area for human exploration after the initial effects were over. Some three hundred years later an earthquake caused a subsidence of approximately 0.4m. This event would have caused low-lying ground near the coast to be subjected to more extensive flooding during the monthly spring tides and heavy rainstorms, as described above. A higher water table may also have increased the areas of swamp, and possibly caused minor changes in the main river channel. Note that the maps included here show the reconstructed environment that existed between c. AD 1650-1850. The third change resulted from Māori forest clearance. As this deforestation was patchy, with some areas being allowed to regenerate, the results are not easy to ascertain. It seems certain, however, that erosion caused by clearance on the foothills coinciding with heavy storms would have resulted in flash flooding and inundation of the land below.